4 * Copyright (C) 1991, 1992 Linus Torvalds
8 * Some corrections by tytso.
11 /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
14 /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
17 #include <linux/init.h>
18 #include <linux/module.h>
19 #include <linux/slab.h>
21 #include <linux/namei.h>
22 #include <linux/pagemap.h>
23 #include <linux/fsnotify.h>
24 #include <linux/personality.h>
25 #include <linux/security.h>
26 #include <linux/ima.h>
27 #include <linux/syscalls.h>
28 #include <linux/mount.h>
29 #include <linux/audit.h>
30 #include <linux/capability.h>
31 #include <linux/file.h>
32 #include <linux/fcntl.h>
33 #include <linux/device_cgroup.h>
34 #include <linux/fs_struct.h>
35 #include <asm/uaccess.h>
39 /* [Feb-1997 T. Schoebel-Theuer]
40 * Fundamental changes in the pathname lookup mechanisms (namei)
41 * were necessary because of omirr. The reason is that omirr needs
42 * to know the _real_ pathname, not the user-supplied one, in case
43 * of symlinks (and also when transname replacements occur).
45 * The new code replaces the old recursive symlink resolution with
46 * an iterative one (in case of non-nested symlink chains). It does
47 * this with calls to <fs>_follow_link().
48 * As a side effect, dir_namei(), _namei() and follow_link() are now
49 * replaced with a single function lookup_dentry() that can handle all
50 * the special cases of the former code.
52 * With the new dcache, the pathname is stored at each inode, at least as
53 * long as the refcount of the inode is positive. As a side effect, the
54 * size of the dcache depends on the inode cache and thus is dynamic.
56 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
57 * resolution to correspond with current state of the code.
59 * Note that the symlink resolution is not *completely* iterative.
60 * There is still a significant amount of tail- and mid- recursion in
61 * the algorithm. Also, note that <fs>_readlink() is not used in
62 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
63 * may return different results than <fs>_follow_link(). Many virtual
64 * filesystems (including /proc) exhibit this behavior.
67 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
68 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
69 * and the name already exists in form of a symlink, try to create the new
70 * name indicated by the symlink. The old code always complained that the
71 * name already exists, due to not following the symlink even if its target
72 * is nonexistent. The new semantics affects also mknod() and link() when
73 * the name is a symlink pointing to a non-existant name.
75 * I don't know which semantics is the right one, since I have no access
76 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
77 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
78 * "old" one. Personally, I think the new semantics is much more logical.
79 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
80 * file does succeed in both HP-UX and SunOs, but not in Solaris
81 * and in the old Linux semantics.
84 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
85 * semantics. See the comments in "open_namei" and "do_link" below.
87 * [10-Sep-98 Alan Modra] Another symlink change.
90 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
91 * inside the path - always follow.
92 * in the last component in creation/removal/renaming - never follow.
93 * if LOOKUP_FOLLOW passed - follow.
94 * if the pathname has trailing slashes - follow.
95 * otherwise - don't follow.
96 * (applied in that order).
98 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
99 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
100 * During the 2.4 we need to fix the userland stuff depending on it -
101 * hopefully we will be able to get rid of that wart in 2.5. So far only
102 * XEmacs seems to be relying on it...
105 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
106 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
107 * any extra contention...
110 /* In order to reduce some races, while at the same time doing additional
111 * checking and hopefully speeding things up, we copy filenames to the
112 * kernel data space before using them..
114 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
115 * PATH_MAX includes the nul terminator --RR.
117 static int do_getname(const char __user *filename, char *page)
120 unsigned long len = PATH_MAX;
122 if (!segment_eq(get_fs(), KERNEL_DS)) {
123 if ((unsigned long) filename >= TASK_SIZE)
125 if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
126 len = TASK_SIZE - (unsigned long) filename;
129 retval = strncpy_from_user(page, filename, len);
133 return -ENAMETOOLONG;
139 char * getname(const char __user * filename)
143 result = ERR_PTR(-ENOMEM);
146 int retval = do_getname(filename, tmp);
151 result = ERR_PTR(retval);
154 audit_getname(result);
158 #ifdef CONFIG_AUDITSYSCALL
159 void putname(const char *name)
161 if (unlikely(!audit_dummy_context()))
166 EXPORT_SYMBOL(putname);
170 * This does basic POSIX ACL permission checking
172 static inline int __acl_permission_check(struct inode *inode, int mask,
173 int (*check_acl)(struct inode *inode, int mask), int rcu)
175 umode_t mode = inode->i_mode;
177 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
179 if (current_fsuid() == inode->i_uid)
182 if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
186 int error = check_acl(inode, mask);
187 if (error != -EAGAIN)
192 if (in_group_p(inode->i_gid))
197 * If the DACs are ok we don't need any capability check.
199 if ((mask & ~mode) == 0)
204 static inline int acl_permission_check(struct inode *inode, int mask,
205 int (*check_acl)(struct inode *inode, int mask))
207 return __acl_permission_check(inode, mask, check_acl, 0);
211 * generic_permission - check for access rights on a Posix-like filesystem
212 * @inode: inode to check access rights for
213 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
214 * @check_acl: optional callback to check for Posix ACLs
216 * Used to check for read/write/execute permissions on a file.
217 * We use "fsuid" for this, letting us set arbitrary permissions
218 * for filesystem access without changing the "normal" uids which
219 * are used for other things..
221 int generic_permission(struct inode *inode, int mask,
222 int (*check_acl)(struct inode *inode, int mask))
227 * Do the basic POSIX ACL permission checks.
229 ret = acl_permission_check(inode, mask, check_acl);
234 * Read/write DACs are always overridable.
235 * Executable DACs are overridable if at least one exec bit is set.
237 if (!(mask & MAY_EXEC) || execute_ok(inode))
238 if (capable(CAP_DAC_OVERRIDE))
242 * Searching includes executable on directories, else just read.
244 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
245 if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
246 if (capable(CAP_DAC_READ_SEARCH))
253 * inode_permission - check for access rights to a given inode
254 * @inode: inode to check permission on
255 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
257 * Used to check for read/write/execute permissions on an inode.
258 * We use "fsuid" for this, letting us set arbitrary permissions
259 * for filesystem access without changing the "normal" uids which
260 * are used for other things.
262 int inode_permission(struct inode *inode, int mask)
266 if (mask & MAY_WRITE) {
267 umode_t mode = inode->i_mode;
270 * Nobody gets write access to a read-only fs.
272 if (IS_RDONLY(inode) &&
273 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
277 * Nobody gets write access to an immutable file.
279 if (IS_IMMUTABLE(inode))
283 if (inode->i_op->permission)
284 retval = inode->i_op->permission(inode, mask);
286 retval = generic_permission(inode, mask, inode->i_op->check_acl);
291 retval = devcgroup_inode_permission(inode, mask);
295 return security_inode_permission(inode, mask);
299 * file_permission - check for additional access rights to a given file
300 * @file: file to check access rights for
301 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
303 * Used to check for read/write/execute permissions on an already opened
307 * Do not use this function in new code. All access checks should
308 * be done using inode_permission().
