| 1 | /* |
| 2 | * linux/fs/namespace.c |
| 3 | * |
| 4 | * (C) Copyright Al Viro 2000, 2001 |
| 5 | * Released under GPL v2. |
| 6 | * |
| 7 | * Based on code from fs/super.c, copyright Linus Torvalds and others. |
| 8 | * Heavily rewritten. |
| 9 | */ |
| 10 | |
| 11 | #include <linux/syscalls.h> |
| 12 | #include <linux/export.h> |
| 13 | #include <linux/capability.h> |
| 14 | #include <linux/mnt_namespace.h> |
| 15 | #include <linux/namei.h> |
| 16 | #include <linux/security.h> |
| 17 | #include <linux/idr.h> |
| 18 | #include <linux/acct.h> /* acct_auto_close_mnt */ |
| 19 | #include <linux/ramfs.h> /* init_rootfs */ |
| 20 | #include <linux/fs_struct.h> /* get_fs_root et.al. */ |
| 21 | #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */ |
| 22 | #include <linux/uaccess.h> |
| 23 | #include "pnode.h" |
| 24 | #include "internal.h" |
| 25 | |
| 26 | #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) |
| 27 | #define HASH_SIZE (1UL << HASH_SHIFT) |
| 28 | |
| 29 | static int event; |
| 30 | static DEFINE_IDA(mnt_id_ida); |
| 31 | static DEFINE_IDA(mnt_group_ida); |
| 32 | static DEFINE_SPINLOCK(mnt_id_lock); |
| 33 | static int mnt_id_start = 0; |
| 34 | static int mnt_group_start = 1; |
| 35 | |
| 36 | static struct list_head *mount_hashtable __read_mostly; |
| 37 | static struct kmem_cache *mnt_cache __read_mostly; |
| 38 | static struct rw_semaphore namespace_sem; |
| 39 | |
| 40 | /* /sys/fs */ |
| 41 | struct kobject *fs_kobj; |
| 42 | EXPORT_SYMBOL_GPL(fs_kobj); |
| 43 | |
| 44 | /* |
| 45 | * vfsmount lock may be taken for read to prevent changes to the |
| 46 | * vfsmount hash, ie. during mountpoint lookups or walking back |
| 47 | * up the tree. |
| 48 | * |
| 49 | * It should be taken for write in all cases where the vfsmount |
| 50 | * tree or hash is modified or when a vfsmount structure is modified. |
| 51 | */ |
| 52 | DEFINE_BRLOCK(vfsmount_lock); |
| 53 | |
| 54 | static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) |
| 55 | { |
| 56 | unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); |
| 57 | tmp += ((unsigned long)dentry / L1_CACHE_BYTES); |
| 58 | tmp = tmp + (tmp >> HASH_SHIFT); |
| 59 | return tmp & (HASH_SIZE - 1); |
| 60 | } |
| 61 | |
| 62 | #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16) |
| 63 | |
| 64 | /* |
| 65 | * allocation is serialized by namespace_sem, but we need the spinlock to |
| 66 | * serialize with freeing. |
| 67 | */ |
| 68 | static int mnt_alloc_id(struct mount *mnt) |
| 69 | { |
| 70 | int res; |
| 71 | |
| 72 | retry: |
| 73 | ida_pre_get(&mnt_id_ida, GFP_KERNEL); |
| 74 | spin_lock(&mnt_id_lock); |
| 75 | res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id); |
| 76 | if (!res) |
| 77 | mnt_id_start = mnt->mnt_id + 1; |
| 78 | spin_unlock(&mnt_id_lock); |
| 79 | if (res == -EAGAIN) |
| 80 | goto retry; |
| 81 | |
| 82 | return res; |
| 83 | } |
| 84 | |
| 85 | static void mnt_free_id(struct mount *mnt) |
| 86 | { |
| 87 | int id = mnt->mnt_id; |
| 88 | spin_lock(&mnt_id_lock); |
| 89 | ida_remove(&mnt_id_ida, id); |
| 90 | if (mnt_id_start > id) |
| 91 | mnt_id_start = id; |
| 92 | spin_unlock(&mnt_id_lock); |
| 93 | } |
| 94 | |
| 95 | /* |
| 96 | * Allocate a new peer group ID |
| 97 | * |
| 98 | * mnt_group_ida is protected by namespace_sem |
| 99 | */ |
| 100 | static int mnt_alloc_group_id(struct mount *mnt) |
| 101 | { |
| 102 | int res; |
| 103 | |
| 104 | if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL)) |
| 105 | return -ENOMEM; |
| 106 | |
| 107 | res = ida_get_new_above(&mnt_group_ida, |
| 108 | mnt_group_start, |
| 109 | &mnt->mnt_group_id); |
| 110 | if (!res) |
| 111 | mnt_group_start = mnt->mnt_group_id + 1; |
| 112 | |
| 113 | return res; |
| 114 | } |
| 115 | |
| 116 | /* |
| 117 | * Release a peer group ID |
| 118 | */ |
| 119 | void mnt_release_group_id(struct mount *mnt) |
| 120 | { |
| 121 | int id = mnt->mnt_group_id; |
| 122 | ida_remove(&mnt_group_ida, id); |
| 123 | if (mnt_group_start > id) |
| 124 | mnt_group_start = id; |
| 125 | mnt->mnt_group_id = 0; |
| 126 | } |
| 127 | |
| 128 | /* |
| 129 | * vfsmount lock must be held for read |
| 130 | */ |
| 131 | static inline void mnt_add_count(struct mount *mnt, int n) |
| 132 | { |
| 133 | #ifdef CONFIG_SMP |
| 134 | this_cpu_add(mnt->mnt_pcp->mnt_count, n); |
| 135 | #else |
| 136 | preempt_disable(); |
| 137 | mnt->mnt_count += n; |
| 138 | preempt_enable(); |
| 139 | #endif |
| 140 | } |
| 141 | |
| 142 | /* |
| 143 | * vfsmount lock must be held for write |
| 144 | */ |
| 145 | unsigned int mnt_get_count(struct mount *mnt) |
| 146 | { |
| 147 | #ifdef CONFIG_SMP |
| 148 | unsigned int count = 0; |
| 149 | int cpu; |
| 150 | |
| 151 | for_each_possible_cpu(cpu) { |
| 152 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; |
| 153 | } |
| 154 | |
| 155 | return count; |
| 156 | #else |
| 157 | return mnt->mnt_count; |
| 158 | #endif |
| 159 | } |
| 160 | |
| 161 | static struct mount *alloc_vfsmnt(const char *name) |
| 162 | { |
| 163 | struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); |
| 164 | if (mnt) { |
| 165 | int err; |
| 166 | |
| 167 | err = mnt_alloc_id(mnt); |
| 168 | if (err) |
| 169 | goto out_free_cache; |
| 170 | |
| 171 | if (name) { |
| 172 | mnt->mnt_devname = kstrdup(name, GFP_KERNEL); |
| 173 | if (!mnt->mnt_devname) |
| 174 | goto out_free_id; |
| 175 | } |
| 176 | |
| 177 | #ifdef CONFIG_SMP |
| 178 | mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); |
| 179 | if (!mnt->mnt_pcp) |
| 180 | goto out_free_devname; |
| 181 | |
| 182 | this_cpu_add(mnt->mnt_pcp->mnt_count, 1); |
| 183 | #else |
| 184 | mnt->mnt_count = 1; |
| 185 | mnt->mnt_writers = 0; |
| 186 | #endif |
| 187 | |
| 188 | INIT_LIST_HEAD(&mnt->mnt_hash); |
| 189 | INIT_LIST_HEAD(&mnt->mnt_child); |
| 190 | INIT_LIST_HEAD(&mnt->mnt_mounts); |
| 191 | INIT_LIST_HEAD(&mnt->mnt_list); |
| 192 | INIT_LIST_HEAD(&mnt->mnt_expire); |
| 193 | INIT_LIST_HEAD(&mnt->mnt_share); |
| 194 | INIT_LIST_HEAD(&mnt->mnt_slave_list); |
| 195 | INIT_LIST_HEAD(&mnt->mnt_slave); |
| 196 | #ifdef CONFIG_FSNOTIFY |
| 197 | INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks); |
| 198 | #endif |
| 199 | } |
| 200 | return mnt; |
| 201 | |
| 202 | #ifdef CONFIG_SMP |
| 203 | out_free_devname: |
| 204 | kfree(mnt->mnt_devname); |
| 205 | #endif |
| 206 | out_free_id: |
| 207 | mnt_free_id(mnt); |
| 208 | out_free_cache: |
| 209 | kmem_cache_free(mnt_cache, mnt); |
| 210 | return NULL; |
| 211 | } |
| 212 | |
| 213 | /* |
| 214 | * Most r/o checks on a fs are for operations that take |
| 215 | * discrete amounts of time, like a write() or unlink(). |
| 216 | * We must keep track of when those operations start |
| 217 | * (for permission checks) and when they end, so that |
| 218 | * we can determine when writes are able to occur to |
| 219 | * a filesystem. |
| 220 | */ |
| 221 | /* |
| 222 | * __mnt_is_readonly: check whether a mount is read-only |
| 223 | * @mnt: the mount to check for its write status |
| 224 | * |
| 225 | * This shouldn't be used directly ouside of the VFS. |
| 226 | * It does not guarantee that the filesystem will stay |
| 227 | * r/w, just that it is right *now*. This can not and |
| 228 | * should not be used in place of IS_RDONLY(inode). |
| 229 | * mnt_want/drop_write() will _keep_ the filesystem |
| 230 | * r/w. |
| 231 | */ |
| 232 | int __mnt_is_readonly(struct vfsmount *mnt) |
| 233 | { |
| 234 | if (mnt->mnt_flags & MNT_READONLY) |
| 235 | return 1; |
| 236 | if (mnt->mnt_sb->s_flags & MS_RDONLY) |
| 237 | return 1; |
| 238 | return 0; |
| 239 | } |
| 240 | EXPORT_SYMBOL_GPL(__mnt_is_readonly); |
| 241 | |
| 242 | static inline void mnt_inc_writers(struct mount *mnt) |
| 243 | { |
| 244 | #ifdef CONFIG_SMP |
| 245 | this_cpu_inc(mnt->mnt_pcp->mnt_writers); |
| 246 | #else |
| 247 | mnt->mnt_writers++; |
| 248 | #endif |
| 249 | } |
| 250 | |
| 251 | static inline void mnt_dec_writers(struct mount *mnt) |
| 252 | { |
| 253 | #ifdef CONFIG_SMP |
| 254 | this_cpu_dec(mnt->mnt_pcp->mnt_writers); |
| 255 | #else |
| 256 | mnt->mnt_writers--; |
| 257 | #endif |
| 258 | } |
| 259 | |
| 260 | static unsigned int mnt_get_writers(struct mount *mnt) |
| 261 | { |
| 262 | #ifdef CONFIG_SMP |
| 263 | unsigned int count = 0; |
| 264 | int cpu; |
| 265 | |
| 266 | for_each_possible_cpu(cpu) { |
| 267 | count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; |
| 268 | } |
| 269 | |
| 270 | return count; |
| 271 | #else |
| 272 | return mnt->mnt_writers; |
| 273 | #endif |
| 274 | } |
| 275 | |
| 276 | /* |
| 277 | * Most r/o checks on a fs are for operations that take |
| 278 | * discrete amounts of time, like a write() or unlink(). |
| 279 | * We must keep track of when those operations start |
| 280 | * (for permission checks) and when they end, so that |
| 281 | * we can determine when writes are able to occur to |
| 282 | * a filesystem. |
| 283 | */ |
| 284 | /** |
| 285 | * mnt_want_write - get write access to a mount |
| 286 | * @m: the mount on which to take a write |
| 287 | * |
| 288 | * This tells the low-level filesystem that a write is |
| 289 | * about to be performed to it, and makes sure that |
| 290 | * writes are allowed before returning success. When |
| 291 | * the write operation is finished, mnt_drop_write() |
| 292 | * must be called. This is effectively a refcount. |
| 293 | */ |
| 294 | int mnt_want_write(struct vfsmount *m) |
| 295 | { |
| 296 | struct mount *mnt = real_mount(m); |
| 297 | int ret = 0; |
| 298 | |
| 299 | preempt_disable(); |
| 300 | mnt_inc_writers(mnt); |
| 301 | /* |
| 302 | * The store to mnt_inc_writers must be visible before we pass |
| 303 | * MNT_WRITE_HOLD loop below, so that the slowpath can see our |
| 304 | * incremented count after it has set MNT_WRITE_HOLD. |
| 305 | */ |
| 306 | smp_mb(); |
| 307 | while (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) |
| 308 | cpu_relax(); |
| 309 | /* |
| 310 | * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will |
| 311 | * be set to match its requirements. So we must not load that until |
| 312 | * MNT_WRITE_HOLD is cleared. |
| 313 | */ |
| 314 | smp_rmb(); |
| 315 | if (__mnt_is_readonly(m)) { |
| 316 | mnt_dec_writers(mnt); |
| 317 | ret = -EROFS; |
| 318 | goto out; |
| 319 | } |
| 320 | out: |
| 321 | preempt_enable(); |
| 322 | return ret; |
| 323 | } |
| 324 | EXPORT_SYMBOL_GPL(mnt_want_write); |
| 325 | |
| 326 | /** |
| 327 | * mnt_clone_write - get write access to a mount |
| 328 | * @mnt: the mount on which to take a write |
| 329 | * |
| 330 | * This is effectively like mnt_want_write, except |
| 331 | * it must only be used to take an extra write reference |
| 332 | * on a mountpoint that we already know has a write reference |
| 333 | * on it. This allows some optimisation. |
| 334 | * |
| 335 | * After finished, mnt_drop_write must be called as usual to |
