| 1 | /* |
| 2 | * linux/fs/namei.c |
| 3 | * |
| 4 | * Copyright (C) 1991, 1992 Linus Torvalds |
| 5 | */ |
| 6 | |
| 7 | /* |
| 8 | * Some corrections by tytso. |
| 9 | */ |
| 10 | |
| 11 | /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname |
| 12 | * lookup logic. |
| 13 | */ |
| 14 | /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture. |
| 15 | */ |
| 16 | |
| 17 | #include <linux/init.h> |
| 18 | #include <linux/export.h> |
| 19 | #include <linux/kernel.h> |
| 20 | #include <linux/slab.h> |
| 21 | #include <linux/fs.h> |
| 22 | #include <linux/namei.h> |
| 23 | #include <linux/pagemap.h> |
| 24 | #include <linux/fsnotify.h> |
| 25 | #include <linux/personality.h> |
| 26 | #include <linux/security.h> |
| 27 | #include <linux/ima.h> |
| 28 | #include <linux/syscalls.h> |
| 29 | #include <linux/mount.h> |
| 30 | #include <linux/audit.h> |
| 31 | #include <linux/capability.h> |
| 32 | #include <linux/file.h> |
| 33 | #include <linux/fcntl.h> |
| 34 | #include <linux/device_cgroup.h> |
| 35 | #include <linux/fs_struct.h> |
| 36 | #include <linux/posix_acl.h> |
| 37 | #include <asm/uaccess.h> |
| 38 | |
| 39 | #include "internal.h" |
| 40 | #include "mount.h" |
| 41 | |
| 42 | /* [Feb-1997 T. Schoebel-Theuer] |
| 43 | * Fundamental changes in the pathname lookup mechanisms (namei) |
| 44 | * were necessary because of omirr. The reason is that omirr needs |
| 45 | * to know the _real_ pathname, not the user-supplied one, in case |
| 46 | * of symlinks (and also when transname replacements occur). |
| 47 | * |
| 48 | * The new code replaces the old recursive symlink resolution with |
| 49 | * an iterative one (in case of non-nested symlink chains). It does |
| 50 | * this with calls to <fs>_follow_link(). |
| 51 | * As a side effect, dir_namei(), _namei() and follow_link() are now |
| 52 | * replaced with a single function lookup_dentry() that can handle all |
| 53 | * the special cases of the former code. |
| 54 | * |
| 55 | * With the new dcache, the pathname is stored at each inode, at least as |
| 56 | * long as the refcount of the inode is positive. As a side effect, the |
| 57 | * size of the dcache depends on the inode cache and thus is dynamic. |
| 58 | * |
| 59 | * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink |
| 60 | * resolution to correspond with current state of the code. |
| 61 | * |
| 62 | * Note that the symlink resolution is not *completely* iterative. |
| 63 | * There is still a significant amount of tail- and mid- recursion in |
| 64 | * the algorithm. Also, note that <fs>_readlink() is not used in |
| 65 | * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink() |
| 66 | * may return different results than <fs>_follow_link(). Many virtual |
| 67 | * filesystems (including /proc) exhibit this behavior. |
| 68 | */ |
| 69 | |
| 70 | /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation: |
| 71 | * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL |
| 72 | * and the name already exists in form of a symlink, try to create the new |
| 73 | * name indicated by the symlink. The old code always complained that the |
| 74 | * name already exists, due to not following the symlink even if its target |
| 75 | * is nonexistent. The new semantics affects also mknod() and link() when |
| 76 | * the name is a symlink pointing to a non-existent name. |
| 77 | * |
| 78 | * I don't know which semantics is the right one, since I have no access |
| 79 | * to standards. But I found by trial that HP-UX 9.0 has the full "new" |
| 80 | * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the |
| 81 | * "old" one. Personally, I think the new semantics is much more logical. |
| 82 | * Note that "ln old new" where "new" is a symlink pointing to a non-existing |
| 83 | * file does succeed in both HP-UX and SunOs, but not in Solaris |
| 84 | * and in the old Linux semantics. |
| 85 | */ |
| 86 | |
| 87 | /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink |
| 88 | * semantics. See the comments in "open_namei" and "do_link" below. |
| 89 | * |
| 90 | * [10-Sep-98 Alan Modra] Another symlink change. |
| 91 | */ |
| 92 | |
| 93 | /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks: |
| 94 | * inside the path - always follow. |
| 95 | * in the last component in creation/removal/renaming - never follow. |
| 96 | * if LOOKUP_FOLLOW passed - follow. |
| 97 | * if the pathname has trailing slashes - follow. |
| 98 | * otherwise - don't follow. |
| 99 | * (applied in that order). |
| 100 | * |
| 101 | * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT |
| 102 | * restored for 2.4. This is the last surviving part of old 4.2BSD bug. |
| 103 | * During the 2.4 we need to fix the userland stuff depending on it - |
| 104 | * hopefully we will be able to get rid of that wart in 2.5. So far only |
| 105 | * XEmacs seems to be relying on it... |
| 106 | */ |
| 107 | /* |
| 108 | * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland) |
| 109 | * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives |
| 110 | * any extra contention... |
| 111 | */ |
| 112 | |
| 113 | /* In order to reduce some races, while at the same time doing additional |
| 114 | * checking and hopefully speeding things up, we copy filenames to the |
| 115 | * kernel data space before using them.. |
| 116 | * |
| 117 | * POSIX.1 2.4: an empty pathname is invalid (ENOENT). |
| 118 | * PATH_MAX includes the nul terminator --RR. |
| 119 | */ |
| 120 | void final_putname(struct filename *name) |
| 121 | { |
| 122 | if (name->separate) { |
| 123 | __putname(name->name); |
| 124 | kfree(name); |
| 125 | } else { |
| 126 | __putname(name); |
| 127 | } |
| 128 | } |
| 129 | |
| 130 | #define EMBEDDED_NAME_MAX (PATH_MAX - sizeof(struct filename)) |
| 131 | |
| 132 | static struct filename * |
| 133 | getname_flags(const char __user *filename, int flags, int *empty) |
| 134 | { |
| 135 | struct filename *result, *err; |
| 136 | int len; |
| 137 | long max; |
| 138 | char *kname; |
| 139 | |
| 140 | result = audit_reusename(filename); |
| 141 | if (result) |
| 142 | return result; |
| 143 | |
| 144 | result = __getname(); |
| 145 | if (unlikely(!result)) |
| 146 | return ERR_PTR(-ENOMEM); |
| 147 | |
| 148 | /* |
| 149 | * First, try to embed the struct filename inside the names_cache |
| 150 | * allocation |
| 151 | */ |
| 152 | kname = (char *)result + sizeof(*result); |
| 153 | result->name = kname; |
| 154 | result->separate = false; |
| 155 | max = EMBEDDED_NAME_MAX; |
| 156 | |
| 157 | recopy: |
| 158 | len = strncpy_from_user(kname, filename, max); |
| 159 | if (unlikely(len < 0)) { |
| 160 | err = ERR_PTR(len); |
| 161 | goto error; |
| 162 | } |
| 163 | |
| 164 | /* |
| 165 | * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a |
| 166 | * separate struct filename so we can dedicate the entire |
| 167 | * names_cache allocation for the pathname, and re-do the copy from |
| 168 | * userland. |
| 169 | */ |
| 170 | if (len == EMBEDDED_NAME_MAX && max == EMBEDDED_NAME_MAX) { |
| 171 | kname = (char *)result; |
| 172 | |
| 173 | result = kzalloc(sizeof(*result), GFP_KERNEL); |
| 174 | if (!result) { |
| 175 | err = ERR_PTR(-ENOMEM); |
| 176 | result = (struct filename *)kname; |
| 177 | goto error; |
| 178 | } |
| 179 | result->name = kname; |
| 180 | result->separate = true; |
| 181 | max = PATH_MAX; |
| 182 | goto recopy; |
| 183 | } |
| 184 | |
| 185 | /* The empty path is special. */ |
| 186 | if (unlikely(!len)) { |
| 187 | if (empty) |
| 188 | *empty = 1; |
| 189 | err = ERR_PTR(-ENOENT); |
| 190 | if (!(flags & LOOKUP_EMPTY)) |
| 191 | goto error; |
| 192 | } |
| 193 | |
| 194 | err = ERR_PTR(-ENAMETOOLONG); |
| 195 | if (unlikely(len >= PATH_MAX)) |
| 196 | goto error; |
| 197 | |
| 198 | result->uptr = filename; |
| 199 | result->aname = NULL; |
| 200 | audit_getname(result); |
| 201 | return result; |
| 202 | |
| 203 | error: |
| 204 | final_putname(result); |
| 205 | return err; |
| 206 | } |
| 207 | |
| 208 | struct filename * |
| 209 | getname(const char __user * filename) |
| 210 | { |
| 211 | return getname_flags(filename, 0, NULL); |
| 212 | } |
| 213 | |
| 214 | /* |
| 215 | * The "getname_kernel()" interface doesn't do pathnames longer |
| 216 | * than EMBEDDED_NAME_MAX. Deal with it - you're a kernel user. |
| 217 | */ |
| 218 | struct filename * |
| 219 | getname_kernel(const char * filename) |
| 220 | { |
| 221 | struct filename *result; |
| 222 | char *kname; |
| 223 | int len; |
| 224 | |
| 225 | len = strlen(filename); |
| 226 | if (len >= EMBEDDED_NAME_MAX) |
| 227 | return ERR_PTR(-ENAMETOOLONG); |
| 228 | |
| 229 | result = __getname(); |
| 230 | if (unlikely(!result)) |
| 231 | return ERR_PTR(-ENOMEM); |
| 232 | |
| 233 | kname = (char *)result + sizeof(*result); |
| 234 | result->name = kname; |
| 235 | result->uptr = NULL; |
| 236 | result->aname = NULL; |
| 237 | result->separate = false; |
| 238 | |
| 239 | strlcpy(kname, filename, EMBEDDED_NAME_MAX); |
| 240 | return result; |
| 241 | } |
| 242 | |
| 243 | #ifdef CONFIG_AUDITSYSCALL |
| 244 | void putname(struct filename *name) |
| 245 | { |
| 246 | if (unlikely(!audit_dummy_context())) |
| 247 | return audit_putname(name); |
| 248 | final_putname(name); |
| 249 | } |
| 250 | #endif |
| 251 | |
| 252 | static int check_acl(struct inode *inode, int mask) |
| 253 | { |
| 254 | #ifdef CONFIG_FS_POSIX_ACL |
| 255 | struct posix_acl *acl; |
| 256 | |
| 257 | if (mask & MAY_NOT_BLOCK) { |
| 258 | acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS); |
| 259 | if (!acl) |
| 260 | return -EAGAIN; |
| 261 | /* no ->get_acl() calls in RCU mode... */ |
| 262 | if (acl == ACL_NOT_CACHED) |
| 263 | return -ECHILD; |
| 264 | return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK); |
| 265 | } |
| 266 | |
| 267 | acl = get_acl(inode, ACL_TYPE_ACCESS); |
| 268 | if (IS_ERR(acl)) |
| 269 | return PTR_ERR(acl); |
| 270 | if (acl) { |
| 271 | int error = posix_acl_permission(inode, acl, mask); |
| 272 | posix_acl_release(acl); |
| 273 | return error; |
| 274 | } |
| 275 | #endif |
| 276 | |
| 277 | return -EAGAIN; |
| 278 | } |
| 279 | |
| 280 | /* |
| 281 | * This does the basic permission checking |
| 282 | */ |
| 283 | static int acl_permission_check(struct inode *inode, int mask) |
| 284 | { |
| 285 | unsigned int mode = inode->i_mode; |
| 286 | |
| 287 | if (likely(uid_eq(current_fsuid(), inode->i_uid))) |
| 288 | mode >>= 6; |
| 289 | else { |
| 290 | if (IS_POSIXACL(inode) && (mode & S_IRWXG)) { |
| 291 | int error = check_acl(inode, mask); |
| 292 | if (error != -EAGAIN) |
| 293 | return error; |
| 294 | } |
| 295 | |
| 296 | if (in_group_p(inode->i_gid)) |
| 297 | mode >>= 3; |
| 298 | } |
| 299 | |
| 300 | /* |
| 301 | * If the DACs are ok we don't need any capability check. |
| 302 | */ |
| 303 | if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0) |
| 304 | return 0; |
| 305 | return -EACCES; |
| 306 | } |
| 307 | |
| 308 | /** |
| 309 | * generic_permission - check for access rights on a Posix-like filesystem |
| 310 | * @inode: inode to check access rights for |
| 311 | * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...) |
| 312 | * |
| 313 | * Used to check for read/write/execute permissions on a file. |
| 314 | * We use "fsuid" for this, letting us set arbitrary permissions |
| 315 | * for filesystem access without changing the "normal" uids which |
| 316 | * are used for other things. |
| 317 | * |
| 318 | * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk |
| 319 | * request cannot be satisfied (eg. requires blocking or too much complexity). |
| 320 | * It would then be called again in ref-walk mode. |
| 321 | */ |
| 322 | int generic_permission(struct inode *inode, int mask) |
| 323 | { |
| 324 | int ret; |
| 325 | |
| 326 | /* |
| 327 | * Do the basic permission checks. |
| 328 | */ |
| 329 | ret = acl_permission_check(inode, mask); |
| 330 | if (ret != -EACCES) |
| 331 | return ret; |
| 332 | |
| 333 | if (S_ISDIR(inode->i_mode)) { |
| 334 | /* DACs are overridable for directories */ |
| 335 | if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) |
| 336 | return 0; |
| 337 | if (!(mask & MAY_WRITE)) |
| 338 | if (capable_wrt_inode_uidgid(inode, |
| 339 | CAP_DAC_READ_SEARCH)) |
| 340 | return 0; |
| 341 | return -EACCES; |
| 342 | } |
| 343 | /* |
| 344 | * Read/write DACs are always overridable. |
| 345 | * Executable DACs are overridable when there is |
| 346 | * at least one exec bit set. |
| 347 | */ |
| 348 | if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO)) |
| 349 | if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) |
| 350 | return 0; |
| 351 | |
| 352 | /* |
| 353 | * Searching includes executable on directories, else just read. |
| 354 | */ |
| 355 | mask &= MAY_READ | MAY_WRITE | MAY_EXEC; |
| 356 | if (mask == MAY_READ) |
| 357 | if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH)) |
| 358 | return 0; |
| 359 | |
| 360 | return -EACCES; |
| 361 | } |
| 362 | EXPORT_SYMBOL(generic_permission); |
| 363 | |
| 364 | /* |
| 365 | * We _really_ want to just do "generic_permission()" without |
| 366 | * even looking at the inode->i_op values. So we keep a cache |
| 367 | * flag in inode->i_opflags, that says "this has not special |
| 368 | * permission function, use the fast case". |
| 369 | */ |
| 370 | static inline int do_inode_permission(struct inode *inode, int mask) |
| 371 | { |
| 372 | if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) { |
| 373 | if (likely(inode->i_op->permission)) |
| 374 | return inode->i_op->permission(inode, mask); |
| 375 | |
| 376 | /* This gets set once for the inode lifetime */ |
| 377 | spin_lock(&inode->i_lock); |
| 378 | inode->i_opflags |= IOP_FASTPERM; |
| 379 | spin_unlock(&inode->i_lock); |
| 380 | } |
| 381 | return generic_permission(inode, mask); |
| 382 | } |
| 383 | |
| 384 | /** |
| 385 | * __inode_permission - Check for access rights to a given inode |
| 386 | * @inode: Inode to check permission on |
| 387 | * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) |
| 388 | * |
| 389 | * Check for read/write/execute permissions on an inode. |
| 390 | * |
| 391 | * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. |
| 392 | * |
| 393 | * This does not check for a read-only file system. You probably want |
| 394 | * inode_permission(). |
| 395 | */ |
| 396 | int __inode_permission(struct inode *inode, int mask) |
| 397 | { |
| 398 | int retval; |
| 399 | |
| 400 | if (unlikely(mask & MAY_WRITE)) { |
| 401 | /* |
| 402 | * Nobody gets write access to an immutable file. |
| 403 | */ |
| 404 | if (IS_IMMUTABLE(inode)) |
| 405 | return -EACCES; |
| 406 | } |
| 407 | |
| 408 | retval = do_inode_permission(inode, mask); |
| 409 | if (retval) |
| 410 | return retval; |
| 411 | |
| 412 | retval = devcgroup_inode_permission(inode, mask); |
| 413 | if (retval) |
| 414 | return retval; |
| 415 | |
| 416 | return security_inode_permission(inode, mask); |
| 417 | } |
| 418 | |
| 419 | /** |
| 420 | * sb_permission - Check superblock-level permissions |
| 421 | * @sb: Superblock of inode to check permission on |
| 422 | * @inode: Inode to check permission on |
| 423 | * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) |
| 424 | * |
| 425 | * Separate out file-system wide checks from inode-specific permission checks. |
| 426 | */ |
| 427 | static int sb_permission(struct super_block *sb, struct inode *inode, int mask) |
| 428 | { |
| 429 | if (unlikely(mask & MAY_WRITE)) { |
| 430 | umode_t mode = inode->i_mode; |
| 431 | |
| 432 | /* Nobody gets write access to a read-only fs. */ |
| 433 | if ((sb->s_flags & MS_RDONLY) && |
| 434 | (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) |
| 435 | return -EROFS; |
| 436 | } |
| 437 | return 0; |
| 438 | } |
| 439 | |
| 440 | /** |
| 441 | * inode_permission - Check for access rights to a given inode |
| 442 | * @inode: Inode to check permission on |
| 443 | * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) |
| 444 | * |
| 445 | * Check for read/write/execute permissions on an inode. We use fs[ug]id for |
| 446 | * this, letting us set arbitrary permissions for filesystem access without |
| 447 | * changing the "normal" UIDs which are used for other things. |
| 448 | * |
| 449 | * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. |
| 450 | */ |
| 451 | int inode_permission(struct inode *inode, int mask) |
| 452 | { |
| 453 | int retval; |
| 454 | |
| 455 | retval = sb_permission(inode->i_sb, inode, mask); |
| 456 | if (retval) |
| 457 | return retval; |
| 458 | return __inode_permission(inode, mask); |
| 459 | } |
| 460 | EXPORT_SYMBOL(inode_permission); |
| 461 | |
| 462 | /** |
| 463 | * path_get - get a reference to a path |
| 464 | * @path: path to get the reference to |
| 465 | * |
| 466 | * Given a path increment the reference count to the dentry and the vfsmount. |
| 467 | */ |
| 468 | void path_get(const struct path *path) |
| 469 | { |
| 470 | mntget(path->mnt); |
| 471 | dget(path->dentry); |
| 472 | } |
| 473 | EXPORT_SYMBOL(path_get); |
| 474 | |
| 475 | /** |
| 476 | * path_put - put a reference to a path |
| 477 | * @path: path to put the reference to |
| 478 | * |
| 479 | * Given a path decrement the reference count to the dentry and the vfsmount. |
| 480 | */ |
| 481 | void path_put(const struct path *path) |
| 482 | { |
| 483 | dput(path->dentry); |
| 484 | mntput(path->mnt); |
| 485 | } |
| 486 | EXPORT_SYMBOL(path_put); |
| 487 | |
| 488 | /* |
| 489 | * Path walking has 2 modes, rcu-walk and ref-walk (see |
| 490 | * Documentation/filesystems/path-lookup.txt). In situations when we can't |
| 491 | * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab |
| 492 | * normal reference counts on dentries and vfsmounts to transition to rcu-walk |
| 493 | * mode. Refcounts are grabbed at the last known good point before rcu-walk |
| 494 | * got stuck, so ref-walk may continue from there. If this is not successful |
| 495 | * (eg. a seqcount has changed), then failure is returned and it's up to caller |
| 496 | * to restart the path walk from the beginning in ref-walk mode. |
| 497 | */ |
| 498 | |
| 499 | /** |
| 500 | * unlazy_walk - try to switch to ref-walk mode. |
| 501 | * @nd: nameidata pathwalk data |
| 502 | * @dentry: child of nd->path.dentry or NULL |
| 503 | * Returns: 0 on success, -ECHILD on failure |
| 504 | * |
| 505 | * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry |
| 506 | * for ref-walk mode. @dentry must be a path found by a do_lookup call on |
| 507 | * @nd or NULL. Must be called from rcu-walk context. |
| 508 | */ |
| 509 | static int unlazy_walk(struct nameidata *nd, struct dentry *dentry) |
| 510 | { |
| 511 | struct fs_struct *fs = current->fs; |
| 512 | struct dentry *parent = nd->path.dentry; |
| 513 | |
| 514 | BUG_ON(!(nd->flags & LOOKUP_RCU)); |
| 515 | |
| 516 | /* |
| 517 | * After legitimizing the bastards, terminate_walk() |
| 518 | * will do the right thing for non-RCU mode, and all our |
| 519 | * subsequent exit cases should rcu_read_unlock() |
| 520 | * before returning. Do vfsmount first; if dentry |
| 521 | * can't be legitimized, just set nd->path.dentry to NULL |
| 522 | * and rely on dput(NULL) being a no-op. |
| 523 | */ |
| 524 | if (!legitimize_mnt(nd->path.mnt, nd->m_seq)) |
| 525 | return -ECHILD; |