310 int file_permission(struct file *file, int mask)
312 return inode_permission(file->f_path.dentry->d_inode, mask);
316 * get_write_access() gets write permission for a file.
317 * put_write_access() releases this write permission.
318 * This is used for regular files.
319 * We cannot support write (and maybe mmap read-write shared) accesses and
320 * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
321 * can have the following values:
322 * 0: no writers, no VM_DENYWRITE mappings
323 * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
324 * > 0: (i_writecount) users are writing to the file.
326 * Normally we operate on that counter with atomic_{inc,dec} and it's safe
327 * except for the cases where we don't hold i_writecount yet. Then we need to
328 * use {get,deny}_write_access() - these functions check the sign and refuse
329 * to do the change if sign is wrong. Exclusion between them is provided by
330 * the inode->i_lock spinlock.
333 int get_write_access(struct inode * inode)
335 spin_lock(&inode->i_lock);
336 if (atomic_read(&inode->i_writecount) < 0) {
337 spin_unlock(&inode->i_lock);
340 atomic_inc(&inode->i_writecount);
341 spin_unlock(&inode->i_lock);
346 int deny_write_access(struct file * file)
348 struct inode *inode = file->f_path.dentry->d_inode;
350 spin_lock(&inode->i_lock);
351 if (atomic_read(&inode->i_writecount) > 0) {
352 spin_unlock(&inode->i_lock);
355 atomic_dec(&inode->i_writecount);
356 spin_unlock(&inode->i_lock);
362 * path_get - get a reference to a path
363 * @path: path to get the reference to
365 * Given a path increment the reference count to the dentry and the vfsmount.
367 void path_get(struct path *path)
372 EXPORT_SYMBOL(path_get);
375 * path_put - put a reference to a path
376 * @path: path to put the reference to
378 * Given a path decrement the reference count to the dentry and the vfsmount.
380 void path_put(struct path *path)
385 EXPORT_SYMBOL(path_put);
388 * nameidata_drop_rcu - drop this nameidata out of rcu-walk
389 * @nd: nameidata pathwalk data to drop
390 * @Returns: 0 on success, -ECHLID on failure
392 * Path walking has 2 modes, rcu-walk and ref-walk (see
393 * Documentation/filesystems/path-lookup.txt). __drop_rcu* functions attempt
394 * to drop out of rcu-walk mode and take normal reference counts on dentries
395 * and vfsmounts to transition to rcu-walk mode. __drop_rcu* functions take
396 * refcounts at the last known good point before rcu-walk got stuck, so
397 * ref-walk may continue from there. If this is not successful (eg. a seqcount
398 * has changed), then failure is returned and path walk restarts from the
399 * beginning in ref-walk mode.
401 * nameidata_drop_rcu attempts to drop the current nd->path and nd->root into
402 * ref-walk. Must be called from rcu-walk context.
404 static int nameidata_drop_rcu(struct nameidata *nd)
406 struct fs_struct *fs = current->fs;
407 struct dentry *dentry = nd->path.dentry;
409 BUG_ON(!(nd->flags & LOOKUP_RCU));
411 spin_lock(&fs->lock);
412 if (nd->root.mnt != fs->root.mnt ||
413 nd->root.dentry != fs->root.dentry)
416 spin_lock(&dentry->d_lock);
417 if (!__d_rcu_to_refcount(dentry, nd->seq))
419 BUG_ON(nd->inode != dentry->d_inode);
420 spin_unlock(&dentry->d_lock);
423 spin_unlock(&fs->lock);
425 mntget(nd->path.mnt);
428 br_read_unlock(vfsmount_lock);
429 nd->flags &= ~LOOKUP_RCU;
432 spin_unlock(&dentry->d_lock);
435 spin_unlock(&fs->lock);
439 /* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
440 static inline int nameidata_drop_rcu_maybe(struct nameidata *nd)
442 if (nd->flags & LOOKUP_RCU)
443 return nameidata_drop_rcu(nd);
448 * nameidata_dentry_drop_rcu - drop nameidata and dentry out of rcu-walk
449 * @nd: nameidata pathwalk data to drop
450 * @dentry: dentry to drop
451 * @Returns: 0 on success, -ECHLID on failure
453 * nameidata_dentry_drop_rcu attempts to drop the current nd->path and nd->root,
454 * and dentry into ref-walk. @dentry must be a path found by a do_lookup call on
455 * @nd. Must be called from rcu-walk context.
457 static int nameidata_dentry_drop_rcu(struct nameidata *nd, struct dentry *dentry)
459 struct fs_struct *fs = current->fs;
460 struct dentry *parent = nd->path.dentry;
462 BUG_ON(!(nd->flags & LOOKUP_RCU));
464 spin_lock(&fs->lock);
465 if (nd->root.mnt != fs->root.mnt ||
466 nd->root.dentry != fs->root.dentry)
469 spin_lock(&parent->d_lock);
470 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
471 if (!__d_rcu_to_refcount(dentry, nd->seq))
474 * If the sequence check on the child dentry passed, then the child has
475 * not been removed from its parent. This means the parent dentry must
476 * be valid and able to take a reference at this point.
478 BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
479 BUG_ON(!parent->d_count);
481 spin_unlock(&dentry->d_lock);
482 spin_unlock(&parent->d_lock);
485 spin_unlock(&fs->lock);
487 mntget(nd->path.mnt);
490 br_read_unlock(vfsmount_lock);
491 nd->flags &= ~LOOKUP_RCU;
494 spin_unlock(&dentry->d_lock);
495 spin_unlock(&parent->d_lock);
498 spin_unlock(&fs->lock);
502 /* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
503 static inline int nameidata_dentry_drop_rcu_maybe(struct nameidata *nd, struct dentry *dentry)
505 if (nd->flags & LOOKUP_RCU)
506 return nameidata_dentry_drop_rcu(nd, dentry);
511 * nameidata_drop_rcu_last - drop nameidata ending path walk out of rcu-walk
512 * @nd: nameidata pathwalk data to drop
513 * @Returns: 0 on success, -ECHLID on failure
515 * nameidata_drop_rcu_last attempts to drop the current nd->path into ref-walk.
516 * nd->path should be the final element of the lookup, so nd->root is discarded.
517 * Must be called from rcu-walk context.
519 static int nameidata_drop_rcu_last(struct nameidata *nd)
521 struct dentry *dentry = nd->path.dentry;
523 BUG_ON(!(nd->flags & LOOKUP_RCU));
524 nd->flags &= ~LOOKUP_RCU;
526 spin_lock(&dentry->d_lock);
527 if (!__d_rcu_to_refcount(dentry, nd->seq))
529 BUG_ON(nd->inode != dentry->d_inode);
530 spin_unlock(&dentry->d_lock);
532 mntget(nd->path.mnt);
535 br_read_unlock(vfsmount_lock);
540 spin_unlock(&dentry->d_lock);
542 br_read_unlock(vfsmount_lock);
546 /* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
547 static inline int nameidata_drop_rcu_last_maybe(struct nameidata *nd)
549 if (likely(nd->flags & LOOKUP_RCU))
550 return nameidata_drop_rcu_last(nd);
555 * release_open_intent - free up open intent resources
556 * @nd: pointer to nameidata
558 void release_open_intent(struct nameidata *nd)
560 if (nd->intent.open.file->f_path.dentry == NULL)
561 put_filp(nd->intent.open.file);
563 fput(nd->intent.open.file);
566 static int d_revalidate(struct dentry *dentry, struct nameidata *nd)
570 status = dentry->d_op->d_revalidate(dentry, nd);
571 if (status == -ECHILD) {
572 if (nameidata_dentry_drop_rcu(nd, dentry))
574 status = dentry->d_op->d_revalidate(dentry, nd);
580 static inline struct dentry *
581 do_revalidate(struct dentry *dentry, struct nameidata *nd)
585 status = d_revalidate(dentry, nd);
586 if (unlikely(status <= 0)) {
588 * The dentry failed validation.