| 336 | * drop the reference. |
| 337 | */ |
| 338 | int mnt_clone_write(struct vfsmount *mnt) |
| 339 | { |
| 340 | /* superblock may be r/o */ |
| 341 | if (__mnt_is_readonly(mnt)) |
| 342 | return -EROFS; |
| 343 | preempt_disable(); |
| 344 | mnt_inc_writers(real_mount(mnt)); |
| 345 | preempt_enable(); |
| 346 | return 0; |
| 347 | } |
| 348 | EXPORT_SYMBOL_GPL(mnt_clone_write); |
| 349 | |
| 350 | /** |
| 351 | * mnt_want_write_file - get write access to a file's mount |
| 352 | * @file: the file who's mount on which to take a write |
| 353 | * |
| 354 | * This is like mnt_want_write, but it takes a file and can |
| 355 | * do some optimisations if the file is open for write already |
| 356 | */ |
| 357 | int mnt_want_write_file(struct file *file) |
| 358 | { |
| 359 | struct inode *inode = file->f_dentry->d_inode; |
| 360 | if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode)) |
| 361 | return mnt_want_write(file->f_path.mnt); |
| 362 | else |
| 363 | return mnt_clone_write(file->f_path.mnt); |
| 364 | } |
| 365 | EXPORT_SYMBOL_GPL(mnt_want_write_file); |
| 366 | |
| 367 | /** |
| 368 | * mnt_drop_write - give up write access to a mount |
| 369 | * @mnt: the mount on which to give up write access |
| 370 | * |
| 371 | * Tells the low-level filesystem that we are done |
| 372 | * performing writes to it. Must be matched with |
| 373 | * mnt_want_write() call above. |
| 374 | */ |
| 375 | void mnt_drop_write(struct vfsmount *mnt) |
| 376 | { |
| 377 | preempt_disable(); |
| 378 | mnt_dec_writers(real_mount(mnt)); |
| 379 | preempt_enable(); |
| 380 | } |
| 381 | EXPORT_SYMBOL_GPL(mnt_drop_write); |
| 382 | |
| 383 | void mnt_drop_write_file(struct file *file) |
| 384 | { |
| 385 | mnt_drop_write(file->f_path.mnt); |
| 386 | } |
| 387 | EXPORT_SYMBOL(mnt_drop_write_file); |
| 388 | |
| 389 | static int mnt_make_readonly(struct mount *mnt) |
| 390 | { |
| 391 | int ret = 0; |
| 392 | |
| 393 | br_write_lock(vfsmount_lock); |
| 394 | mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; |
| 395 | /* |
| 396 | * After storing MNT_WRITE_HOLD, we'll read the counters. This store |
| 397 | * should be visible before we do. |
| 398 | */ |
| 399 | smp_mb(); |
| 400 | |
| 401 | /* |
| 402 | * With writers on hold, if this value is zero, then there are |
| 403 | * definitely no active writers (although held writers may subsequently |
| 404 | * increment the count, they'll have to wait, and decrement it after |
| 405 | * seeing MNT_READONLY). |
| 406 | * |
| 407 | * It is OK to have counter incremented on one CPU and decremented on |
| 408 | * another: the sum will add up correctly. The danger would be when we |
| 409 | * sum up each counter, if we read a counter before it is incremented, |
| 410 | * but then read another CPU's count which it has been subsequently |
| 411 | * decremented from -- we would see more decrements than we should. |
| 412 | * MNT_WRITE_HOLD protects against this scenario, because |
| 413 | * mnt_want_write first increments count, then smp_mb, then spins on |
| 414 | * MNT_WRITE_HOLD, so it can't be decremented by another CPU while |
| 415 | * we're counting up here. |
| 416 | */ |
| 417 | if (mnt_get_writers(mnt) > 0) |
| 418 | ret = -EBUSY; |
| 419 | else |
| 420 | mnt->mnt.mnt_flags |= MNT_READONLY; |
| 421 | /* |
| 422 | * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers |
| 423 | * that become unheld will see MNT_READONLY. |
| 424 | */ |
| 425 | smp_wmb(); |
| 426 | mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; |
| 427 | br_write_unlock(vfsmount_lock); |
| 428 | return ret; |
| 429 | } |
| 430 | |
| 431 | static void __mnt_unmake_readonly(struct mount *mnt) |
| 432 | { |
| 433 | br_write_lock(vfsmount_lock); |
| 434 | mnt->mnt.mnt_flags &= ~MNT_READONLY; |
| 435 | br_write_unlock(vfsmount_lock); |
| 436 | } |
| 437 | |
| 438 | static void free_vfsmnt(struct mount *mnt) |
| 439 | { |
| 440 | kfree(mnt->mnt_devname); |
| 441 | mnt_free_id(mnt); |
| 442 | #ifdef CONFIG_SMP |
| 443 | free_percpu(mnt->mnt_pcp); |
| 444 | #endif |
| 445 | kmem_cache_free(mnt_cache, mnt); |
| 446 | } |
| 447 | |
| 448 | /* |
| 449 | * find the first or last mount at @dentry on vfsmount @mnt depending on |
| 450 | * @dir. If @dir is set return the first mount else return the last mount. |
| 451 | * vfsmount_lock must be held for read or write. |
| 452 | */ |
| 453 | struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, |
| 454 | int dir) |
| 455 | { |
| 456 | struct list_head *head = mount_hashtable + hash(mnt, dentry); |
| 457 | struct list_head *tmp = head; |
| 458 | struct mount *p, *found = NULL; |
| 459 | |
| 460 | for (;;) { |
| 461 | tmp = dir ? tmp->next : tmp->prev; |
| 462 | p = NULL; |
| 463 | if (tmp == head) |
| 464 | break; |
| 465 | p = list_entry(tmp, struct mount, mnt_hash); |
| 466 | if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) { |
| 467 | found = p; |
| 468 | break; |
| 469 | } |
| 470 | } |
| 471 | return found; |
| 472 | } |
| 473 | |
| 474 | /* |
| 475 | * lookup_mnt increments the ref count before returning |
| 476 | * the vfsmount struct. |
| 477 | */ |
| 478 | struct vfsmount *lookup_mnt(struct path *path) |
| 479 | { |
| 480 | struct mount *child_mnt; |
| 481 | |
| 482 | br_read_lock(vfsmount_lock); |
| 483 | child_mnt = __lookup_mnt(path->mnt, path->dentry, 1); |
| 484 | if (child_mnt) { |
| 485 | mnt_add_count(child_mnt, 1); |
| 486 | br_read_unlock(vfsmount_lock); |
| 487 | return &child_mnt->mnt; |
| 488 | } else { |
| 489 | br_read_unlock(vfsmount_lock); |
| 490 | return NULL; |
| 491 | } |
| 492 | } |
| 493 | |
| 494 | static inline int check_mnt(struct mount *mnt) |
| 495 | { |
| 496 | return mnt->mnt_ns == current->nsproxy->mnt_ns; |
| 497 | } |
| 498 | |
| 499 | /* |
| 500 | * vfsmount lock must be held for write |
| 501 | */ |
| 502 | static void touch_mnt_namespace(struct mnt_namespace *ns) |
| 503 | { |
| 504 | if (ns) { |
| 505 | ns->event = ++event; |
| 506 | wake_up_interruptible(&ns->poll); |
| 507 | } |
| 508 | } |
| 509 | |
| 510 | /* |
| 511 | * vfsmount lock must be held for write |
| 512 | */ |
| 513 | static void __touch_mnt_namespace(struct mnt_namespace *ns) |
| 514 | { |
| 515 | if (ns && ns->event != event) { |
| 516 | ns->event = event; |
| 517 | wake_up_interruptible(&ns->poll); |
| 518 | } |
| 519 | } |
| 520 | |
| 521 | /* |
| 522 | * Clear dentry's mounted state if it has no remaining mounts. |
| 523 | * vfsmount_lock must be held for write. |
| 524 | */ |
| 525 | static void dentry_reset_mounted(struct dentry *dentry) |
| 526 | { |
| 527 | unsigned u; |
| 528 | |
| 529 | for (u = 0; u < HASH_SIZE; u++) { |
| 530 | struct mount *p; |
| 531 | |
| 532 | list_for_each_entry(p, &mount_hashtable[u], mnt_hash) { |
| 533 | if (p->mnt_mountpoint == dentry) |
| 534 | return; |
| 535 | } |
| 536 | } |
| 537 | spin_lock(&dentry->d_lock); |
| 538 | dentry->d_flags &= ~DCACHE_MOUNTED; |
| 539 | spin_unlock(&dentry->d_lock); |
| 540 | } |
| 541 | |
| 542 | /* |
| 543 | * vfsmount lock must be held for write |
| 544 | */ |
| 545 | static void detach_mnt(struct mount *mnt, struct path *old_path) |
| 546 | { |
| 547 | old_path->dentry = mnt->mnt_mountpoint; |
| 548 | old_path->mnt = &mnt->mnt_parent->mnt; |
| 549 | mnt->mnt_parent = mnt; |
| 550 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
| 551 | list_del_init(&mnt->mnt_child); |
| 552 | list_del_init(&mnt->mnt_hash); |
| 553 | dentry_reset_mounted(old_path->dentry); |
| 554 | } |
| 555 | |
| 556 | /* |
| 557 | * vfsmount lock must be held for write |
| 558 | */ |
| 559 | void mnt_set_mountpoint(struct mount *mnt, struct dentry *dentry, |
| 560 | struct mount *child_mnt) |
| 561 | { |
| 562 | mnt_add_count(mnt, 1); /* essentially, that's mntget */ |
| 563 | child_mnt->mnt_mountpoint = dget(dentry); |
| 564 | child_mnt->mnt_parent = mnt; |
| 565 | spin_lock(&dentry->d_lock); |
| 566 | dentry->d_flags |= DCACHE_MOUNTED; |
| 567 | spin_unlock(&dentry->d_lock); |
| 568 | } |
| 569 | |
| 570 | /* |
| 571 | * vfsmount lock must be held for write |
| 572 | */ |
| 573 | static void attach_mnt(struct mount *mnt, struct path *path) |
| 574 | { |
| 575 | mnt_set_mountpoint(real_mount(path->mnt), path->dentry, mnt); |
| 576 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
| 577 | hash(path->mnt, path->dentry)); |
| 578 | list_add_tail(&mnt->mnt_child, &real_mount(path->mnt)->mnt_mounts); |
| 579 | } |
| 580 | |
| 581 | static inline void __mnt_make_longterm(struct mount *mnt) |
| 582 | { |
| 583 | #ifdef CONFIG_SMP |
| 584 | atomic_inc(&mnt->mnt_longterm); |
| 585 | #endif |
| 586 | } |
| 587 | |
| 588 | /* needs vfsmount lock for write */ |
| 589 | static inline void __mnt_make_shortterm(struct mount *mnt) |
| 590 | { |
| 591 | #ifdef CONFIG_SMP |
| 592 | atomic_dec(&mnt->mnt_longterm); |
| 593 | #endif |
| 594 | } |
| 595 | |
| 596 | /* |
| 597 | * vfsmount lock must be held for write |
| 598 | */ |
| 599 | static void commit_tree(struct mount *mnt) |
| 600 | { |
| 601 | struct mount *parent = mnt->mnt_parent; |
| 602 | struct mount *m; |
| 603 | LIST_HEAD(head); |
| 604 | struct mnt_namespace *n = parent->mnt_ns; |
| 605 | |
| 606 | BUG_ON(parent == mnt); |
| 607 | |
| 608 | list_add_tail(&head, &mnt->mnt_list); |
| 609 | list_for_each_entry(m, &head, mnt_list) { |
| 610 | m->mnt_ns = n; |
| 611 | __mnt_make_longterm(m); |
| 612 | } |
| 613 | |
| 614 | list_splice(&head, n->list.prev); |
| 615 | |
| 616 | list_add_tail(&mnt->mnt_hash, mount_hashtable + |
| 617 | hash(&parent->mnt, mnt->mnt_mountpoint)); |
| 618 | list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); |
| 619 | touch_mnt_namespace(n); |
| 620 | } |
| 621 | |
| 622 | static struct mount *next_mnt(struct mount *p, struct mount *root) |
| 623 | { |
| 624 | struct list_head *next = p->mnt_mounts.next; |
| 625 | if (next == &p->mnt_mounts) { |
| 626 | while (1) { |
| 627 | if (p == root) |
| 628 | return NULL; |
| 629 | next = p->mnt_child.next; |
| 630 | if (next != &p->mnt_parent->mnt_mounts) |
| 631 | break; |
| 632 | p = p->mnt_parent; |
| 633 | } |
| 634 | } |
| 635 | return list_entry(next, struct mount, mnt_child); |
| 636 | } |
| 637 | |
| 638 | static struct mount *skip_mnt_tree(struct mount *p) |
| 639 | { |
| 640 | struct list_head *prev = p->mnt_mounts.prev; |
| 641 | while (prev != &p->mnt_mounts) { |
| 642 | p = list_entry(prev, struct mount, mnt_child); |
| 643 | prev = p->mnt_mounts.prev; |
| 644 | } |
| 645 | return p; |
| 646 | } |
| 647 | |
| 648 | struct vfsmount * |
| 649 | vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data) |
| 650 | { |
| 651 | struct mount *mnt; |
| 652 | struct dentry *root; |
| 653 | |
| 654 | if (!type) |
| 655 | return ERR_PTR(-ENODEV); |
| 656 | |
| 657 | mnt = alloc_vfsmnt(name); |
| 658 | if (!mnt) |
| 659 | return ERR_PTR(-ENOMEM); |
| 660 | |
| 661 | if (flags & MS_KERNMOUNT) |