| 526 | nd->flags &= ~LOOKUP_RCU; |
| 527 | |
| 528 | if (!lockref_get_not_dead(&parent->d_lockref)) { |
| 529 | nd->path.dentry = NULL; |
| 530 | goto out; |
| 531 | } |
| 532 | |
| 533 | /* |
| 534 | * For a negative lookup, the lookup sequence point is the parents |
| 535 | * sequence point, and it only needs to revalidate the parent dentry. |
| 536 | * |
| 537 | * For a positive lookup, we need to move both the parent and the |
| 538 | * dentry from the RCU domain to be properly refcounted. And the |
| 539 | * sequence number in the dentry validates *both* dentry counters, |
| 540 | * since we checked the sequence number of the parent after we got |
| 541 | * the child sequence number. So we know the parent must still |
| 542 | * be valid if the child sequence number is still valid. |
| 543 | */ |
| 544 | if (!dentry) { |
| 545 | if (read_seqcount_retry(&parent->d_seq, nd->seq)) |
| 546 | goto out; |
| 547 | BUG_ON(nd->inode != parent->d_inode); |
| 548 | } else { |
| 549 | if (!lockref_get_not_dead(&dentry->d_lockref)) |
| 550 | goto out; |
| 551 | if (read_seqcount_retry(&dentry->d_seq, nd->seq)) |
| 552 | goto drop_dentry; |
| 553 | } |
| 554 | |
| 555 | /* |
| 556 | * Sequence counts matched. Now make sure that the root is |
| 557 | * still valid and get it if required. |
| 558 | */ |
| 559 | if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { |
| 560 | spin_lock(&fs->lock); |
| 561 | if (nd->root.mnt != fs->root.mnt || nd->root.dentry != fs->root.dentry) |
| 562 | goto unlock_and_drop_dentry; |
| 563 | path_get(&nd->root); |
| 564 | spin_unlock(&fs->lock); |
| 565 | } |
| 566 | |
| 567 | rcu_read_unlock(); |
| 568 | return 0; |
| 569 | |
| 570 | unlock_and_drop_dentry: |
| 571 | spin_unlock(&fs->lock); |
| 572 | drop_dentry: |
| 573 | rcu_read_unlock(); |
| 574 | dput(dentry); |
| 575 | goto drop_root_mnt; |
| 576 | out: |
| 577 | rcu_read_unlock(); |
| 578 | drop_root_mnt: |
| 579 | if (!(nd->flags & LOOKUP_ROOT)) |
| 580 | nd->root.mnt = NULL; |
| 581 | return -ECHILD; |
| 582 | } |
| 583 | |
| 584 | static inline int d_revalidate(struct dentry *dentry, unsigned int flags) |
| 585 | { |
| 586 | return dentry->d_op->d_revalidate(dentry, flags); |
| 587 | } |
| 588 | |
| 589 | /** |
| 590 | * complete_walk - successful completion of path walk |
| 591 | * @nd: pointer nameidata |
| 592 | * |
| 593 | * If we had been in RCU mode, drop out of it and legitimize nd->path. |
| 594 | * Revalidate the final result, unless we'd already done that during |
| 595 | * the path walk or the filesystem doesn't ask for it. Return 0 on |
| 596 | * success, -error on failure. In case of failure caller does not |
| 597 | * need to drop nd->path. |
| 598 | */ |
| 599 | static int complete_walk(struct nameidata *nd) |
| 600 | { |
| 601 | struct dentry *dentry = nd->path.dentry; |
| 602 | int status; |
| 603 | |
| 604 | if (nd->flags & LOOKUP_RCU) { |
| 605 | nd->flags &= ~LOOKUP_RCU; |
| 606 | if (!(nd->flags & LOOKUP_ROOT)) |
| 607 | nd->root.mnt = NULL; |
| 608 | |
| 609 | if (!legitimize_mnt(nd->path.mnt, nd->m_seq)) { |
| 610 | rcu_read_unlock(); |
| 611 | return -ECHILD; |
| 612 | } |
| 613 | if (unlikely(!lockref_get_not_dead(&dentry->d_lockref))) { |
| 614 | rcu_read_unlock(); |
| 615 | mntput(nd->path.mnt); |
| 616 | return -ECHILD; |
| 617 | } |
| 618 | if (read_seqcount_retry(&dentry->d_seq, nd->seq)) { |
| 619 | rcu_read_unlock(); |
| 620 | dput(dentry); |
| 621 | mntput(nd->path.mnt); |
| 622 | return -ECHILD; |
| 623 | } |
| 624 | rcu_read_unlock(); |
| 625 | } |
| 626 | |
| 627 | if (likely(!(nd->flags & LOOKUP_JUMPED))) |
| 628 | return 0; |
| 629 | |
| 630 | if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE))) |
| 631 | return 0; |
| 632 | |
| 633 | status = dentry->d_op->d_weak_revalidate(dentry, nd->flags); |
| 634 | if (status > 0) |
| 635 | return 0; |
| 636 | |
| 637 | if (!status) |
| 638 | status = -ESTALE; |
| 639 | |
| 640 | path_put(&nd->path); |
| 641 | return status; |
| 642 | } |
| 643 | |
| 644 | static __always_inline void set_root(struct nameidata *nd) |
| 645 | { |
| 646 | get_fs_root(current->fs, &nd->root); |
| 647 | } |
| 648 | |
| 649 | static int link_path_walk(const char *, struct nameidata *); |
| 650 | |
| 651 | static __always_inline unsigned set_root_rcu(struct nameidata *nd) |
| 652 | { |
| 653 | struct fs_struct *fs = current->fs; |
| 654 | unsigned seq, res; |
| 655 | |
| 656 | do { |
| 657 | seq = read_seqcount_begin(&fs->seq); |
| 658 | nd->root = fs->root; |
| 659 | res = __read_seqcount_begin(&nd->root.dentry->d_seq); |
| 660 | } while (read_seqcount_retry(&fs->seq, seq)); |
| 661 | return res; |
| 662 | } |
| 663 | |
| 664 | static void path_put_conditional(struct path *path, struct nameidata *nd) |
| 665 | { |
| 666 | dput(path->dentry); |
| 667 | if (path->mnt != nd->path.mnt) |
| 668 | mntput(path->mnt); |
| 669 | } |
| 670 | |
| 671 | static inline void path_to_nameidata(const struct path *path, |
| 672 | struct nameidata *nd) |
| 673 | { |
| 674 | if (!(nd->flags & LOOKUP_RCU)) { |
| 675 | dput(nd->path.dentry); |
| 676 | if (nd->path.mnt != path->mnt) |
| 677 | mntput(nd->path.mnt); |
| 678 | } |
| 679 | nd->path.mnt = path->mnt; |
| 680 | nd->path.dentry = path->dentry; |
| 681 | } |
| 682 | |
| 683 | /* |
| 684 | * Helper to directly jump to a known parsed path from ->follow_link, |
| 685 | * caller must have taken a reference to path beforehand. |
| 686 | */ |
| 687 | void nd_jump_link(struct nameidata *nd, struct path *path) |
| 688 | { |
| 689 | path_put(&nd->path); |
| 690 | |
| 691 | nd->path = *path; |
| 692 | nd->inode = nd->path.dentry->d_inode; |
| 693 | nd->flags |= LOOKUP_JUMPED; |
| 694 | } |
| 695 | |
| 696 | static inline void put_link(struct nameidata *nd, struct path *link, void *cookie) |
| 697 | { |
| 698 | struct inode *inode = link->dentry->d_inode; |
| 699 | if (inode->i_op->put_link) |
| 700 | inode->i_op->put_link(link->dentry, nd, cookie); |
| 701 | path_put(link); |
| 702 | } |
| 703 | |
| 704 | int sysctl_protected_symlinks __read_mostly = 0; |
| 705 | int sysctl_protected_hardlinks __read_mostly = 0; |
| 706 | |
| 707 | /** |
| 708 | * may_follow_link - Check symlink following for unsafe situations |
| 709 | * @link: The path of the symlink |
| 710 | * @nd: nameidata pathwalk data |
| 711 | * |
| 712 | * In the case of the sysctl_protected_symlinks sysctl being enabled, |
| 713 | * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is |
| 714 | * in a sticky world-writable directory. This is to protect privileged |
| 715 | * processes from failing races against path names that may change out |
| 716 | * from under them by way of other users creating malicious symlinks. |
| 717 | * It will permit symlinks to be followed only when outside a sticky |
| 718 | * world-writable directory, or when the uid of the symlink and follower |
| 719 | * match, or when the directory owner matches the symlink's owner. |
| 720 | * |
| 721 | * Returns 0 if following the symlink is allowed, -ve on error. |
| 722 | */ |
| 723 | static inline int may_follow_link(struct path *link, struct nameidata *nd) |
| 724 | { |
| 725 | const struct inode *inode; |
| 726 | const struct inode *parent; |
| 727 | |
| 728 | if (!sysctl_protected_symlinks) |
| 729 | return 0; |
| 730 | |
| 731 | /* Allowed if owner and follower match. */ |
| 732 | inode = link->dentry->d_inode; |
| 733 | if (uid_eq(current_cred()->fsuid, inode->i_uid)) |
| 734 | return 0; |
| 735 | |
| 736 | /* Allowed if parent directory not sticky and world-writable. */ |
| 737 | parent = nd->path.dentry->d_inode; |
| 738 | if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH)) |
| 739 | return 0; |
| 740 | |
| 741 | /* Allowed if parent directory and link owner match. */ |
| 742 | if (uid_eq(parent->i_uid, inode->i_uid)) |
| 743 | return 0; |
| 744 | |
| 745 | audit_log_link_denied("follow_link", link); |
| 746 | path_put_conditional(link, nd); |
| 747 | path_put(&nd->path); |
| 748 | return -EACCES; |
| 749 | } |
| 750 | |
| 751 | /** |
| 752 | * safe_hardlink_source - Check for safe hardlink conditions |
| 753 | * @inode: the source inode to hardlink from |
| 754 | * |
| 755 | * Return false if at least one of the following conditions: |
| 756 | * - inode is not a regular file |
| 757 | * - inode is setuid |
| 758 | * - inode is setgid and group-exec |
| 759 | * - access failure for read and write |
| 760 | * |
| 761 | * Otherwise returns true. |
| 762 | */ |
| 763 | static bool safe_hardlink_source(struct inode *inode) |
| 764 | { |
| 765 | umode_t mode = inode->i_mode; |
| 766 | |
| 767 | /* Special files should not get pinned to the filesystem. */ |
| 768 | if (!S_ISREG(mode)) |
| 769 | return false; |
| 770 | |
| 771 | /* Setuid files should not get pinned to the filesystem. */ |
| 772 | if (mode & S_ISUID) |
| 773 | return false; |
| 774 | |
| 775 | /* Executable setgid files should not get pinned to the filesystem. */ |
| 776 | if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) |
| 777 | return false; |
| 778 | |
| 779 | /* Hardlinking to unreadable or unwritable sources is dangerous. */ |
| 780 | if (inode_permission(inode, MAY_READ | MAY_WRITE)) |
| 781 | return false; |
| 782 | |
| 783 | return true; |
| 784 | } |
| 785 | |
| 786 | /** |
| 787 | * may_linkat - Check permissions for creating a hardlink |
| 788 | * @link: the source to hardlink from |
| 789 | * |
| 790 | * Block hardlink when all of: |
| 791 | * - sysctl_protected_hardlinks enabled |
| 792 | * - fsuid does not match inode |
| 793 | * - hardlink source is unsafe (see safe_hardlink_source() above) |
| 794 | * - not CAP_FOWNER |
| 795 | * |
| 796 | * Returns 0 if successful, -ve on error. |
| 797 | */ |
| 798 | static int may_linkat(struct path *link) |
| 799 | { |
| 800 | const struct cred *cred; |
| 801 | struct inode *inode; |
| 802 | |
| 803 | if (!sysctl_protected_hardlinks) |
| 804 | return 0; |
| 805 | |
| 806 | cred = current_cred(); |
| 807 | inode = link->dentry->d_inode; |
| 808 | |
| 809 | /* Source inode owner (or CAP_FOWNER) can hardlink all they like, |
| 810 | * otherwise, it must be a safe source. |
| 811 | */ |
| 812 | if (uid_eq(cred->fsuid, inode->i_uid) || safe_hardlink_source(inode) || |
| 813 | capable(CAP_FOWNER)) |
| 814 | return 0; |
| 815 | |
| 816 | audit_log_link_denied("linkat", link); |
| 817 | return -EPERM; |
| 818 | } |
| 819 | |
| 820 | static __always_inline int |
| 821 | follow_link(struct path *link, struct nameidata *nd, void **p) |
| 822 | { |
| 823 | struct dentry *dentry = link->dentry; |
| 824 | int error; |
| 825 | char *s; |
| 826 | |
| 827 | BUG_ON(nd->flags & LOOKUP_RCU); |
| 828 | |
| 829 | if (link->mnt == nd->path.mnt) |
| 830 | mntget(link->mnt); |
| 831 | |
| 832 | error = -ELOOP; |
| 833 | if (unlikely(current->total_link_count >= 40)) |
| 834 | goto out_put_nd_path; |
| 835 | |
| 836 | cond_resched(); |
| 837 | current->total_link_count++; |
| 838 | |
| 839 | touch_atime(link); |
| 840 | nd_set_link(nd, NULL); |
| 841 | |
| 842 | error = security_inode_follow_link(link->dentry, nd); |
| 843 | if (error) |
| 844 | goto out_put_nd_path; |
| 845 | |
| 846 | nd->last_type = LAST_BIND; |
| 847 | *p = dentry->d_inode->i_op->follow_link(dentry, nd); |
| 848 | error = PTR_ERR(*p); |
| 849 | if (IS_ERR(*p)) |
| 850 | goto out_put_nd_path; |
| 851 | |
| 852 | error = 0; |
| 853 | s = nd_get_link(nd); |
| 854 | if (s) { |
| 855 | if (unlikely(IS_ERR(s))) { |
| 856 | path_put(&nd->path); |
| 857 | put_link(nd, link, *p); |
| 858 | return PTR_ERR(s); |
| 859 | } |
| 860 | if (*s == '/') { |
| 861 | if (!nd->root.mnt) |
| 862 | set_root(nd); |
| 863 | path_put(&nd->path); |
| 864 | nd->path = nd->root; |
| 865 | path_get(&nd->root); |
| 866 | nd->flags |= LOOKUP_JUMPED; |
| 867 | } |
| 868 | nd->inode = nd->path.dentry->d_inode; |
| 869 | error = link_path_walk(s, nd); |
| 870 | if (unlikely(error)) |
| 871 | put_link(nd, link, *p); |
| 872 | } |
| 873 | |
| 874 | return error; |
| 875 | |
| 876 | out_put_nd_path: |
| 877 | *p = NULL; |
| 878 | path_put(&nd->path); |
| 879 | path_put(link); |
| 880 | return error; |
| 881 | } |
| 882 | |
| 883 | static int follow_up_rcu(struct path *path) |
| 884 | { |
| 885 | struct mount *mnt = real_mount(path->mnt); |
| 886 | struct mount *parent; |
| 887 | struct dentry *mountpoint; |
| 888 | |
| 889 | parent = mnt->mnt_parent; |
| 890 | if (&parent->mnt == path->mnt) |
| 891 | return 0; |
| 892 | mountpoint = mnt->mnt_mountpoint; |
| 893 | path->dentry = mountpoint; |
| 894 | path->mnt = &parent->mnt; |
| 895 | return 1; |
| 896 | } |
| 897 | |
| 898 | /* |
| 899 | * follow_up - Find the mountpoint of path's vfsmount |
| 900 | * |
| 901 | * Given a path, find the mountpoint of its source file system. |
| 902 | * Replace @path with the path of the mountpoint in the parent mount. |
| 903 | * Up is towards /. |
| 904 | * |
| 905 | * Return 1 if we went up a level and 0 if we were already at the |
| 906 | * root. |
| 907 | */ |
| 908 | int follow_up(struct path *path) |
| 909 | { |
| 910 | struct mount *mnt = real_mount(path->mnt); |
| 911 | struct mount *parent; |
| 912 | struct dentry *mountpoint; |
| 913 | |
| 914 | read_seqlock_excl(&mount_lock); |
| 915 | parent = mnt->mnt_parent; |
| 916 | if (parent == mnt) { |
| 917 | read_sequnlock_excl(&mount_lock); |
| 918 | return 0; |
| 919 | } |
| 920 | mntget(&parent->mnt); |
| 921 | mountpoint = dget(mnt->mnt_mountpoint); |
| 922 | read_sequnlock_excl(&mount_lock); |
| 923 | dput(path->dentry); |
| 924 | path->dentry = mountpoint; |
| 925 | mntput(path->mnt); |
| 926 | path->mnt = &parent->mnt; |
| 927 | return 1; |
| 928 | } |
| 929 | EXPORT_SYMBOL(follow_up); |
| 930 | |
| 931 | /* |
| 932 | * Perform an automount |
| 933 | * - return -EISDIR to tell follow_managed() to stop and return the path we |
| 934 | * were called with. |
| 935 | */ |
| 936 | static int follow_automount(struct path *path, unsigned flags, |
| 937 | bool *need_mntput) |
| 938 | { |
| 939 | struct vfsmount *mnt; |
| 940 | int err; |
| 941 | |
| 942 | if (!path->dentry->d_op || !path->dentry->d_op->d_automount) |
| 943 | return -EREMOTE; |
| 944 | |
| 945 | /* We don't want to mount if someone's just doing a stat - |
| 946 | * unless they're stat'ing a directory and appended a '/' to |
| 947 | * the name. |
| 948 | * |
| 949 | * We do, however, want to mount if someone wants to open or |
| 950 | * create a file of any type under the mountpoint, wants to |
| 951 | * traverse through the mountpoint or wants to open the |
| 952 | * mounted directory. Also, autofs may mark negative dentries |
| 953 | * as being automount points. These will need the attentions |
| 954 | * of the daemon to instantiate them before they can be used. |
| 955 | */ |
| 956 | if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | |
| 957 | LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) && |
| 958 | path->dentry->d_inode) |
| 959 | return -EISDIR; |
| 960 | |
| 961 | current->total_link_count++; |
| 962 | if (current->total_link_count >= 40) |
| 963 | return -ELOOP; |
| 964 | |
| 965 | mnt = path->dentry->d_op->d_automount(path); |
| 966 | if (IS_ERR(mnt)) { |
| 967 | /* |
| 968 | * The filesystem is allowed to return -EISDIR here to indicate |
| 969 | * it doesn't want to automount. For instance, autofs would do |
| 970 | * this so that its userspace daemon can mount on this dentry. |
| 971 | * |
| 972 | * However, we can only permit this if it's a terminal point in |
| 973 | * the path being looked up; if it wasn't then the remainder of |
| 974 | * the path is inaccessible and we should say so. |
| 975 | */ |
| 976 | if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT)) |
| 977 | return -EREMOTE; |
| 978 | return PTR_ERR(mnt); |
| 979 | } |
| 980 | |
| 981 | if (!mnt) /* mount collision */ |
| 982 | return 0; |
| 983 | |
| 984 | if (!*need_mntput) { |
| 985 | /* lock_mount() may release path->mnt on error */ |
| 986 | mntget(path->mnt); |
| 987 | *need_mntput = true; |
| 988 | } |
| 989 | err = finish_automount(mnt, path); |
| 990 | |
| 991 | switch (err) { |
| 992 | case -EBUSY: |
| 993 | /* Someone else made a mount here whilst we were busy */ |
| 994 | return 0; |
| 995 | case 0: |
| 996 | path_put(path); |
| 997 | path->mnt = mnt; |
| 998 | path->dentry = dget(mnt->mnt_root); |
| 999 | return 0; |
| 1000 | default: |
| 1001 | return err; |
| 1002 | } |
| 1003 | |
| 1004 | } |
| 1005 | |
| 1006 | /* |
| 1007 | * Handle a dentry that is managed in some way. |
| 1008 | * - Flagged for transit management (autofs) |
| 1009 | * - Flagged as mountpoint |
| 1010 | * - Flagged as automount point |
| 1011 | * |
| 1012 | * This may only be called in refwalk mode. |
| 1013 | * |
| 1014 | * Serialization is taken care of in namespace.c |
| 1015 | */ |
| 1016 | static int follow_managed(struct path *path, unsigned flags) |
| 1017 | { |
| 1018 | struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */ |
| 1019 | unsigned managed; |
| 1020 | bool need_mntput = false; |
| 1021 | int ret = 0; |
| 1022 | |
| 1023 | /* Given that we're not holding a lock here, we retain the value in a |
| 1024 | * local variable for each dentry as we look at it so that we don't see |
| 1025 | * the components of that value change under us */ |
| 1026 | while (managed = ACCESS_ONCE(path->dentry->d_flags), |
| 1027 | managed &= DCACHE_MANAGED_DENTRY, |
| 1028 | unlikely(managed != 0)) { |
| 1029 | /* Allow the filesystem to manage the transit without i_mutex |
| 1030 | * being held. */ |
| 1031 | if (managed & DCACHE_MANAGE_TRANSIT) { |
| 1032 | BUG_ON(!path->dentry->d_op); |
| 1033 | BUG_ON(!path->dentry->d_op->d_manage); |
| 1034 | ret = path->dentry->d_op->d_manage(path->dentry, false); |
| 1035 | if (ret < 0) |
| 1036 | break; |
| 1037 | } |
| 1038 | |
| 1039 | /* Transit to a mounted filesystem. */ |
| 1040 | if (managed & DCACHE_MOUNTED) { |
| 1041 | struct vfsmount *mounted = lookup_mnt(path); |
| 1042 | if (mounted) { |
| 1043 | dput(path->dentry); |
| 1044 | if (need_mntput) |
| 1045 | mntput(path->mnt); |
| 1046 | path->mnt = mounted; |
| 1047 | path->dentry = dget(mounted->mnt_root); |
| 1048 | need_mntput = true; |
| 1049 | continue; |
| 1050 | } |
| 1051 | |
| 1052 | /* Something is mounted on this dentry in another |
| 1053 | * namespace and/or whatever was mounted there in this |
| 1054 | * namespace got unmounted before lookup_mnt() could |
| 1055 | * get it */ |
| 1056 | } |
| 1057 | |
| 1058 | /* Handle an automount point */ |
| 1059 | if (managed & DCACHE_NEED_AUTOMOUNT) { |
| 1060 | ret = follow_automount(path, flags, &need_mntput); |
| 1061 | if (ret < 0) |
| 1062 | break; |
| 1063 | continue; |
| 1064 | } |
| 1065 | |
| 1066 | /* We didn't change the current path point */ |
| 1067 | break; |
| 1068 | } |
| 1069 | |
| 1070 | if (need_mntput && path->mnt == mnt) |
| 1071 | mntput(path->mnt); |
| 1072 | if (ret == -EISDIR) |
| 1073 | ret = 0; |
| 1074 | return ret < 0 ? ret : need_mntput; |
| 1075 | } |
| 1076 | |
| 1077 | int follow_down_one(struct path *path) |
| 1078 | { |
| 1079 | struct vfsmount *mounted; |
| 1080 | |
| 1081 | mounted = lookup_mnt(path); |
| 1082 | if (mounted) { |
| 1083 | dput(path->dentry); |
| 1084 | mntput(path->mnt); |
| 1085 | path->mnt = mounted; |
| 1086 | path->dentry = dget(mounted->mnt_root); |