589 * If d_revalidate returned 0 attempt to invalidate
590 * the dentry otherwise d_revalidate is asking us
591 * to return a fail status.
594 /* If we're in rcu-walk, we don't have a ref */
595 if (!(nd->flags & LOOKUP_RCU))
597 dentry = ERR_PTR(status);
600 /* Don't d_invalidate in rcu-walk mode */
601 if (nameidata_dentry_drop_rcu_maybe(nd, dentry))
602 return ERR_PTR(-ECHILD);
603 if (!d_invalidate(dentry)) {
612 static inline int need_reval_dot(struct dentry *dentry)
614 if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
617 if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
624 * force_reval_path - force revalidation of a dentry
626 * In some situations the path walking code will trust dentries without
627 * revalidating them. This causes problems for filesystems that depend on
628 * d_revalidate to handle file opens (e.g. NFSv4). When FS_REVAL_DOT is set
629 * (which indicates that it's possible for the dentry to go stale), force
630 * a d_revalidate call before proceeding.
632 * Returns 0 if the revalidation was successful. If the revalidation fails,
633 * either return the error returned by d_revalidate or -ESTALE if the
634 * revalidation it just returned 0. If d_revalidate returns 0, we attempt to
635 * invalidate the dentry. It's up to the caller to handle putting references
636 * to the path if necessary.
639 force_reval_path(struct path *path, struct nameidata *nd)
642 struct dentry *dentry = path->dentry;
645 * only check on filesystems where it's possible for the dentry to
648 if (!need_reval_dot(dentry))
651 status = d_revalidate(dentry, nd);
656 d_invalidate(dentry);
663 * Short-cut version of permission(), for calling on directories
664 * during pathname resolution. Combines parts of permission()
665 * and generic_permission(), and tests ONLY for MAY_EXEC permission.
667 * If appropriate, check DAC only. If not appropriate, or
668 * short-cut DAC fails, then call ->permission() to do more
669 * complete permission check.
671 static inline int __exec_permission(struct inode *inode, int rcu)
675 if (inode->i_op->permission) {
678 ret = inode->i_op->permission(inode, MAY_EXEC);
683 ret = __acl_permission_check(inode, MAY_EXEC, inode->i_op->check_acl, rcu);
686 if (rcu && ret == -ECHILD)
689 if (capable(CAP_DAC_OVERRIDE) || capable(CAP_DAC_READ_SEARCH))
694 return security_inode_exec_permission(inode, rcu);
697 static int exec_permission(struct inode *inode)
699 return __exec_permission(inode, 0);
702 static int exec_permission_rcu(struct inode *inode)
704 return __exec_permission(inode, 1);
707 static __always_inline void set_root(struct nameidata *nd)
710 get_fs_root(current->fs, &nd->root);
713 static int link_path_walk(const char *, struct nameidata *);
715 static __always_inline void set_root_rcu(struct nameidata *nd)
718 struct fs_struct *fs = current->fs;
722 seq = read_seqcount_begin(&fs->seq);
724 } while (read_seqcount_retry(&fs->seq, seq));
728 static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
741 nd->inode = nd->path.dentry->d_inode;
743 ret = link_path_walk(link, nd);
747 return PTR_ERR(link);
750 static void path_put_conditional(struct path *path, struct nameidata *nd)
753 if (path->mnt != nd->path.mnt)
757 static inline void path_to_nameidata(struct path *path, struct nameidata *nd)
759 if (!(nd->flags & LOOKUP_RCU)) {
760 dput(nd->path.dentry);
761 if (nd->path.mnt != path->mnt)
762 mntput(nd->path.mnt);
764 nd->path.mnt = path->mnt;
765 nd->path.dentry = path->dentry;
768 static __always_inline int
769 __do_follow_link(struct path *path, struct nameidata *nd, void **p)
772 struct dentry *dentry = path->dentry;
774 touch_atime(path->mnt, dentry);
775 nd_set_link(nd, NULL);
777 if (path->mnt != nd->path.mnt) {
778 path_to_nameidata(path, nd);
779 nd->inode = nd->path.dentry->d_inode;
784 nd->last_type = LAST_BIND;
785 *p = dentry->d_inode->i_op->follow_link(dentry, nd);
788 char *s = nd_get_link(nd);
791 error = __vfs_follow_link(nd, s);
792 else if (nd->last_type == LAST_BIND) {
793 error = force_reval_path(&nd->path, nd);
802 * This limits recursive symlink follows to 8, while
803 * limiting consecutive symlinks to 40.
805 * Without that kind of total limit, nasty chains of consecutive
806 * symlinks can cause almost arbitrarily long lookups.