| 662 | mnt->mnt.mnt_flags = MNT_INTERNAL; |
| 663 | |
| 664 | root = mount_fs(type, flags, name, data); |
| 665 | if (IS_ERR(root)) { |
| 666 | free_vfsmnt(mnt); |
| 667 | return ERR_CAST(root); |
| 668 | } |
| 669 | |
| 670 | mnt->mnt.mnt_root = root; |
| 671 | mnt->mnt.mnt_sb = root->d_sb; |
| 672 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
| 673 | mnt->mnt_parent = mnt; |
| 674 | return &mnt->mnt; |
| 675 | } |
| 676 | EXPORT_SYMBOL_GPL(vfs_kern_mount); |
| 677 | |
| 678 | static struct mount *clone_mnt(struct mount *old, struct dentry *root, |
| 679 | int flag) |
| 680 | { |
| 681 | struct super_block *sb = old->mnt.mnt_sb; |
| 682 | struct mount *mnt = alloc_vfsmnt(old->mnt_devname); |
| 683 | |
| 684 | if (mnt) { |
| 685 | if (flag & (CL_SLAVE | CL_PRIVATE)) |
| 686 | mnt->mnt_group_id = 0; /* not a peer of original */ |
| 687 | else |
| 688 | mnt->mnt_group_id = old->mnt_group_id; |
| 689 | |
| 690 | if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { |
| 691 | int err = mnt_alloc_group_id(mnt); |
| 692 | if (err) |
| 693 | goto out_free; |
| 694 | } |
| 695 | |
| 696 | mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD; |
| 697 | atomic_inc(&sb->s_active); |
| 698 | mnt->mnt.mnt_sb = sb; |
| 699 | mnt->mnt.mnt_root = dget(root); |
| 700 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
| 701 | mnt->mnt_parent = mnt; |
| 702 | |
| 703 | if (flag & CL_SLAVE) { |
| 704 | list_add(&mnt->mnt_slave, &old->mnt_slave_list); |
| 705 | mnt->mnt_master = old; |
| 706 | CLEAR_MNT_SHARED(mnt); |
| 707 | } else if (!(flag & CL_PRIVATE)) { |
| 708 | if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) |
| 709 | list_add(&mnt->mnt_share, &old->mnt_share); |
| 710 | if (IS_MNT_SLAVE(old)) |
| 711 | list_add(&mnt->mnt_slave, &old->mnt_slave); |
| 712 | mnt->mnt_master = old->mnt_master; |
| 713 | } |
| 714 | if (flag & CL_MAKE_SHARED) |
| 715 | set_mnt_shared(mnt); |
| 716 | |
| 717 | /* stick the duplicate mount on the same expiry list |
| 718 | * as the original if that was on one */ |
| 719 | if (flag & CL_EXPIRE) { |
| 720 | if (!list_empty(&old->mnt_expire)) |
| 721 | list_add(&mnt->mnt_expire, &old->mnt_expire); |
| 722 | } |
| 723 | } |
| 724 | return mnt; |
| 725 | |
| 726 | out_free: |
| 727 | free_vfsmnt(mnt); |
| 728 | return NULL; |
| 729 | } |
| 730 | |
| 731 | static inline void mntfree(struct mount *mnt) |
| 732 | { |
| 733 | struct vfsmount *m = &mnt->mnt; |
| 734 | struct super_block *sb = m->mnt_sb; |
| 735 | |
| 736 | /* |
| 737 | * This probably indicates that somebody messed |
| 738 | * up a mnt_want/drop_write() pair. If this |
| 739 | * happens, the filesystem was probably unable |
| 740 | * to make r/w->r/o transitions. |
| 741 | */ |
| 742 | /* |
| 743 | * The locking used to deal with mnt_count decrement provides barriers, |
| 744 | * so mnt_get_writers() below is safe. |
| 745 | */ |
| 746 | WARN_ON(mnt_get_writers(mnt)); |
| 747 | fsnotify_vfsmount_delete(m); |
| 748 | dput(m->mnt_root); |
| 749 | free_vfsmnt(mnt); |
| 750 | deactivate_super(sb); |
| 751 | } |
| 752 | |
| 753 | static void mntput_no_expire(struct mount *mnt) |
| 754 | { |
| 755 | put_again: |
| 756 | #ifdef CONFIG_SMP |
| 757 | br_read_lock(vfsmount_lock); |
| 758 | if (likely(atomic_read(&mnt->mnt_longterm))) { |
| 759 | mnt_add_count(mnt, -1); |
| 760 | br_read_unlock(vfsmount_lock); |
| 761 | return; |
| 762 | } |
| 763 | br_read_unlock(vfsmount_lock); |
| 764 | |
| 765 | br_write_lock(vfsmount_lock); |
| 766 | mnt_add_count(mnt, -1); |
| 767 | if (mnt_get_count(mnt)) { |
| 768 | br_write_unlock(vfsmount_lock); |
| 769 | return; |
| 770 | } |
| 771 | #else |
| 772 | mnt_add_count(mnt, -1); |
| 773 | if (likely(mnt_get_count(mnt))) |
| 774 | return; |
| 775 | br_write_lock(vfsmount_lock); |
| 776 | #endif |
| 777 | if (unlikely(mnt->mnt_pinned)) { |
| 778 | mnt_add_count(mnt, mnt->mnt_pinned + 1); |
| 779 | mnt->mnt_pinned = 0; |
| 780 | br_write_unlock(vfsmount_lock); |
| 781 | acct_auto_close_mnt(&mnt->mnt); |
| 782 | goto put_again; |
| 783 | } |
| 784 | br_write_unlock(vfsmount_lock); |
| 785 | mntfree(mnt); |
| 786 | } |
| 787 | |
| 788 | void mntput(struct vfsmount *mnt) |
| 789 | { |
| 790 | if (mnt) { |
| 791 | struct mount *m = real_mount(mnt); |
| 792 | /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ |
| 793 | if (unlikely(m->mnt_expiry_mark)) |
| 794 | m->mnt_expiry_mark = 0; |
| 795 | mntput_no_expire(m); |
| 796 | } |
| 797 | } |
| 798 | EXPORT_SYMBOL(mntput); |
| 799 | |
| 800 | struct vfsmount *mntget(struct vfsmount *mnt) |
| 801 | { |
| 802 | if (mnt) |
| 803 | mnt_add_count(real_mount(mnt), 1); |
| 804 | return mnt; |
| 805 | } |
| 806 | EXPORT_SYMBOL(mntget); |
| 807 | |
| 808 | void mnt_pin(struct vfsmount *mnt) |
| 809 | { |
| 810 | br_write_lock(vfsmount_lock); |
| 811 | real_mount(mnt)->mnt_pinned++; |
| 812 | br_write_unlock(vfsmount_lock); |
| 813 | } |
| 814 | EXPORT_SYMBOL(mnt_pin); |
| 815 | |
| 816 | void mnt_unpin(struct vfsmount *m) |
| 817 | { |
| 818 | struct mount *mnt = real_mount(m); |
| 819 | br_write_lock(vfsmount_lock); |
| 820 | if (mnt->mnt_pinned) { |
| 821 | mnt_add_count(mnt, 1); |
| 822 | mnt->mnt_pinned--; |
| 823 | } |
| 824 | br_write_unlock(vfsmount_lock); |
| 825 | } |
| 826 | EXPORT_SYMBOL(mnt_unpin); |
| 827 | |
| 828 | static inline void mangle(struct seq_file *m, const char *s) |
| 829 | { |
| 830 | seq_escape(m, s, " \t\n\\"); |
| 831 | } |
| 832 | |
| 833 | /* |
| 834 | * Simple .show_options callback for filesystems which don't want to |
| 835 | * implement more complex mount option showing. |
| 836 | * |
| 837 | * See also save_mount_options(). |
| 838 | */ |
| 839 | int generic_show_options(struct seq_file *m, struct vfsmount *mnt) |
| 840 | { |
| 841 | const char *options; |
| 842 | |
| 843 | rcu_read_lock(); |
| 844 | options = rcu_dereference(mnt->mnt_sb->s_options); |
| 845 | |
| 846 | if (options != NULL && options[0]) { |
| 847 | seq_putc(m, ','); |
| 848 | mangle(m, options); |
| 849 | } |
| 850 | rcu_read_unlock(); |
| 851 | |
| 852 | return 0; |
| 853 | } |
| 854 | EXPORT_SYMBOL(generic_show_options); |
| 855 | |
| 856 | /* |
| 857 | * If filesystem uses generic_show_options(), this function should be |
| 858 | * called from the fill_super() callback. |
| 859 | * |
| 860 | * The .remount_fs callback usually needs to be handled in a special |
| 861 | * way, to make sure, that previous options are not overwritten if the |
| 862 | * remount fails. |
| 863 | * |
| 864 | * Also note, that if the filesystem's .remount_fs function doesn't |
| 865 | * reset all options to their default value, but changes only newly |
| 866 | * given options, then the displayed options will not reflect reality |
| 867 | * any more. |
| 868 | */ |
| 869 | void save_mount_options(struct super_block *sb, char *options) |
| 870 | { |
| 871 | BUG_ON(sb->s_options); |
| 872 | rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL)); |
| 873 | } |
| 874 | EXPORT_SYMBOL(save_mount_options); |
| 875 | |
| 876 | void replace_mount_options(struct super_block *sb, char *options) |
| 877 | { |
| 878 | char *old = sb->s_options; |
| 879 | rcu_assign_pointer(sb->s_options, options); |
| 880 | if (old) { |
| 881 | synchronize_rcu(); |
| 882 | kfree(old); |
| 883 | } |
| 884 | } |
| 885 | EXPORT_SYMBOL(replace_mount_options); |
| 886 | |
| 887 | #ifdef CONFIG_PROC_FS |
| 888 | /* iterator; we want it to have access to namespace_sem, thus here... */ |
| 889 | static void *m_start(struct seq_file *m, loff_t *pos) |
| 890 | { |
| 891 | struct proc_mounts *p = container_of(m, struct proc_mounts, m); |
| 892 | |
| 893 | down_read(&namespace_sem); |
| 894 | return seq_list_start(&p->ns->list, *pos); |
| 895 | } |
| 896 | |
| 897 | static void *m_next(struct seq_file *m, void *v, loff_t *pos) |
| 898 | { |
| 899 | struct proc_mounts *p = container_of(m, struct proc_mounts, m); |
| 900 | |
| 901 | return seq_list_next(v, &p->ns->list, pos); |
| 902 | } |
| 903 | |
| 904 | static void m_stop(struct seq_file *m, void *v) |
| 905 | { |
| 906 | up_read(&namespace_sem); |
| 907 | } |
| 908 | |
| 909 | static int m_show(struct seq_file *m, void *v) |
| 910 | { |
| 911 | struct proc_mounts *p = container_of(m, struct proc_mounts, m); |
| 912 | struct mount *r = list_entry(v, struct mount, mnt_list); |
| 913 | return p->show(m, &r->mnt); |
| 914 | } |
| 915 | |
| 916 | const struct seq_operations mounts_op = { |
| 917 | .start = m_start, |
| 918 | .next = m_next, |
| 919 | .stop = m_stop, |
| 920 | .show = m_show, |
| 921 | }; |
| 922 | #endif /* CONFIG_PROC_FS */ |
| 923 | |
| 924 | /** |
| 925 | * may_umount_tree - check if a mount tree is busy |
| 926 | * @mnt: root of mount tree |
| 927 | * |
| 928 | * This is called to check if a tree of mounts has any |
| 929 | * open files, pwds, chroots or sub mounts that are |
| 930 | * busy. |
| 931 | */ |
| 932 | int may_umount_tree(struct vfsmount *m) |
| 933 | { |
| 934 | struct mount *mnt = real_mount(m); |
| 935 | int actual_refs = 0; |
| 936 | int minimum_refs = 0; |
| 937 | struct mount *p; |
| 938 | BUG_ON(!m); |
| 939 | |
| 940 | /* write lock needed for mnt_get_count */ |
| 941 | br_write_lock(vfsmount_lock); |
| 942 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
| 943 | actual_refs += mnt_get_count(p); |
| 944 | minimum_refs += 2; |
| 945 | } |
| 946 | br_write_unlock(vfsmount_lock); |
| 947 | |
| 948 | if (actual_refs > minimum_refs) |
| 949 | return 0; |
| 950 | |
| 951 | return 1; |
| 952 | } |
| 953 | |
| 954 | EXPORT_SYMBOL(may_umount_tree); |
| 955 | |
| 956 | /** |
| 957 | * may_umount - check if a mount point is busy |
| 958 | * @mnt: root of mount |
| 959 | * |
| 960 | * This is called to check if a mount point has any |
| 961 | * open files, pwds, chroots or sub mounts. If the |
| 962 | * mount has sub mounts this will return busy |
| 963 | * regardless of whether the sub mounts are busy. |
| 964 | * |
| 965 | * Doesn't take quota and stuff into account. IOW, in some cases it will |
| 966 | * give false negatives. The main reason why it's here is that we need |
| 967 | * a non-destructive way to look for easily umountable filesystems. |
| 968 | */ |
| 969 | int may_umount(struct vfsmount *mnt) |
| 970 | { |
| 971 | int ret = 1; |
| 972 | down_read(&namespace_sem); |
| 973 | br_write_lock(vfsmount_lock); |
| 974 | if (propagate_mount_busy(real_mount(mnt), 2)) |
| 975 | ret = 0; |
| 976 | br_write_unlock(vfsmount_lock); |
| 977 | up_read(&namespace_sem); |
| 978 | return ret; |
| 979 | } |
| 980 | |
| 981 | EXPORT_SYMBOL(may_umount); |
| 982 | |
| 983 | void release_mounts(struct list_head *head) |
| 984 | { |
| 985 | struct mount *mnt; |
| 986 | while (!list_empty(head)) { |
| 987 | mnt = list_first_entry(head, struct mount, mnt_hash); |
| 988 | list_del_init(&mnt->mnt_hash); |
| 989 | if (mnt_has_parent(mnt)) { |
| 990 | struct dentry *dentry; |