| 1087 | return 1; |
| 1088 | } |
| 1089 | return 0; |
| 1090 | } |
| 1091 | EXPORT_SYMBOL(follow_down_one); |
| 1092 | |
| 1093 | static inline int managed_dentry_rcu(struct dentry *dentry) |
| 1094 | { |
| 1095 | return (dentry->d_flags & DCACHE_MANAGE_TRANSIT) ? |
| 1096 | dentry->d_op->d_manage(dentry, true) : 0; |
| 1097 | } |
| 1098 | |
| 1099 | /* |
| 1100 | * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if |
| 1101 | * we meet a managed dentry that would need blocking. |
| 1102 | */ |
| 1103 | static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, |
| 1104 | struct inode **inode) |
| 1105 | { |
| 1106 | for (;;) { |
| 1107 | struct mount *mounted; |
| 1108 | /* |
| 1109 | * Don't forget we might have a non-mountpoint managed dentry |
| 1110 | * that wants to block transit. |
| 1111 | */ |
| 1112 | switch (managed_dentry_rcu(path->dentry)) { |
| 1113 | case -ECHILD: |
| 1114 | default: |
| 1115 | return false; |
| 1116 | case -EISDIR: |
| 1117 | return true; |
| 1118 | case 0: |
| 1119 | break; |
| 1120 | } |
| 1121 | |
| 1122 | if (!d_mountpoint(path->dentry)) |
| 1123 | return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT); |
| 1124 | |
| 1125 | mounted = __lookup_mnt(path->mnt, path->dentry); |
| 1126 | if (!mounted) |
| 1127 | break; |
| 1128 | path->mnt = &mounted->mnt; |
| 1129 | path->dentry = mounted->mnt.mnt_root; |
| 1130 | nd->flags |= LOOKUP_JUMPED; |
| 1131 | nd->seq = read_seqcount_begin(&path->dentry->d_seq); |
| 1132 | /* |
| 1133 | * Update the inode too. We don't need to re-check the |
| 1134 | * dentry sequence number here after this d_inode read, |
| 1135 | * because a mount-point is always pinned. |
| 1136 | */ |
| 1137 | *inode = path->dentry->d_inode; |
| 1138 | } |
| 1139 | return !read_seqretry(&mount_lock, nd->m_seq) && |
| 1140 | !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT); |
| 1141 | } |
| 1142 | |
| 1143 | static int follow_dotdot_rcu(struct nameidata *nd) |
| 1144 | { |
| 1145 | if (!nd->root.mnt) |
| 1146 | set_root_rcu(nd); |
| 1147 | |
| 1148 | while (1) { |
| 1149 | if (nd->path.dentry == nd->root.dentry && |
| 1150 | nd->path.mnt == nd->root.mnt) { |
| 1151 | break; |
| 1152 | } |
| 1153 | if (nd->path.dentry != nd->path.mnt->mnt_root) { |
| 1154 | struct dentry *old = nd->path.dentry; |
| 1155 | struct dentry *parent = old->d_parent; |
| 1156 | unsigned seq; |
| 1157 | |
| 1158 | seq = read_seqcount_begin(&parent->d_seq); |
| 1159 | if (read_seqcount_retry(&old->d_seq, nd->seq)) |
| 1160 | goto failed; |
| 1161 | nd->path.dentry = parent; |
| 1162 | nd->seq = seq; |
| 1163 | break; |
| 1164 | } |
| 1165 | if (!follow_up_rcu(&nd->path)) |
| 1166 | break; |
| 1167 | nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); |
| 1168 | } |
| 1169 | while (d_mountpoint(nd->path.dentry)) { |
| 1170 | struct mount *mounted; |
| 1171 | mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry); |
| 1172 | if (!mounted) |
| 1173 | break; |
| 1174 | nd->path.mnt = &mounted->mnt; |
| 1175 | nd->path.dentry = mounted->mnt.mnt_root; |
| 1176 | nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); |
| 1177 | if (read_seqretry(&mount_lock, nd->m_seq)) |
| 1178 | goto failed; |
| 1179 | } |
| 1180 | nd->inode = nd->path.dentry->d_inode; |
| 1181 | return 0; |
| 1182 | |
| 1183 | failed: |
| 1184 | nd->flags &= ~LOOKUP_RCU; |
| 1185 | if (!(nd->flags & LOOKUP_ROOT)) |
| 1186 | nd->root.mnt = NULL; |
| 1187 | rcu_read_unlock(); |
| 1188 | return -ECHILD; |
| 1189 | } |
| 1190 | |
| 1191 | /* |
| 1192 | * Follow down to the covering mount currently visible to userspace. At each |
| 1193 | * point, the filesystem owning that dentry may be queried as to whether the |
| 1194 | * caller is permitted to proceed or not. |
| 1195 | */ |
| 1196 | int follow_down(struct path *path) |
| 1197 | { |
| 1198 | unsigned managed; |
| 1199 | int ret; |
| 1200 | |
| 1201 | while (managed = ACCESS_ONCE(path->dentry->d_flags), |
| 1202 | unlikely(managed & DCACHE_MANAGED_DENTRY)) { |
| 1203 | /* Allow the filesystem to manage the transit without i_mutex |
| 1204 | * being held. |
| 1205 | * |
| 1206 | * We indicate to the filesystem if someone is trying to mount |
| 1207 | * something here. This gives autofs the chance to deny anyone |
| 1208 | * other than its daemon the right to mount on its |
| 1209 | * superstructure. |
| 1210 | * |
| 1211 | * The filesystem may sleep at this point. |
| 1212 | */ |
| 1213 | if (managed & DCACHE_MANAGE_TRANSIT) { |
| 1214 | BUG_ON(!path->dentry->d_op); |
| 1215 | BUG_ON(!path->dentry->d_op->d_manage); |
| 1216 | ret = path->dentry->d_op->d_manage( |
| 1217 | path->dentry, false); |
| 1218 | if (ret < 0) |
| 1219 | return ret == -EISDIR ? 0 : ret; |
| 1220 | } |
| 1221 | |
| 1222 | /* Transit to a mounted filesystem. */ |
| 1223 | if (managed & DCACHE_MOUNTED) { |
| 1224 | struct vfsmount *mounted = lookup_mnt(path); |
| 1225 | if (!mounted) |
| 1226 | break; |
| 1227 | dput(path->dentry); |
| 1228 | mntput(path->mnt); |
| 1229 | path->mnt = mounted; |
| 1230 | path->dentry = dget(mounted->mnt_root); |
| 1231 | continue; |
| 1232 | } |
| 1233 | |
| 1234 | /* Don't handle automount points here */ |
| 1235 | break; |
| 1236 | } |
| 1237 | return 0; |
| 1238 | } |
| 1239 | EXPORT_SYMBOL(follow_down); |
| 1240 | |
| 1241 | /* |
| 1242 | * Skip to top of mountpoint pile in refwalk mode for follow_dotdot() |
| 1243 | */ |
| 1244 | static void follow_mount(struct path *path) |
| 1245 | { |
| 1246 | while (d_mountpoint(path->dentry)) { |
| 1247 | struct vfsmount *mounted = lookup_mnt(path); |
| 1248 | if (!mounted) |
| 1249 | break; |
| 1250 | dput(path->dentry); |
| 1251 | mntput(path->mnt); |
| 1252 | path->mnt = mounted; |
| 1253 | path->dentry = dget(mounted->mnt_root); |
| 1254 | } |
| 1255 | } |
| 1256 | |
| 1257 | static void follow_dotdot(struct nameidata *nd) |
| 1258 | { |
| 1259 | if (!nd->root.mnt) |
| 1260 | set_root(nd); |
| 1261 | |
| 1262 | while(1) { |
| 1263 | struct dentry *old = nd->path.dentry; |
| 1264 | |
| 1265 | if (nd->path.dentry == nd->root.dentry && |
| 1266 | nd->path.mnt == nd->root.mnt) { |
| 1267 | break; |
| 1268 | } |
| 1269 | if (nd->path.dentry != nd->path.mnt->mnt_root) { |
| 1270 | /* rare case of legitimate dget_parent()... */ |
| 1271 | nd->path.dentry = dget_parent(nd->path.dentry); |
| 1272 | dput(old); |
| 1273 | break; |
| 1274 | } |
| 1275 | if (!follow_up(&nd->path)) |
| 1276 | break; |
| 1277 | } |
| 1278 | follow_mount(&nd->path); |
| 1279 | nd->inode = nd->path.dentry->d_inode; |
| 1280 | } |
| 1281 | |
| 1282 | /* |
| 1283 | * This looks up the name in dcache, possibly revalidates the old dentry and |
| 1284 | * allocates a new one if not found or not valid. In the need_lookup argument |
| 1285 | * returns whether i_op->lookup is necessary. |
| 1286 | * |
| 1287 | * dir->d_inode->i_mutex must be held |
| 1288 | */ |
| 1289 | static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir, |
| 1290 | unsigned int flags, bool *need_lookup) |
| 1291 | { |
| 1292 | struct dentry *dentry; |
| 1293 | int error; |
| 1294 | |
| 1295 | *need_lookup = false; |
| 1296 | dentry = d_lookup(dir, name); |
| 1297 | if (dentry) { |
| 1298 | if (dentry->d_flags & DCACHE_OP_REVALIDATE) { |
| 1299 | error = d_revalidate(dentry, flags); |
| 1300 | if (unlikely(error <= 0)) { |
| 1301 | if (error < 0) { |
| 1302 | dput(dentry); |
| 1303 | return ERR_PTR(error); |
| 1304 | } else if (!d_invalidate(dentry)) { |
| 1305 | dput(dentry); |
| 1306 | dentry = NULL; |
| 1307 | } |
| 1308 | } |
| 1309 | } |
| 1310 | } |
| 1311 | |
| 1312 | if (!dentry) { |
| 1313 | dentry = d_alloc(dir, name); |
| 1314 | if (unlikely(!dentry)) |
| 1315 | return ERR_PTR(-ENOMEM); |
| 1316 | |
| 1317 | *need_lookup = true; |
| 1318 | } |
| 1319 | return dentry; |
| 1320 | } |
| 1321 | |
| 1322 | /* |
| 1323 | * Call i_op->lookup on the dentry. The dentry must be negative and |
| 1324 | * unhashed. |
| 1325 | * |
| 1326 | * dir->d_inode->i_mutex must be held |
| 1327 | */ |
| 1328 | static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry, |
| 1329 | unsigned int flags) |
| 1330 | { |
| 1331 | struct dentry *old; |
| 1332 | |
| 1333 | /* Don't create child dentry for a dead directory. */ |
| 1334 | if (unlikely(IS_DEADDIR(dir))) { |
| 1335 | dput(dentry); |
| 1336 | return ERR_PTR(-ENOENT); |
| 1337 | } |
| 1338 | |
| 1339 | old = dir->i_op->lookup(dir, dentry, flags); |
| 1340 | if (unlikely(old)) { |
| 1341 | dput(dentry); |
| 1342 | dentry = old; |
| 1343 | } |
| 1344 | return dentry; |
| 1345 | } |
| 1346 | |
| 1347 | static struct dentry *__lookup_hash(struct qstr *name, |
| 1348 | struct dentry *base, unsigned int flags) |
| 1349 | { |
| 1350 | bool need_lookup; |
| 1351 | struct dentry *dentry; |
| 1352 | |
| 1353 | dentry = lookup_dcache(name, base, flags, &need_lookup); |
| 1354 | if (!need_lookup) |
| 1355 | return dentry; |
| 1356 | |
| 1357 | return lookup_real(base->d_inode, dentry, flags); |
| 1358 | } |
| 1359 | |
| 1360 | /* |
| 1361 | * It's more convoluted than I'd like it to be, but... it's still fairly |
| 1362 | * small and for now I'd prefer to have fast path as straight as possible. |
| 1363 | * It _is_ time-critical. |
| 1364 | */ |
| 1365 | static int lookup_fast(struct nameidata *nd, |
| 1366 | struct path *path, struct inode **inode) |
| 1367 | { |
| 1368 | struct vfsmount *mnt = nd->path.mnt; |
| 1369 | struct dentry *dentry, *parent = nd->path.dentry; |
| 1370 | int need_reval = 1; |
| 1371 | int status = 1; |
| 1372 | int err; |
| 1373 | |
| 1374 | /* |
| 1375 | * Rename seqlock is not required here because in the off chance |
| 1376 | * of a false negative due to a concurrent rename, we're going to |
| 1377 | * do the non-racy lookup, below. |
| 1378 | */ |
| 1379 | if (nd->flags & LOOKUP_RCU) { |
| 1380 | unsigned seq; |
| 1381 | dentry = __d_lookup_rcu(parent, &nd->last, &seq); |
| 1382 | if (!dentry) |
| 1383 | goto unlazy; |
| 1384 | |
| 1385 | /* |
| 1386 | * This sequence count validates that the inode matches |
| 1387 | * the dentry name information from lookup. |
| 1388 | */ |
| 1389 | *inode = dentry->d_inode; |
| 1390 | if (read_seqcount_retry(&dentry->d_seq, seq)) |
| 1391 | return -ECHILD; |
| 1392 | |
| 1393 | /* |
| 1394 | * This sequence count validates that the parent had no |
| 1395 | * changes while we did the lookup of the dentry above. |
| 1396 | * |
| 1397 | * The memory barrier in read_seqcount_begin of child is |
| 1398 | * enough, we can use __read_seqcount_retry here. |
| 1399 | */ |
| 1400 | if (__read_seqcount_retry(&parent->d_seq, nd->seq)) |
| 1401 | return -ECHILD; |
| 1402 | nd->seq = seq; |
| 1403 | |
| 1404 | if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) { |
| 1405 | status = d_revalidate(dentry, nd->flags); |
| 1406 | if (unlikely(status <= 0)) { |
| 1407 | if (status != -ECHILD) |
| 1408 | need_reval = 0; |
| 1409 | goto unlazy; |
| 1410 | } |
| 1411 | } |
| 1412 | path->mnt = mnt; |
| 1413 | path->dentry = dentry; |
| 1414 | if (likely(__follow_mount_rcu(nd, path, inode))) |
| 1415 | return 0; |
| 1416 | unlazy: |
| 1417 | if (unlazy_walk(nd, dentry)) |
| 1418 | return -ECHILD; |
| 1419 | } else { |
| 1420 | dentry = __d_lookup(parent, &nd->last); |
| 1421 | } |
| 1422 | |
| 1423 | if (unlikely(!dentry)) |
| 1424 | goto need_lookup; |
| 1425 | |
| 1426 | if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval) |
| 1427 | status = d_revalidate(dentry, nd->flags); |
| 1428 | if (unlikely(status <= 0)) { |
| 1429 | if (status < 0) { |
| 1430 | dput(dentry); |
| 1431 | return status; |
| 1432 | } |
| 1433 | if (!d_invalidate(dentry)) { |
| 1434 | dput(dentry); |
| 1435 | goto need_lookup; |
| 1436 | } |
| 1437 | } |
| 1438 | |
| 1439 | path->mnt = mnt; |
| 1440 | path->dentry = dentry; |
| 1441 | err = follow_managed(path, nd->flags); |
| 1442 | if (unlikely(err < 0)) { |
| 1443 | path_put_conditional(path, nd); |
| 1444 | return err; |
| 1445 | } |
| 1446 | if (err) |
| 1447 | nd->flags |= LOOKUP_JUMPED; |
| 1448 | *inode = path->dentry->d_inode; |
| 1449 | return 0; |
| 1450 | |
| 1451 | need_lookup: |
| 1452 | return 1; |
| 1453 | } |
| 1454 | |
| 1455 | /* Fast lookup failed, do it the slow way */ |
| 1456 | static int lookup_slow(struct nameidata *nd, struct path *path) |
| 1457 | { |
| 1458 | struct dentry *dentry, *parent; |
| 1459 | int err; |
| 1460 | |
| 1461 | parent = nd->path.dentry; |
| 1462 | BUG_ON(nd->inode != parent->d_inode); |
| 1463 | |
| 1464 | mutex_lock(&parent->d_inode->i_mutex); |
| 1465 | dentry = __lookup_hash(&nd->last, parent, nd->flags); |
| 1466 | mutex_unlock(&parent->d_inode->i_mutex); |
| 1467 | if (IS_ERR(dentry)) |
| 1468 | return PTR_ERR(dentry); |
| 1469 | path->mnt = nd->path.mnt; |
| 1470 | path->dentry = dentry; |
| 1471 | err = follow_managed(path, nd->flags); |
| 1472 | if (unlikely(err < 0)) { |
| 1473 | path_put_conditional(path, nd); |
| 1474 | return err; |
| 1475 | } |
| 1476 | if (err) |
| 1477 | nd->flags |= LOOKUP_JUMPED; |
| 1478 | return 0; |
| 1479 | } |
| 1480 | |
| 1481 | static inline int may_lookup(struct nameidata *nd) |
| 1482 | { |
| 1483 | if (nd->flags & LOOKUP_RCU) { |
| 1484 | int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK); |
| 1485 | if (err != -ECHILD) |
| 1486 | return err; |
| 1487 | if (unlazy_walk(nd, NULL)) |
| 1488 | return -ECHILD; |
| 1489 | } |
| 1490 | return inode_permission(nd->inode, MAY_EXEC); |
| 1491 | } |
| 1492 | |
| 1493 | static inline int handle_dots(struct nameidata *nd, int type) |
| 1494 | { |
| 1495 | if (type == LAST_DOTDOT) { |
| 1496 | if (nd->flags & LOOKUP_RCU) { |
| 1497 | if (follow_dotdot_rcu(nd)) |
| 1498 | return -ECHILD; |
| 1499 | } else |
| 1500 | follow_dotdot(nd); |
| 1501 | } |
| 1502 | return 0; |
| 1503 | } |
| 1504 | |
| 1505 | static void terminate_walk(struct nameidata *nd) |
| 1506 | { |
| 1507 | if (!(nd->flags & LOOKUP_RCU)) { |
| 1508 | path_put(&nd->path); |
| 1509 | } else { |
| 1510 | nd->flags &= ~LOOKUP_RCU; |
| 1511 | if (!(nd->flags & LOOKUP_ROOT)) |
| 1512 | nd->root.mnt = NULL; |
| 1513 | rcu_read_unlock(); |
| 1514 | } |
| 1515 | } |
| 1516 | |
| 1517 | /* |
| 1518 | * Do we need to follow links? We _really_ want to be able |
| 1519 | * to do this check without having to look at inode->i_op, |
| 1520 | * so we keep a cache of "no, this doesn't need follow_link" |
| 1521 | * for the common case. |
| 1522 | */ |
| 1523 | static inline int should_follow_link(struct dentry *dentry, int follow) |
| 1524 | { |
| 1525 | return unlikely(d_is_symlink(dentry)) ? follow : 0; |
| 1526 | } |
| 1527 | |
| 1528 | static inline int walk_component(struct nameidata *nd, struct path *path, |
| 1529 | int follow) |
| 1530 | { |
| 1531 | struct inode *inode; |
| 1532 | int err; |
| 1533 | /* |
| 1534 | * "." and ".." are special - ".." especially so because it has |
| 1535 | * to be able to know about the current root directory and |
| 1536 | * parent relationships. |
| 1537 | */ |
| 1538 | if (unlikely(nd->last_type != LAST_NORM)) |
| 1539 | return handle_dots(nd, nd->last_type); |
| 1540 | err = lookup_fast(nd, path, &inode); |
| 1541 | if (unlikely(err)) { |
| 1542 | if (err < 0) |
| 1543 | goto out_err; |
| 1544 | |
| 1545 | err = lookup_slow(nd, path); |
| 1546 | if (err < 0) |
| 1547 | goto out_err; |
| 1548 | |
| 1549 | inode = path->dentry->d_inode; |
| 1550 | } |
| 1551 | err = -ENOENT; |
| 1552 | if (!inode || d_is_negative(path->dentry)) |
| 1553 | goto out_path_put; |
| 1554 | |
| 1555 | if (should_follow_link(path->dentry, follow)) { |
| 1556 | if (nd->flags & LOOKUP_RCU) { |
| 1557 | if (unlikely(unlazy_walk(nd, path->dentry))) { |
| 1558 | err = -ECHILD; |
| 1559 | goto out_err; |
| 1560 | } |
| 1561 | } |
| 1562 | BUG_ON(inode != path->dentry->d_inode); |
| 1563 | return 1; |
| 1564 | } |
| 1565 | path_to_nameidata(path, nd); |
| 1566 | nd->inode = inode; |
| 1567 | return 0; |
| 1568 | |
| 1569 | out_path_put: |
| 1570 | path_to_nameidata(path, nd); |
| 1571 | out_err: |
| 1572 | terminate_walk(nd); |
| 1573 | return err; |
| 1574 | } |
| 1575 | |
| 1576 | /* |
| 1577 | * This limits recursive symlink follows to 8, while |
| 1578 | * limiting consecutive symlinks to 40. |
| 1579 | * |
| 1580 | * Without that kind of total limit, nasty chains of consecutive |
| 1581 | * symlinks can cause almost arbitrarily long lookups. |
| 1582 | */ |
| 1583 | static inline int nested_symlink(struct path *path, struct nameidata *nd) |
| 1584 | { |
| 1585 | int res; |
| 1586 | |
| 1587 | if (unlikely(current->link_count >= MAX_NESTED_LINKS)) { |
| 1588 | path_put_conditional(path, nd); |
| 1589 | path_put(&nd->path); |
| 1590 | return -ELOOP; |
| 1591 | } |
| 1592 | BUG_ON(nd->depth >= MAX_NESTED_LINKS); |
| 1593 | |
| 1594 | nd->depth++; |
| 1595 | current->link_count++; |
| 1596 | |
| 1597 | do { |
| 1598 | struct path link = *path; |
| 1599 | void *cookie; |
| 1600 | |
| 1601 | res = follow_link(&link, nd, &cookie); |
| 1602 | if (res) |
| 1603 | break; |
| 1604 | res = walk_component(nd, path, LOOKUP_FOLLOW); |
| 1605 | put_link(nd, &link, cookie); |
| 1606 | } while (res > 0); |
| 1607 | |
| 1608 | current->link_count--; |
| 1609 | nd->depth--; |
| 1610 | return res; |
| 1611 | } |
| 1612 | |
| 1613 | /* |
| 1614 | * We can do the critical dentry name comparison and hashing |
| 1615 | * operations one word at a time, but we are limited to: |
| 1616 | * |
| 1617 | * - Architectures with fast unaligned word accesses. We could |
| 1618 | * do a "get_unaligned()" if this helps and is sufficiently |
| 1619 | * fast. |
| 1620 | * |
| 1621 | * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we |
| 1622 | * do not trap on the (extremely unlikely) case of a page |
| 1623 | * crossing operation. |
| 1624 | * |
| 1625 | * - Furthermore, we need an efficient 64-bit compile for the |
| 1626 | * 64-bit case in order to generate the "number of bytes in |
| 1627 | * the final mask". Again, that could be replaced with a |
| 1628 | * efficient population count instruction or similar. |
| 1629 | */ |
| 1630 | #ifdef CONFIG_DCACHE_WORD_ACCESS |
| 1631 | |
| 1632 | #include <asm/word-at-a-time.h> |
| 1633 | |
| 1634 | #ifdef CONFIG_64BIT |
| 1635 | |
| 1636 | static inline unsigned int fold_hash(unsigned long hash) |
| 1637 | { |
| 1638 | hash += hash >> (8*sizeof(int)); |
| 1639 | return hash; |
| 1640 | } |
| 1641 | |
| 1642 | #else /* 32-bit case */ |
| 1643 | |
| 1644 | #define fold_hash(x) (x) |
| 1645 | |
| 1646 | #endif |
| 1647 | |
| 1648 | unsigned int full_name_hash(const unsigned char *name, unsigned int len) |
| 1649 | { |
| 1650 | unsigned long a, mask; |
| 1651 | unsigned long hash = 0; |
| 1652 | |
| 1653 | for (;;) { |
| 1654 | a = load_unaligned_zeropad(name); |
| 1655 | if (len < sizeof(unsigned long)) |
| 1656 | break; |
| 1657 | hash += a; |
| 1658 | hash *= 9; |
| 1659 | name += sizeof(unsigned long); |
| 1660 | len -= sizeof(unsigned long); |
| 1661 | if (!len) |
| 1662 | goto done; |
| 1663 | } |
| 1664 | mask = bytemask_from_count(len); |
| 1665 | hash += mask & a; |
| 1666 | done: |
| 1667 | return fold_hash(hash); |
| 1668 | } |
| 1669 | EXPORT_SYMBOL(full_name_hash); |
| 1670 | |
| 1671 | /* |
| 1672 | * Calculate the length and hash of the path component, and |
| 1673 | * return the length of the component; |
| 1674 | */ |