808 static inline int do_follow_link(struct path *path, struct nameidata *nd)
812 if (current->link_count >= MAX_NESTED_LINKS)
814 if (current->total_link_count >= 40)
816 BUG_ON(nd->depth >= MAX_NESTED_LINKS);
818 err = security_inode_follow_link(path->dentry, nd);
821 current->link_count++;
822 current->total_link_count++;
824 err = __do_follow_link(path, nd, &cookie);
825 if (!IS_ERR(cookie) && path->dentry->d_inode->i_op->put_link)
826 path->dentry->d_inode->i_op->put_link(path->dentry, nd, cookie);
828 current->link_count--;
832 path_put_conditional(path, nd);
837 static int follow_up_rcu(struct path *path)
839 struct vfsmount *parent;
840 struct dentry *mountpoint;
842 parent = path->mnt->mnt_parent;
843 if (parent == path->mnt)
845 mountpoint = path->mnt->mnt_mountpoint;
846 path->dentry = mountpoint;
851 int follow_up(struct path *path)
853 struct vfsmount *parent;
854 struct dentry *mountpoint;
856 br_read_lock(vfsmount_lock);
857 parent = path->mnt->mnt_parent;
858 if (parent == path->mnt) {
859 br_read_unlock(vfsmount_lock);
863 mountpoint = dget(path->mnt->mnt_mountpoint);
864 br_read_unlock(vfsmount_lock);
866 path->dentry = mountpoint;
873 * serialization is taken care of in namespace.c
875 static void __follow_mount_rcu(struct nameidata *nd, struct path *path,
876 struct inode **inode)
878 while (d_mountpoint(path->dentry)) {
879 struct vfsmount *mounted;
880 mounted = __lookup_mnt(path->mnt, path->dentry, 1);
884 path->dentry = mounted->mnt_root;
885 nd->seq = read_seqcount_begin(&path->dentry->d_seq);
886 *inode = path->dentry->d_inode;
890 static int __follow_mount(struct path *path)
893 while (d_mountpoint(path->dentry)) {
894 struct vfsmount *mounted = lookup_mnt(path);
901 path->dentry = dget(mounted->mnt_root);
907 static void follow_mount(struct path *path)
909 while (d_mountpoint(path->dentry)) {
910 struct vfsmount *mounted = lookup_mnt(path);
916 path->dentry = dget(mounted->mnt_root);
920 int follow_down(struct path *path)
922 struct vfsmount *mounted;
924 mounted = lookup_mnt(path);
929 path->dentry = dget(mounted->mnt_root);
935 static int follow_dotdot_rcu(struct nameidata *nd)
937 struct inode *inode = nd->inode;
942 if (nd->path.dentry == nd->root.dentry &&
943 nd->path.mnt == nd->root.mnt) {
946 if (nd->path.dentry != nd->path.mnt->mnt_root) {
947 struct dentry *old = nd->path.dentry;
948 struct dentry *parent = old->d_parent;
951 seq = read_seqcount_begin(&parent->d_seq);
952 if (read_seqcount_retry(&old->d_seq, nd->seq))
954 inode = parent->d_inode;
955 nd->path.dentry = parent;
959 if (!follow_up_rcu(&nd->path))
961 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
962 inode = nd->path.dentry->d_inode;
964 __follow_mount_rcu(nd, &nd->path, &inode);
970 static void follow_dotdot(struct nameidata *nd)
975 struct dentry *old = nd->path.dentry;
977 if (nd->path.dentry == nd->root.dentry &&
978 nd->path.mnt == nd->root.mnt) {
981 if (nd->path.dentry != nd->path.mnt->mnt_root) {
982 /* rare case of legitimate dget_parent()... */
983 nd->path.dentry = dget_parent(nd->path.dentry);
987 if (!follow_up(&nd->path))
990 follow_mount(&nd->path);
991 nd->inode = nd->path.dentry->d_inode;
995 * Allocate a dentry with name and parent, and perform a parent
996 * directory ->lookup on it. Returns the new dentry, or ERR_PTR
997 * on error. parent->d_inode->i_mutex must be held. d_lookup must
998 * have verified that no child exists while under i_mutex.
1000 static struct dentry *d_alloc_and_lookup(struct dentry *parent,
1001 struct qstr *name, struct nameidata *nd)
1003 struct inode *inode = parent->d_inode;
1004 struct dentry *dentry;
1007 /* Don't create child dentry for a dead directory. */
1008 if (unlikely(IS_DEADDIR(inode)))
1009 return ERR_PTR(-ENOENT);
1011 dentry = d_alloc(parent, name);
1012 if (unlikely(!dentry))
1013 return ERR_PTR(-ENOMEM);
1015 old = inode->i_op->lookup(inode, dentry, nd);
1016 if (unlikely(old)) {
1024 * It's more convoluted than I'd like it to be, but... it's still fairly
1025 * small and for now I'd prefer to have fast path as straight as possible.
1026 * It _is_ time-critical.
1028 static int do_lookup(struct nameidata *nd, struct qstr *name,
1029 struct path *path, struct inode **inode)
1031 struct vfsmount *mnt = nd->path.mnt;
1032 struct dentry *dentry, *parent = nd->path.dentry;
1035 * See if the low-level filesystem might want
1036 * to use its own hash..
1038 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
1039 int err = parent->d_op->d_hash(parent, nd->inode, name);
1045 * Rename seqlock is not required here because in the off chance
1046 * of a false negative due to a concurrent rename, we're going to
1047 * do the non-racy lookup, below.
1049 if (nd->flags & LOOKUP_RCU) {
1053 dentry = __d_lookup_rcu(parent, name, &seq, inode);
1055 if (nameidata_drop_rcu(nd))
1059 /* Memory barrier in read_seqcount_begin of child is enough */
1060 if (__read_seqcount_retry(&parent->d_seq, nd->seq))
1064 if (dentry->d_flags & DCACHE_OP_REVALIDATE)
1065 goto need_revalidate;
1067 path->dentry = dentry;
1068 __follow_mount_rcu(nd, path, inode);
1070 dentry = __d_lookup(parent, name);
1074 if (dentry->d_flags & DCACHE_OP_REVALIDATE)
1075 goto need_revalidate;
1078 path->dentry = dentry;
1079 __follow_mount(path);
1080 *inode = path->dentry->d_inode;
1085 dir = parent->d_inode;
1086 BUG_ON(nd->inode != dir);
1088 mutex_lock(&dir->i_mutex);
1090 * First re-do the cached lookup just in case it was created
1091 * while we waited for the directory semaphore, or the first
1092 * lookup failed due to an unrelated rename.
1094 * This could use version numbering or similar to avoid unnecessary
1095 * cache lookups, but then we'd have to do the first lookup in the
1096 * non-racy way. However in the common case here, everything should
1097 * be hot in cache, so would it be a big win?
1099 dentry = d_lookup(parent, name);
1100 if (likely(!dentry)) {
1101 dentry = d_alloc_and_lookup(parent, name, nd);
1102 mutex_unlock(&dir->i_mutex);
1108 * Uhhuh! Nasty case: the cache was re-populated while
1109 * we waited on the semaphore. Need to revalidate.
1111 mutex_unlock(&dir->i_mutex);
1115 dentry = do_revalidate(dentry, nd);
1123 return PTR_ERR(dentry);
1127 * This is a temporary kludge to deal with "automount" symlinks; proper
1128 * solution is to trigger them on follow_mount(), so that do_lookup()
1129 * would DTRT. To be killed before 2.6.34-final.
1131 static inline int follow_on_final(struct inode *inode, unsigned lookup_flags)
1133 return inode && unlikely(inode->i_op->follow_link) &&
1134 ((lookup_flags & LOOKUP_FOLLOW) || S_ISDIR(inode->i_mode));
1139 * This is the basic name resolution function, turning a pathname into
1140 * the final dentry. We expect 'base' to be positive and a directory.
1142 * Returns 0 and nd will have valid dentry and mnt on success.
1143 * Returns error and drops reference to input namei data on failure.
1145 static int link_path_walk(const char *name, struct nameidata *nd)
1149 unsigned int lookup_flags = nd->flags;
1157 lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);
1159 /* At this point we know we have a real path component. */
1161 struct inode *inode;
1166 nd->flags |= LOOKUP_CONTINUE;
1167 if (nd->flags & LOOKUP_RCU) {
1168 err = exec_permission_rcu(nd->inode);
1169 if (err == -ECHILD) {
1170 if (nameidata_drop_rcu(nd))
1176 err = exec_permission(nd->inode);
1182 c = *(const unsigned char *)name;
1184 hash = init_name_hash();
1187 hash = partial_name_hash(c, hash);
1188 c = *(const unsigned char *)name;
1189 } while (c && (c != '/'));
1190 this.len = name - (const char *) this.name;
1191 this.hash = end_name_hash(hash);
1193 /* remove trailing slashes? */
1195 goto last_component;
1196 while (*++name == '/');
1198 goto last_with_slashes;
1201 * "." and ".." are special - ".." especially so because it has
1202 * to be able to know about the current root directory and
1203 * parent relationships.