| 991 | struct mount *m; |
| 992 | |
| 993 | br_write_lock(vfsmount_lock); |
| 994 | dentry = mnt->mnt_mountpoint; |
| 995 | m = mnt->mnt_parent; |
| 996 | mnt->mnt_mountpoint = mnt->mnt.mnt_root; |
| 997 | mnt->mnt_parent = mnt; |
| 998 | m->mnt_ghosts--; |
| 999 | br_write_unlock(vfsmount_lock); |
| 1000 | dput(dentry); |
| 1001 | mntput(&m->mnt); |
| 1002 | } |
| 1003 | mntput(&mnt->mnt); |
| 1004 | } |
| 1005 | } |
| 1006 | |
| 1007 | /* |
| 1008 | * vfsmount lock must be held for write |
| 1009 | * namespace_sem must be held for write |
| 1010 | */ |
| 1011 | void umount_tree(struct mount *mnt, int propagate, struct list_head *kill) |
| 1012 | { |
| 1013 | LIST_HEAD(tmp_list); |
| 1014 | struct mount *p; |
| 1015 | |
| 1016 | for (p = mnt; p; p = next_mnt(p, mnt)) |
| 1017 | list_move(&p->mnt_hash, &tmp_list); |
| 1018 | |
| 1019 | if (propagate) |
| 1020 | propagate_umount(&tmp_list); |
| 1021 | |
| 1022 | list_for_each_entry(p, &tmp_list, mnt_hash) { |
| 1023 | list_del_init(&p->mnt_expire); |
| 1024 | list_del_init(&p->mnt_list); |
| 1025 | __touch_mnt_namespace(p->mnt_ns); |
| 1026 | p->mnt_ns = NULL; |
| 1027 | __mnt_make_shortterm(p); |
| 1028 | list_del_init(&p->mnt_child); |
| 1029 | if (mnt_has_parent(p)) { |
| 1030 | p->mnt_parent->mnt_ghosts++; |
| 1031 | dentry_reset_mounted(p->mnt_mountpoint); |
| 1032 | } |
| 1033 | change_mnt_propagation(p, MS_PRIVATE); |
| 1034 | } |
| 1035 | list_splice(&tmp_list, kill); |
| 1036 | } |
| 1037 | |
| 1038 | static void shrink_submounts(struct mount *mnt, struct list_head *umounts); |
| 1039 | |
| 1040 | static int do_umount(struct mount *mnt, int flags) |
| 1041 | { |
| 1042 | struct super_block *sb = mnt->mnt.mnt_sb; |
| 1043 | int retval; |
| 1044 | LIST_HEAD(umount_list); |
| 1045 | |
| 1046 | retval = security_sb_umount(&mnt->mnt, flags); |
| 1047 | if (retval) |
| 1048 | return retval; |
| 1049 | |
| 1050 | /* |
| 1051 | * Allow userspace to request a mountpoint be expired rather than |
| 1052 | * unmounting unconditionally. Unmount only happens if: |
| 1053 | * (1) the mark is already set (the mark is cleared by mntput()) |
| 1054 | * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] |
| 1055 | */ |
| 1056 | if (flags & MNT_EXPIRE) { |
| 1057 | if (&mnt->mnt == current->fs->root.mnt || |
| 1058 | flags & (MNT_FORCE | MNT_DETACH)) |
| 1059 | return -EINVAL; |
| 1060 | |
| 1061 | /* |
| 1062 | * probably don't strictly need the lock here if we examined |
| 1063 | * all race cases, but it's a slowpath. |
| 1064 | */ |
| 1065 | br_write_lock(vfsmount_lock); |
| 1066 | if (mnt_get_count(mnt) != 2) { |
| 1067 | br_write_unlock(vfsmount_lock); |
| 1068 | return -EBUSY; |
| 1069 | } |
| 1070 | br_write_unlock(vfsmount_lock); |
| 1071 | |
| 1072 | if (!xchg(&mnt->mnt_expiry_mark, 1)) |
| 1073 | return -EAGAIN; |
| 1074 | } |
| 1075 | |
| 1076 | /* |
| 1077 | * If we may have to abort operations to get out of this |
| 1078 | * mount, and they will themselves hold resources we must |
| 1079 | * allow the fs to do things. In the Unix tradition of |
| 1080 | * 'Gee thats tricky lets do it in userspace' the umount_begin |
| 1081 | * might fail to complete on the first run through as other tasks |
| 1082 | * must return, and the like. Thats for the mount program to worry |
| 1083 | * about for the moment. |
| 1084 | */ |
| 1085 | |
| 1086 | if (flags & MNT_FORCE && sb->s_op->umount_begin) { |
| 1087 | sb->s_op->umount_begin(sb); |
| 1088 | } |
| 1089 | |
| 1090 | /* |
| 1091 | * No sense to grab the lock for this test, but test itself looks |
| 1092 | * somewhat bogus. Suggestions for better replacement? |
| 1093 | * Ho-hum... In principle, we might treat that as umount + switch |
| 1094 | * to rootfs. GC would eventually take care of the old vfsmount. |
| 1095 | * Actually it makes sense, especially if rootfs would contain a |
| 1096 | * /reboot - static binary that would close all descriptors and |
| 1097 | * call reboot(9). Then init(8) could umount root and exec /reboot. |
| 1098 | */ |
| 1099 | if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { |
| 1100 | /* |
| 1101 | * Special case for "unmounting" root ... |
| 1102 | * we just try to remount it readonly. |
| 1103 | */ |
| 1104 | down_write(&sb->s_umount); |
| 1105 | if (!(sb->s_flags & MS_RDONLY)) |
| 1106 | retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); |
| 1107 | up_write(&sb->s_umount); |
| 1108 | return retval; |
| 1109 | } |
| 1110 | |
| 1111 | down_write(&namespace_sem); |
| 1112 | br_write_lock(vfsmount_lock); |
| 1113 | event++; |
| 1114 | |
| 1115 | if (!(flags & MNT_DETACH)) |
| 1116 | shrink_submounts(mnt, &umount_list); |
| 1117 | |
| 1118 | retval = -EBUSY; |
| 1119 | if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { |
| 1120 | if (!list_empty(&mnt->mnt_list)) |
| 1121 | umount_tree(mnt, 1, &umount_list); |
| 1122 | retval = 0; |
| 1123 | } |
| 1124 | br_write_unlock(vfsmount_lock); |
| 1125 | up_write(&namespace_sem); |
| 1126 | release_mounts(&umount_list); |
| 1127 | return retval; |
| 1128 | } |
| 1129 | |
| 1130 | /* |
| 1131 | * Now umount can handle mount points as well as block devices. |
| 1132 | * This is important for filesystems which use unnamed block devices. |
| 1133 | * |
| 1134 | * We now support a flag for forced unmount like the other 'big iron' |
| 1135 | * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD |
| 1136 | */ |
| 1137 | |
| 1138 | SYSCALL_DEFINE2(umount, char __user *, name, int, flags) |
| 1139 | { |
| 1140 | struct path path; |
| 1141 | struct mount *mnt; |
| 1142 | int retval; |
| 1143 | int lookup_flags = 0; |
| 1144 | |
| 1145 | if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) |
| 1146 | return -EINVAL; |
| 1147 | |
| 1148 | if (!(flags & UMOUNT_NOFOLLOW)) |
| 1149 | lookup_flags |= LOOKUP_FOLLOW; |
| 1150 | |
| 1151 | retval = user_path_at(AT_FDCWD, name, lookup_flags, &path); |
| 1152 | if (retval) |
| 1153 | goto out; |
| 1154 | mnt = real_mount(path.mnt); |
| 1155 | retval = -EINVAL; |
| 1156 | if (path.dentry != path.mnt->mnt_root) |
| 1157 | goto dput_and_out; |
| 1158 | if (!check_mnt(mnt)) |
| 1159 | goto dput_and_out; |
| 1160 | |
| 1161 | retval = -EPERM; |
| 1162 | if (!capable(CAP_SYS_ADMIN)) |
| 1163 | goto dput_and_out; |
| 1164 | |
| 1165 | retval = do_umount(mnt, flags); |
| 1166 | dput_and_out: |
| 1167 | /* we mustn't call path_put() as that would clear mnt_expiry_mark */ |
| 1168 | dput(path.dentry); |
| 1169 | mntput_no_expire(mnt); |
| 1170 | out: |
| 1171 | return retval; |
| 1172 | } |
| 1173 | |
| 1174 | #ifdef __ARCH_WANT_SYS_OLDUMOUNT |
| 1175 | |
| 1176 | /* |
| 1177 | * The 2.0 compatible umount. No flags. |
| 1178 | */ |
| 1179 | SYSCALL_DEFINE1(oldumount, char __user *, name) |
| 1180 | { |
| 1181 | return sys_umount(name, 0); |
| 1182 | } |
| 1183 | |
| 1184 | #endif |
| 1185 | |
| 1186 | static int mount_is_safe(struct path *path) |
| 1187 | { |
| 1188 | if (capable(CAP_SYS_ADMIN)) |
| 1189 | return 0; |
| 1190 | return -EPERM; |
| 1191 | #ifdef notyet |
| 1192 | if (S_ISLNK(path->dentry->d_inode->i_mode)) |
| 1193 | return -EPERM; |
| 1194 | if (path->dentry->d_inode->i_mode & S_ISVTX) { |
| 1195 | if (current_uid() != path->dentry->d_inode->i_uid) |
| 1196 | return -EPERM; |
| 1197 | } |
| 1198 | if (inode_permission(path->dentry->d_inode, MAY_WRITE)) |
| 1199 | return -EPERM; |
| 1200 | return 0; |
| 1201 | #endif |
| 1202 | } |
| 1203 | |
| 1204 | struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, |
| 1205 | int flag) |
| 1206 | { |
| 1207 | struct mount *res, *p, *q, *r; |
| 1208 | struct path path; |
| 1209 | |
| 1210 | if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) |
| 1211 | return NULL; |
| 1212 | |
| 1213 | res = q = clone_mnt(mnt, dentry, flag); |
| 1214 | if (!q) |
| 1215 | goto Enomem; |
| 1216 | q->mnt_mountpoint = mnt->mnt_mountpoint; |
| 1217 | |
| 1218 | p = mnt; |
| 1219 | list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { |
| 1220 | struct mount *s; |
| 1221 | if (!is_subdir(r->mnt_mountpoint, dentry)) |
| 1222 | continue; |
| 1223 | |
| 1224 | for (s = r; s; s = next_mnt(s, r)) { |
| 1225 | if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) { |
| 1226 | s = skip_mnt_tree(s); |
| 1227 | continue; |
| 1228 | } |
| 1229 | while (p != s->mnt_parent) { |
| 1230 | p = p->mnt_parent; |
| 1231 | q = q->mnt_parent; |
| 1232 | } |
| 1233 | p = s; |
| 1234 | path.mnt = &q->mnt; |
| 1235 | path.dentry = p->mnt_mountpoint; |
| 1236 | q = clone_mnt(p, p->mnt.mnt_root, flag); |
| 1237 | if (!q) |
| 1238 | goto Enomem; |
| 1239 | br_write_lock(vfsmount_lock); |
| 1240 | list_add_tail(&q->mnt_list, &res->mnt_list); |
| 1241 | attach_mnt(q, &path); |
| 1242 | br_write_unlock(vfsmount_lock); |
| 1243 | } |
| 1244 | } |
| 1245 | return res; |
| 1246 | Enomem: |
| 1247 | if (res) { |
| 1248 | LIST_HEAD(umount_list); |
| 1249 | br_write_lock(vfsmount_lock); |
| 1250 | umount_tree(res, 0, &umount_list); |
| 1251 | br_write_unlock(vfsmount_lock); |
| 1252 | release_mounts(&umount_list); |
| 1253 | } |
| 1254 | return NULL; |
| 1255 | } |
| 1256 | |
| 1257 | struct vfsmount *collect_mounts(struct path *path) |
| 1258 | { |
| 1259 | struct mount *tree; |
| 1260 | down_write(&namespace_sem); |
| 1261 | tree = copy_tree(real_mount(path->mnt), path->dentry, |
| 1262 | CL_COPY_ALL | CL_PRIVATE); |
| 1263 | up_write(&namespace_sem); |
| 1264 | return tree ? &tree->mnt : NULL; |
| 1265 | } |
| 1266 | |
| 1267 | void drop_collected_mounts(struct vfsmount *mnt) |
| 1268 | { |
| 1269 | LIST_HEAD(umount_list); |
| 1270 | down_write(&namespace_sem); |
| 1271 | br_write_lock(vfsmount_lock); |
| 1272 | umount_tree(real_mount(mnt), 0, &umount_list); |
| 1273 | br_write_unlock(vfsmount_lock); |
| 1274 | up_write(&namespace_sem); |
| 1275 | release_mounts(&umount_list); |
| 1276 | } |
| 1277 | |
| 1278 | int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, |
| 1279 | struct vfsmount *root) |
| 1280 | { |
| 1281 | struct mount *mnt; |
| 1282 | int res = f(root, arg); |
| 1283 | if (res) |
| 1284 | return res; |
| 1285 | list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { |
| 1286 | res = f(&mnt->mnt, arg); |
| 1287 | if (res) |
| 1288 | return res; |
| 1289 | } |
| 1290 | return 0; |
| 1291 | } |
| 1292 | |
| 1293 | static void cleanup_group_ids(struct mount *mnt, struct mount *end) |
| 1294 | { |
| 1295 | struct mount *p; |
| 1296 | |
| 1297 | for (p = mnt; p != end; p = next_mnt(p, mnt)) { |
| 1298 | if (p->mnt_group_id && !IS_MNT_SHARED(p)) |
| 1299 | mnt_release_group_id(p); |
| 1300 | } |
| 1301 | } |
| 1302 | |
| 1303 | static int invent_group_ids(struct mount *mnt, bool recurse) |
| 1304 | { |
| 1305 | struct mount *p; |
| 1306 | |
| 1307 | for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { |
| 1308 | if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { |
| 1309 | int err = mnt_alloc_group_id(p); |