| 1675 | static inline unsigned long hash_name(const char *name, unsigned int *hashp) |
| 1676 | { |
| 1677 | unsigned long a, b, adata, bdata, mask, hash, len; |
| 1678 | const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; |
| 1679 | |
| 1680 | hash = a = 0; |
| 1681 | len = -sizeof(unsigned long); |
| 1682 | do { |
| 1683 | hash = (hash + a) * 9; |
| 1684 | len += sizeof(unsigned long); |
| 1685 | a = load_unaligned_zeropad(name+len); |
| 1686 | b = a ^ REPEAT_BYTE('/'); |
| 1687 | } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants))); |
| 1688 | |
| 1689 | adata = prep_zero_mask(a, adata, &constants); |
| 1690 | bdata = prep_zero_mask(b, bdata, &constants); |
| 1691 | |
| 1692 | mask = create_zero_mask(adata | bdata); |
| 1693 | |
| 1694 | hash += a & zero_bytemask(mask); |
| 1695 | *hashp = fold_hash(hash); |
| 1696 | |
| 1697 | return len + find_zero(mask); |
| 1698 | } |
| 1699 | |
| 1700 | #else |
| 1701 | |
| 1702 | unsigned int full_name_hash(const unsigned char *name, unsigned int len) |
| 1703 | { |
| 1704 | unsigned long hash = init_name_hash(); |
| 1705 | while (len--) |
| 1706 | hash = partial_name_hash(*name++, hash); |
| 1707 | return end_name_hash(hash); |
| 1708 | } |
| 1709 | EXPORT_SYMBOL(full_name_hash); |
| 1710 | |
| 1711 | /* |
| 1712 | * We know there's a real path component here of at least |
| 1713 | * one character. |
| 1714 | */ |
| 1715 | static inline unsigned long hash_name(const char *name, unsigned int *hashp) |
| 1716 | { |
| 1717 | unsigned long hash = init_name_hash(); |
| 1718 | unsigned long len = 0, c; |
| 1719 | |
| 1720 | c = (unsigned char)*name; |
| 1721 | do { |
| 1722 | len++; |
| 1723 | hash = partial_name_hash(c, hash); |
| 1724 | c = (unsigned char)name[len]; |
| 1725 | } while (c && c != '/'); |
| 1726 | *hashp = end_name_hash(hash); |
| 1727 | return len; |
| 1728 | } |
| 1729 | |
| 1730 | #endif |
| 1731 | |
| 1732 | /* |
| 1733 | * Name resolution. |
| 1734 | * This is the basic name resolution function, turning a pathname into |
| 1735 | * the final dentry. We expect 'base' to be positive and a directory. |
| 1736 | * |
| 1737 | * Returns 0 and nd will have valid dentry and mnt on success. |
| 1738 | * Returns error and drops reference to input namei data on failure. |
| 1739 | */ |
| 1740 | static int link_path_walk(const char *name, struct nameidata *nd) |
| 1741 | { |
| 1742 | struct path next; |
| 1743 | int err; |
| 1744 | |
| 1745 | while (*name=='/') |
| 1746 | name++; |
| 1747 | if (!*name) |
| 1748 | return 0; |
| 1749 | |
| 1750 | /* At this point we know we have a real path component. */ |
| 1751 | for(;;) { |
| 1752 | struct qstr this; |
| 1753 | long len; |
| 1754 | int type; |
| 1755 | |
| 1756 | err = may_lookup(nd); |
| 1757 | if (err) |
| 1758 | break; |
| 1759 | |
| 1760 | len = hash_name(name, &this.hash); |
| 1761 | this.name = name; |
| 1762 | this.len = len; |
| 1763 | |
| 1764 | type = LAST_NORM; |
| 1765 | if (name[0] == '.') switch (len) { |
| 1766 | case 2: |
| 1767 | if (name[1] == '.') { |
| 1768 | type = LAST_DOTDOT; |
| 1769 | nd->flags |= LOOKUP_JUMPED; |
| 1770 | } |
| 1771 | break; |
| 1772 | case 1: |
| 1773 | type = LAST_DOT; |
| 1774 | } |
| 1775 | if (likely(type == LAST_NORM)) { |
| 1776 | struct dentry *parent = nd->path.dentry; |
| 1777 | nd->flags &= ~LOOKUP_JUMPED; |
| 1778 | if (unlikely(parent->d_flags & DCACHE_OP_HASH)) { |
| 1779 | err = parent->d_op->d_hash(parent, &this); |
| 1780 | if (err < 0) |
| 1781 | break; |
| 1782 | } |
| 1783 | } |
| 1784 | |
| 1785 | nd->last = this; |
| 1786 | nd->last_type = type; |
| 1787 | |
| 1788 | if (!name[len]) |
| 1789 | return 0; |
| 1790 | /* |
| 1791 | * If it wasn't NUL, we know it was '/'. Skip that |
| 1792 | * slash, and continue until no more slashes. |
| 1793 | */ |
| 1794 | do { |
| 1795 | len++; |
| 1796 | } while (unlikely(name[len] == '/')); |
| 1797 | if (!name[len]) |
| 1798 | return 0; |
| 1799 | |
| 1800 | name += len; |
| 1801 | |
| 1802 | err = walk_component(nd, &next, LOOKUP_FOLLOW); |
| 1803 | if (err < 0) |
| 1804 | return err; |
| 1805 | |
| 1806 | if (err) { |
| 1807 | err = nested_symlink(&next, nd); |
| 1808 | if (err) |
| 1809 | return err; |
| 1810 | } |
| 1811 | if (!d_can_lookup(nd->path.dentry)) { |
| 1812 | err = -ENOTDIR; |
| 1813 | break; |
| 1814 | } |
| 1815 | } |
| 1816 | terminate_walk(nd); |
| 1817 | return err; |
| 1818 | } |
| 1819 | |
| 1820 | static int path_init(int dfd, const char *name, unsigned int flags, |
| 1821 | struct nameidata *nd, struct file **fp) |
| 1822 | { |
| 1823 | int retval = 0; |
| 1824 | |
| 1825 | nd->last_type = LAST_ROOT; /* if there are only slashes... */ |
| 1826 | nd->flags = flags | LOOKUP_JUMPED; |
| 1827 | nd->depth = 0; |
| 1828 | if (flags & LOOKUP_ROOT) { |
| 1829 | struct dentry *root = nd->root.dentry; |
| 1830 | struct inode *inode = root->d_inode; |
| 1831 | if (*name) { |
| 1832 | if (!d_can_lookup(root)) |
| 1833 | return -ENOTDIR; |
| 1834 | retval = inode_permission(inode, MAY_EXEC); |
| 1835 | if (retval) |
| 1836 | return retval; |
| 1837 | } |
| 1838 | nd->path = nd->root; |
| 1839 | nd->inode = inode; |
| 1840 | if (flags & LOOKUP_RCU) { |
| 1841 | rcu_read_lock(); |
| 1842 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); |
| 1843 | nd->m_seq = read_seqbegin(&mount_lock); |
| 1844 | } else { |
| 1845 | path_get(&nd->path); |
| 1846 | } |
| 1847 | return 0; |
| 1848 | } |
| 1849 | |
| 1850 | nd->root.mnt = NULL; |
| 1851 | |
| 1852 | nd->m_seq = read_seqbegin(&mount_lock); |
| 1853 | if (*name=='/') { |
| 1854 | if (flags & LOOKUP_RCU) { |
| 1855 | rcu_read_lock(); |
| 1856 | nd->seq = set_root_rcu(nd); |
| 1857 | } else { |
| 1858 | set_root(nd); |
| 1859 | path_get(&nd->root); |
| 1860 | } |
| 1861 | nd->path = nd->root; |
| 1862 | } else if (dfd == AT_FDCWD) { |
| 1863 | if (flags & LOOKUP_RCU) { |
| 1864 | struct fs_struct *fs = current->fs; |
| 1865 | unsigned seq; |
| 1866 | |
| 1867 | rcu_read_lock(); |
| 1868 | |
| 1869 | do { |
| 1870 | seq = read_seqcount_begin(&fs->seq); |
| 1871 | nd->path = fs->pwd; |
| 1872 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); |
| 1873 | } while (read_seqcount_retry(&fs->seq, seq)); |
| 1874 | } else { |
| 1875 | get_fs_pwd(current->fs, &nd->path); |
| 1876 | } |
| 1877 | } else { |
| 1878 | /* Caller must check execute permissions on the starting path component */ |
| 1879 | struct fd f = fdget_raw(dfd); |
| 1880 | struct dentry *dentry; |
| 1881 | |
| 1882 | if (!f.file) |
| 1883 | return -EBADF; |
| 1884 | |
| 1885 | dentry = f.file->f_path.dentry; |
| 1886 | |
| 1887 | if (*name) { |
| 1888 | if (!d_can_lookup(dentry)) { |
| 1889 | fdput(f); |
| 1890 | return -ENOTDIR; |
| 1891 | } |
| 1892 | } |
| 1893 | |
| 1894 | nd->path = f.file->f_path; |
| 1895 | if (flags & LOOKUP_RCU) { |
| 1896 | if (f.flags & FDPUT_FPUT) |
| 1897 | *fp = f.file; |
| 1898 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); |
| 1899 | rcu_read_lock(); |
| 1900 | } else { |
| 1901 | path_get(&nd->path); |
| 1902 | fdput(f); |
| 1903 | } |
| 1904 | } |
| 1905 | |
| 1906 | nd->inode = nd->path.dentry->d_inode; |
| 1907 | return 0; |
| 1908 | } |
| 1909 | |
| 1910 | static inline int lookup_last(struct nameidata *nd, struct path *path) |
| 1911 | { |
| 1912 | if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len]) |
| 1913 | nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; |
| 1914 | |
| 1915 | nd->flags &= ~LOOKUP_PARENT; |
| 1916 | return walk_component(nd, path, nd->flags & LOOKUP_FOLLOW); |
| 1917 | } |
| 1918 | |
| 1919 | /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ |
| 1920 | static int path_lookupat(int dfd, const char *name, |
| 1921 | unsigned int flags, struct nameidata *nd) |
| 1922 | { |
| 1923 | struct file *base = NULL; |
| 1924 | struct path path; |
| 1925 | int err; |
| 1926 | |
| 1927 | /* |
| 1928 | * Path walking is largely split up into 2 different synchronisation |
| 1929 | * schemes, rcu-walk and ref-walk (explained in |
| 1930 | * Documentation/filesystems/path-lookup.txt). These share much of the |
| 1931 | * path walk code, but some things particularly setup, cleanup, and |
| 1932 | * following mounts are sufficiently divergent that functions are |
| 1933 | * duplicated. Typically there is a function foo(), and its RCU |
| 1934 | * analogue, foo_rcu(). |
| 1935 | * |
| 1936 | * -ECHILD is the error number of choice (just to avoid clashes) that |
| 1937 | * is returned if some aspect of an rcu-walk fails. Such an error must |
| 1938 | * be handled by restarting a traditional ref-walk (which will always |
| 1939 | * be able to complete). |
| 1940 | */ |
| 1941 | err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base); |
| 1942 | |
| 1943 | if (unlikely(err)) |
| 1944 | return err; |
| 1945 | |
| 1946 | current->total_link_count = 0; |
| 1947 | err = link_path_walk(name, nd); |
| 1948 | |
| 1949 | if (!err && !(flags & LOOKUP_PARENT)) { |
| 1950 | err = lookup_last(nd, &path); |
| 1951 | while (err > 0) { |
| 1952 | void *cookie; |
| 1953 | struct path link = path; |
| 1954 | err = may_follow_link(&link, nd); |
| 1955 | if (unlikely(err)) |
| 1956 | break; |
| 1957 | nd->flags |= LOOKUP_PARENT; |
| 1958 | err = follow_link(&link, nd, &cookie); |
| 1959 | if (err) |
| 1960 | break; |
| 1961 | err = lookup_last(nd, &path); |
| 1962 | put_link(nd, &link, cookie); |
| 1963 | } |
| 1964 | } |
| 1965 | |
| 1966 | if (!err) |
| 1967 | err = complete_walk(nd); |
| 1968 | |
| 1969 | if (!err && nd->flags & LOOKUP_DIRECTORY) { |
| 1970 | if (!d_can_lookup(nd->path.dentry)) { |
| 1971 | path_put(&nd->path); |
| 1972 | err = -ENOTDIR; |
| 1973 | } |
| 1974 | } |
| 1975 | |
| 1976 | if (base) |
| 1977 | fput(base); |
| 1978 | |
| 1979 | if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { |
| 1980 | path_put(&nd->root); |
| 1981 | nd->root.mnt = NULL; |
| 1982 | } |
| 1983 | return err; |
| 1984 | } |
| 1985 | |
| 1986 | static int filename_lookup(int dfd, struct filename *name, |
| 1987 | unsigned int flags, struct nameidata *nd) |
| 1988 | { |
| 1989 | int retval = path_lookupat(dfd, name->name, flags | LOOKUP_RCU, nd); |
| 1990 | if (unlikely(retval == -ECHILD)) |
| 1991 | retval = path_lookupat(dfd, name->name, flags, nd); |
| 1992 | if (unlikely(retval == -ESTALE)) |
| 1993 | retval = path_lookupat(dfd, name->name, |
| 1994 | flags | LOOKUP_REVAL, nd); |
| 1995 | |
| 1996 | if (likely(!retval)) |
| 1997 | audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT); |
| 1998 | return retval; |
| 1999 | } |
| 2000 | |
| 2001 | static int do_path_lookup(int dfd, const char *name, |
| 2002 | unsigned int flags, struct nameidata *nd) |
| 2003 | { |
| 2004 | struct filename filename = { .name = name }; |
| 2005 | |
| 2006 | return filename_lookup(dfd, &filename, flags, nd); |
| 2007 | } |
| 2008 | |
| 2009 | /* does lookup, returns the object with parent locked */ |
| 2010 | struct dentry *kern_path_locked(const char *name, struct path *path) |
| 2011 | { |
| 2012 | struct nameidata nd; |
| 2013 | struct dentry *d; |
| 2014 | int err = do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, &nd); |
| 2015 | if (err) |
| 2016 | return ERR_PTR(err); |
| 2017 | if (nd.last_type != LAST_NORM) { |
| 2018 | path_put(&nd.path); |
| 2019 | return ERR_PTR(-EINVAL); |
| 2020 | } |
| 2021 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); |
| 2022 | d = __lookup_hash(&nd.last, nd.path.dentry, 0); |
| 2023 | if (IS_ERR(d)) { |
| 2024 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
| 2025 | path_put(&nd.path); |
| 2026 | return d; |
| 2027 | } |
| 2028 | *path = nd.path; |
| 2029 | return d; |
| 2030 | } |
| 2031 | |
| 2032 | int kern_path(const char *name, unsigned int flags, struct path *path) |
| 2033 | { |
| 2034 | struct nameidata nd; |
| 2035 | int res = do_path_lookup(AT_FDCWD, name, flags, &nd); |
| 2036 | if (!res) |
| 2037 | *path = nd.path; |
| 2038 | return res; |
| 2039 | } |
| 2040 | EXPORT_SYMBOL(kern_path); |
| 2041 | |
| 2042 | /** |
| 2043 | * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair |
| 2044 | * @dentry: pointer to dentry of the base directory |
| 2045 | * @mnt: pointer to vfs mount of the base directory |
| 2046 | * @name: pointer to file name |
| 2047 | * @flags: lookup flags |
| 2048 | * @path: pointer to struct path to fill |
| 2049 | */ |
| 2050 | int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, |
| 2051 | const char *name, unsigned int flags, |
| 2052 | struct path *path) |
| 2053 | { |
| 2054 | struct nameidata nd; |
| 2055 | int err; |
| 2056 | nd.root.dentry = dentry; |
| 2057 | nd.root.mnt = mnt; |
| 2058 | BUG_ON(flags & LOOKUP_PARENT); |
| 2059 | /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */ |
| 2060 | err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd); |
| 2061 | if (!err) |
| 2062 | *path = nd.path; |
| 2063 | return err; |
| 2064 | } |
| 2065 | EXPORT_SYMBOL(vfs_path_lookup); |
| 2066 | |
| 2067 | /* |
| 2068 | * Restricted form of lookup. Doesn't follow links, single-component only, |
| 2069 | * needs parent already locked. Doesn't follow mounts. |
| 2070 | * SMP-safe. |
| 2071 | */ |
| 2072 | static struct dentry *lookup_hash(struct nameidata *nd) |
| 2073 | { |
| 2074 | return __lookup_hash(&nd->last, nd->path.dentry, nd->flags); |
| 2075 | } |
| 2076 | |
| 2077 | /** |
| 2078 | * lookup_one_len - filesystem helper to lookup single pathname component |
| 2079 | * @name: pathname component to lookup |
| 2080 | * @base: base directory to lookup from |
| 2081 | * @len: maximum length @len should be interpreted to |
| 2082 | * |
| 2083 | * Note that this routine is purely a helper for filesystem usage and should |
| 2084 | * not be called by generic code. Also note that by using this function the |
| 2085 | * nameidata argument is passed to the filesystem methods and a filesystem |
| 2086 | * using this helper needs to be prepared for that. |
| 2087 | */ |
| 2088 | struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) |
| 2089 | { |
| 2090 | struct qstr this; |
| 2091 | unsigned int c; |
| 2092 | int err; |
| 2093 | |
| 2094 | WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex)); |
| 2095 | |
| 2096 | this.name = name; |
| 2097 | this.len = len; |
| 2098 | this.hash = full_name_hash(name, len); |
| 2099 | if (!len) |
| 2100 | return ERR_PTR(-EACCES); |
| 2101 | |
| 2102 | if (unlikely(name[0] == '.')) { |
| 2103 | if (len < 2 || (len == 2 && name[1] == '.')) |
| 2104 | return ERR_PTR(-EACCES); |
| 2105 | } |
| 2106 | |
| 2107 | while (len--) { |
| 2108 | c = *(const unsigned char *)name++; |
| 2109 | if (c == '/' || c == '\0') |
| 2110 | return ERR_PTR(-EACCES); |
| 2111 | } |
| 2112 | /* |
| 2113 | * See if the low-level filesystem might want |
| 2114 | * to use its own hash.. |
| 2115 | */ |
| 2116 | if (base->d_flags & DCACHE_OP_HASH) { |
| 2117 | int err = base->d_op->d_hash(base, &this); |
| 2118 | if (err < 0) |
| 2119 | return ERR_PTR(err); |
| 2120 | } |
| 2121 | |
| 2122 | err = inode_permission(base->d_inode, MAY_EXEC); |
| 2123 | if (err) |
| 2124 | return ERR_PTR(err); |
| 2125 | |
| 2126 | return __lookup_hash(&this, base, 0); |
| 2127 | } |
| 2128 | EXPORT_SYMBOL(lookup_one_len); |
| 2129 | |
| 2130 | int user_path_at_empty(int dfd, const char __user *name, unsigned flags, |
| 2131 | struct path *path, int *empty) |
| 2132 | { |
| 2133 | struct nameidata nd; |
| 2134 | struct filename *tmp = getname_flags(name, flags, empty); |
| 2135 | int err = PTR_ERR(tmp); |
| 2136 | if (!IS_ERR(tmp)) { |
| 2137 | |
| 2138 | BUG_ON(flags & LOOKUP_PARENT); |
| 2139 | |
| 2140 | err = filename_lookup(dfd, tmp, flags, &nd); |
| 2141 | putname(tmp); |
| 2142 | if (!err) |
| 2143 | *path = nd.path; |
| 2144 | } |
| 2145 | return err; |
| 2146 | } |
| 2147 | |
| 2148 | int user_path_at(int dfd, const char __user *name, unsigned flags, |
| 2149 | struct path *path) |
| 2150 | { |
| 2151 | return user_path_at_empty(dfd, name, flags, path, NULL); |
| 2152 | } |
| 2153 | EXPORT_SYMBOL(user_path_at); |
| 2154 | |
| 2155 | /* |
| 2156 | * NB: most callers don't do anything directly with the reference to the |
| 2157 | * to struct filename, but the nd->last pointer points into the name string |
| 2158 | * allocated by getname. So we must hold the reference to it until all |
| 2159 | * path-walking is complete. |
| 2160 | */ |
| 2161 | static struct filename * |
| 2162 | user_path_parent(int dfd, const char __user *path, struct nameidata *nd, |
| 2163 | unsigned int flags) |
| 2164 | { |
| 2165 | struct filename *s = getname(path); |
| 2166 | int error; |
| 2167 | |
| 2168 | /* only LOOKUP_REVAL is allowed in extra flags */ |
| 2169 | flags &= LOOKUP_REVAL; |
| 2170 | |
| 2171 | if (IS_ERR(s)) |
| 2172 | return s; |
| 2173 | |
| 2174 | error = filename_lookup(dfd, s, flags | LOOKUP_PARENT, nd); |
| 2175 | if (error) { |
| 2176 | putname(s); |
| 2177 | return ERR_PTR(error); |
| 2178 | } |
| 2179 | |
| 2180 | return s; |
| 2181 | } |
| 2182 | |
| 2183 | /** |
| 2184 | * mountpoint_last - look up last component for umount |
| 2185 | * @nd: pathwalk nameidata - currently pointing at parent directory of "last" |
| 2186 | * @path: pointer to container for result |
| 2187 | * |
| 2188 | * This is a special lookup_last function just for umount. In this case, we |
| 2189 | * need to resolve the path without doing any revalidation. |
| 2190 | * |
| 2191 | * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since |
| 2192 | * mountpoints are always pinned in the dcache, their ancestors are too. Thus, |
| 2193 | * in almost all cases, this lookup will be served out of the dcache. The only |
| 2194 | * cases where it won't are if nd->last refers to a symlink or the path is |
| 2195 | * bogus and it doesn't exist. |
| 2196 | * |
| 2197 | * Returns: |
| 2198 | * -error: if there was an error during lookup. This includes -ENOENT if the |
| 2199 | * lookup found a negative dentry. The nd->path reference will also be |
| 2200 | * put in this case. |
| 2201 | * |
| 2202 | * 0: if we successfully resolved nd->path and found it to not to be a |
| 2203 | * symlink that needs to be followed. "path" will also be populated. |
| 2204 | * The nd->path reference will also be put. |
| 2205 | * |
| 2206 | * 1: if we successfully resolved nd->last and found it to be a symlink |
| 2207 | * that needs to be followed. "path" will be populated with the path |
| 2208 | * to the link, and nd->path will *not* be put. |
| 2209 | */ |
| 2210 | static int |
| 2211 | mountpoint_last(struct nameidata *nd, struct path *path) |
| 2212 | { |
| 2213 | int error = 0; |
| 2214 | struct dentry *dentry; |
| 2215 | struct dentry *dir = nd->path.dentry; |
| 2216 | |
| 2217 | /* If we're in rcuwalk, drop out of it to handle last component */ |
| 2218 | if (nd->flags & LOOKUP_RCU) { |
| 2219 | if (unlazy_walk(nd, NULL)) { |
| 2220 | error = -ECHILD; |
| 2221 | goto out; |
| 2222 | } |
| 2223 | } |
| 2224 | |
| 2225 | nd->flags &= ~LOOKUP_PARENT; |
| 2226 | |
| 2227 | if (unlikely(nd->last_type != LAST_NORM)) { |
| 2228 | error = handle_dots(nd, nd->last_type); |
| 2229 | if (error) |
| 2230 | goto out; |
| 2231 | dentry = dget(nd->path.dentry); |
| 2232 | goto done; |
| 2233 | } |
| 2234 | |
| 2235 | mutex_lock(&dir->d_inode->i_mutex); |
| 2236 | dentry = d_lookup(dir, &nd->last); |