1205 if (this.name[0] == '.') switch (this.len) {
1209 if (this.name[1] != '.')
1211 if (nd->flags & LOOKUP_RCU) {
1212 if (follow_dotdot_rcu(nd))
1220 /* This does the actual lookups.. */
1221 err = do_lookup(nd, &this, &next, &inode);
1228 if (inode->i_op->follow_link) {
1229 /* We commonly drop rcu-walk here */
1230 if (nameidata_dentry_drop_rcu_maybe(nd, next.dentry))
1232 BUG_ON(inode != next.dentry->d_inode);
1233 err = do_follow_link(&next, nd);
1236 nd->inode = nd->path.dentry->d_inode;
1241 path_to_nameidata(&next, nd);
1245 if (!nd->inode->i_op->lookup)
1248 /* here ends the main loop */
1251 lookup_flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
1253 /* Clear LOOKUP_CONTINUE iff it was previously unset */
1254 nd->flags &= lookup_flags | ~LOOKUP_CONTINUE;
1255 if (lookup_flags & LOOKUP_PARENT)
1257 if (this.name[0] == '.') switch (this.len) {
1261 if (this.name[1] != '.')
1263 if (nd->flags & LOOKUP_RCU) {
1264 if (follow_dotdot_rcu(nd))
1272 err = do_lookup(nd, &this, &next, &inode);
1275 if (follow_on_final(inode, lookup_flags)) {
1276 if (nameidata_dentry_drop_rcu_maybe(nd, next.dentry))
1278 BUG_ON(inode != next.dentry->d_inode);
1279 err = do_follow_link(&next, nd);
1282 nd->inode = nd->path.dentry->d_inode;
1284 path_to_nameidata(&next, nd);
1290 if (lookup_flags & LOOKUP_DIRECTORY) {
1292 if (!nd->inode->i_op->lookup)
1298 nd->last_type = LAST_NORM;
1299 if (this.name[0] != '.')
1302 nd->last_type = LAST_DOT;
1303 else if (this.len == 2 && this.name[1] == '.')
1304 nd->last_type = LAST_DOTDOT;
1309 * We bypassed the ordinary revalidation routines.
1310 * We may need to check the cached dentry for staleness.
1312 if (need_reval_dot(nd->path.dentry)) {
1313 /* Note: we do not d_invalidate() */
1314 err = d_revalidate(nd->path.dentry, nd);
1321 if (nameidata_drop_rcu_last_maybe(nd))
1325 if (!(nd->flags & LOOKUP_RCU))
1326 path_put_conditional(&next, nd);
1329 if (!(nd->flags & LOOKUP_RCU))
1330 path_put(&nd->path);
1335 static inline int path_walk_rcu(const char *name, struct nameidata *nd)
1337 current->total_link_count = 0;
1339 return link_path_walk(name, nd);
1342 static inline int path_walk_simple(const char *name, struct nameidata *nd)
1344 current->total_link_count = 0;
1346 return link_path_walk(name, nd);
1349 static int path_walk(const char *name, struct nameidata *nd)
1351 struct path save = nd->path;
1354 current->total_link_count = 0;
1356 /* make sure the stuff we saved doesn't go away */
1359 result = link_path_walk(name, nd);
1360 if (result == -ESTALE) {
1361 /* nd->path had been dropped */
1362 current->total_link_count = 0;
1364 path_get(&nd->path);
1365 nd->flags |= LOOKUP_REVAL;
1366 result = link_path_walk(name, nd);
1374 static void path_finish_rcu(struct nameidata *nd)
1376 if (nd->flags & LOOKUP_RCU) {
1377 /* RCU dangling. Cancel it. */
1378 nd->flags &= ~LOOKUP_RCU;
1379 nd->root.mnt = NULL;
1381 br_read_unlock(vfsmount_lock);
1387 static int path_init_rcu(int dfd, const char *name, unsigned int flags, struct nameidata *nd)
1393 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1394 nd->flags = flags | LOOKUP_RCU;
1396 nd->root.mnt = NULL;
1400 struct fs_struct *fs = current->fs;
1403 br_read_lock(vfsmount_lock);
1407 seq = read_seqcount_begin(&fs->seq);
1408 nd->root = fs->root;
1409 nd->path = nd->root;
1410 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1411 } while (read_seqcount_retry(&fs->seq, seq));
1413 } else if (dfd == AT_FDCWD) {
1414 struct fs_struct *fs = current->fs;
1417 br_read_lock(vfsmount_lock);
1421 seq = read_seqcount_begin(&fs->seq);
1423 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1424 } while (read_seqcount_retry(&fs->seq, seq));
1427 struct dentry *dentry;
1429 file = fget_light(dfd, &fput_needed);
1434 dentry = file->f_path.dentry;
1437 if (!S_ISDIR(dentry->d_inode->i_mode))
1440 retval = file_permission(file, MAY_EXEC);
1444 nd->path = file->f_path;
1448 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1449 br_read_lock(vfsmount_lock);
1452 nd->inode = nd->path.dentry->d_inode;
1456 fput_light(file, fput_needed);
1461 static int path_init(int dfd, const char *name, unsigned int flags, struct nameidata *nd)
1467 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1470 nd->root.mnt = NULL;
1474 nd->path = nd->root;
1475 path_get(&nd->root);
1476 } else if (dfd == AT_FDCWD) {
1477 get_fs_pwd(current->fs, &nd->path);
1479 struct dentry *dentry;
1481 file = fget_light(dfd, &fput_needed);
1486 dentry = file->f_path.dentry;
1489 if (!S_ISDIR(dentry->d_inode->i_mode))
1492 retval = file_permission(file, MAY_EXEC);
1496 nd->path = file->f_path;
1497 path_get(&file->f_path);
1499 fput_light(file, fput_needed);
1501 nd->inode = nd->path.dentry->d_inode;
1505 fput_light(file, fput_needed);
1510 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1511 static int do_path_lookup(int dfd, const char *name,
1512 unsigned int flags, struct nameidata *nd)
1517 * Path walking is largely split up into 2 different synchronisation
1518 * schemes, rcu-walk and ref-walk (explained in
1519 * Documentation/filesystems/path-lookup.txt). These share much of the
1520 * path walk code, but some things particularly setup, cleanup, and
1521 * following mounts are sufficiently divergent that functions are
1522 * duplicated. Typically there is a function foo(), and its RCU
1523 * analogue, foo_rcu().
1525 * -ECHILD is the error number of choice (just to avoid clashes) that
1526 * is returned if some aspect of an rcu-walk fails. Such an error must
1527 * be handled by restarting a traditional ref-walk (which will always
1528 * be able to complete).