| 1310 | if (err) { |
| 1311 | cleanup_group_ids(mnt, p); |
| 1312 | return err; |
| 1313 | } |
| 1314 | } |
| 1315 | } |
| 1316 | |
| 1317 | return 0; |
| 1318 | } |
| 1319 | |
| 1320 | /* |
| 1321 | * @source_mnt : mount tree to be attached |
| 1322 | * @nd : place the mount tree @source_mnt is attached |
| 1323 | * @parent_nd : if non-null, detach the source_mnt from its parent and |
| 1324 | * store the parent mount and mountpoint dentry. |
| 1325 | * (done when source_mnt is moved) |
| 1326 | * |
| 1327 | * NOTE: in the table below explains the semantics when a source mount |
| 1328 | * of a given type is attached to a destination mount of a given type. |
| 1329 | * --------------------------------------------------------------------------- |
| 1330 | * | BIND MOUNT OPERATION | |
| 1331 | * |************************************************************************** |
| 1332 | * | source-->| shared | private | slave | unbindable | |
| 1333 | * | dest | | | | | |
| 1334 | * | | | | | | | |
| 1335 | * | v | | | | | |
| 1336 | * |************************************************************************** |
| 1337 | * | shared | shared (++) | shared (+) | shared(+++)| invalid | |
| 1338 | * | | | | | | |
| 1339 | * |non-shared| shared (+) | private | slave (*) | invalid | |
| 1340 | * *************************************************************************** |
| 1341 | * A bind operation clones the source mount and mounts the clone on the |
| 1342 | * destination mount. |
| 1343 | * |
| 1344 | * (++) the cloned mount is propagated to all the mounts in the propagation |
| 1345 | * tree of the destination mount and the cloned mount is added to |
| 1346 | * the peer group of the source mount. |
| 1347 | * (+) the cloned mount is created under the destination mount and is marked |
| 1348 | * as shared. The cloned mount is added to the peer group of the source |
| 1349 | * mount. |
| 1350 | * (+++) the mount is propagated to all the mounts in the propagation tree |
| 1351 | * of the destination mount and the cloned mount is made slave |
| 1352 | * of the same master as that of the source mount. The cloned mount |
| 1353 | * is marked as 'shared and slave'. |
| 1354 | * (*) the cloned mount is made a slave of the same master as that of the |
| 1355 | * source mount. |
| 1356 | * |
| 1357 | * --------------------------------------------------------------------------- |
| 1358 | * | MOVE MOUNT OPERATION | |
| 1359 | * |************************************************************************** |
| 1360 | * | source-->| shared | private | slave | unbindable | |
| 1361 | * | dest | | | | | |
| 1362 | * | | | | | | | |
| 1363 | * | v | | | | | |
| 1364 | * |************************************************************************** |
| 1365 | * | shared | shared (+) | shared (+) | shared(+++) | invalid | |
| 1366 | * | | | | | | |
| 1367 | * |non-shared| shared (+*) | private | slave (*) | unbindable | |
| 1368 | * *************************************************************************** |
| 1369 | * |
| 1370 | * (+) the mount is moved to the destination. And is then propagated to |
| 1371 | * all the mounts in the propagation tree of the destination mount. |
| 1372 | * (+*) the mount is moved to the destination. |
| 1373 | * (+++) the mount is moved to the destination and is then propagated to |
| 1374 | * all the mounts belonging to the destination mount's propagation tree. |
| 1375 | * the mount is marked as 'shared and slave'. |
| 1376 | * (*) the mount continues to be a slave at the new location. |
| 1377 | * |
| 1378 | * if the source mount is a tree, the operations explained above is |
| 1379 | * applied to each mount in the tree. |
| 1380 | * Must be called without spinlocks held, since this function can sleep |
| 1381 | * in allocations. |
| 1382 | */ |
| 1383 | static int attach_recursive_mnt(struct mount *source_mnt, |
| 1384 | struct path *path, struct path *parent_path) |
| 1385 | { |
| 1386 | LIST_HEAD(tree_list); |
| 1387 | struct mount *dest_mnt = real_mount(path->mnt); |
| 1388 | struct dentry *dest_dentry = path->dentry; |
| 1389 | struct mount *child, *p; |
| 1390 | int err; |
| 1391 | |
| 1392 | if (IS_MNT_SHARED(dest_mnt)) { |
| 1393 | err = invent_group_ids(source_mnt, true); |
| 1394 | if (err) |
| 1395 | goto out; |
| 1396 | } |
| 1397 | err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list); |
| 1398 | if (err) |
| 1399 | goto out_cleanup_ids; |
| 1400 | |
| 1401 | br_write_lock(vfsmount_lock); |
| 1402 | |
| 1403 | if (IS_MNT_SHARED(dest_mnt)) { |
| 1404 | for (p = source_mnt; p; p = next_mnt(p, source_mnt)) |
| 1405 | set_mnt_shared(p); |
| 1406 | } |
| 1407 | if (parent_path) { |
| 1408 | detach_mnt(source_mnt, parent_path); |
| 1409 | attach_mnt(source_mnt, path); |
| 1410 | touch_mnt_namespace(source_mnt->mnt_ns); |
| 1411 | } else { |
| 1412 | mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt); |
| 1413 | commit_tree(source_mnt); |
| 1414 | } |
| 1415 | |
| 1416 | list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { |
| 1417 | list_del_init(&child->mnt_hash); |
| 1418 | commit_tree(child); |
| 1419 | } |
| 1420 | br_write_unlock(vfsmount_lock); |
| 1421 | |
| 1422 | return 0; |
| 1423 | |
| 1424 | out_cleanup_ids: |
| 1425 | if (IS_MNT_SHARED(dest_mnt)) |
| 1426 | cleanup_group_ids(source_mnt, NULL); |
| 1427 | out: |
| 1428 | return err; |
| 1429 | } |
| 1430 | |
| 1431 | static int lock_mount(struct path *path) |
| 1432 | { |
| 1433 | struct vfsmount *mnt; |
| 1434 | retry: |
| 1435 | mutex_lock(&path->dentry->d_inode->i_mutex); |
| 1436 | if (unlikely(cant_mount(path->dentry))) { |
| 1437 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
| 1438 | return -ENOENT; |
| 1439 | } |
| 1440 | down_write(&namespace_sem); |
| 1441 | mnt = lookup_mnt(path); |
| 1442 | if (likely(!mnt)) |
| 1443 | return 0; |
| 1444 | up_write(&namespace_sem); |
| 1445 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
| 1446 | path_put(path); |
| 1447 | path->mnt = mnt; |
| 1448 | path->dentry = dget(mnt->mnt_root); |
| 1449 | goto retry; |
| 1450 | } |
| 1451 | |
| 1452 | static void unlock_mount(struct path *path) |
| 1453 | { |
| 1454 | up_write(&namespace_sem); |
| 1455 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
| 1456 | } |
| 1457 | |
| 1458 | static int graft_tree(struct mount *mnt, struct path *path) |
| 1459 | { |
| 1460 | if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER) |
| 1461 | return -EINVAL; |
| 1462 | |
| 1463 | if (S_ISDIR(path->dentry->d_inode->i_mode) != |
| 1464 | S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode)) |
| 1465 | return -ENOTDIR; |
| 1466 | |
| 1467 | if (d_unlinked(path->dentry)) |
| 1468 | return -ENOENT; |
| 1469 | |
| 1470 | return attach_recursive_mnt(mnt, path, NULL); |
| 1471 | } |
| 1472 | |
| 1473 | /* |
| 1474 | * Sanity check the flags to change_mnt_propagation. |
| 1475 | */ |
| 1476 | |
| 1477 | static int flags_to_propagation_type(int flags) |
| 1478 | { |
| 1479 | int type = flags & ~(MS_REC | MS_SILENT); |
| 1480 | |
| 1481 | /* Fail if any non-propagation flags are set */ |
| 1482 | if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
| 1483 | return 0; |
| 1484 | /* Only one propagation flag should be set */ |
| 1485 | if (!is_power_of_2(type)) |
| 1486 | return 0; |
| 1487 | return type; |
| 1488 | } |
| 1489 | |
| 1490 | /* |
| 1491 | * recursively change the type of the mountpoint. |
| 1492 | */ |
| 1493 | static int do_change_type(struct path *path, int flag) |
| 1494 | { |
| 1495 | struct mount *m; |
| 1496 | struct mount *mnt = real_mount(path->mnt); |
| 1497 | int recurse = flag & MS_REC; |
| 1498 | int type; |
| 1499 | int err = 0; |
| 1500 | |
| 1501 | if (!capable(CAP_SYS_ADMIN)) |
| 1502 | return -EPERM; |
| 1503 | |
| 1504 | if (path->dentry != path->mnt->mnt_root) |
| 1505 | return -EINVAL; |
| 1506 | |
| 1507 | type = flags_to_propagation_type(flag); |
| 1508 | if (!type) |
| 1509 | return -EINVAL; |
| 1510 | |
| 1511 | down_write(&namespace_sem); |
| 1512 | if (type == MS_SHARED) { |
| 1513 | err = invent_group_ids(mnt, recurse); |
| 1514 | if (err) |
| 1515 | goto out_unlock; |
| 1516 | } |
| 1517 | |
| 1518 | br_write_lock(vfsmount_lock); |
| 1519 | for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) |
| 1520 | change_mnt_propagation(m, type); |
| 1521 | br_write_unlock(vfsmount_lock); |
| 1522 | |
| 1523 | out_unlock: |
| 1524 | up_write(&namespace_sem); |
| 1525 | return err; |
| 1526 | } |
| 1527 | |
| 1528 | /* |
| 1529 | * do loopback mount. |
| 1530 | */ |
| 1531 | static int do_loopback(struct path *path, char *old_name, |
| 1532 | int recurse) |
| 1533 | { |
| 1534 | LIST_HEAD(umount_list); |
| 1535 | struct path old_path; |
| 1536 | struct mount *mnt = NULL, *old; |
| 1537 | int err = mount_is_safe(path); |
| 1538 | if (err) |
| 1539 | return err; |
| 1540 | if (!old_name || !*old_name) |
| 1541 | return -EINVAL; |
| 1542 | err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); |
| 1543 | if (err) |
| 1544 | return err; |
| 1545 | |
| 1546 | err = lock_mount(path); |
| 1547 | if (err) |
| 1548 | goto out; |
| 1549 | |
| 1550 | old = real_mount(old_path.mnt); |
| 1551 | |
| 1552 | err = -EINVAL; |
| 1553 | if (IS_MNT_UNBINDABLE(old)) |
| 1554 | goto out2; |
| 1555 | |
| 1556 | if (!check_mnt(real_mount(path->mnt)) || !check_mnt(old)) |
| 1557 | goto out2; |
| 1558 | |
| 1559 | err = -ENOMEM; |
| 1560 | if (recurse) |
| 1561 | mnt = copy_tree(old, old_path.dentry, 0); |
| 1562 | else |
| 1563 | mnt = clone_mnt(old, old_path.dentry, 0); |
| 1564 | |
| 1565 | if (!mnt) |
| 1566 | goto out2; |
| 1567 | |
| 1568 | err = graft_tree(mnt, path); |
| 1569 | if (err) { |
| 1570 | br_write_lock(vfsmount_lock); |
| 1571 | umount_tree(mnt, 0, &umount_list); |
| 1572 | br_write_unlock(vfsmount_lock); |
| 1573 | } |
| 1574 | out2: |
| 1575 | unlock_mount(path); |
| 1576 | release_mounts(&umount_list); |
| 1577 | out: |
| 1578 | path_put(&old_path); |
| 1579 | return err; |
| 1580 | } |
| 1581 | |
| 1582 | static int change_mount_flags(struct vfsmount *mnt, int ms_flags) |
| 1583 | { |
| 1584 | int error = 0; |
| 1585 | int readonly_request = 0; |
| 1586 | |
| 1587 | if (ms_flags & MS_RDONLY) |
| 1588 | readonly_request = 1; |
| 1589 | if (readonly_request == __mnt_is_readonly(mnt)) |
| 1590 | return 0; |
| 1591 | |
| 1592 | if (readonly_request) |
| 1593 | error = mnt_make_readonly(real_mount(mnt)); |
| 1594 | else |
| 1595 | __mnt_unmake_readonly(real_mount(mnt)); |
| 1596 | return error; |
| 1597 | } |
| 1598 | |
| 1599 | /* |
| 1600 | * change filesystem flags. dir should be a physical root of filesystem. |
| 1601 | * If you've mounted a non-root directory somewhere and want to do remount |
| 1602 | * on it - tough luck. |
| 1603 | */ |
| 1604 | static int do_remount(struct path *path, int flags, int mnt_flags, |