| 2237 | if (!dentry) { |
| 2238 | /* |
| 2239 | * No cached dentry. Mounted dentries are pinned in the cache, |
| 2240 | * so that means that this dentry is probably a symlink or the |
| 2241 | * path doesn't actually point to a mounted dentry. |
| 2242 | */ |
| 2243 | dentry = d_alloc(dir, &nd->last); |
| 2244 | if (!dentry) { |
| 2245 | error = -ENOMEM; |
| 2246 | mutex_unlock(&dir->d_inode->i_mutex); |
| 2247 | goto out; |
| 2248 | } |
| 2249 | dentry = lookup_real(dir->d_inode, dentry, nd->flags); |
| 2250 | error = PTR_ERR(dentry); |
| 2251 | if (IS_ERR(dentry)) { |
| 2252 | mutex_unlock(&dir->d_inode->i_mutex); |
| 2253 | goto out; |
| 2254 | } |
| 2255 | } |
| 2256 | mutex_unlock(&dir->d_inode->i_mutex); |
| 2257 | |
| 2258 | done: |
| 2259 | if (!dentry->d_inode || d_is_negative(dentry)) { |
| 2260 | error = -ENOENT; |
| 2261 | dput(dentry); |
| 2262 | goto out; |
| 2263 | } |
| 2264 | path->dentry = dentry; |
| 2265 | path->mnt = nd->path.mnt; |
| 2266 | if (should_follow_link(dentry, nd->flags & LOOKUP_FOLLOW)) |
| 2267 | return 1; |
| 2268 | mntget(path->mnt); |
| 2269 | follow_mount(path); |
| 2270 | error = 0; |
| 2271 | out: |
| 2272 | terminate_walk(nd); |
| 2273 | return error; |
| 2274 | } |
| 2275 | |
| 2276 | /** |
| 2277 | * path_mountpoint - look up a path to be umounted |
| 2278 | * @dfd: directory file descriptor to start walk from |
| 2279 | * @name: full pathname to walk |
| 2280 | * @path: pointer to container for result |
| 2281 | * @flags: lookup flags |
| 2282 | * |
| 2283 | * Look up the given name, but don't attempt to revalidate the last component. |
| 2284 | * Returns 0 and "path" will be valid on success; Returns error otherwise. |
| 2285 | */ |
| 2286 | static int |
| 2287 | path_mountpoint(int dfd, const char *name, struct path *path, unsigned int flags) |
| 2288 | { |
| 2289 | struct file *base = NULL; |
| 2290 | struct nameidata nd; |
| 2291 | int err; |
| 2292 | |
| 2293 | err = path_init(dfd, name, flags | LOOKUP_PARENT, &nd, &base); |
| 2294 | if (unlikely(err)) |
| 2295 | return err; |
| 2296 | |
| 2297 | current->total_link_count = 0; |
| 2298 | err = link_path_walk(name, &nd); |
| 2299 | if (err) |
| 2300 | goto out; |
| 2301 | |
| 2302 | err = mountpoint_last(&nd, path); |
| 2303 | while (err > 0) { |
| 2304 | void *cookie; |
| 2305 | struct path link = *path; |
| 2306 | err = may_follow_link(&link, &nd); |
| 2307 | if (unlikely(err)) |
| 2308 | break; |
| 2309 | nd.flags |= LOOKUP_PARENT; |
| 2310 | err = follow_link(&link, &nd, &cookie); |
| 2311 | if (err) |
| 2312 | break; |
| 2313 | err = mountpoint_last(&nd, path); |
| 2314 | put_link(&nd, &link, cookie); |
| 2315 | } |
| 2316 | out: |
| 2317 | if (base) |
| 2318 | fput(base); |
| 2319 | |
| 2320 | if (nd.root.mnt && !(nd.flags & LOOKUP_ROOT)) |
| 2321 | path_put(&nd.root); |
| 2322 | |
| 2323 | return err; |
| 2324 | } |
| 2325 | |
| 2326 | static int |
| 2327 | filename_mountpoint(int dfd, struct filename *s, struct path *path, |
| 2328 | unsigned int flags) |
| 2329 | { |
| 2330 | int error = path_mountpoint(dfd, s->name, path, flags | LOOKUP_RCU); |
| 2331 | if (unlikely(error == -ECHILD)) |
| 2332 | error = path_mountpoint(dfd, s->name, path, flags); |
| 2333 | if (unlikely(error == -ESTALE)) |
| 2334 | error = path_mountpoint(dfd, s->name, path, flags | LOOKUP_REVAL); |
| 2335 | if (likely(!error)) |
| 2336 | audit_inode(s, path->dentry, 0); |
| 2337 | return error; |
| 2338 | } |
| 2339 | |
| 2340 | /** |
| 2341 | * user_path_mountpoint_at - lookup a path from userland in order to umount it |
| 2342 | * @dfd: directory file descriptor |
| 2343 | * @name: pathname from userland |
| 2344 | * @flags: lookup flags |
| 2345 | * @path: pointer to container to hold result |
| 2346 | * |
| 2347 | * A umount is a special case for path walking. We're not actually interested |
| 2348 | * in the inode in this situation, and ESTALE errors can be a problem. We |
| 2349 | * simply want track down the dentry and vfsmount attached at the mountpoint |
| 2350 | * and avoid revalidating the last component. |
| 2351 | * |
| 2352 | * Returns 0 and populates "path" on success. |
| 2353 | */ |
| 2354 | int |
| 2355 | user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags, |
| 2356 | struct path *path) |
| 2357 | { |
| 2358 | struct filename *s = getname(name); |
| 2359 | int error; |
| 2360 | if (IS_ERR(s)) |
| 2361 | return PTR_ERR(s); |
| 2362 | error = filename_mountpoint(dfd, s, path, flags); |
| 2363 | putname(s); |
| 2364 | return error; |
| 2365 | } |
| 2366 | |
| 2367 | int |
| 2368 | kern_path_mountpoint(int dfd, const char *name, struct path *path, |
| 2369 | unsigned int flags) |
| 2370 | { |
| 2371 | struct filename s = {.name = name}; |
| 2372 | return filename_mountpoint(dfd, &s, path, flags); |
| 2373 | } |
| 2374 | EXPORT_SYMBOL(kern_path_mountpoint); |
| 2375 | |
| 2376 | /* |
| 2377 | * It's inline, so penalty for filesystems that don't use sticky bit is |
| 2378 | * minimal. |
| 2379 | */ |
| 2380 | static inline int check_sticky(struct inode *dir, struct inode *inode) |
| 2381 | { |
| 2382 | kuid_t fsuid = current_fsuid(); |
| 2383 | |
| 2384 | if (!(dir->i_mode & S_ISVTX)) |
| 2385 | return 0; |
| 2386 | if (uid_eq(inode->i_uid, fsuid)) |
| 2387 | return 0; |
| 2388 | if (uid_eq(dir->i_uid, fsuid)) |
| 2389 | return 0; |
| 2390 | return !capable_wrt_inode_uidgid(inode, CAP_FOWNER); |
| 2391 | } |
| 2392 | |
| 2393 | /* |
| 2394 | * Check whether we can remove a link victim from directory dir, check |
| 2395 | * whether the type of victim is right. |
| 2396 | * 1. We can't do it if dir is read-only (done in permission()) |
| 2397 | * 2. We should have write and exec permissions on dir |
| 2398 | * 3. We can't remove anything from append-only dir |
| 2399 | * 4. We can't do anything with immutable dir (done in permission()) |
| 2400 | * 5. If the sticky bit on dir is set we should either |
| 2401 | * a. be owner of dir, or |
| 2402 | * b. be owner of victim, or |
| 2403 | * c. have CAP_FOWNER capability |
| 2404 | * 6. If the victim is append-only or immutable we can't do antyhing with |
| 2405 | * links pointing to it. |
| 2406 | * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR. |
| 2407 | * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR. |
| 2408 | * 9. We can't remove a root or mountpoint. |
| 2409 | * 10. We don't allow removal of NFS sillyrenamed files; it's handled by |
| 2410 | * nfs_async_unlink(). |
| 2411 | */ |
| 2412 | static int may_delete(struct inode *dir, struct dentry *victim, bool isdir) |
| 2413 | { |
| 2414 | struct inode *inode = victim->d_inode; |
| 2415 | int error; |
| 2416 | |
| 2417 | if (d_is_negative(victim)) |
| 2418 | return -ENOENT; |
| 2419 | BUG_ON(!inode); |
| 2420 | |
| 2421 | BUG_ON(victim->d_parent->d_inode != dir); |
| 2422 | audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE); |
| 2423 | |
| 2424 | error = inode_permission(dir, MAY_WRITE | MAY_EXEC); |
| 2425 | if (error) |
| 2426 | return error; |
| 2427 | if (IS_APPEND(dir)) |
| 2428 | return -EPERM; |
| 2429 | |
| 2430 | if (check_sticky(dir, inode) || IS_APPEND(inode) || |
| 2431 | IS_IMMUTABLE(inode) || IS_SWAPFILE(inode)) |
| 2432 | return -EPERM; |
| 2433 | if (isdir) { |
| 2434 | if (!d_is_dir(victim)) |
| 2435 | return -ENOTDIR; |
| 2436 | if (IS_ROOT(victim)) |
| 2437 | return -EBUSY; |
| 2438 | } else if (d_is_dir(victim)) |
| 2439 | return -EISDIR; |
| 2440 | if (IS_DEADDIR(dir)) |
| 2441 | return -ENOENT; |
| 2442 | if (victim->d_flags & DCACHE_NFSFS_RENAMED) |
| 2443 | return -EBUSY; |
| 2444 | return 0; |
| 2445 | } |
| 2446 | |
| 2447 | /* Check whether we can create an object with dentry child in directory |
| 2448 | * dir. |
| 2449 | * 1. We can't do it if child already exists (open has special treatment for |
| 2450 | * this case, but since we are inlined it's OK) |
| 2451 | * 2. We can't do it if dir is read-only (done in permission()) |
| 2452 | * 3. We should have write and exec permissions on dir |
| 2453 | * 4. We can't do it if dir is immutable (done in permission()) |
| 2454 | */ |
| 2455 | static inline int may_create(struct inode *dir, struct dentry *child) |
| 2456 | { |
| 2457 | audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE); |
| 2458 | if (child->d_inode) |
| 2459 | return -EEXIST; |
| 2460 | if (IS_DEADDIR(dir)) |
| 2461 | return -ENOENT; |
| 2462 | return inode_permission(dir, MAY_WRITE | MAY_EXEC); |
| 2463 | } |
| 2464 | |
| 2465 | /* |
| 2466 | * p1 and p2 should be directories on the same fs. |
| 2467 | */ |
| 2468 | struct dentry *lock_rename(struct dentry *p1, struct dentry *p2) |
| 2469 | { |
| 2470 | struct dentry *p; |
| 2471 | |
| 2472 | if (p1 == p2) { |
| 2473 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); |
| 2474 | return NULL; |
| 2475 | } |
| 2476 | |
| 2477 | mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex); |
| 2478 | |
| 2479 | p = d_ancestor(p2, p1); |
| 2480 | if (p) { |
| 2481 | mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT); |
| 2482 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD); |
| 2483 | return p; |
| 2484 | } |
| 2485 | |
| 2486 | p = d_ancestor(p1, p2); |
| 2487 | if (p) { |
| 2488 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); |
| 2489 | mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD); |
| 2490 | return p; |
| 2491 | } |
| 2492 | |
| 2493 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); |
| 2494 | mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD); |
| 2495 | return NULL; |
| 2496 | } |
| 2497 | EXPORT_SYMBOL(lock_rename); |
| 2498 | |
| 2499 | void unlock_rename(struct dentry *p1, struct dentry *p2) |
| 2500 | { |
| 2501 | mutex_unlock(&p1->d_inode->i_mutex); |
| 2502 | if (p1 != p2) { |
| 2503 | mutex_unlock(&p2->d_inode->i_mutex); |
| 2504 | mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex); |
| 2505 | } |
| 2506 | } |
| 2507 | EXPORT_SYMBOL(unlock_rename); |
| 2508 | |
| 2509 | int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, |
| 2510 | bool want_excl) |
| 2511 | { |
| 2512 | int error = may_create(dir, dentry); |
| 2513 | if (error) |
| 2514 | return error; |
| 2515 | |
| 2516 | if (!dir->i_op->create) |
| 2517 | return -EACCES; /* shouldn't it be ENOSYS? */ |
| 2518 | mode &= S_IALLUGO; |
| 2519 | mode |= S_IFREG; |
| 2520 | error = security_inode_create(dir, dentry, mode); |
| 2521 | if (error) |
| 2522 | return error; |
| 2523 | error = dir->i_op->create(dir, dentry, mode, want_excl); |
| 2524 | if (!error) |
| 2525 | fsnotify_create(dir, dentry); |
| 2526 | return error; |
| 2527 | } |
| 2528 | EXPORT_SYMBOL(vfs_create); |
| 2529 | |
| 2530 | static int may_open(struct path *path, int acc_mode, int flag) |
| 2531 | { |
| 2532 | struct dentry *dentry = path->dentry; |
| 2533 | struct inode *inode = dentry->d_inode; |
| 2534 | int error; |
| 2535 | |
| 2536 | /* O_PATH? */ |
| 2537 | if (!acc_mode) |
| 2538 | return 0; |
| 2539 | |
| 2540 | if (!inode) |
| 2541 | return -ENOENT; |
| 2542 | |
| 2543 | switch (inode->i_mode & S_IFMT) { |
| 2544 | case S_IFLNK: |
| 2545 | return -ELOOP; |
| 2546 | case S_IFDIR: |
| 2547 | if (acc_mode & MAY_WRITE) |
| 2548 | return -EISDIR; |
| 2549 | break; |
| 2550 | case S_IFBLK: |
| 2551 | case S_IFCHR: |
| 2552 | if (path->mnt->mnt_flags & MNT_NODEV) |
| 2553 | return -EACCES; |
| 2554 | /*FALLTHRU*/ |
| 2555 | case S_IFIFO: |
| 2556 | case S_IFSOCK: |
| 2557 | flag &= ~O_TRUNC; |
| 2558 | break; |
| 2559 | } |
| 2560 | |
| 2561 | error = inode_permission(inode, acc_mode); |
| 2562 | if (error) |
| 2563 | return error; |
| 2564 | |
| 2565 | /* |
| 2566 | * An append-only file must be opened in append mode for writing. |
| 2567 | */ |
| 2568 | if (IS_APPEND(inode)) { |
| 2569 | if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) |
| 2570 | return -EPERM; |
| 2571 | if (flag & O_TRUNC) |
| 2572 | return -EPERM; |
| 2573 | } |
| 2574 | |
| 2575 | /* O_NOATIME can only be set by the owner or superuser */ |
| 2576 | if (flag & O_NOATIME && !inode_owner_or_capable(inode)) |
| 2577 | return -EPERM; |
| 2578 | |
| 2579 | return 0; |
| 2580 | } |
| 2581 | |
| 2582 | static int handle_truncate(struct file *filp) |
| 2583 | { |
| 2584 | struct path *path = &filp->f_path; |
| 2585 | struct inode *inode = path->dentry->d_inode; |
| 2586 | int error = get_write_access(inode); |
| 2587 | if (error) |
| 2588 | return error; |
| 2589 | /* |
| 2590 | * Refuse to truncate files with mandatory locks held on them. |
| 2591 | */ |
| 2592 | error = locks_verify_locked(filp); |
| 2593 | if (!error) |
| 2594 | error = security_path_truncate(path); |
| 2595 | if (!error) { |
| 2596 | error = do_truncate(path->dentry, 0, |
| 2597 | ATTR_MTIME|ATTR_CTIME|ATTR_OPEN, |
| 2598 | filp); |
| 2599 | } |
| 2600 | put_write_access(inode); |
| 2601 | return error; |
| 2602 | } |
| 2603 | |
| 2604 | static inline int open_to_namei_flags(int flag) |
| 2605 | { |
| 2606 | if ((flag & O_ACCMODE) == 3) |
| 2607 | flag--; |
| 2608 | return flag; |
| 2609 | } |
| 2610 | |
| 2611 | static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode) |
| 2612 | { |
| 2613 | int error = security_path_mknod(dir, dentry, mode, 0); |
| 2614 | if (error) |
| 2615 | return error; |
| 2616 | |
| 2617 | error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC); |
| 2618 | if (error) |
| 2619 | return error; |
| 2620 | |
| 2621 | return security_inode_create(dir->dentry->d_inode, dentry, mode); |
| 2622 | } |
| 2623 | |
| 2624 | /* |
| 2625 | * Attempt to atomically look up, create and open a file from a negative |
| 2626 | * dentry. |
| 2627 | * |
| 2628 | * Returns 0 if successful. The file will have been created and attached to |
| 2629 | * @file by the filesystem calling finish_open(). |
| 2630 | * |
| 2631 | * Returns 1 if the file was looked up only or didn't need creating. The |
| 2632 | * caller will need to perform the open themselves. @path will have been |
| 2633 | * updated to point to the new dentry. This may be negative. |
| 2634 | * |
| 2635 | * Returns an error code otherwise. |
| 2636 | */ |
| 2637 | static int atomic_open(struct nameidata *nd, struct dentry *dentry, |
| 2638 | struct path *path, struct file *file, |
| 2639 | const struct open_flags *op, |
| 2640 | bool got_write, bool need_lookup, |
| 2641 | int *opened) |
| 2642 | { |
| 2643 | struct inode *dir = nd->path.dentry->d_inode; |
| 2644 | unsigned open_flag = open_to_namei_flags(op->open_flag); |
| 2645 | umode_t mode; |
| 2646 | int error; |
| 2647 | int acc_mode; |
| 2648 | int create_error = 0; |
| 2649 | struct dentry *const DENTRY_NOT_SET = (void *) -1UL; |
| 2650 | bool excl; |
| 2651 | |
| 2652 | BUG_ON(dentry->d_inode); |
| 2653 | |
| 2654 | /* Don't create child dentry for a dead directory. */ |
| 2655 | if (unlikely(IS_DEADDIR(dir))) { |
| 2656 | error = -ENOENT; |
| 2657 | goto out; |
| 2658 | } |
| 2659 | |
| 2660 | mode = op->mode; |
| 2661 | if ((open_flag & O_CREAT) && !IS_POSIXACL(dir)) |
| 2662 | mode &= ~current_umask(); |
| 2663 | |
| 2664 | excl = (open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT); |
| 2665 | if (excl) |
| 2666 | open_flag &= ~O_TRUNC; |
| 2667 | |
| 2668 | /* |
| 2669 | * Checking write permission is tricky, bacuse we don't know if we are |
| 2670 | * going to actually need it: O_CREAT opens should work as long as the |
| 2671 | * file exists. But checking existence breaks atomicity. The trick is |
| 2672 | * to check access and if not granted clear O_CREAT from the flags. |
| 2673 | * |
| 2674 | * Another problem is returing the "right" error value (e.g. for an |
| 2675 | * O_EXCL open we want to return EEXIST not EROFS). |
| 2676 | */ |
| 2677 | if (((open_flag & (O_CREAT | O_TRUNC)) || |
| 2678 | (open_flag & O_ACCMODE) != O_RDONLY) && unlikely(!got_write)) { |
| 2679 | if (!(open_flag & O_CREAT)) { |
| 2680 | /* |
| 2681 | * No O_CREATE -> atomicity not a requirement -> fall |
| 2682 | * back to lookup + open |
| 2683 | */ |
| 2684 | goto no_open; |
| 2685 | } else if (open_flag & (O_EXCL | O_TRUNC)) { |
| 2686 | /* Fall back and fail with the right error */ |
| 2687 | create_error = -EROFS; |
| 2688 | goto no_open; |
| 2689 | } else { |
| 2690 | /* No side effects, safe to clear O_CREAT */ |
| 2691 | create_error = -EROFS; |
| 2692 | open_flag &= ~O_CREAT; |
| 2693 | } |
| 2694 | } |
| 2695 | |
| 2696 | if (open_flag & O_CREAT) { |
| 2697 | error = may_o_create(&nd->path, dentry, mode); |
| 2698 | if (error) { |
| 2699 | create_error = error; |
| 2700 | if (open_flag & O_EXCL) |
| 2701 | goto no_open; |
| 2702 | open_flag &= ~O_CREAT; |
| 2703 | } |
| 2704 | } |
| 2705 | |
| 2706 | if (nd->flags & LOOKUP_DIRECTORY) |
| 2707 | open_flag |= O_DIRECTORY; |
| 2708 | |
| 2709 | file->f_path.dentry = DENTRY_NOT_SET; |
| 2710 | file->f_path.mnt = nd->path.mnt; |
| 2711 | error = dir->i_op->atomic_open(dir, dentry, file, open_flag, mode, |
| 2712 | opened); |
| 2713 | if (error < 0) { |
| 2714 | if (create_error && error == -ENOENT) |
| 2715 | error = create_error; |
| 2716 | goto out; |
| 2717 | } |
| 2718 | |
| 2719 | if (error) { /* returned 1, that is */ |
| 2720 | if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) { |
| 2721 | error = -EIO; |
| 2722 | goto out; |
| 2723 | } |
| 2724 | if (file->f_path.dentry) { |
| 2725 | dput(dentry); |
| 2726 | dentry = file->f_path.dentry; |
| 2727 | } |
| 2728 | if (*opened & FILE_CREATED) |
| 2729 | fsnotify_create(dir, dentry); |
| 2730 | if (!dentry->d_inode) { |
| 2731 | WARN_ON(*opened & FILE_CREATED); |
| 2732 | if (create_error) { |
| 2733 | error = create_error; |
| 2734 | goto out; |
| 2735 | } |
| 2736 | } else { |
| 2737 | if (excl && !(*opened & FILE_CREATED)) { |
| 2738 | error = -EEXIST; |
| 2739 | goto out; |
| 2740 | } |
| 2741 | } |
| 2742 | goto looked_up; |
| 2743 | } |
| 2744 | |
| 2745 | /* |
| 2746 | * We didn't have the inode before the open, so check open permission |
| 2747 | * here. |
| 2748 | */ |
| 2749 | acc_mode = op->acc_mode; |
| 2750 | if (*opened & FILE_CREATED) { |
| 2751 | WARN_ON(!(open_flag & O_CREAT)); |
| 2752 | fsnotify_create(dir, dentry); |
| 2753 | acc_mode = MAY_OPEN; |
| 2754 | } |
| 2755 | error = may_open(&file->f_path, acc_mode, open_flag); |
| 2756 | if (error) |
| 2757 | fput(file); |
| 2758 | |
| 2759 | out: |
| 2760 | dput(dentry); |
| 2761 | return error; |
| 2762 | |
| 2763 | no_open: |
| 2764 | if (need_lookup) { |
| 2765 | dentry = lookup_real(dir, dentry, nd->flags); |
| 2766 | if (IS_ERR(dentry)) |
| 2767 | return PTR_ERR(dentry); |
| 2768 | |
| 2769 | if (create_error) { |
| 2770 | int open_flag = op->open_flag; |
| 2771 | |
| 2772 | error = create_error; |
| 2773 | if ((open_flag & O_EXCL)) { |
| 2774 | if (!dentry->d_inode) |
| 2775 | goto out; |
| 2776 | } else if (!dentry->d_inode) { |
| 2777 | goto out; |
| 2778 | } else if ((open_flag & O_TRUNC) && |
| 2779 | S_ISREG(dentry->d_inode->i_mode)) { |
| 2780 | goto out; |
| 2781 | } |
| 2782 | /* will fail later, go on to get the right error */ |
| 2783 | } |
| 2784 | } |
| 2785 | looked_up: |
| 2786 | path->dentry = dentry; |
| 2787 | path->mnt = nd->path.mnt; |
| 2788 | return 1; |
| 2789 | } |
| 2790 | |
| 2791 | /* |
| 2792 | * Look up and maybe create and open the last component. |
| 2793 | * |
| 2794 | * Must be called with i_mutex held on parent. |