1530 retval = path_init_rcu(dfd, name, flags, nd);
1531 if (unlikely(retval))
1533 retval = path_walk_rcu(name, nd);
1534 path_finish_rcu(nd);
1536 path_put(&nd->root);
1537 nd->root.mnt = NULL;
1540 if (unlikely(retval == -ECHILD || retval == -ESTALE)) {
1541 /* slower, locked walk */
1542 if (retval == -ESTALE)
1543 flags |= LOOKUP_REVAL;
1544 retval = path_init(dfd, name, flags, nd);
1545 if (unlikely(retval))
1547 retval = path_walk(name, nd);
1549 path_put(&nd->root);
1550 nd->root.mnt = NULL;
1554 if (likely(!retval)) {
1555 if (unlikely(!audit_dummy_context())) {
1556 if (nd->path.dentry && nd->inode)
1557 audit_inode(name, nd->path.dentry);
1564 int path_lookup(const char *name, unsigned int flags,
1565 struct nameidata *nd)
1567 return do_path_lookup(AT_FDCWD, name, flags, nd);
1570 int kern_path(const char *name, unsigned int flags, struct path *path)
1572 struct nameidata nd;
1573 int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
1580 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
1581 * @dentry: pointer to dentry of the base directory
1582 * @mnt: pointer to vfs mount of the base directory
1583 * @name: pointer to file name
1584 * @flags: lookup flags
1585 * @nd: pointer to nameidata
1587 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
1588 const char *name, unsigned int flags,
1589 struct nameidata *nd)
1593 /* same as do_path_lookup */
1594 nd->last_type = LAST_ROOT;
1598 nd->path.dentry = dentry;
1600 path_get(&nd->path);
1601 nd->root = nd->path;
1602 path_get(&nd->root);
1603 nd->inode = nd->path.dentry->d_inode;
1605 retval = path_walk(name, nd);
1606 if (unlikely(!retval && !audit_dummy_context() && nd->path.dentry &&
1608 audit_inode(name, nd->path.dentry);
1610 path_put(&nd->root);
1611 nd->root.mnt = NULL;
1616 static struct dentry *__lookup_hash(struct qstr *name,
1617 struct dentry *base, struct nameidata *nd)
1619 struct inode *inode = base->d_inode;
1620 struct dentry *dentry;
1623 err = exec_permission(inode);
1625 return ERR_PTR(err);
1628 * See if the low-level filesystem might want
1629 * to use its own hash..
1631 if (base->d_flags & DCACHE_OP_HASH) {
1632 err = base->d_op->d_hash(base, inode, name);
1633 dentry = ERR_PTR(err);
1639 * Don't bother with __d_lookup: callers are for creat as
1640 * well as unlink, so a lot of the time it would cost
1643 dentry = d_lookup(base, name);
1645 if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE))
1646 dentry = do_revalidate(dentry, nd);
1649 dentry = d_alloc_and_lookup(base, name, nd);
1655 * Restricted form of lookup. Doesn't follow links, single-component only,
1656 * needs parent already locked. Doesn't follow mounts.
1659 static struct dentry *lookup_hash(struct nameidata *nd)
1661 return __lookup_hash(&nd->last, nd->path.dentry, nd);
1664 static int __lookup_one_len(const char *name, struct qstr *this,
1665 struct dentry *base, int len)
1675 hash = init_name_hash();
1677 c = *(const unsigned char *)name++;
1678 if (c == '/' || c == '\0')
1680 hash = partial_name_hash(c, hash);
1682 this->hash = end_name_hash(hash);
1687 * lookup_one_len - filesystem helper to lookup single pathname component
1688 * @name: pathname component to lookup
1689 * @base: base directory to lookup from
1690 * @len: maximum length @len should be interpreted to
1692 * Note that this routine is purely a helper for filesystem usage and should
1693 * not be called by generic code. Also note that by using this function the
1694 * nameidata argument is passed to the filesystem methods and a filesystem
1695 * using this helper needs to be prepared for that.
1697 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
1702 WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
1704 err = __lookup_one_len(name, &this, base, len);
1706 return ERR_PTR(err);
1708 return __lookup_hash(&this, base, NULL);
1711 int user_path_at(int dfd, const char __user *name, unsigned flags,
1714 struct nameidata nd;
1715 char *tmp = getname(name);
1716 int err = PTR_ERR(tmp);
1719 BUG_ON(flags & LOOKUP_PARENT);
1721 err = do_path_lookup(dfd, tmp, flags, &nd);
1729 static int user_path_parent(int dfd, const char __user *path,
1730 struct nameidata *nd, char **name)
1732 char *s = getname(path);
1738 error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd);
1748 * It's inline, so penalty for filesystems that don't use sticky bit is
1751 static inline int check_sticky(struct inode *dir, struct inode *inode)
1753 uid_t fsuid = current_fsuid();
1755 if (!(dir->i_mode & S_ISVTX))
1757 if (inode->i_uid == fsuid)
1759 if (dir->i_uid == fsuid)
1761 return !capable(CAP_FOWNER);
1765 * Check whether we can remove a link victim from directory dir, check
1766 * whether the type of victim is right.
1767 * 1. We can't do it if dir is read-only (done in permission())
1768 * 2. We should have write and exec permissions on dir
1769 * 3. We can't remove anything from append-only dir
1770 * 4. We can't do anything with immutable dir (done in permission())
1771 * 5. If the sticky bit on dir is set we should either
1772 * a. be owner of dir, or
1773 * b. be owner of victim, or
1774 * c. have CAP_FOWNER capability
1775 * 6. If the victim is append-only or immutable we can't do antyhing with
1776 * links pointing to it.
1777 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
1778 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
1779 * 9. We can't remove a root or mountpoint.
1780 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
1781 * nfs_async_unlink().
1783 static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
1787 if (!victim->d_inode)
1790 BUG_ON(victim->d_parent->d_inode != dir);
1791 audit_inode_child(victim, dir);
1793 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
1798 if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
1799 IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
1802 if (!S_ISDIR(victim->d_inode->i_mode))
1804 if (IS_ROOT(victim))
1806 } else if (S_ISDIR(victim->d_inode->i_mode))
1808 if (IS_DEADDIR(dir))
1810 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
1815 /* Check whether we can create an object with dentry child in directory
1817 * 1. We can't do it if child already exists (open has special treatment for
1818 * this case, but since we are inlined it's OK)
1819 * 2. We can't do it if dir is read-only (done in permission())
1820 * 3. We should have write and exec permissions on dir
1821 * 4. We can't do it if dir is immutable (done in permission())
1823 static inline int may_create(struct inode *dir, struct dentry *child)
1827 if (IS_DEADDIR(dir))
1829 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
1833 * p1 and p2 should be directories on the same fs.