| 1605 | void *data) |
| 1606 | { |
| 1607 | int err; |
| 1608 | struct super_block *sb = path->mnt->mnt_sb; |
| 1609 | struct mount *mnt = real_mount(path->mnt); |
| 1610 | |
| 1611 | if (!capable(CAP_SYS_ADMIN)) |
| 1612 | return -EPERM; |
| 1613 | |
| 1614 | if (!check_mnt(mnt)) |
| 1615 | return -EINVAL; |
| 1616 | |
| 1617 | if (path->dentry != path->mnt->mnt_root) |
| 1618 | return -EINVAL; |
| 1619 | |
| 1620 | err = security_sb_remount(sb, data); |
| 1621 | if (err) |
| 1622 | return err; |
| 1623 | |
| 1624 | down_write(&sb->s_umount); |
| 1625 | if (flags & MS_BIND) |
| 1626 | err = change_mount_flags(path->mnt, flags); |
| 1627 | else |
| 1628 | err = do_remount_sb(sb, flags, data, 0); |
| 1629 | if (!err) { |
| 1630 | br_write_lock(vfsmount_lock); |
| 1631 | mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK; |
| 1632 | mnt->mnt.mnt_flags = mnt_flags; |
| 1633 | br_write_unlock(vfsmount_lock); |
| 1634 | } |
| 1635 | up_write(&sb->s_umount); |
| 1636 | if (!err) { |
| 1637 | br_write_lock(vfsmount_lock); |
| 1638 | touch_mnt_namespace(mnt->mnt_ns); |
| 1639 | br_write_unlock(vfsmount_lock); |
| 1640 | } |
| 1641 | return err; |
| 1642 | } |
| 1643 | |
| 1644 | static inline int tree_contains_unbindable(struct mount *mnt) |
| 1645 | { |
| 1646 | struct mount *p; |
| 1647 | for (p = mnt; p; p = next_mnt(p, mnt)) { |
| 1648 | if (IS_MNT_UNBINDABLE(p)) |
| 1649 | return 1; |
| 1650 | } |
| 1651 | return 0; |
| 1652 | } |
| 1653 | |
| 1654 | static int do_move_mount(struct path *path, char *old_name) |
| 1655 | { |
| 1656 | struct path old_path, parent_path; |
| 1657 | struct mount *p; |
| 1658 | struct mount *old; |
| 1659 | int err = 0; |
| 1660 | if (!capable(CAP_SYS_ADMIN)) |
| 1661 | return -EPERM; |
| 1662 | if (!old_name || !*old_name) |
| 1663 | return -EINVAL; |
| 1664 | err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); |
| 1665 | if (err) |
| 1666 | return err; |
| 1667 | |
| 1668 | err = lock_mount(path); |
| 1669 | if (err < 0) |
| 1670 | goto out; |
| 1671 | |
| 1672 | old = real_mount(old_path.mnt); |
| 1673 | p = real_mount(path->mnt); |
| 1674 | |
| 1675 | err = -EINVAL; |
| 1676 | if (!check_mnt(p) || !check_mnt(old)) |
| 1677 | goto out1; |
| 1678 | |
| 1679 | if (d_unlinked(path->dentry)) |
| 1680 | goto out1; |
| 1681 | |
| 1682 | err = -EINVAL; |
| 1683 | if (old_path.dentry != old_path.mnt->mnt_root) |
| 1684 | goto out1; |
| 1685 | |
| 1686 | if (!mnt_has_parent(old)) |
| 1687 | goto out1; |
| 1688 | |
| 1689 | if (S_ISDIR(path->dentry->d_inode->i_mode) != |
| 1690 | S_ISDIR(old_path.dentry->d_inode->i_mode)) |
| 1691 | goto out1; |
| 1692 | /* |
| 1693 | * Don't move a mount residing in a shared parent. |
| 1694 | */ |
| 1695 | if (IS_MNT_SHARED(old->mnt_parent)) |
| 1696 | goto out1; |
| 1697 | /* |
| 1698 | * Don't move a mount tree containing unbindable mounts to a destination |
| 1699 | * mount which is shared. |
| 1700 | */ |
| 1701 | if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) |
| 1702 | goto out1; |
| 1703 | err = -ELOOP; |
| 1704 | for (; mnt_has_parent(p); p = p->mnt_parent) |
| 1705 | if (p == old) |
| 1706 | goto out1; |
| 1707 | |
| 1708 | err = attach_recursive_mnt(old, path, &parent_path); |
| 1709 | if (err) |
| 1710 | goto out1; |
| 1711 | |
| 1712 | /* if the mount is moved, it should no longer be expire |
| 1713 | * automatically */ |
| 1714 | list_del_init(&old->mnt_expire); |
| 1715 | out1: |
| 1716 | unlock_mount(path); |
| 1717 | out: |
| 1718 | if (!err) |
| 1719 | path_put(&parent_path); |
| 1720 | path_put(&old_path); |
| 1721 | return err; |
| 1722 | } |
| 1723 | |
| 1724 | static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) |
| 1725 | { |
| 1726 | int err; |
| 1727 | const char *subtype = strchr(fstype, '.'); |
| 1728 | if (subtype) { |
| 1729 | subtype++; |
| 1730 | err = -EINVAL; |
| 1731 | if (!subtype[0]) |
| 1732 | goto err; |
| 1733 | } else |
| 1734 | subtype = ""; |
| 1735 | |
| 1736 | mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL); |
| 1737 | err = -ENOMEM; |
| 1738 | if (!mnt->mnt_sb->s_subtype) |
| 1739 | goto err; |
| 1740 | return mnt; |
| 1741 | |
| 1742 | err: |
| 1743 | mntput(mnt); |
| 1744 | return ERR_PTR(err); |
| 1745 | } |
| 1746 | |
| 1747 | static struct vfsmount * |
| 1748 | do_kern_mount(const char *fstype, int flags, const char *name, void *data) |
| 1749 | { |
| 1750 | struct file_system_type *type = get_fs_type(fstype); |
| 1751 | struct vfsmount *mnt; |
| 1752 | if (!type) |
| 1753 | return ERR_PTR(-ENODEV); |
| 1754 | mnt = vfs_kern_mount(type, flags, name, data); |
| 1755 | if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && |
| 1756 | !mnt->mnt_sb->s_subtype) |
| 1757 | mnt = fs_set_subtype(mnt, fstype); |
| 1758 | put_filesystem(type); |
| 1759 | return mnt; |
| 1760 | } |
| 1761 | |
| 1762 | /* |
| 1763 | * add a mount into a namespace's mount tree |
| 1764 | */ |
| 1765 | static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) |
| 1766 | { |
| 1767 | int err; |
| 1768 | |
| 1769 | mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL); |
| 1770 | |
| 1771 | err = lock_mount(path); |
| 1772 | if (err) |
| 1773 | return err; |
| 1774 | |
| 1775 | err = -EINVAL; |
| 1776 | if (!(mnt_flags & MNT_SHRINKABLE) && !check_mnt(real_mount(path->mnt))) |
| 1777 | goto unlock; |
| 1778 | |
| 1779 | /* Refuse the same filesystem on the same mount point */ |
| 1780 | err = -EBUSY; |
| 1781 | if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && |
| 1782 | path->mnt->mnt_root == path->dentry) |
| 1783 | goto unlock; |
| 1784 | |
| 1785 | err = -EINVAL; |
| 1786 | if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode)) |
| 1787 | goto unlock; |
| 1788 | |
| 1789 | newmnt->mnt.mnt_flags = mnt_flags; |
| 1790 | err = graft_tree(newmnt, path); |
| 1791 | |
| 1792 | unlock: |
| 1793 | unlock_mount(path); |
| 1794 | return err; |
| 1795 | } |
| 1796 | |
| 1797 | /* |
| 1798 | * create a new mount for userspace and request it to be added into the |
| 1799 | * namespace's tree |
| 1800 | */ |
| 1801 | static int do_new_mount(struct path *path, char *type, int flags, |
| 1802 | int mnt_flags, char *name, void *data) |
| 1803 | { |
| 1804 | struct vfsmount *mnt; |
| 1805 | int err; |
| 1806 | |
| 1807 | if (!type) |
| 1808 | return -EINVAL; |
| 1809 | |
| 1810 | /* we need capabilities... */ |
| 1811 | if (!capable(CAP_SYS_ADMIN)) |
| 1812 | return -EPERM; |
| 1813 | |
| 1814 | mnt = do_kern_mount(type, flags, name, data); |
| 1815 | if (IS_ERR(mnt)) |
| 1816 | return PTR_ERR(mnt); |
| 1817 | |
| 1818 | err = do_add_mount(real_mount(mnt), path, mnt_flags); |
| 1819 | if (err) |
| 1820 | mntput(mnt); |
| 1821 | return err; |
| 1822 | } |
| 1823 | |
| 1824 | int finish_automount(struct vfsmount *m, struct path *path) |
| 1825 | { |
| 1826 | struct mount *mnt = real_mount(m); |
| 1827 | int err; |
| 1828 | /* The new mount record should have at least 2 refs to prevent it being |
| 1829 | * expired before we get a chance to add it |
| 1830 | */ |
| 1831 | BUG_ON(mnt_get_count(mnt) < 2); |
| 1832 | |
| 1833 | if (m->mnt_sb == path->mnt->mnt_sb && |
| 1834 | m->mnt_root == path->dentry) { |
| 1835 | err = -ELOOP; |
| 1836 | goto fail; |
| 1837 | } |
| 1838 | |
| 1839 | err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE); |
| 1840 | if (!err) |
| 1841 | return 0; |
| 1842 | fail: |
| 1843 | /* remove m from any expiration list it may be on */ |
| 1844 | if (!list_empty(&mnt->mnt_expire)) { |
| 1845 | down_write(&namespace_sem); |
| 1846 | br_write_lock(vfsmount_lock); |
| 1847 | list_del_init(&mnt->mnt_expire); |
| 1848 | br_write_unlock(vfsmount_lock); |
| 1849 | up_write(&namespace_sem); |
| 1850 | } |
| 1851 | mntput(m); |
| 1852 | mntput(m); |
| 1853 | return err; |
| 1854 | } |
| 1855 | |
| 1856 | /** |
| 1857 | * mnt_set_expiry - Put a mount on an expiration list |
| 1858 | * @mnt: The mount to list. |
| 1859 | * @expiry_list: The list to add the mount to. |
| 1860 | */ |
| 1861 | void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) |
| 1862 | { |
| 1863 | down_write(&namespace_sem); |
| 1864 | br_write_lock(vfsmount_lock); |
| 1865 | |
| 1866 | list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); |
| 1867 | |
| 1868 | br_write_unlock(vfsmount_lock); |
| 1869 | up_write(&namespace_sem); |
| 1870 | } |
| 1871 | EXPORT_SYMBOL(mnt_set_expiry); |
| 1872 | |
| 1873 | /* |
| 1874 | * process a list of expirable mountpoints with the intent of discarding any |
| 1875 | * mountpoints that aren't in use and haven't been touched since last we came |
| 1876 | * here |
| 1877 | */ |
| 1878 | void mark_mounts_for_expiry(struct list_head *mounts) |
| 1879 | { |
| 1880 | struct mount *mnt, *next; |
| 1881 | LIST_HEAD(graveyard); |
| 1882 | LIST_HEAD(umounts); |
| 1883 | |
| 1884 | if (list_empty(mounts)) |
| 1885 | return; |
| 1886 | |
| 1887 | down_write(&namespace_sem); |
| 1888 | br_write_lock(vfsmount_lock); |
| 1889 | |
| 1890 | /* extract from the expiration list every vfsmount that matches the |
| 1891 | * following criteria: |
| 1892 | * - only referenced by its parent vfsmount |
| 1893 | * - still marked for expiry (marked on the last call here; marks are |
| 1894 | * cleared by mntput()) |
| 1895 | */ |
| 1896 | list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { |
| 1897 | if (!xchg(&mnt->mnt_expiry_mark, 1) || |
| 1898 | propagate_mount_busy(mnt, 1)) |
| 1899 | continue; |
| 1900 | list_move(&mnt->mnt_expire, &graveyard); |
| 1901 | } |
| 1902 | while (!list_empty(&graveyard)) { |
| 1903 | mnt = list_first_entry(&graveyard, struct mount, mnt_expire); |
| 1904 | touch_mnt_namespace(mnt->mnt_ns); |
| 1905 | umount_tree(mnt, 1, &umounts); |
| 1906 | } |
| 1907 | br_write_unlock(vfsmount_lock); |
| 1908 | up_write(&namespace_sem); |
| 1909 | |
| 1910 | release_mounts(&umounts); |
| 1911 | } |
| 1912 | |
| 1913 | EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); |
| 1914 | |
| 1915 | /* |
| 1916 | * Ripoff of 'select_parent()' |
| 1917 | * |
| 1918 | * search the list of submounts for a given mountpoint, and move any |
| 1919 | * shrinkable submounts to the 'graveyard' list. |
| 1920 | */ |
| 1921 | static int select_submounts(struct mount *parent, struct list_head *graveyard) |
| 1922 | { |
| 1923 | struct mount *this_parent = parent; |
| 1924 | struct list_head *next; |
| 1925 | int found = 0; |
| 1926 | |
| 1927 | repeat: |
| 1928 | next = this_parent->mnt_mounts.next; |
| 1929 | resume: |
| 1930 | while (next != &this_parent->mnt_mounts) { |
| 1931 | struct list_head *tmp = next; |
| 1932 | struct mount *mnt = list_entry(tmp, struct mount, mnt_child); |
| 1933 | |
| 1934 | next = tmp->next; |
| 1935 | if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) |
| 1936 | continue; |
| 1937 | /* |
| 1938 | * Descend a level if the d_mounts list is non-empty. |
| 1939 | */ |
| 1940 | if (!list_empty(&mnt->mnt_mounts)) { |