| 2795 | * |
| 2796 | * Returns 0 if the file was successfully atomically created (if necessary) and |
| 2797 | * opened. In this case the file will be returned attached to @file. |
| 2798 | * |
| 2799 | * Returns 1 if the file was not completely opened at this time, though lookups |
| 2800 | * and creations will have been performed and the dentry returned in @path will |
| 2801 | * be positive upon return if O_CREAT was specified. If O_CREAT wasn't |
| 2802 | * specified then a negative dentry may be returned. |
| 2803 | * |
| 2804 | * An error code is returned otherwise. |
| 2805 | * |
| 2806 | * FILE_CREATE will be set in @*opened if the dentry was created and will be |
| 2807 | * cleared otherwise prior to returning. |
| 2808 | */ |
| 2809 | static int lookup_open(struct nameidata *nd, struct path *path, |
| 2810 | struct file *file, |
| 2811 | const struct open_flags *op, |
| 2812 | bool got_write, int *opened) |
| 2813 | { |
| 2814 | struct dentry *dir = nd->path.dentry; |
| 2815 | struct inode *dir_inode = dir->d_inode; |
| 2816 | struct dentry *dentry; |
| 2817 | int error; |
| 2818 | bool need_lookup; |
| 2819 | |
| 2820 | *opened &= ~FILE_CREATED; |
| 2821 | dentry = lookup_dcache(&nd->last, dir, nd->flags, &need_lookup); |
| 2822 | if (IS_ERR(dentry)) |
| 2823 | return PTR_ERR(dentry); |
| 2824 | |
| 2825 | /* Cached positive dentry: will open in f_op->open */ |
| 2826 | if (!need_lookup && dentry->d_inode) |
| 2827 | goto out_no_open; |
| 2828 | |
| 2829 | if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) { |
| 2830 | return atomic_open(nd, dentry, path, file, op, got_write, |
| 2831 | need_lookup, opened); |
| 2832 | } |
| 2833 | |
| 2834 | if (need_lookup) { |
| 2835 | BUG_ON(dentry->d_inode); |
| 2836 | |
| 2837 | dentry = lookup_real(dir_inode, dentry, nd->flags); |
| 2838 | if (IS_ERR(dentry)) |
| 2839 | return PTR_ERR(dentry); |
| 2840 | } |
| 2841 | |
| 2842 | /* Negative dentry, just create the file */ |
| 2843 | if (!dentry->d_inode && (op->open_flag & O_CREAT)) { |
| 2844 | umode_t mode = op->mode; |
| 2845 | if (!IS_POSIXACL(dir->d_inode)) |
| 2846 | mode &= ~current_umask(); |
| 2847 | /* |
| 2848 | * This write is needed to ensure that a |
| 2849 | * rw->ro transition does not occur between |
| 2850 | * the time when the file is created and when |
| 2851 | * a permanent write count is taken through |
| 2852 | * the 'struct file' in finish_open(). |
| 2853 | */ |
| 2854 | if (!got_write) { |
| 2855 | error = -EROFS; |
| 2856 | goto out_dput; |
| 2857 | } |
| 2858 | *opened |= FILE_CREATED; |
| 2859 | error = security_path_mknod(&nd->path, dentry, mode, 0); |
| 2860 | if (error) |
| 2861 | goto out_dput; |
| 2862 | error = vfs_create(dir->d_inode, dentry, mode, |
| 2863 | nd->flags & LOOKUP_EXCL); |
| 2864 | if (error) |
| 2865 | goto out_dput; |
| 2866 | } |
| 2867 | out_no_open: |
| 2868 | path->dentry = dentry; |
| 2869 | path->mnt = nd->path.mnt; |
| 2870 | return 1; |
| 2871 | |
| 2872 | out_dput: |
| 2873 | dput(dentry); |
| 2874 | return error; |
| 2875 | } |
| 2876 | |
| 2877 | /* |
| 2878 | * Handle the last step of open() |
| 2879 | */ |
| 2880 | static int do_last(struct nameidata *nd, struct path *path, |
| 2881 | struct file *file, const struct open_flags *op, |
| 2882 | int *opened, struct filename *name) |
| 2883 | { |
| 2884 | struct dentry *dir = nd->path.dentry; |
| 2885 | int open_flag = op->open_flag; |
| 2886 | bool will_truncate = (open_flag & O_TRUNC) != 0; |
| 2887 | bool got_write = false; |
| 2888 | int acc_mode = op->acc_mode; |
| 2889 | struct inode *inode; |
| 2890 | bool symlink_ok = false; |
| 2891 | struct path save_parent = { .dentry = NULL, .mnt = NULL }; |
| 2892 | bool retried = false; |
| 2893 | int error; |
| 2894 | |
| 2895 | nd->flags &= ~LOOKUP_PARENT; |
| 2896 | nd->flags |= op->intent; |
| 2897 | |
| 2898 | if (nd->last_type != LAST_NORM) { |
| 2899 | error = handle_dots(nd, nd->last_type); |
| 2900 | if (error) |
| 2901 | return error; |
| 2902 | goto finish_open; |
| 2903 | } |
| 2904 | |
| 2905 | if (!(open_flag & O_CREAT)) { |
| 2906 | if (nd->last.name[nd->last.len]) |
| 2907 | nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; |
| 2908 | if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW)) |
| 2909 | symlink_ok = true; |
| 2910 | /* we _can_ be in RCU mode here */ |
| 2911 | error = lookup_fast(nd, path, &inode); |
| 2912 | if (likely(!error)) |
| 2913 | goto finish_lookup; |
| 2914 | |
| 2915 | if (error < 0) |
| 2916 | goto out; |
| 2917 | |
| 2918 | BUG_ON(nd->inode != dir->d_inode); |
| 2919 | } else { |
| 2920 | /* create side of things */ |
| 2921 | /* |
| 2922 | * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED |
| 2923 | * has been cleared when we got to the last component we are |
| 2924 | * about to look up |
| 2925 | */ |
| 2926 | error = complete_walk(nd); |
| 2927 | if (error) |
| 2928 | return error; |
| 2929 | |
| 2930 | audit_inode(name, dir, LOOKUP_PARENT); |
| 2931 | error = -EISDIR; |
| 2932 | /* trailing slashes? */ |
| 2933 | if (nd->last.name[nd->last.len]) |
| 2934 | goto out; |
| 2935 | } |
| 2936 | |
| 2937 | retry_lookup: |
| 2938 | if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) { |
| 2939 | error = mnt_want_write(nd->path.mnt); |
| 2940 | if (!error) |
| 2941 | got_write = true; |
| 2942 | /* |
| 2943 | * do _not_ fail yet - we might not need that or fail with |
| 2944 | * a different error; let lookup_open() decide; we'll be |
| 2945 | * dropping this one anyway. |
| 2946 | */ |
| 2947 | } |
| 2948 | mutex_lock(&dir->d_inode->i_mutex); |
| 2949 | error = lookup_open(nd, path, file, op, got_write, opened); |
| 2950 | mutex_unlock(&dir->d_inode->i_mutex); |
| 2951 | |
| 2952 | if (error <= 0) { |
| 2953 | if (error) |
| 2954 | goto out; |
| 2955 | |
| 2956 | if ((*opened & FILE_CREATED) || |
| 2957 | !S_ISREG(file_inode(file)->i_mode)) |
| 2958 | will_truncate = false; |
| 2959 | |
| 2960 | audit_inode(name, file->f_path.dentry, 0); |
| 2961 | goto opened; |
| 2962 | } |
| 2963 | |
| 2964 | if (*opened & FILE_CREATED) { |
| 2965 | /* Don't check for write permission, don't truncate */ |
| 2966 | open_flag &= ~O_TRUNC; |
| 2967 | will_truncate = false; |
| 2968 | acc_mode = MAY_OPEN; |
| 2969 | path_to_nameidata(path, nd); |
| 2970 | goto finish_open_created; |
| 2971 | } |
| 2972 | |
| 2973 | /* |
| 2974 | * create/update audit record if it already exists. |
| 2975 | */ |
| 2976 | if (d_is_positive(path->dentry)) |
| 2977 | audit_inode(name, path->dentry, 0); |
| 2978 | |
| 2979 | /* |
| 2980 | * If atomic_open() acquired write access it is dropped now due to |
| 2981 | * possible mount and symlink following (this might be optimized away if |
| 2982 | * necessary...) |
| 2983 | */ |
| 2984 | if (got_write) { |
| 2985 | mnt_drop_write(nd->path.mnt); |
| 2986 | got_write = false; |
| 2987 | } |
| 2988 | |
| 2989 | error = -EEXIST; |
| 2990 | if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT)) |
| 2991 | goto exit_dput; |
| 2992 | |
| 2993 | error = follow_managed(path, nd->flags); |
| 2994 | if (error < 0) |
| 2995 | goto exit_dput; |
| 2996 | |
| 2997 | if (error) |
| 2998 | nd->flags |= LOOKUP_JUMPED; |
| 2999 | |
| 3000 | BUG_ON(nd->flags & LOOKUP_RCU); |
| 3001 | inode = path->dentry->d_inode; |
| 3002 | finish_lookup: |
| 3003 | /* we _can_ be in RCU mode here */ |
| 3004 | error = -ENOENT; |
| 3005 | if (!inode || d_is_negative(path->dentry)) { |
| 3006 | path_to_nameidata(path, nd); |
| 3007 | goto out; |
| 3008 | } |
| 3009 | |
| 3010 | if (should_follow_link(path->dentry, !symlink_ok)) { |
| 3011 | if (nd->flags & LOOKUP_RCU) { |
| 3012 | if (unlikely(unlazy_walk(nd, path->dentry))) { |
| 3013 | error = -ECHILD; |
| 3014 | goto out; |
| 3015 | } |
| 3016 | } |
| 3017 | BUG_ON(inode != path->dentry->d_inode); |
| 3018 | return 1; |
| 3019 | } |
| 3020 | |
| 3021 | if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path->mnt) { |
| 3022 | path_to_nameidata(path, nd); |
| 3023 | } else { |
| 3024 | save_parent.dentry = nd->path.dentry; |
| 3025 | save_parent.mnt = mntget(path->mnt); |
| 3026 | nd->path.dentry = path->dentry; |
| 3027 | |
| 3028 | } |
| 3029 | nd->inode = inode; |
| 3030 | /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */ |
| 3031 | finish_open: |
| 3032 | error = complete_walk(nd); |
| 3033 | if (error) { |
| 3034 | path_put(&save_parent); |
| 3035 | return error; |
| 3036 | } |
| 3037 | audit_inode(name, nd->path.dentry, 0); |
| 3038 | error = -EISDIR; |
| 3039 | if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry)) |
| 3040 | goto out; |
| 3041 | error = -ENOTDIR; |
| 3042 | if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry)) |
| 3043 | goto out; |
| 3044 | if (!S_ISREG(nd->inode->i_mode)) |
| 3045 | will_truncate = false; |
| 3046 | |
| 3047 | if (will_truncate) { |
| 3048 | error = mnt_want_write(nd->path.mnt); |
| 3049 | if (error) |
| 3050 | goto out; |
| 3051 | got_write = true; |
| 3052 | } |
| 3053 | finish_open_created: |
| 3054 | error = may_open(&nd->path, acc_mode, open_flag); |
| 3055 | if (error) |
| 3056 | goto out; |
| 3057 | file->f_path.mnt = nd->path.mnt; |
| 3058 | error = finish_open(file, nd->path.dentry, NULL, opened); |
| 3059 | if (error) { |
| 3060 | if (error == -EOPENSTALE) |
| 3061 | goto stale_open; |
| 3062 | goto out; |
| 3063 | } |
| 3064 | opened: |
| 3065 | error = open_check_o_direct(file); |
| 3066 | if (error) |
| 3067 | goto exit_fput; |
| 3068 | error = ima_file_check(file, op->acc_mode); |
| 3069 | if (error) |
| 3070 | goto exit_fput; |
| 3071 | |
| 3072 | if (will_truncate) { |
| 3073 | error = handle_truncate(file); |
| 3074 | if (error) |
| 3075 | goto exit_fput; |
| 3076 | } |
| 3077 | out: |
| 3078 | if (got_write) |
| 3079 | mnt_drop_write(nd->path.mnt); |
| 3080 | path_put(&save_parent); |
| 3081 | terminate_walk(nd); |
| 3082 | return error; |
| 3083 | |
| 3084 | exit_dput: |
| 3085 | path_put_conditional(path, nd); |
| 3086 | goto out; |
| 3087 | exit_fput: |
| 3088 | fput(file); |
| 3089 | goto out; |
| 3090 | |
| 3091 | stale_open: |
| 3092 | /* If no saved parent or already retried then can't retry */ |
| 3093 | if (!save_parent.dentry || retried) |
| 3094 | goto out; |
| 3095 | |
| 3096 | BUG_ON(save_parent.dentry != dir); |
| 3097 | path_put(&nd->path); |
| 3098 | nd->path = save_parent; |
| 3099 | nd->inode = dir->d_inode; |
| 3100 | save_parent.mnt = NULL; |
| 3101 | save_parent.dentry = NULL; |
| 3102 | if (got_write) { |
| 3103 | mnt_drop_write(nd->path.mnt); |
| 3104 | got_write = false; |
| 3105 | } |
| 3106 | retried = true; |
| 3107 | goto retry_lookup; |
| 3108 | } |
| 3109 | |
| 3110 | static int do_tmpfile(int dfd, struct filename *pathname, |
| 3111 | struct nameidata *nd, int flags, |
| 3112 | const struct open_flags *op, |
| 3113 | struct file *file, int *opened) |
| 3114 | { |
| 3115 | static const struct qstr name = QSTR_INIT("/", 1); |
| 3116 | struct dentry *dentry, *child; |
| 3117 | struct inode *dir; |
| 3118 | int error = path_lookupat(dfd, pathname->name, |
| 3119 | flags | LOOKUP_DIRECTORY, nd); |
| 3120 | if (unlikely(error)) |
| 3121 | return error; |
| 3122 | error = mnt_want_write(nd->path.mnt); |
| 3123 | if (unlikely(error)) |
| 3124 | goto out; |
| 3125 | /* we want directory to be writable */ |
| 3126 | error = inode_permission(nd->inode, MAY_WRITE | MAY_EXEC); |
| 3127 | if (error) |
| 3128 | goto out2; |
| 3129 | dentry = nd->path.dentry; |
| 3130 | dir = dentry->d_inode; |
| 3131 | if (!dir->i_op->tmpfile) { |
| 3132 | error = -EOPNOTSUPP; |
| 3133 | goto out2; |
| 3134 | } |
| 3135 | child = d_alloc(dentry, &name); |
| 3136 | if (unlikely(!child)) { |
| 3137 | error = -ENOMEM; |
| 3138 | goto out2; |
| 3139 | } |
| 3140 | nd->flags &= ~LOOKUP_DIRECTORY; |
| 3141 | nd->flags |= op->intent; |
| 3142 | dput(nd->path.dentry); |
| 3143 | nd->path.dentry = child; |
| 3144 | error = dir->i_op->tmpfile(dir, nd->path.dentry, op->mode); |
| 3145 | if (error) |
| 3146 | goto out2; |
| 3147 | audit_inode(pathname, nd->path.dentry, 0); |
| 3148 | error = may_open(&nd->path, op->acc_mode, op->open_flag); |
| 3149 | if (error) |
| 3150 | goto out2; |
| 3151 | file->f_path.mnt = nd->path.mnt; |
| 3152 | error = finish_open(file, nd->path.dentry, NULL, opened); |
| 3153 | if (error) |
| 3154 | goto out2; |
| 3155 | error = open_check_o_direct(file); |
| 3156 | if (error) { |
| 3157 | fput(file); |
| 3158 | } else if (!(op->open_flag & O_EXCL)) { |
| 3159 | struct inode *inode = file_inode(file); |
| 3160 | spin_lock(&inode->i_lock); |
| 3161 | inode->i_state |= I_LINKABLE; |
| 3162 | spin_unlock(&inode->i_lock); |
| 3163 | } |
| 3164 | out2: |
| 3165 | mnt_drop_write(nd->path.mnt); |
| 3166 | out: |
| 3167 | path_put(&nd->path); |
| 3168 | return error; |
| 3169 | } |
| 3170 | |
| 3171 | static struct file *path_openat(int dfd, struct filename *pathname, |
| 3172 | struct nameidata *nd, const struct open_flags *op, int flags) |
| 3173 | { |
| 3174 | struct file *base = NULL; |
| 3175 | struct file *file; |
| 3176 | struct path path; |
| 3177 | int opened = 0; |
| 3178 | int error; |
| 3179 | |
| 3180 | file = get_empty_filp(); |
| 3181 | if (IS_ERR(file)) |
| 3182 | return file; |
| 3183 | |
| 3184 | file->f_flags = op->open_flag; |
| 3185 | |
| 3186 | if (unlikely(file->f_flags & __O_TMPFILE)) { |
| 3187 | error = do_tmpfile(dfd, pathname, nd, flags, op, file, &opened); |
| 3188 | goto out; |
| 3189 | } |
| 3190 | |
| 3191 | error = path_init(dfd, pathname->name, flags | LOOKUP_PARENT, nd, &base); |
| 3192 | if (unlikely(error)) |
| 3193 | goto out; |
| 3194 | |
| 3195 | current->total_link_count = 0; |
| 3196 | error = link_path_walk(pathname->name, nd); |
| 3197 | if (unlikely(error)) |
| 3198 | goto out; |
| 3199 | |
| 3200 | error = do_last(nd, &path, file, op, &opened, pathname); |
| 3201 | while (unlikely(error > 0)) { /* trailing symlink */ |
| 3202 | struct path link = path; |
| 3203 | void *cookie; |
| 3204 | if (!(nd->flags & LOOKUP_FOLLOW)) { |
| 3205 | path_put_conditional(&path, nd); |
| 3206 | path_put(&nd->path); |
| 3207 | error = -ELOOP; |
| 3208 | break; |
| 3209 | } |
| 3210 | error = may_follow_link(&link, nd); |
| 3211 | if (unlikely(error)) |
| 3212 | break; |
| 3213 | nd->flags |= LOOKUP_PARENT; |
| 3214 | nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL); |
| 3215 | error = follow_link(&link, nd, &cookie); |
| 3216 | if (unlikely(error)) |
| 3217 | break; |
| 3218 | error = do_last(nd, &path, file, op, &opened, pathname); |
| 3219 | put_link(nd, &link, cookie); |
| 3220 | } |
| 3221 | out: |
| 3222 | if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) |
| 3223 | path_put(&nd->root); |
| 3224 | if (base) |
| 3225 | fput(base); |
| 3226 | if (!(opened & FILE_OPENED)) { |
| 3227 | BUG_ON(!error); |
| 3228 | put_filp(file); |
| 3229 | } |
| 3230 | if (unlikely(error)) { |
| 3231 | if (error == -EOPENSTALE) { |
| 3232 | if (flags & LOOKUP_RCU) |
| 3233 | error = -ECHILD; |
| 3234 | else |
| 3235 | error = -ESTALE; |
| 3236 | } |
| 3237 | file = ERR_PTR(error); |
| 3238 | } |
| 3239 | return file; |
| 3240 | } |
| 3241 | |
| 3242 | struct file *do_filp_open(int dfd, struct filename *pathname, |
| 3243 | const struct open_flags *op) |
| 3244 | { |
| 3245 | struct nameidata nd; |
| 3246 | int flags = op->lookup_flags; |
| 3247 | struct file *filp; |
| 3248 | |
| 3249 | filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU); |
| 3250 | if (unlikely(filp == ERR_PTR(-ECHILD))) |
| 3251 | filp = path_openat(dfd, pathname, &nd, op, flags); |
| 3252 | if (unlikely(filp == ERR_PTR(-ESTALE))) |
| 3253 | filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL); |
| 3254 | return filp; |
| 3255 | } |
| 3256 | |
| 3257 | struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt, |
| 3258 | const char *name, const struct open_flags *op) |
| 3259 | { |
| 3260 | struct nameidata nd; |
| 3261 | struct file *file; |
| 3262 | struct filename filename = { .name = name }; |
| 3263 | int flags = op->lookup_flags | LOOKUP_ROOT; |
| 3264 | |
| 3265 | nd.root.mnt = mnt; |
| 3266 | nd.root.dentry = dentry; |
| 3267 | |
| 3268 | if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN) |
| 3269 | return ERR_PTR(-ELOOP); |
| 3270 | |
| 3271 | file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_RCU); |
| 3272 | if (unlikely(file == ERR_PTR(-ECHILD))) |
| 3273 | file = path_openat(-1, &filename, &nd, op, flags); |
| 3274 | if (unlikely(file == ERR_PTR(-ESTALE))) |
| 3275 | file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_REVAL); |
| 3276 | return file; |
| 3277 | } |
| 3278 | |
| 3279 | struct dentry *kern_path_create(int dfd, const char *pathname, |
| 3280 | struct path *path, unsigned int lookup_flags) |
| 3281 | { |
| 3282 | struct dentry *dentry = ERR_PTR(-EEXIST); |
| 3283 | struct nameidata nd; |
| 3284 | int err2; |
| 3285 | int error; |
| 3286 | bool is_dir = (lookup_flags & LOOKUP_DIRECTORY); |
| 3287 | |
| 3288 | /* |
| 3289 | * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any |
| 3290 | * other flags passed in are ignored! |
| 3291 | */ |
| 3292 | lookup_flags &= LOOKUP_REVAL; |
| 3293 | |
| 3294 | error = do_path_lookup(dfd, pathname, LOOKUP_PARENT|lookup_flags, &nd); |
| 3295 | if (error) |
| 3296 | return ERR_PTR(error); |
| 3297 | |
| 3298 | /* |
| 3299 | * Yucky last component or no last component at all? |
| 3300 | * (foo/., foo/.., /////) |
| 3301 | */ |
| 3302 | if (nd.last_type != LAST_NORM) |
| 3303 | goto out; |
| 3304 | nd.flags &= ~LOOKUP_PARENT; |
| 3305 | nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL; |
| 3306 | |
| 3307 | /* don't fail immediately if it's r/o, at least try to report other errors */ |
| 3308 | err2 = mnt_want_write(nd.path.mnt); |
| 3309 | /* |
| 3310 | * Do the final lookup. |
| 3311 | */ |
| 3312 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); |
| 3313 | dentry = lookup_hash(&nd); |
| 3314 | if (IS_ERR(dentry)) |
| 3315 | goto unlock; |
| 3316 | |
| 3317 | error = -EEXIST; |
| 3318 | if (d_is_positive(dentry)) |
| 3319 | goto fail; |
| 3320 | |
| 3321 | /* |
| 3322 | * Special case - lookup gave negative, but... we had foo/bar/ |
| 3323 | * From the vfs_mknod() POV we just have a negative dentry - |
| 3324 | * all is fine. Let's be bastards - you had / on the end, you've |
| 3325 | * been asking for (non-existent) directory. -ENOENT for you. |
| 3326 | */ |
| 3327 | if (unlikely(!is_dir && nd.last.name[nd.last.len])) { |
| 3328 | error = -ENOENT; |
| 3329 | goto fail; |
| 3330 | } |
| 3331 | if (unlikely(err2)) { |
| 3332 | error = err2; |
| 3333 | goto fail; |
| 3334 | } |
| 3335 | *path = nd.path; |
| 3336 | return dentry; |
| 3337 | fail: |
| 3338 | dput(dentry); |
| 3339 | dentry = ERR_PTR(error); |
| 3340 | unlock: |
| 3341 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
| 3342 | if (!err2) |
| 3343 | mnt_drop_write(nd.path.mnt); |
| 3344 | out: |
| 3345 | path_put(&nd.path); |
| 3346 | return dentry; |
| 3347 | } |
| 3348 | EXPORT_SYMBOL(kern_path_create); |
| 3349 | |
| 3350 | void done_path_create(struct path *path, struct dentry *dentry) |
| 3351 | { |
| 3352 | dput(dentry); |
| 3353 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
| 3354 | mnt_drop_write(path->mnt); |
| 3355 | path_put(path); |
| 3356 | } |