1835 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
1840 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1844 mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
1846 p = d_ancestor(p2, p1);
1848 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
1849 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
1853 p = d_ancestor(p1, p2);
1855 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1856 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
1860 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1861 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
1865 void unlock_rename(struct dentry *p1, struct dentry *p2)
1867 mutex_unlock(&p1->d_inode->i_mutex);
1869 mutex_unlock(&p2->d_inode->i_mutex);
1870 mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
1874 int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
1875 struct nameidata *nd)
1877 int error = may_create(dir, dentry);
1882 if (!dir->i_op->create)
1883 return -EACCES; /* shouldn't it be ENOSYS? */
1886 error = security_inode_create(dir, dentry, mode);
1889 error = dir->i_op->create(dir, dentry, mode, nd);
1891 fsnotify_create(dir, dentry);
1895 int may_open(struct path *path, int acc_mode, int flag)
1897 struct dentry *dentry = path->dentry;
1898 struct inode *inode = dentry->d_inode;
1904 switch (inode->i_mode & S_IFMT) {
1908 if (acc_mode & MAY_WRITE)
1913 if (path->mnt->mnt_flags & MNT_NODEV)
1922 error = inode_permission(inode, acc_mode);
1927 * An append-only file must be opened in append mode for writing.
1929 if (IS_APPEND(inode)) {
1930 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
1936 /* O_NOATIME can only be set by the owner or superuser */
1937 if (flag & O_NOATIME && !is_owner_or_cap(inode))
1941 * Ensure there are no outstanding leases on the file.
1943 return break_lease(inode, flag);
1946 static int handle_truncate(struct path *path)
1948 struct inode *inode = path->dentry->d_inode;
1949 int error = get_write_access(inode);
1953 * Refuse to truncate files with mandatory locks held on them.
1955 error = locks_verify_locked(inode);
1957 error = security_path_truncate(path);
1959 error = do_truncate(path->dentry, 0,
1960 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
1963 put_write_access(inode);
1968 * Be careful about ever adding any more callers of this
1969 * function. Its flags must be in the namei format, not
1970 * what get passed to sys_open().
1972 static int __open_namei_create(struct nameidata *nd, struct path *path,
1973 int open_flag, int mode)
1976 struct dentry *dir = nd->path.dentry;
1978 if (!IS_POSIXACL(dir->d_inode))
1979 mode &= ~current_umask();
1980 error = security_path_mknod(&nd->path, path->dentry, mode, 0);
1983 error = vfs_create(dir->d_inode, path->dentry, mode, nd);
1985 mutex_unlock(&dir->d_inode->i_mutex);
1986 dput(nd->path.dentry);
1987 nd->path.dentry = path->dentry;
1991 /* Don't check for write permission, don't truncate */
1992 return may_open(&nd->path, 0, open_flag & ~O_TRUNC);
1996 * Note that while the flag value (low two bits) for sys_open means:
2001 * it is changed into
2002 * 00 - no permissions needed
2003 * 01 - read-permission
2004 * 10 - write-permission
2006 * for the internal routines (ie open_namei()/follow_link() etc)
2007 * This is more logical, and also allows the 00 "no perm needed"
2008 * to be used for symlinks (where the permissions are checked
2012 static inline int open_to_namei_flags(int flag)
2014 if ((flag+1) & O_ACCMODE)
2019 static int open_will_truncate(int flag, struct inode *inode)
2022 * We'll never write to the fs underlying
2025 if (special_file(inode->i_mode))
2027 return (flag & O_TRUNC);
2030 static struct file *finish_open(struct nameidata *nd,
2031 int open_flag, int acc_mode)
2037 will_truncate = open_will_truncate(open_flag, nd->path.dentry->d_inode);
2038 if (will_truncate) {
2039 error = mnt_want_write(nd->path.mnt);
2043 error = may_open(&nd->path, acc_mode, open_flag);
2046 mnt_drop_write(nd->path.mnt);
2049 filp = nameidata_to_filp(nd);
2050 if (!IS_ERR(filp)) {
2051 error = ima_file_check(filp, acc_mode);
2054 filp = ERR_PTR(error);
2057 if (!IS_ERR(filp)) {
2058 if (will_truncate) {
2059 error = handle_truncate(&nd->path);
2062 filp = ERR_PTR(error);
2067 * It is now safe to drop the mnt write
2068 * because the filp has had a write taken
2072 mnt_drop_write(nd->path.mnt);
2073 path_put(&nd->path);
2077 if (!IS_ERR(nd->intent.open.file))
2078 release_open_intent(nd);
2079 path_put(&nd->path);
2080 return ERR_PTR(error);
2084 * Handle O_CREAT case for do_filp_open
2086 static struct file *do_last(struct nameidata *nd, struct path *path,
2087 int open_flag, int acc_mode,
2088 int mode, const char *pathname)
2090 struct dentry *dir = nd->path.dentry;
2092 int error = -EISDIR;
2094 switch (nd->last_type) {
2097 dir = nd->path.dentry;
2099 if (need_reval_dot(dir)) {
2100 error = d_revalidate(nd->path.dentry, nd);
2110 audit_inode(pathname, dir);
2114 /* trailing slashes? */
2115 if (nd->last.name[nd->last.len])
2118 mutex_lock(&dir->d_inode->i_mutex);
2120 path->dentry = lookup_hash(nd);
2121 path->mnt = nd->path.mnt;
2123 error = PTR_ERR(path->dentry);
2124 if (IS_ERR(path->dentry)) {
2125 mutex_unlock(&dir->d_inode->i_mutex);
2129 if (IS_ERR(nd->intent.open.file)) {
2130 error = PTR_ERR(nd->intent.open.file);
2131 goto exit_mutex_unlock;
2134 /* Negative dentry, just create the file */
2135 if (!path->dentry->d_inode) {
2137 * This write is needed to ensure that a
2138 * ro->rw transition does not occur between
2139 * the time when the file is created and when
2140 * a permanent write count is taken through
2141 * the 'struct file' in nameidata_to_filp().
2143 error = mnt_want_write(nd->path.mnt);
2145 goto exit_mutex_unlock;
2146 error = __open_namei_create(nd, path, open_flag, mode);
2148 mnt_drop_write(nd->path.mnt);
2151 filp = nameidata_to_filp(nd);
2152 mnt_drop_write(nd->path.mnt);
2153 path_put(&nd->path);
2154 if (!IS_ERR(filp)) {
2155 error = ima_file_check(filp, acc_mode);
2158 filp = ERR_PTR(error);
2165 * It already exists.
2167 mutex_unlock(&dir->d_inode->i_mutex);
2168 audit_inode(pathname, path->dentry);
2171 if (open_flag & O_EXCL)
2174 if (__follow_mount(path)) {
2176 if (open_flag & O_NOFOLLOW)
2181 if (!path->dentry->d_inode)
2184 if (path->dentry->d_inode->i_op->follow_link)
2187 path_to_nameidata(path, nd);
2188 nd->inode = path->dentry->d_inode;
2190 if (S_ISDIR(nd->inode->i_mode))
2193 filp = finish_open(nd, open_flag, acc_mode);
2197 mutex_unlock(&dir->d_inode->i_mutex);
2199 path_put_conditional(path, nd);
2201 if (!IS_ERR(nd->intent.open.file))
2202 release_open_intent(nd);
2203 path_put(&nd->path);
2204 return ERR_PTR(error);
2208 * Note that the low bits of the passed in "open_flag"
2209 * are not the same as in the local variable "flag". See
2210 * open_to_namei_flags() for more details.