| 1941 | this_parent = mnt; |
| 1942 | goto repeat; |
| 1943 | } |
| 1944 | |
| 1945 | if (!propagate_mount_busy(mnt, 1)) { |
| 1946 | list_move_tail(&mnt->mnt_expire, graveyard); |
| 1947 | found++; |
| 1948 | } |
| 1949 | } |
| 1950 | /* |
| 1951 | * All done at this level ... ascend and resume the search |
| 1952 | */ |
| 1953 | if (this_parent != parent) { |
| 1954 | next = this_parent->mnt_child.next; |
| 1955 | this_parent = this_parent->mnt_parent; |
| 1956 | goto resume; |
| 1957 | } |
| 1958 | return found; |
| 1959 | } |
| 1960 | |
| 1961 | /* |
| 1962 | * process a list of expirable mountpoints with the intent of discarding any |
| 1963 | * submounts of a specific parent mountpoint |
| 1964 | * |
| 1965 | * vfsmount_lock must be held for write |
| 1966 | */ |
| 1967 | static void shrink_submounts(struct mount *mnt, struct list_head *umounts) |
| 1968 | { |
| 1969 | LIST_HEAD(graveyard); |
| 1970 | struct mount *m; |
| 1971 | |
| 1972 | /* extract submounts of 'mountpoint' from the expiration list */ |
| 1973 | while (select_submounts(mnt, &graveyard)) { |
| 1974 | while (!list_empty(&graveyard)) { |
| 1975 | m = list_first_entry(&graveyard, struct mount, |
| 1976 | mnt_expire); |
| 1977 | touch_mnt_namespace(m->mnt_ns); |
| 1978 | umount_tree(m, 1, umounts); |
| 1979 | } |
| 1980 | } |
| 1981 | } |
| 1982 | |
| 1983 | /* |
| 1984 | * Some copy_from_user() implementations do not return the exact number of |
| 1985 | * bytes remaining to copy on a fault. But copy_mount_options() requires that. |
| 1986 | * Note that this function differs from copy_from_user() in that it will oops |
| 1987 | * on bad values of `to', rather than returning a short copy. |
| 1988 | */ |
| 1989 | static long exact_copy_from_user(void *to, const void __user * from, |
| 1990 | unsigned long n) |
| 1991 | { |
| 1992 | char *t = to; |
| 1993 | const char __user *f = from; |
| 1994 | char c; |
| 1995 | |
| 1996 | if (!access_ok(VERIFY_READ, from, n)) |
| 1997 | return n; |
| 1998 | |
| 1999 | while (n) { |
| 2000 | if (__get_user(c, f)) { |
| 2001 | memset(t, 0, n); |
| 2002 | break; |
| 2003 | } |
| 2004 | *t++ = c; |
| 2005 | f++; |
| 2006 | n--; |
| 2007 | } |
| 2008 | return n; |
| 2009 | } |
| 2010 | |
| 2011 | int copy_mount_options(const void __user * data, unsigned long *where) |
| 2012 | { |
| 2013 | int i; |
| 2014 | unsigned long page; |
| 2015 | unsigned long size; |
| 2016 | |
| 2017 | *where = 0; |
| 2018 | if (!data) |
| 2019 | return 0; |
| 2020 | |
| 2021 | if (!(page = __get_free_page(GFP_KERNEL))) |
| 2022 | return -ENOMEM; |
| 2023 | |
| 2024 | /* We only care that *some* data at the address the user |
| 2025 | * gave us is valid. Just in case, we'll zero |
| 2026 | * the remainder of the page. |
| 2027 | */ |
| 2028 | /* copy_from_user cannot cross TASK_SIZE ! */ |
| 2029 | size = TASK_SIZE - (unsigned long)data; |
| 2030 | if (size > PAGE_SIZE) |
| 2031 | size = PAGE_SIZE; |
| 2032 | |
| 2033 | i = size - exact_copy_from_user((void *)page, data, size); |
| 2034 | if (!i) { |
| 2035 | free_page(page); |
| 2036 | return -EFAULT; |
| 2037 | } |
| 2038 | if (i != PAGE_SIZE) |
| 2039 | memset((char *)page + i, 0, PAGE_SIZE - i); |
| 2040 | *where = page; |
| 2041 | return 0; |
| 2042 | } |
| 2043 | |
| 2044 | int copy_mount_string(const void __user *data, char **where) |
| 2045 | { |
| 2046 | char *tmp; |
| 2047 | |
| 2048 | if (!data) { |
| 2049 | *where = NULL; |
| 2050 | return 0; |
| 2051 | } |
| 2052 | |
| 2053 | tmp = strndup_user(data, PAGE_SIZE); |
| 2054 | if (IS_ERR(tmp)) |
| 2055 | return PTR_ERR(tmp); |
| 2056 | |
| 2057 | *where = tmp; |
| 2058 | return 0; |
| 2059 | } |
| 2060 | |
| 2061 | /* |
| 2062 | * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to |
| 2063 | * be given to the mount() call (ie: read-only, no-dev, no-suid etc). |
| 2064 | * |
| 2065 | * data is a (void *) that can point to any structure up to |
| 2066 | * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent |
| 2067 | * information (or be NULL). |
| 2068 | * |
| 2069 | * Pre-0.97 versions of mount() didn't have a flags word. |
| 2070 | * When the flags word was introduced its top half was required |
| 2071 | * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. |
| 2072 | * Therefore, if this magic number is present, it carries no information |
| 2073 | * and must be discarded. |
| 2074 | */ |
| 2075 | long do_mount(char *dev_name, char *dir_name, char *type_page, |
| 2076 | unsigned long flags, void *data_page) |
| 2077 | { |
| 2078 | struct path path; |
| 2079 | int retval = 0; |
| 2080 | int mnt_flags = 0; |
| 2081 | |
| 2082 | /* Discard magic */ |
| 2083 | if ((flags & MS_MGC_MSK) == MS_MGC_VAL) |
| 2084 | flags &= ~MS_MGC_MSK; |
| 2085 | |
| 2086 | /* Basic sanity checks */ |
| 2087 | |
| 2088 | if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) |
| 2089 | return -EINVAL; |
| 2090 | |
| 2091 | if (data_page) |
| 2092 | ((char *)data_page)[PAGE_SIZE - 1] = 0; |
| 2093 | |
| 2094 | /* ... and get the mountpoint */ |
| 2095 | retval = kern_path(dir_name, LOOKUP_FOLLOW, &path); |
| 2096 | if (retval) |
| 2097 | return retval; |
| 2098 | |
| 2099 | retval = security_sb_mount(dev_name, &path, |
| 2100 | type_page, flags, data_page); |
| 2101 | if (retval) |
| 2102 | goto dput_out; |
| 2103 | |
| 2104 | /* Default to relatime unless overriden */ |
| 2105 | if (!(flags & MS_NOATIME)) |
| 2106 | mnt_flags |= MNT_RELATIME; |
| 2107 | |
| 2108 | /* Separate the per-mountpoint flags */ |
| 2109 | if (flags & MS_NOSUID) |
| 2110 | mnt_flags |= MNT_NOSUID; |
| 2111 | if (flags & MS_NODEV) |
| 2112 | mnt_flags |= MNT_NODEV; |
| 2113 | if (flags & MS_NOEXEC) |
| 2114 | mnt_flags |= MNT_NOEXEC; |
| 2115 | if (flags & MS_NOATIME) |
| 2116 | mnt_flags |= MNT_NOATIME; |
| 2117 | if (flags & MS_NODIRATIME) |
| 2118 | mnt_flags |= MNT_NODIRATIME; |
| 2119 | if (flags & MS_STRICTATIME) |
| 2120 | mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); |
| 2121 | if (flags & MS_RDONLY) |
| 2122 | mnt_flags |= MNT_READONLY; |
| 2123 | |
| 2124 | flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | |
| 2125 | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | |
| 2126 | MS_STRICTATIME); |
| 2127 | |
| 2128 | if (flags & MS_REMOUNT) |
| 2129 | retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags, |
| 2130 | data_page); |
| 2131 | else if (flags & MS_BIND) |
| 2132 | retval = do_loopback(&path, dev_name, flags & MS_REC); |
| 2133 | else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) |
| 2134 | retval = do_change_type(&path, flags); |
| 2135 | else if (flags & MS_MOVE) |
| 2136 | retval = do_move_mount(&path, dev_name); |
| 2137 | else |
| 2138 | retval = do_new_mount(&path, type_page, flags, mnt_flags, |
| 2139 | dev_name, data_page); |
| 2140 | dput_out: |
| 2141 | path_put(&path); |
| 2142 | return retval; |
| 2143 | } |
| 2144 | |
| 2145 | static struct mnt_namespace *alloc_mnt_ns(void) |
| 2146 | { |
| 2147 | struct mnt_namespace *new_ns; |
| 2148 | |
| 2149 | new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); |
| 2150 | if (!new_ns) |
| 2151 | return ERR_PTR(-ENOMEM); |
| 2152 | atomic_set(&new_ns->count, 1); |
| 2153 | new_ns->root = NULL; |
| 2154 | INIT_LIST_HEAD(&new_ns->list); |
| 2155 | init_waitqueue_head(&new_ns->poll); |
| 2156 | new_ns->event = 0; |
| 2157 | return new_ns; |
| 2158 | } |
| 2159 | |
| 2160 | void mnt_make_longterm(struct vfsmount *mnt) |
| 2161 | { |
| 2162 | __mnt_make_longterm(real_mount(mnt)); |
| 2163 | } |
| 2164 | |
| 2165 | void mnt_make_shortterm(struct vfsmount *m) |
| 2166 | { |
| 2167 | #ifdef CONFIG_SMP |
| 2168 | struct mount *mnt = real_mount(m); |
| 2169 | if (atomic_add_unless(&mnt->mnt_longterm, -1, 1)) |
| 2170 | return; |
| 2171 | br_write_lock(vfsmount_lock); |
| 2172 | atomic_dec(&mnt->mnt_longterm); |
| 2173 | br_write_unlock(vfsmount_lock); |
| 2174 | #endif |
| 2175 | } |
| 2176 | |
| 2177 | /* |
| 2178 | * Allocate a new namespace structure and populate it with contents |
| 2179 | * copied from the namespace of the passed in task structure. |
| 2180 | */ |
| 2181 | static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, |
| 2182 | struct fs_struct *fs) |
| 2183 | { |
| 2184 | struct mnt_namespace *new_ns; |
| 2185 | struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; |
| 2186 | struct mount *p, *q; |
| 2187 | struct mount *old = mnt_ns->root; |
| 2188 | struct mount *new; |
| 2189 | |
| 2190 | new_ns = alloc_mnt_ns(); |
| 2191 | if (IS_ERR(new_ns)) |
| 2192 | return new_ns; |
| 2193 | |
| 2194 | down_write(&namespace_sem); |
| 2195 | /* First pass: copy the tree topology */ |
| 2196 | new = copy_tree(old, old->mnt.mnt_root, CL_COPY_ALL | CL_EXPIRE); |
| 2197 | if (!new) { |
| 2198 | up_write(&namespace_sem); |
| 2199 | kfree(new_ns); |
| 2200 | return ERR_PTR(-ENOMEM); |
| 2201 | } |
| 2202 | new_ns->root = new; |
| 2203 | br_write_lock(vfsmount_lock); |
| 2204 | list_add_tail(&new_ns->list, &new->mnt_list); |
| 2205 | br_write_unlock(vfsmount_lock); |
| 2206 | |
| 2207 | /* |
| 2208 | * Second pass: switch the tsk->fs->* elements and mark new vfsmounts |
| 2209 | * as belonging to new namespace. We have already acquired a private |
| 2210 | * fs_struct, so tsk->fs->lock is not needed. |
| 2211 | */ |
| 2212 | p = old; |
| 2213 | q = new; |
| 2214 | while (p) { |
| 2215 | q->mnt_ns = new_ns; |
| 2216 | __mnt_make_longterm(q); |
| 2217 | if (fs) { |
| 2218 | if (&p->mnt == fs->root.mnt) { |
| 2219 | fs->root.mnt = mntget(&q->mnt); |
| 2220 | __mnt_make_longterm(q); |
| 2221 | mnt_make_shortterm(&p->mnt); |
| 2222 | rootmnt = &p->mnt; |
| 2223 | } |
| 2224 | if (&p->mnt == fs->pwd.mnt) { |
| 2225 | fs->pwd.mnt = mntget(&q->mnt); |
| 2226 | __mnt_make_longterm(q); |
| 2227 | mnt_make_shortterm(&p->mnt); |
| 2228 | pwdmnt = &p->mnt; |
| 2229 | } |
| 2230 | } |
| 2231 | p = next_mnt(p, old); |
| 2232 | q = next_mnt(q, new); |
| 2233 | } |
| 2234 | up_write(&namespace_sem); |
| 2235 | |
| 2236 | if (rootmnt) |
| 2237 | mntput(rootmnt); |
| 2238 | if (pwdmnt) |
| 2239 | mntput(pwdmnt); |
| 2240 | |
| 2241 | return new_ns; |
| 2242 | } |
| 2243 | |
| 2244 | struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, |
| 2245 | struct fs_struct *new_fs) |
| 2246 | { |
| 2247 | struct mnt_namespace *new_ns; |
| 2248 | |
| 2249 | BUG_ON(!ns); |
| 2250 | get_mnt_ns(ns); |
| 2251 | |
| 2252 | if (!(flags & CLONE_NEWNS)) |
| 2253 | return ns; |
| 2254 | |
| 2255 | new_ns = dup_mnt_ns(ns, new_fs); |
| 2256 | |
| 2257 | put_mnt_ns(ns); |
| 2258 | return new_ns; |
| 2259 | } |
| 2260 | |
| 2261 | /** |
| 2262 | * create_mnt_ns - creates a private namespace and adds a root filesystem |
| 2263 | * @mnt: pointer to the new root filesystem mountpoint |
| 2264 | */ |
| 2265 | static struct mnt_namespace *create_mnt_ns(struct vfsmount *m) |
| 2266 | { |