| 3357 | EXPORT_SYMBOL(done_path_create); |
| 3358 | |
| 3359 | struct dentry *user_path_create(int dfd, const char __user *pathname, |
| 3360 | struct path *path, unsigned int lookup_flags) |
| 3361 | { |
| 3362 | struct filename *tmp = getname(pathname); |
| 3363 | struct dentry *res; |
| 3364 | if (IS_ERR(tmp)) |
| 3365 | return ERR_CAST(tmp); |
| 3366 | res = kern_path_create(dfd, tmp->name, path, lookup_flags); |
| 3367 | putname(tmp); |
| 3368 | return res; |
| 3369 | } |
| 3370 | EXPORT_SYMBOL(user_path_create); |
| 3371 | |
| 3372 | int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) |
| 3373 | { |
| 3374 | int error = may_create(dir, dentry); |
| 3375 | |
| 3376 | if (error) |
| 3377 | return error; |
| 3378 | |
| 3379 | if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD)) |
| 3380 | return -EPERM; |
| 3381 | |
| 3382 | if (!dir->i_op->mknod) |
| 3383 | return -EPERM; |
| 3384 | |
| 3385 | error = devcgroup_inode_mknod(mode, dev); |
| 3386 | if (error) |
| 3387 | return error; |
| 3388 | |
| 3389 | error = security_inode_mknod(dir, dentry, mode, dev); |
| 3390 | if (error) |
| 3391 | return error; |
| 3392 | |
| 3393 | error = dir->i_op->mknod(dir, dentry, mode, dev); |
| 3394 | if (!error) |
| 3395 | fsnotify_create(dir, dentry); |
| 3396 | return error; |
| 3397 | } |
| 3398 | EXPORT_SYMBOL(vfs_mknod); |
| 3399 | |
| 3400 | static int may_mknod(umode_t mode) |
| 3401 | { |
| 3402 | switch (mode & S_IFMT) { |
| 3403 | case S_IFREG: |
| 3404 | case S_IFCHR: |
| 3405 | case S_IFBLK: |
| 3406 | case S_IFIFO: |
| 3407 | case S_IFSOCK: |
| 3408 | case 0: /* zero mode translates to S_IFREG */ |
| 3409 | return 0; |
| 3410 | case S_IFDIR: |
| 3411 | return -EPERM; |
| 3412 | default: |
| 3413 | return -EINVAL; |
| 3414 | } |
| 3415 | } |
| 3416 | |
| 3417 | SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode, |
| 3418 | unsigned, dev) |
| 3419 | { |
| 3420 | struct dentry *dentry; |
| 3421 | struct path path; |
| 3422 | int error; |
| 3423 | unsigned int lookup_flags = 0; |
| 3424 | |
| 3425 | error = may_mknod(mode); |
| 3426 | if (error) |
| 3427 | return error; |
| 3428 | retry: |
| 3429 | dentry = user_path_create(dfd, filename, &path, lookup_flags); |
| 3430 | if (IS_ERR(dentry)) |
| 3431 | return PTR_ERR(dentry); |
| 3432 | |
| 3433 | if (!IS_POSIXACL(path.dentry->d_inode)) |
| 3434 | mode &= ~current_umask(); |
| 3435 | error = security_path_mknod(&path, dentry, mode, dev); |
| 3436 | if (error) |
| 3437 | goto out; |
| 3438 | switch (mode & S_IFMT) { |
| 3439 | case 0: case S_IFREG: |
| 3440 | error = vfs_create(path.dentry->d_inode,dentry,mode,true); |
| 3441 | break; |
| 3442 | case S_IFCHR: case S_IFBLK: |
| 3443 | error = vfs_mknod(path.dentry->d_inode,dentry,mode, |
| 3444 | new_decode_dev(dev)); |
| 3445 | break; |
| 3446 | case S_IFIFO: case S_IFSOCK: |
| 3447 | error = vfs_mknod(path.dentry->d_inode,dentry,mode,0); |
| 3448 | break; |
| 3449 | } |
| 3450 | out: |
| 3451 | done_path_create(&path, dentry); |
| 3452 | if (retry_estale(error, lookup_flags)) { |
| 3453 | lookup_flags |= LOOKUP_REVAL; |
| 3454 | goto retry; |
| 3455 | } |
| 3456 | return error; |
| 3457 | } |
| 3458 | |
| 3459 | SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev) |
| 3460 | { |
| 3461 | return sys_mknodat(AT_FDCWD, filename, mode, dev); |
| 3462 | } |
| 3463 | |
| 3464 | int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) |
| 3465 | { |
| 3466 | int error = may_create(dir, dentry); |
| 3467 | unsigned max_links = dir->i_sb->s_max_links; |
| 3468 | |
| 3469 | if (error) |
| 3470 | return error; |
| 3471 | |
| 3472 | if (!dir->i_op->mkdir) |
| 3473 | return -EPERM; |
| 3474 | |
| 3475 | mode &= (S_IRWXUGO|S_ISVTX); |
| 3476 | error = security_inode_mkdir(dir, dentry, mode); |
| 3477 | if (error) |
| 3478 | return error; |
| 3479 | |
| 3480 | if (max_links && dir->i_nlink >= max_links) |
| 3481 | return -EMLINK; |
| 3482 | |
| 3483 | error = dir->i_op->mkdir(dir, dentry, mode); |
| 3484 | if (!error) |
| 3485 | fsnotify_mkdir(dir, dentry); |
| 3486 | return error; |
| 3487 | } |
| 3488 | EXPORT_SYMBOL(vfs_mkdir); |
| 3489 | |
| 3490 | SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode) |
| 3491 | { |
| 3492 | struct dentry *dentry; |
| 3493 | struct path path; |
| 3494 | int error; |
| 3495 | unsigned int lookup_flags = LOOKUP_DIRECTORY; |
| 3496 | |
| 3497 | retry: |
| 3498 | dentry = user_path_create(dfd, pathname, &path, lookup_flags); |
| 3499 | if (IS_ERR(dentry)) |
| 3500 | return PTR_ERR(dentry); |
| 3501 | |
| 3502 | if (!IS_POSIXACL(path.dentry->d_inode)) |
| 3503 | mode &= ~current_umask(); |
| 3504 | error = security_path_mkdir(&path, dentry, mode); |
| 3505 | if (!error) |
| 3506 | error = vfs_mkdir(path.dentry->d_inode, dentry, mode); |
| 3507 | done_path_create(&path, dentry); |
| 3508 | if (retry_estale(error, lookup_flags)) { |
| 3509 | lookup_flags |= LOOKUP_REVAL; |
| 3510 | goto retry; |
| 3511 | } |
| 3512 | return error; |
| 3513 | } |
| 3514 | |
| 3515 | SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode) |
| 3516 | { |
| 3517 | return sys_mkdirat(AT_FDCWD, pathname, mode); |
| 3518 | } |
| 3519 | |
| 3520 | /* |
| 3521 | * The dentry_unhash() helper will try to drop the dentry early: we |
| 3522 | * should have a usage count of 1 if we're the only user of this |
| 3523 | * dentry, and if that is true (possibly after pruning the dcache), |
| 3524 | * then we drop the dentry now. |
| 3525 | * |
| 3526 | * A low-level filesystem can, if it choses, legally |
| 3527 | * do a |
| 3528 | * |
| 3529 | * if (!d_unhashed(dentry)) |
| 3530 | * return -EBUSY; |
| 3531 | * |
| 3532 | * if it cannot handle the case of removing a directory |
| 3533 | * that is still in use by something else.. |
| 3534 | */ |
| 3535 | void dentry_unhash(struct dentry *dentry) |
| 3536 | { |
| 3537 | shrink_dcache_parent(dentry); |
| 3538 | spin_lock(&dentry->d_lock); |
| 3539 | if (dentry->d_lockref.count == 1) |
| 3540 | __d_drop(dentry); |
| 3541 | spin_unlock(&dentry->d_lock); |
| 3542 | } |
| 3543 | EXPORT_SYMBOL(dentry_unhash); |
| 3544 | |
| 3545 | int vfs_rmdir(struct inode *dir, struct dentry *dentry) |
| 3546 | { |
| 3547 | int error = may_delete(dir, dentry, 1); |
| 3548 | |
| 3549 | if (error) |
| 3550 | return error; |
| 3551 | |
| 3552 | if (!dir->i_op->rmdir) |
| 3553 | return -EPERM; |
| 3554 | |
| 3555 | dget(dentry); |
| 3556 | mutex_lock(&dentry->d_inode->i_mutex); |
| 3557 | |
| 3558 | error = -EBUSY; |
| 3559 | if (d_mountpoint(dentry)) |
| 3560 | goto out; |
| 3561 | |
| 3562 | error = security_inode_rmdir(dir, dentry); |
| 3563 | if (error) |
| 3564 | goto out; |
| 3565 | |
| 3566 | shrink_dcache_parent(dentry); |
| 3567 | error = dir->i_op->rmdir(dir, dentry); |
| 3568 | if (error) |
| 3569 | goto out; |
| 3570 | |
| 3571 | dentry->d_inode->i_flags |= S_DEAD; |
| 3572 | dont_mount(dentry); |
| 3573 | |
| 3574 | out: |
| 3575 | mutex_unlock(&dentry->d_inode->i_mutex); |
| 3576 | dput(dentry); |
| 3577 | if (!error) |
| 3578 | d_delete(dentry); |
| 3579 | return error; |
| 3580 | } |
| 3581 | EXPORT_SYMBOL(vfs_rmdir); |
| 3582 | |
| 3583 | static long do_rmdir(int dfd, const char __user *pathname) |
| 3584 | { |
| 3585 | int error = 0; |
| 3586 | struct filename *name; |
| 3587 | struct dentry *dentry; |
| 3588 | struct nameidata nd; |
| 3589 | unsigned int lookup_flags = 0; |
| 3590 | retry: |
| 3591 | name = user_path_parent(dfd, pathname, &nd, lookup_flags); |
| 3592 | if (IS_ERR(name)) |
| 3593 | return PTR_ERR(name); |
| 3594 | |
| 3595 | switch(nd.last_type) { |
| 3596 | case LAST_DOTDOT: |
| 3597 | error = -ENOTEMPTY; |
| 3598 | goto exit1; |
| 3599 | case LAST_DOT: |
| 3600 | error = -EINVAL; |
| 3601 | goto exit1; |
| 3602 | case LAST_ROOT: |
| 3603 | error = -EBUSY; |
| 3604 | goto exit1; |
| 3605 | } |
| 3606 | |
| 3607 | nd.flags &= ~LOOKUP_PARENT; |
| 3608 | error = mnt_want_write(nd.path.mnt); |
| 3609 | if (error) |
| 3610 | goto exit1; |
| 3611 | |
| 3612 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); |
| 3613 | dentry = lookup_hash(&nd); |
| 3614 | error = PTR_ERR(dentry); |
| 3615 | if (IS_ERR(dentry)) |
| 3616 | goto exit2; |
| 3617 | if (!dentry->d_inode) { |
| 3618 | error = -ENOENT; |
| 3619 | goto exit3; |
| 3620 | } |
| 3621 | error = security_path_rmdir(&nd.path, dentry); |
| 3622 | if (error) |
| 3623 | goto exit3; |
| 3624 | error = vfs_rmdir(nd.path.dentry->d_inode, dentry); |
| 3625 | exit3: |
| 3626 | dput(dentry); |
| 3627 | exit2: |
| 3628 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
| 3629 | mnt_drop_write(nd.path.mnt); |
| 3630 | exit1: |
| 3631 | path_put(&nd.path); |
| 3632 | putname(name); |
| 3633 | if (retry_estale(error, lookup_flags)) { |
| 3634 | lookup_flags |= LOOKUP_REVAL; |
| 3635 | goto retry; |
| 3636 | } |
| 3637 | return error; |
| 3638 | } |
| 3639 | |
| 3640 | SYSCALL_DEFINE1(rmdir, const char __user *, pathname) |
| 3641 | { |
| 3642 | return do_rmdir(AT_FDCWD, pathname); |
| 3643 | } |
| 3644 | |
| 3645 | /** |
| 3646 | * vfs_unlink - unlink a filesystem object |
| 3647 | * @dir: parent directory |
| 3648 | * @dentry: victim |
| 3649 | * @delegated_inode: returns victim inode, if the inode is delegated. |
| 3650 | * |
| 3651 | * The caller must hold dir->i_mutex. |
| 3652 | * |
| 3653 | * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and |
| 3654 | * return a reference to the inode in delegated_inode. The caller |
| 3655 | * should then break the delegation on that inode and retry. Because |
| 3656 | * breaking a delegation may take a long time, the caller should drop |
| 3657 | * dir->i_mutex before doing so. |
| 3658 | * |
| 3659 | * Alternatively, a caller may pass NULL for delegated_inode. This may |
| 3660 | * be appropriate for callers that expect the underlying filesystem not |
| 3661 | * to be NFS exported. |
| 3662 | */ |
| 3663 | int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode) |
| 3664 | { |
| 3665 | struct inode *target = dentry->d_inode; |
| 3666 | int error = may_delete(dir, dentry, 0); |
| 3667 | |
| 3668 | if (error) |
| 3669 | return error; |
| 3670 | |
| 3671 | if (!dir->i_op->unlink) |
| 3672 | return -EPERM; |
| 3673 | |
| 3674 | mutex_lock(&target->i_mutex); |
| 3675 | if (d_mountpoint(dentry)) |
| 3676 | error = -EBUSY; |
| 3677 | else { |
| 3678 | error = security_inode_unlink(dir, dentry); |
| 3679 | if (!error) { |
| 3680 | error = try_break_deleg(target, delegated_inode); |
| 3681 | if (error) |
| 3682 | goto out; |
| 3683 | error = dir->i_op->unlink(dir, dentry); |
| 3684 | if (!error) |
| 3685 | dont_mount(dentry); |
| 3686 | } |
| 3687 | } |
| 3688 | out: |
| 3689 | mutex_unlock(&target->i_mutex); |
| 3690 | |
| 3691 | /* We don't d_delete() NFS sillyrenamed files--they still exist. */ |
| 3692 | if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) { |
| 3693 | fsnotify_link_count(target); |
| 3694 | d_delete(dentry); |
| 3695 | } |
| 3696 | |
| 3697 | return error; |
| 3698 | } |
| 3699 | EXPORT_SYMBOL(vfs_unlink); |
| 3700 | |
| 3701 | /* |
| 3702 | * Make sure that the actual truncation of the file will occur outside its |
| 3703 | * directory's i_mutex. Truncate can take a long time if there is a lot of |
| 3704 | * writeout happening, and we don't want to prevent access to the directory |
| 3705 | * while waiting on the I/O. |
| 3706 | */ |
| 3707 | static long do_unlinkat(int dfd, const char __user *pathname) |
| 3708 | { |
| 3709 | int error; |
| 3710 | struct filename *name; |
| 3711 | struct dentry *dentry; |
| 3712 | struct nameidata nd; |
| 3713 | struct inode *inode = NULL; |
| 3714 | struct inode *delegated_inode = NULL; |
| 3715 | unsigned int lookup_flags = 0; |
| 3716 | retry: |
| 3717 | name = user_path_parent(dfd, pathname, &nd, lookup_flags); |
| 3718 | if (IS_ERR(name)) |
| 3719 | return PTR_ERR(name); |
| 3720 | |
| 3721 | error = -EISDIR; |
| 3722 | if (nd.last_type != LAST_NORM) |
| 3723 | goto exit1; |
| 3724 | |
| 3725 | nd.flags &= ~LOOKUP_PARENT; |
| 3726 | error = mnt_want_write(nd.path.mnt); |
| 3727 | if (error) |
| 3728 | goto exit1; |
| 3729 | retry_deleg: |
| 3730 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); |
| 3731 | dentry = lookup_hash(&nd); |
| 3732 | error = PTR_ERR(dentry); |
| 3733 | if (!IS_ERR(dentry)) { |
| 3734 | /* Why not before? Because we want correct error value */ |
| 3735 | if (nd.last.name[nd.last.len]) |
| 3736 | goto slashes; |
| 3737 | inode = dentry->d_inode; |
| 3738 | if (d_is_negative(dentry)) |
| 3739 | goto slashes; |
| 3740 | ihold(inode); |
| 3741 | error = security_path_unlink(&nd.path, dentry); |
| 3742 | if (error) |
| 3743 | goto exit2; |
| 3744 | error = vfs_unlink(nd.path.dentry->d_inode, dentry, &delegated_inode); |
| 3745 | exit2: |
| 3746 | dput(dentry); |
| 3747 | } |
| 3748 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
| 3749 | if (inode) |
| 3750 | iput(inode); /* truncate the inode here */ |
| 3751 | inode = NULL; |
| 3752 | if (delegated_inode) { |
| 3753 | error = break_deleg_wait(&delegated_inode); |
| 3754 | if (!error) |
| 3755 | goto retry_deleg; |
| 3756 | } |
| 3757 | mnt_drop_write(nd.path.mnt); |
| 3758 | exit1: |
| 3759 | path_put(&nd.path); |
| 3760 | putname(name); |
| 3761 | if (retry_estale(error, lookup_flags)) { |
| 3762 | lookup_flags |= LOOKUP_REVAL; |
| 3763 | inode = NULL; |
| 3764 | goto retry; |
| 3765 | } |
| 3766 | return error; |
| 3767 | |
| 3768 | slashes: |
| 3769 | if (d_is_negative(dentry)) |
| 3770 | error = -ENOENT; |
| 3771 | else if (d_is_dir(dentry)) |
| 3772 | error = -EISDIR; |
| 3773 | else |
| 3774 | error = -ENOTDIR; |
| 3775 | goto exit2; |
| 3776 | } |
| 3777 | |
| 3778 | SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag) |
| 3779 | { |
| 3780 | if ((flag & ~AT_REMOVEDIR) != 0) |
| 3781 | return -EINVAL; |
| 3782 | |
| 3783 | if (flag & AT_REMOVEDIR) |
| 3784 | return do_rmdir(dfd, pathname); |
| 3785 | |
| 3786 | return do_unlinkat(dfd, pathname); |
| 3787 | } |
| 3788 | |
| 3789 | SYSCALL_DEFINE1(unlink, const char __user *, pathname) |
| 3790 | { |
| 3791 | return do_unlinkat(AT_FDCWD, pathname); |
| 3792 | } |
| 3793 | |
| 3794 | int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname) |
| 3795 | { |
| 3796 | int error = may_create(dir, dentry); |
| 3797 | |
| 3798 | if (error) |
| 3799 | return error; |
| 3800 | |
| 3801 | if (!dir->i_op->symlink) |
| 3802 | return -EPERM; |
| 3803 | |
| 3804 | error = security_inode_symlink(dir, dentry, oldname); |
| 3805 | if (error) |
| 3806 | return error; |
| 3807 | |
| 3808 | error = dir->i_op->symlink(dir, dentry, oldname); |
| 3809 | if (!error) |
| 3810 | fsnotify_create(dir, dentry); |
| 3811 | return error; |
| 3812 | } |
| 3813 | EXPORT_SYMBOL(vfs_symlink); |
| 3814 | |
| 3815 | SYSCALL_DEFINE3(symlinkat, const char __user *, oldname, |
| 3816 | int, newdfd, const char __user *, newname) |
| 3817 | { |
| 3818 | int error; |
| 3819 | struct filename *from; |
| 3820 | struct dentry *dentry; |
| 3821 | struct path path; |
| 3822 | unsigned int lookup_flags = 0; |
| 3823 | |
| 3824 | from = getname(oldname); |
| 3825 | if (IS_ERR(from)) |
| 3826 | return PTR_ERR(from); |
| 3827 | retry: |
| 3828 | dentry = user_path_create(newdfd, newname, &path, lookup_flags); |
| 3829 | error = PTR_ERR(dentry); |
| 3830 | if (IS_ERR(dentry)) |
| 3831 | goto out_putname; |
| 3832 | |
| 3833 | error = security_path_symlink(&path, dentry, from->name); |
| 3834 | if (!error) |
| 3835 | error = vfs_symlink(path.dentry->d_inode, dentry, from->name); |
| 3836 | done_path_create(&path, dentry); |
| 3837 | if (retry_estale(error, lookup_flags)) { |
| 3838 | lookup_flags |= LOOKUP_REVAL; |
| 3839 | goto retry; |
| 3840 | } |
| 3841 | out_putname: |
| 3842 | putname(from); |
| 3843 | return error; |
| 3844 | } |
| 3845 | |
| 3846 | SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname) |
| 3847 | { |
| 3848 | return sys_symlinkat(oldname, AT_FDCWD, newname); |
| 3849 | } |
| 3850 | |
| 3851 | /** |
| 3852 | * vfs_link - create a new link |
| 3853 | * @old_dentry: object to be linked |
| 3854 | * @dir: new parent |
| 3855 | * @new_dentry: where to create the new link |
| 3856 | * @delegated_inode: returns inode needing a delegation break |
| 3857 | * |
| 3858 | * The caller must hold dir->i_mutex |
| 3859 | * |
| 3860 | * If vfs_link discovers a delegation on the to-be-linked file in need |
| 3861 | * of breaking, it will return -EWOULDBLOCK and return a reference to the |
| 3862 | * inode in delegated_inode. The caller should then break the delegation |
| 3863 | * and retry. Because breaking a delegation may take a long time, the |
| 3864 | * caller should drop the i_mutex before doing so. |
| 3865 | * |
| 3866 | * Alternatively, a caller may pass NULL for delegated_inode. This may |
| 3867 | * be appropriate for callers that expect the underlying filesystem not |
| 3868 | * to be NFS exported. |
| 3869 | */ |
| 3870 | int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode) |
| 3871 | { |
| 3872 | struct inode *inode = old_dentry->d_inode; |
| 3873 | unsigned max_links = dir->i_sb->s_max_links; |
| 3874 | int error; |
| 3875 | |
| 3876 | if (!inode) |
| 3877 | return -ENOENT; |
| 3878 | |
| 3879 | error = may_create(dir, new_dentry); |
| 3880 | if (error) |
| 3881 | return error; |
| 3882 | |
| 3883 | if (dir->i_sb != inode->i_sb) |
| 3884 | return -EXDEV; |
| 3885 | |
| 3886 | /* |
| 3887 | * A link to an append-only or immutable file cannot be created. |
| 3888 | */ |
| 3889 | if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) |
| 3890 | return -EPERM; |
| 3891 | if (!dir->i_op->link) |
| 3892 | return -EPERM; |
| 3893 | if (S_ISDIR(inode->i_mode)) |
| 3894 | return -EPERM; |
| 3895 | |
| 3896 | error = security_inode_link(old_dentry, dir, new_dentry); |
| 3897 | if (error) |
| 3898 | return error; |
| 3899 | |
| 3900 | mutex_lock(&inode->i_mutex); |
| 3901 | /* Make sure we don't allow creating hardlink to an unlinked file */ |
| 3902 | if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE)) |
| 3903 | error = -ENOENT; |
| 3904 | else if (max_links && inode->i_nlink >= max_links) |
| 3905 | error = -EMLINK; |
| 3906 | else { |
| 3907 | error = try_break_deleg(inode, delegated_inode); |
| 3908 | if (!error) |
| 3909 | error = dir->i_op->link(old_dentry, dir, new_dentry); |
| 3910 | } |
| 3911 | |
| 3912 | if (!error && (inode->i_state & I_LINKABLE)) { |
| 3913 | spin_lock(&inode->i_lock); |
| 3914 | inode->i_state &= ~I_LINKABLE; |
| 3915 | spin_unlock(&inode->i_lock); |
| 3916 | } |
| 3917 | mutex_unlock(&inode->i_mutex); |
| 3918 | if (!error) |
| 3919 | fsnotify_link(dir, inode, new_dentry); |
| 3920 | return error; |
| 3921 | } |
| 3922 | EXPORT_SYMBOL(vfs_link); |
| 3923 | |
| 3924 | /* |
| 3925 | * Hardlinks are often used in delicate situations. We avoid |
| 3926 | * security-related surprises by not following symlinks on the |
| 3927 | * newname. --KAB |
| 3928 | * |
| 3929 | * We don't follow them on the oldname either to be compatible |
| 3930 | * with linux 2.0, and to avoid hard-linking to directories |
| 3931 | * and other special files. --ADM |
| 3932 | */ |
| 3933 | SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname, |
| 3934 | int, newdfd, const char __user *, newname, int, flags) |
| 3935 | { |
| 3936 | struct dentry *new_dentry; |
| 3937 | struct path old_path, new_path; |
| 3938 | struct inode *delegated_inode = NULL; |
| 3939 | int how = 0; |
| 3940 | int error; |
| 3941 | |
| 3942 | if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) |
| 3943 | return -EINVAL; |
| 3944 | /* |
| 3945 | * To use null names we require CAP_DAC_READ_SEARCH |
| 3946 | * This ensures that not everyone will be able to create |
| 3947 | * handlink using the passed filedescriptor. |
| 3948 | */ |
| 3949 | if (flags & AT_EMPTY_PATH) { |
| 3950 | if (!capable(CAP_DAC_READ_SEARCH)) |
| 3951 | return -ENOENT; |
| 3952 | how = LOOKUP_EMPTY; |
| 3953 | } |
| 3954 | |
| 3955 | if (flags & AT_SYMLINK_FOLLOW) |
| 3956 | how |= LOOKUP_FOLLOW; |
| 3957 | retry: |
| 3958 | error = user_path_at(olddfd, oldname, how, &old_path); |
| 3959 | if (error) |
| 3960 | return error; |
| 3961 | |
| 3962 | new_dentry = user_path_create(newdfd, newname, &new_path, |
| 3963 | (how & LOOKUP_REVAL)); |
| 3964 | error = PTR_ERR(new_dentry); |
| 3965 | if (IS_ERR(new_dentry)) |
| 3966 | goto out; |
| 3967 | |
| 3968 | error = -EXDEV; |
| 3969 | if (old_path.mnt != new_path.mnt) |
| 3970 | goto out_dput; |
| 3971 | error = may_linkat(&old_path); |
| 3972 | if (unlikely(error)) |
| 3973 | goto out_dput; |
| 3974 | error = security_path_link(old_path.dentry, &new_path, new_dentry); |
| 3975 | if (error) |
| 3976 | goto out_dput; |
| 3977 | error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, &delegated_inode); |
| 3978 | out_dput: |
| 3979 | done_path_create(&new_path, new_dentry); |
| 3980 | if (delegated_inode) { |
| 3981 | error = break_deleg_wait(&delegated_inode); |
| 3982 | if (!error) { |
| 3983 | path_put(&old_path); |
| 3984 | goto retry; |
| 3985 | } |
| 3986 | } |
| 3987 | if (retry_estale(error, how)) { |
| 3988 | path_put(&old_path); |
| 3989 | how |= LOOKUP_REVAL; |
| 3990 | goto retry; |
| 3991 | } |
| 3992 | out: |
| 3993 | path_put(&old_path); |
| 3994 | |
| 3995 | return error; |
| 3996 | } |
| 3997 | |
| 3998 | SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname) |
| 3999 | { |
| 4000 | return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0); |
| 4001 | } |
| 4002 | |
| 4003 | /** |
| 4004 | * vfs_rename - rename a filesystem object |
| 4005 | * @old_dir: parent of source |
| 4006 | * @old_dentry: source |
| 4007 | * @new_dir: parent of destination |
| 4008 | * @new_dentry: destination |
| 4009 | * @delegated_inode: returns an inode needing a delegation break |
| 4010 | * @flags: rename flags |
| 4011 | * |
| 4012 | * The caller must hold multiple mutexes--see lock_rename()). |
| 4013 | * |
| 4014 | * If vfs_rename discovers a delegation in need of breaking at either |
| 4015 | * the source or destination, it will return -EWOULDBLOCK and return a |
| 4016 | * reference to the inode in delegated_inode. The caller should then |
| 4017 | * break the delegation and retry. Because breaking a delegation may |
| 4018 | * take a long time, the caller should drop all locks before doing |
| 4019 | * so. |
| 4020 | * |
| 4021 | * Alternatively, a caller may pass NULL for delegated_inode. This may |
| 4022 | * be appropriate for callers that expect the underlying filesystem not |
| 4023 | * to be NFS exported. |
| 4024 | * |
| 4025 | * The worst of all namespace operations - renaming directory. "Perverted" |
| 4026 | * doesn't even start to describe it. Somebody in UCB had a heck of a trip... |
| 4027 | * Problems: |
| 4028 | * a) we can get into loop creation. |
| 4029 | * b) race potential - two innocent renames can create a loop together. |
| 4030 | * That's where 4.4 screws up. Current fix: serialization on |
| 4031 | * sb->s_vfs_rename_mutex. We might be more accurate, but that's another |
| 4032 | * story. |
| 4033 | * c) we have to lock _four_ objects - parents and victim (if it exists), |
| 4034 | * and source (if it is not a directory). |
| 4035 | * And that - after we got ->i_mutex on parents (until then we don't know |
| 4036 | * whether the target exists). Solution: try to be smart with locking |
| 4037 | * order for inodes. We rely on the fact that tree topology may change |
| 4038 | * only under ->s_vfs_rename_mutex _and_ that parent of the object we |
| 4039 | * move will be locked. Thus we can rank directories by the tree |
| 4040 | * (ancestors first) and rank all non-directories after them. |
| 4041 | * That works since everybody except rename does "lock parent, lookup, |
| 4042 | * lock child" and rename is under ->s_vfs_rename_mutex. |
| 4043 | * HOWEVER, it relies on the assumption that any object with ->lookup() |
| 4044 | * has no more than 1 dentry. If "hybrid" objects will ever appear, |
| 4045 | * we'd better make sure that there's no link(2) for them. |
| 4046 | * d) conversion from fhandle to dentry may come in the wrong moment - when |
| 4047 | * we are removing the target. Solution: we will have to grab ->i_mutex |
| 4048 | * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on |
| 4049 | * ->i_mutex on parents, which works but leads to some truly excessive |
| 4050 | * locking]. |
| 4051 | */ |
| 4052 | int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, |
| 4053 | struct inode *new_dir, struct dentry *new_dentry, |
| 4054 | struct inode **delegated_inode, unsigned int flags) |
| 4055 | { |
| 4056 | int error; |
| 4057 | bool is_dir = d_is_dir(old_dentry); |
| 4058 | const unsigned char *old_name; |
| 4059 | struct inode *source = old_dentry->d_inode; |
| 4060 | struct inode *target = new_dentry->d_inode; |
| 4061 | bool new_is_dir = false; |
| 4062 | unsigned max_links = new_dir->i_sb->s_max_links; |
| 4063 | |
| 4064 | if (source == target) |
| 4065 | return 0; |
| 4066 | |
| 4067 | error = may_delete(old_dir, old_dentry, is_dir); |
| 4068 | if (error) |
| 4069 | return error; |
| 4070 | |
| 4071 | if (!target) { |
| 4072 | error = may_create(new_dir, new_dentry); |
| 4073 | } else { |
| 4074 | new_is_dir = d_is_dir(new_dentry); |
| 4075 | |
| 4076 | if (!(flags & RENAME_EXCHANGE)) |
| 4077 | error = may_delete(new_dir, new_dentry, is_dir); |
| 4078 | else |
| 4079 | error = may_delete(new_dir, new_dentry, new_is_dir); |
| 4080 | } |
| 4081 | if (error) |
| 4082 | return error; |
| 4083 | |
| 4084 | if (!old_dir->i_op->rename && !old_dir->i_op->rename2) |
| 4085 | return -EPERM; |
| 4086 | |
| 4087 | if (flags && !old_dir->i_op->rename2) |
| 4088 | return -EINVAL; |
| 4089 | |
| 4090 | /* |
| 4091 | * If we are going to change the parent - check write permissions, |
| 4092 | * we'll need to flip '..'. |
| 4093 | */ |
| 4094 | if (new_dir != old_dir) { |
| 4095 | if (is_dir) { |
| 4096 | error = inode_permission(source, MAY_WRITE); |
| 4097 | if (error) |
| 4098 | return error; |
| 4099 | } |
| 4100 | if ((flags & RENAME_EXCHANGE) && new_is_dir) { |
| 4101 | error = inode_permission(target, MAY_WRITE); |
| 4102 | if (error) |
| 4103 | return error; |
| 4104 | } |
| 4105 | } |
| 4106 | |
| 4107 | error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry, |
| 4108 | flags); |
| 4109 | if (error) |
| 4110 | return error; |
| 4111 | |
| 4112 | old_name = fsnotify_oldname_init(old_dentry->d_name.name); |
| 4113 | dget(new_dentry); |
| 4114 | if (!is_dir || (flags & RENAME_EXCHANGE)) |
| 4115 | lock_two_nondirectories(source, target); |
| 4116 | else if (target) |
| 4117 | mutex_lock(&target->i_mutex); |
| 4118 | |
| 4119 | error = -EBUSY; |
| 4120 | if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry)) |
| 4121 | goto out; |
| 4122 | |
| 4123 | if (max_links && new_dir != old_dir) { |
| 4124 | error = -EMLINK; |
| 4125 | if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links) |
| 4126 | goto out; |
| 4127 | if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir && |
| 4128 | old_dir->i_nlink >= max_links) |
| 4129 | goto out; |
| 4130 | } |
| 4131 | if (is_dir && !(flags & RENAME_EXCHANGE) && target) |
| 4132 | shrink_dcache_parent(new_dentry); |
| 4133 | if (!is_dir) { |
| 4134 | error = try_break_deleg(source, delegated_inode); |
| 4135 | if (error) |
| 4136 | goto out; |
| 4137 | } |
| 4138 | if (target && !new_is_dir) { |
| 4139 | error = try_break_deleg(target, delegated_inode); |
| 4140 | if (error) |
| 4141 | goto out; |
| 4142 | } |
| 4143 | if (!old_dir->i_op->rename2) { |
| 4144 | error = old_dir->i_op->rename(old_dir, old_dentry, |
| 4145 | new_dir, new_dentry); |
| 4146 | } else { |
| 4147 | WARN_ON(old_dir->i_op->rename != NULL); |
| 4148 | error = old_dir->i_op->rename2(old_dir, old_dentry, |
| 4149 | new_dir, new_dentry, flags); |
| 4150 | } |
| 4151 | if (error) |
| 4152 | goto out; |
| 4153 | |
| 4154 | if (!(flags & RENAME_EXCHANGE) && target) { |
| 4155 | if (is_dir) |
| 4156 | target->i_flags |= S_DEAD; |
| 4157 | dont_mount(new_dentry); |
| 4158 | } |
| 4159 | if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) { |
| 4160 | if (!(flags & RENAME_EXCHANGE)) |
| 4161 | d_move(old_dentry, new_dentry); |
| 4162 | else |
| 4163 | d_exchange(old_dentry, new_dentry); |
| 4164 | } |
| 4165 | out: |
| 4166 | if (!is_dir || (flags & RENAME_EXCHANGE)) |
| 4167 | unlock_two_nondirectories(source, target); |
| 4168 | else if (target) |
| 4169 | mutex_unlock(&target->i_mutex); |
| 4170 | dput(new_dentry); |
| 4171 | if (!error) { |
| 4172 | fsnotify_move(old_dir, new_dir, old_name, is_dir, |
| 4173 | !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry); |
| 4174 | if (flags & RENAME_EXCHANGE) { |
| 4175 | fsnotify_move(new_dir, old_dir, old_dentry->d_name.name, |
| 4176 | new_is_dir, NULL, new_dentry); |
| 4177 | } |
| 4178 | } |
| 4179 | fsnotify_oldname_free(old_name); |
| 4180 | |
| 4181 | return error; |
| 4182 | } |
| 4183 | EXPORT_SYMBOL(vfs_rename); |
| 4184 | |
| 4185 | SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname, |
| 4186 | int, newdfd, const char __user *, newname, unsigned int, flags) |
| 4187 | { |
| 4188 | struct dentry *old_dir, *new_dir; |
| 4189 | struct dentry *old_dentry, *new_dentry; |
| 4190 | struct dentry *trap; |
| 4191 | struct nameidata oldnd, newnd; |
| 4192 | struct inode *delegated_inode = NULL; |
| 4193 | struct filename *from; |
| 4194 | struct filename *to; |
| 4195 | unsigned int lookup_flags = 0; |
| 4196 | bool should_retry = false; |
| 4197 | int error; |
| 4198 | |
| 4199 | if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE)) |
| 4200 | return -EINVAL; |
| 4201 | |
| 4202 | if ((flags & RENAME_NOREPLACE) && (flags & RENAME_EXCHANGE)) |
| 4203 | return -EINVAL; |
| 4204 | |
| 4205 | retry: |
| 4206 | from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags); |
| 4207 | if (IS_ERR(from)) { |
| 4208 | error = PTR_ERR(from); |
| 4209 | goto exit; |
| 4210 | } |
| 4211 | |
| 4212 | to = user_path_parent(newdfd, newname, &newnd, lookup_flags); |
| 4213 | if (IS_ERR(to)) { |
| 4214 | error = PTR_ERR(to); |
| 4215 | goto exit1; |
| 4216 | } |
| 4217 | |
| 4218 | error = -EXDEV; |
| 4219 | if (oldnd.path.mnt != newnd.path.mnt) |
| 4220 | goto exit2; |
| 4221 | |
| 4222 | old_dir = oldnd.path.dentry; |
| 4223 | error = -EBUSY; |
| 4224 | if (oldnd.last_type != LAST_NORM) |
| 4225 | goto exit2; |
| 4226 | |
| 4227 | new_dir = newnd.path.dentry; |
| 4228 | if (flags & RENAME_NOREPLACE) |
| 4229 | error = -EEXIST; |
| 4230 | if (newnd.last_type != LAST_NORM) |
| 4231 | goto exit2; |
| 4232 | |
| 4233 | error = mnt_want_write(oldnd.path.mnt); |
| 4234 | if (error) |
| 4235 | goto exit2; |
| 4236 | |
| 4237 | oldnd.flags &= ~LOOKUP_PARENT; |
| 4238 | newnd.flags &= ~LOOKUP_PARENT; |
| 4239 | if (!(flags & RENAME_EXCHANGE)) |
| 4240 | newnd.flags |= LOOKUP_RENAME_TARGET; |
| 4241 | |
| 4242 | retry_deleg: |
| 4243 | trap = lock_rename(new_dir, old_dir); |
| 4244 | |
| 4245 | old_dentry = lookup_hash(&oldnd); |
| 4246 | error = PTR_ERR(old_dentry); |
| 4247 | if (IS_ERR(old_dentry)) |
| 4248 | goto exit3; |
| 4249 | /* source must exist */ |
| 4250 | error = -ENOENT; |
| 4251 | if (d_is_negative(old_dentry)) |
| 4252 | goto exit4; |
| 4253 | new_dentry = lookup_hash(&newnd); |
| 4254 | error = PTR_ERR(new_dentry); |
| 4255 | if (IS_ERR(new_dentry)) |
| 4256 | goto exit4; |
| 4257 | error = -EEXIST; |
| 4258 | if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry)) |
| 4259 | goto exit5; |
| 4260 | if (flags & RENAME_EXCHANGE) { |
| 4261 | error = -ENOENT; |
| 4262 | if (d_is_negative(new_dentry)) |
| 4263 | goto exit5; |
| 4264 | |
| 4265 | if (!d_is_dir(new_dentry)) { |
| 4266 | error = -ENOTDIR; |
| 4267 | if (newnd.last.name[newnd.last.len]) |
| 4268 | goto exit5; |
| 4269 | } |
| 4270 | } |
| 4271 | /* unless the source is a directory trailing slashes give -ENOTDIR */ |
| 4272 | if (!d_is_dir(old_dentry)) { |
| 4273 | error = -ENOTDIR; |
| 4274 | if (oldnd.last.name[oldnd.last.len]) |
| 4275 | goto exit5; |
| 4276 | if (!(flags & RENAME_EXCHANGE) && newnd.last.name[newnd.last.len]) |
| 4277 | goto exit5; |
| 4278 | } |
| 4279 | /* source should not be ancestor of target */ |
| 4280 | error = -EINVAL; |
| 4281 | if (old_dentry == trap) |
| 4282 | goto exit5; |
| 4283 | /* target should not be an ancestor of source */ |
| 4284 | if (!(flags & RENAME_EXCHANGE)) |
| 4285 | error = -ENOTEMPTY; |
| 4286 | if (new_dentry == trap) |
| 4287 | goto exit5; |
| 4288 | |
| 4289 | error = security_path_rename(&oldnd.path, old_dentry, |
| 4290 | &newnd.path, new_dentry, flags); |
| 4291 | if (error) |
| 4292 | goto exit5; |
| 4293 | error = vfs_rename(old_dir->d_inode, old_dentry, |
| 4294 | new_dir->d_inode, new_dentry, |
| 4295 | &delegated_inode, flags); |
| 4296 | exit5: |
| 4297 | dput(new_dentry); |
| 4298 | exit4: |
| 4299 | dput(old_dentry); |
| 4300 | exit3: |
| 4301 | unlock_rename(new_dir, old_dir); |
| 4302 | if (delegated_inode) { |
| 4303 | error = break_deleg_wait(&delegated_inode); |
| 4304 | if (!error) |
| 4305 | goto retry_deleg; |
| 4306 | } |
| 4307 | mnt_drop_write(oldnd.path.mnt); |
| 4308 | exit2: |
| 4309 | if (retry_estale(error, lookup_flags)) |
| 4310 | should_retry = true; |
| 4311 | path_put(&newnd.path); |
| 4312 | putname(to); |
| 4313 | exit1: |
| 4314 | path_put(&oldnd.path); |
| 4315 | putname(from); |
| 4316 | if (should_retry) { |
| 4317 | should_retry = false; |
| 4318 | lookup_flags |= LOOKUP_REVAL; |
| 4319 | goto retry; |
| 4320 | } |
| 4321 | exit: |
| 4322 | return error; |
| 4323 | } |
| 4324 | |
| 4325 | SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname, |
| 4326 | int, newdfd, const char __user *, newname) |
| 4327 | { |
| 4328 | return sys_renameat2(olddfd, oldname, newdfd, newname, 0); |
| 4329 | } |
| 4330 | |
| 4331 | SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname) |
| 4332 | { |
| 4333 | return sys_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0); |
| 4334 | } |
| 4335 | |
| 4336 | int readlink_copy(char __user *buffer, int buflen, const char *link) |
| 4337 | { |
| 4338 | int len = PTR_ERR(link); |
| 4339 | if (IS_ERR(link)) |
| 4340 | goto out; |
| 4341 | |
| 4342 | len = strlen(link); |
| 4343 | if (len > (unsigned) buflen) |
| 4344 | len = buflen; |
| 4345 | if (copy_to_user(buffer, link, len)) |
| 4346 | len = -EFAULT; |
| 4347 | out: |
| 4348 | return len; |
| 4349 | } |
| 4350 | EXPORT_SYMBOL(readlink_copy); |
| 4351 | |
| 4352 | /* |
| 4353 | * A helper for ->readlink(). This should be used *ONLY* for symlinks that |
| 4354 | * have ->follow_link() touching nd only in nd_set_link(). Using (or not |
| 4355 | * using) it for any given inode is up to filesystem. |
| 4356 | */ |
| 4357 | int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen) |
| 4358 | { |
| 4359 | struct nameidata nd; |
| 4360 | void *cookie; |
| 4361 | int res; |
| 4362 | |
| 4363 | nd.depth = 0; |
| 4364 | cookie = dentry->d_inode->i_op->follow_link(dentry, &nd); |
| 4365 | if (IS_ERR(cookie)) |
| 4366 | return PTR_ERR(cookie); |
| 4367 | |
| 4368 | res = readlink_copy(buffer, buflen, nd_get_link(&nd)); |
| 4369 | if (dentry->d_inode->i_op->put_link) |
| 4370 | dentry->d_inode->i_op->put_link(dentry, &nd, cookie); |
| 4371 | return res; |
| 4372 | } |
| 4373 | EXPORT_SYMBOL(generic_readlink); |
| 4374 | |
| 4375 | /* get the link contents into pagecache */ |
| 4376 | static char *page_getlink(struct dentry * dentry, struct page **ppage) |
| 4377 | { |
| 4378 | char *kaddr; |
| 4379 | struct page *page; |
| 4380 | struct address_space *mapping = dentry->d_inode->i_mapping; |
| 4381 | page = read_mapping_page(mapping, 0, NULL); |
| 4382 | if (IS_ERR(page)) |
| 4383 | return (char*)page; |
| 4384 | *ppage = page; |
| 4385 | kaddr = kmap(page); |
| 4386 | nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1); |
| 4387 | return kaddr; |
| 4388 | } |
| 4389 | |
| 4390 | int page_readlink(struct dentry *dentry, char __user *buffer, int buflen) |
| 4391 | { |
| 4392 | struct page *page = NULL; |
| 4393 | int res = readlink_copy(buffer, buflen, page_getlink(dentry, &page)); |
| 4394 | if (page) { |
| 4395 | kunmap(page); |
| 4396 | page_cache_release(page); |
| 4397 | } |
| 4398 | return res; |
| 4399 | } |
| 4400 | EXPORT_SYMBOL(page_readlink); |
| 4401 | |
| 4402 | void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd) |
| 4403 | { |
| 4404 | struct page *page = NULL; |
| 4405 | nd_set_link(nd, page_getlink(dentry, &page)); |
| 4406 | return page; |
| 4407 | } |
| 4408 | EXPORT_SYMBOL(page_follow_link_light); |
| 4409 | |
| 4410 | void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) |
| 4411 | { |
| 4412 | struct page *page = cookie; |
| 4413 | |
| 4414 | if (page) { |
| 4415 | kunmap(page); |
| 4416 | page_cache_release(page); |
| 4417 | } |
| 4418 | } |
| 4419 | EXPORT_SYMBOL(page_put_link); |
| 4420 | |
| 4421 | /* |
| 4422 | * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS |
| 4423 | */ |
| 4424 | int __page_symlink(struct inode *inode, const char *symname, int len, int nofs) |
| 4425 | { |
| 4426 | struct address_space *mapping = inode->i_mapping; |
| 4427 | struct page *page; |
| 4428 | void *fsdata; |
| 4429 | int err; |
| 4430 | char *kaddr; |
| 4431 | unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE; |
| 4432 | if (nofs) |
| 4433 | flags |= AOP_FLAG_NOFS; |
| 4434 | |
| 4435 | retry: |
| 4436 | err = pagecache_write_begin(NULL, mapping, 0, len-1, |
| 4437 | flags, &page, &fsdata); |
| 4438 | if (err) |
| 4439 | goto fail; |
| 4440 | |
| 4441 | kaddr = kmap_atomic(page); |
| 4442 | memcpy(kaddr, symname, len-1); |
| 4443 | kunmap_atomic(kaddr); |
| 4444 | |
| 4445 | err = pagecache_write_end(NULL, mapping, 0, len-1, len-1, |
| 4446 | page, fsdata); |
| 4447 | if (err < 0) |
| 4448 | goto fail; |
| 4449 | if (err < len-1) |
| 4450 | goto retry; |
| 4451 | |
| 4452 | mark_inode_dirty(inode); |
| 4453 | return 0; |
| 4454 | fail: |
| 4455 | return err; |
| 4456 | } |
| 4457 | EXPORT_SYMBOL(__page_symlink); |
| 4458 | |
| 4459 | int page_symlink(struct inode *inode, const char *symname, int len) |
| 4460 | { |
| 4461 | return __page_symlink(inode, symname, len, |
| 4462 | !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS)); |
| 4463 | } |
| 4464 | EXPORT_SYMBOL(page_symlink); |
| 4465 | |
| 4466 | const struct inode_operations page_symlink_inode_operations = { |
| 4467 | .readlink = generic_readlink, |
| 4468 | .follow_link = page_follow_link_light, |
| 4469 | .put_link = page_put_link, |
| 4470 | }; |
| 4471 | EXPORT_SYMBOL(page_symlink_inode_operations); |