| 2267 | struct mnt_namespace *new_ns = alloc_mnt_ns(); |
| 2268 | if (!IS_ERR(new_ns)) { |
| 2269 | struct mount *mnt = real_mount(m); |
| 2270 | mnt->mnt_ns = new_ns; |
| 2271 | __mnt_make_longterm(mnt); |
| 2272 | new_ns->root = mnt; |
| 2273 | list_add(&new_ns->list, &mnt->mnt_list); |
| 2274 | } else { |
| 2275 | mntput(m); |
| 2276 | } |
| 2277 | return new_ns; |
| 2278 | } |
| 2279 | |
| 2280 | struct dentry *mount_subtree(struct vfsmount *mnt, const char *name) |
| 2281 | { |
| 2282 | struct mnt_namespace *ns; |
| 2283 | struct super_block *s; |
| 2284 | struct path path; |
| 2285 | int err; |
| 2286 | |
| 2287 | ns = create_mnt_ns(mnt); |
| 2288 | if (IS_ERR(ns)) |
| 2289 | return ERR_CAST(ns); |
| 2290 | |
| 2291 | err = vfs_path_lookup(mnt->mnt_root, mnt, |
| 2292 | name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); |
| 2293 | |
| 2294 | put_mnt_ns(ns); |
| 2295 | |
| 2296 | if (err) |
| 2297 | return ERR_PTR(err); |
| 2298 | |
| 2299 | /* trade a vfsmount reference for active sb one */ |
| 2300 | s = path.mnt->mnt_sb; |
| 2301 | atomic_inc(&s->s_active); |
| 2302 | mntput(path.mnt); |
| 2303 | /* lock the sucker */ |
| 2304 | down_write(&s->s_umount); |
| 2305 | /* ... and return the root of (sub)tree on it */ |
| 2306 | return path.dentry; |
| 2307 | } |
| 2308 | EXPORT_SYMBOL(mount_subtree); |
| 2309 | |
| 2310 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, |
| 2311 | char __user *, type, unsigned long, flags, void __user *, data) |
| 2312 | { |
| 2313 | int ret; |
| 2314 | char *kernel_type; |
| 2315 | char *kernel_dir; |
| 2316 | char *kernel_dev; |
| 2317 | unsigned long data_page; |
| 2318 | |
| 2319 | ret = copy_mount_string(type, &kernel_type); |
| 2320 | if (ret < 0) |
| 2321 | goto out_type; |
| 2322 | |
| 2323 | kernel_dir = getname(dir_name); |
| 2324 | if (IS_ERR(kernel_dir)) { |
| 2325 | ret = PTR_ERR(kernel_dir); |
| 2326 | goto out_dir; |
| 2327 | } |
| 2328 | |
| 2329 | ret = copy_mount_string(dev_name, &kernel_dev); |
| 2330 | if (ret < 0) |
| 2331 | goto out_dev; |
| 2332 | |
| 2333 | ret = copy_mount_options(data, &data_page); |
| 2334 | if (ret < 0) |
| 2335 | goto out_data; |
| 2336 | |
| 2337 | ret = do_mount(kernel_dev, kernel_dir, kernel_type, flags, |
| 2338 | (void *) data_page); |
| 2339 | |
| 2340 | free_page(data_page); |
| 2341 | out_data: |
| 2342 | kfree(kernel_dev); |
| 2343 | out_dev: |
| 2344 | putname(kernel_dir); |
| 2345 | out_dir: |
| 2346 | kfree(kernel_type); |
| 2347 | out_type: |
| 2348 | return ret; |
| 2349 | } |
| 2350 | |
| 2351 | /* |
| 2352 | * Return true if path is reachable from root |
| 2353 | * |
| 2354 | * namespace_sem or vfsmount_lock is held |
| 2355 | */ |
| 2356 | bool is_path_reachable(struct mount *mnt, struct dentry *dentry, |
| 2357 | const struct path *root) |
| 2358 | { |
| 2359 | while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { |
| 2360 | dentry = mnt->mnt_mountpoint; |
| 2361 | mnt = mnt->mnt_parent; |
| 2362 | } |
| 2363 | return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); |
| 2364 | } |
| 2365 | |
| 2366 | int path_is_under(struct path *path1, struct path *path2) |
| 2367 | { |
| 2368 | int res; |
| 2369 | br_read_lock(vfsmount_lock); |
| 2370 | res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); |
| 2371 | br_read_unlock(vfsmount_lock); |
| 2372 | return res; |
| 2373 | } |
| 2374 | EXPORT_SYMBOL(path_is_under); |
| 2375 | |
| 2376 | /* |
| 2377 | * pivot_root Semantics: |
| 2378 | * Moves the root file system of the current process to the directory put_old, |
| 2379 | * makes new_root as the new root file system of the current process, and sets |
| 2380 | * root/cwd of all processes which had them on the current root to new_root. |
| 2381 | * |
| 2382 | * Restrictions: |
| 2383 | * The new_root and put_old must be directories, and must not be on the |
| 2384 | * same file system as the current process root. The put_old must be |
| 2385 | * underneath new_root, i.e. adding a non-zero number of /.. to the string |
| 2386 | * pointed to by put_old must yield the same directory as new_root. No other |
| 2387 | * file system may be mounted on put_old. After all, new_root is a mountpoint. |
| 2388 | * |
| 2389 | * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. |
| 2390 | * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives |
| 2391 | * in this situation. |
| 2392 | * |
| 2393 | * Notes: |
| 2394 | * - we don't move root/cwd if they are not at the root (reason: if something |
| 2395 | * cared enough to change them, it's probably wrong to force them elsewhere) |
| 2396 | * - it's okay to pick a root that isn't the root of a file system, e.g. |
| 2397 | * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, |
| 2398 | * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root |
| 2399 | * first. |
| 2400 | */ |
| 2401 | SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, |
| 2402 | const char __user *, put_old) |
| 2403 | { |
| 2404 | struct path new, old, parent_path, root_parent, root; |
| 2405 | struct mount *new_mnt, *root_mnt; |
| 2406 | int error; |
| 2407 | |
| 2408 | if (!capable(CAP_SYS_ADMIN)) |
| 2409 | return -EPERM; |
| 2410 | |
| 2411 | error = user_path_dir(new_root, &new); |
| 2412 | if (error) |
| 2413 | goto out0; |
| 2414 | |
| 2415 | error = user_path_dir(put_old, &old); |
| 2416 | if (error) |
| 2417 | goto out1; |
| 2418 | |
| 2419 | error = security_sb_pivotroot(&old, &new); |
| 2420 | if (error) |
| 2421 | goto out2; |
| 2422 | |
| 2423 | get_fs_root(current->fs, &root); |
| 2424 | error = lock_mount(&old); |
| 2425 | if (error) |
| 2426 | goto out3; |
| 2427 | |
| 2428 | error = -EINVAL; |
| 2429 | new_mnt = real_mount(new.mnt); |
| 2430 | root_mnt = real_mount(root.mnt); |
| 2431 | if (IS_MNT_SHARED(real_mount(old.mnt)) || |
| 2432 | IS_MNT_SHARED(new_mnt->mnt_parent) || |
| 2433 | IS_MNT_SHARED(root_mnt->mnt_parent)) |
| 2434 | goto out4; |
| 2435 | if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) |
| 2436 | goto out4; |
| 2437 | error = -ENOENT; |
| 2438 | if (d_unlinked(new.dentry)) |
| 2439 | goto out4; |
| 2440 | if (d_unlinked(old.dentry)) |
| 2441 | goto out4; |
| 2442 | error = -EBUSY; |
| 2443 | if (new.mnt == root.mnt || |
| 2444 | old.mnt == root.mnt) |
| 2445 | goto out4; /* loop, on the same file system */ |
| 2446 | error = -EINVAL; |
| 2447 | if (root.mnt->mnt_root != root.dentry) |
| 2448 | goto out4; /* not a mountpoint */ |
| 2449 | if (!mnt_has_parent(root_mnt)) |
| 2450 | goto out4; /* not attached */ |
| 2451 | if (new.mnt->mnt_root != new.dentry) |
| 2452 | goto out4; /* not a mountpoint */ |
| 2453 | if (!mnt_has_parent(new_mnt)) |
| 2454 | goto out4; /* not attached */ |
| 2455 | /* make sure we can reach put_old from new_root */ |
| 2456 | if (!is_path_reachable(real_mount(old.mnt), old.dentry, &new)) |
| 2457 | goto out4; |
| 2458 | br_write_lock(vfsmount_lock); |
| 2459 | detach_mnt(new_mnt, &parent_path); |
| 2460 | detach_mnt(root_mnt, &root_parent); |
| 2461 | /* mount old root on put_old */ |
| 2462 | attach_mnt(root_mnt, &old); |
| 2463 | /* mount new_root on / */ |
| 2464 | attach_mnt(new_mnt, &root_parent); |
| 2465 | touch_mnt_namespace(current->nsproxy->mnt_ns); |
| 2466 | br_write_unlock(vfsmount_lock); |
| 2467 | chroot_fs_refs(&root, &new); |
| 2468 | error = 0; |
| 2469 | out4: |
| 2470 | unlock_mount(&old); |
| 2471 | if (!error) { |
| 2472 | path_put(&root_parent); |
| 2473 | path_put(&parent_path); |
| 2474 | } |
| 2475 | out3: |
| 2476 | path_put(&root); |
| 2477 | out2: |
| 2478 | path_put(&old); |
| 2479 | out1: |
| 2480 | path_put(&new); |
| 2481 | out0: |
| 2482 | return error; |
| 2483 | } |
| 2484 | |
| 2485 | static void __init init_mount_tree(void) |
| 2486 | { |
| 2487 | struct vfsmount *mnt; |
| 2488 | struct mnt_namespace *ns; |
| 2489 | struct path root; |
| 2490 | |
| 2491 | mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); |
| 2492 | if (IS_ERR(mnt)) |
| 2493 | panic("Can't create rootfs"); |
| 2494 | |
| 2495 | ns = create_mnt_ns(mnt); |
| 2496 | if (IS_ERR(ns)) |
| 2497 | panic("Can't allocate initial namespace"); |
| 2498 | |
| 2499 | init_task.nsproxy->mnt_ns = ns; |
| 2500 | get_mnt_ns(ns); |
| 2501 | |
| 2502 | root.mnt = mnt; |
| 2503 | root.dentry = mnt->mnt_root; |
| 2504 | |
| 2505 | set_fs_pwd(current->fs, &root); |
| 2506 | set_fs_root(current->fs, &root); |
| 2507 | } |
| 2508 | |
| 2509 | void __init mnt_init(void) |
| 2510 | { |
| 2511 | unsigned u; |
| 2512 | int err; |
| 2513 | |
| 2514 | init_rwsem(&namespace_sem); |
| 2515 | |
| 2516 | mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), |
| 2517 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
| 2518 | |
| 2519 | mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); |
| 2520 | |
| 2521 | if (!mount_hashtable) |
| 2522 | panic("Failed to allocate mount hash table\n"); |
| 2523 | |
| 2524 | printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE); |
| 2525 | |
| 2526 | for (u = 0; u < HASH_SIZE; u++) |
| 2527 | INIT_LIST_HEAD(&mount_hashtable[u]); |
| 2528 | |
| 2529 | br_lock_init(vfsmount_lock); |
| 2530 | |
| 2531 | err = sysfs_init(); |
| 2532 | if (err) |
| 2533 | printk(KERN_WARNING "%s: sysfs_init error: %d\n", |
| 2534 | __func__, err); |
| 2535 | fs_kobj = kobject_create_and_add("fs", NULL); |
| 2536 | if (!fs_kobj) |
| 2537 | printk(KERN_WARNING "%s: kobj create error\n", __func__); |
| 2538 | init_rootfs(); |
| 2539 | init_mount_tree(); |
| 2540 | } |
| 2541 | |
| 2542 | void put_mnt_ns(struct mnt_namespace *ns) |
| 2543 | { |
| 2544 | LIST_HEAD(umount_list); |
| 2545 | |
| 2546 | if (!atomic_dec_and_test(&ns->count)) |
| 2547 | return; |
| 2548 | down_write(&namespace_sem); |
| 2549 | br_write_lock(vfsmount_lock); |
| 2550 | umount_tree(ns->root, 0, &umount_list); |
| 2551 | br_write_unlock(vfsmount_lock); |
| 2552 | up_write(&namespace_sem); |
| 2553 | release_mounts(&umount_list); |
| 2554 | kfree(ns); |
| 2555 | } |
| 2556 | |
| 2557 | struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) |
| 2558 | { |
| 2559 | struct vfsmount *mnt; |
| 2560 | mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); |
| 2561 | if (!IS_ERR(mnt)) { |
| 2562 | /* |
| 2563 | * it is a longterm mount, don't release mnt until |
| 2564 | * we unmount before file sys is unregistered |
| 2565 | */ |
| 2566 | mnt_make_longterm(mnt); |
| 2567 | } |
| 2568 | return mnt; |
| 2569 | } |
| 2570 | EXPORT_SYMBOL_GPL(kern_mount_data); |
| 2571 | |
| 2572 | void kern_unmount(struct vfsmount *mnt) |
| 2573 | { |
| 2574 | /* release long term mount so mount point can be released */ |
| 2575 | if (!IS_ERR_OR_NULL(mnt)) { |
| 2576 | mnt_make_shortterm(mnt); |
| 2577 | mntput(mnt); |
| 2578 | } |
| 2579 | } |
| 2580 | EXPORT_SYMBOL(kern_unmount); |
| 2581 | |
| 2582 | bool our_mnt(struct vfsmount *mnt) |
| 2583 | { |
| 2584 | return check_mnt(real_mount(mnt)); |
| 2585 | } |