2212 struct file *do_filp_open(int dfd, const char *pathname,
2213 int open_flag, int mode, int acc_mode)
2216 struct nameidata nd;
2220 int flag = open_to_namei_flags(open_flag);
2223 if (!(open_flag & O_CREAT))
2226 /* Must never be set by userspace */
2227 open_flag &= ~FMODE_NONOTIFY;
2230 * O_SYNC is implemented as __O_SYNC|O_DSYNC. As many places only
2231 * check for O_DSYNC if the need any syncing at all we enforce it's
2232 * always set instead of having to deal with possibly weird behaviour
2233 * for malicious applications setting only __O_SYNC.
2235 if (open_flag & __O_SYNC)
2236 open_flag |= O_DSYNC;
2239 acc_mode = MAY_OPEN | ACC_MODE(open_flag);
2241 /* O_TRUNC implies we need access checks for write permissions */
2242 if (open_flag & O_TRUNC)
2243 acc_mode |= MAY_WRITE;
2245 /* Allow the LSM permission hook to distinguish append
2246 access from general write access. */
2247 if (open_flag & O_APPEND)
2248 acc_mode |= MAY_APPEND;
2250 flags = LOOKUP_OPEN;
2251 if (open_flag & O_CREAT) {
2252 flags |= LOOKUP_CREATE;
2253 if (open_flag & O_EXCL)
2254 flags |= LOOKUP_EXCL;
2256 if (open_flag & O_DIRECTORY)
2257 flags |= LOOKUP_DIRECTORY;
2258 if (!(open_flag & O_NOFOLLOW))
2259 flags |= LOOKUP_FOLLOW;
2261 filp = get_empty_filp();
2263 return ERR_PTR(-ENFILE);
2265 filp->f_flags = open_flag;
2266 nd.intent.open.file = filp;
2267 nd.intent.open.flags = flag;
2268 nd.intent.open.create_mode = mode;
2270 if (open_flag & O_CREAT)
2273 /* !O_CREAT, simple open */
2274 error = do_path_lookup(dfd, pathname, flags, &nd);
2275 if (unlikely(error))
2278 if (!(nd.flags & LOOKUP_FOLLOW)) {
2279 if (nd.inode->i_op->follow_link)
2283 if (nd.flags & LOOKUP_DIRECTORY) {
2284 if (!nd.inode->i_op->lookup)
2287 audit_inode(pathname, nd.path.dentry);
2288 filp = finish_open(&nd, open_flag, acc_mode);
2292 /* OK, have to create the file. Find the parent. */
2293 error = path_init_rcu(dfd, pathname,
2294 LOOKUP_PARENT | (flags & LOOKUP_REVAL), &nd);
2297 error = path_walk_rcu(pathname, &nd);
2298 path_finish_rcu(&nd);
2299 if (unlikely(error == -ECHILD || error == -ESTALE)) {
2300 /* slower, locked walk */
2301 if (error == -ESTALE) {
2303 flags |= LOOKUP_REVAL;
2305 error = path_init(dfd, pathname,
2306 LOOKUP_PARENT | (flags & LOOKUP_REVAL), &nd);
2310 error = path_walk_simple(pathname, &nd);
2312 if (unlikely(error))
2314 if (unlikely(!audit_dummy_context()))
2315 audit_inode(pathname, nd.path.dentry);
2318 * We have the parent and last component.
2321 filp = do_last(&nd, &path, open_flag, acc_mode, mode, pathname);
2322 while (unlikely(!filp)) { /* trailing symlink */
2326 /* S_ISDIR part is a temporary automount kludge */
2327 if (!(nd.flags & LOOKUP_FOLLOW) && !S_ISDIR(nd.inode->i_mode))
2332 * This is subtle. Instead of calling do_follow_link() we do
2333 * the thing by hands. The reason is that this way we have zero
2334 * link_count and path_walk() (called from ->follow_link)
2335 * honoring LOOKUP_PARENT. After that we have the parent and
2336 * last component, i.e. we are in the same situation as after
2337 * the first path_walk(). Well, almost - if the last component
2338 * is normal we get its copy stored in nd->last.name and we will
2339 * have to putname() it when we are done. Procfs-like symlinks
2340 * just set LAST_BIND.
2342 nd.flags |= LOOKUP_PARENT;
2343 error = security_inode_follow_link(path.dentry, &nd);
2346 error = __do_follow_link(&path, &nd, &cookie);
2347 if (unlikely(error)) {
2348 if (!IS_ERR(cookie) && nd.inode->i_op->put_link)
2349 nd.inode->i_op->put_link(path.dentry, &nd, cookie);
2350 /* nd.path had been dropped */
2355 nd.flags &= ~LOOKUP_PARENT;
2356 filp = do_last(&nd, &path, open_flag, acc_mode, mode, pathname);
2357 if (nd.inode->i_op->put_link)
2358 nd.inode->i_op->put_link(holder.dentry, &nd, cookie);
2364 if (filp == ERR_PTR(-ESTALE) && !(flags & LOOKUP_REVAL))
2369 path_put_conditional(&path, &nd);
2373 if (!IS_ERR(nd.intent.open.file))
2374 release_open_intent(&nd);
2375 filp = ERR_PTR(error);
2380 * filp_open - open file and return file pointer
2382 * @filename: path to open
2383 * @flags: open flags as per the open(2) second argument
2384 * @mode: mode for the new file if O_CREAT is set, else ignored
2386 * This is the helper to open a file from kernelspace if you really
2387 * have to. But in generally you should not do this, so please move
2388 * along, nothing to see here..
2390 struct file *filp_open(const char *filename, int flags, int mode)
2392 return do_filp_open(AT_FDCWD, filename, flags, mode, 0);
2394 EXPORT_SYMBOL(filp_open);
2397 * lookup_create - lookup a dentry, creating it if it doesn't exist
2398 * @nd: nameidata info
2399 * @is_dir: directory flag
2401 * Simple function to lookup and return a dentry and create it
2402 * if it doesn't exist. Is SMP-safe.
2404 * Returns with nd->path.dentry->d_inode->i_mutex locked.
2406 struct dentry *lookup_create(struct nameidata *nd, int is_dir)
2408 struct dentry *dentry = ERR_PTR(-EEXIST);
2410 mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2412 * Yucky last component or no last component at all?
2413 * (foo/., foo/.., /////)
2415 if (nd->last_type != LAST_NORM)
2417 nd->flags &= ~LOOKUP_PARENT;
2418 nd->flags |= LOOKUP_CREATE | LOOKUP_EXCL;
2419 nd->intent.open.flags = O_EXCL;
2422 * Do the final lookup.
2424 dentry = lookup_hash(nd);
2428 if (dentry->d_inode)
2431 * Special case - lookup gave negative, but... we had foo/bar/
2432 * From the vfs_mknod() POV we just have a negative dentry -
2433 * all is fine. Let's be bastards - you had / on the end, you've
2434 * been asking for (non-existent) directory. -ENOENT for you.
2436 if (unlikely(!is_dir && nd->last.name[nd->last.len])) {
2438 dentry = ERR_PTR(-ENOENT);
2443 dentry = ERR_PTR(-EEXIST);
2447 EXPORT_SYMBOL_GPL(lookup_create);
2449 int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
2451 int error = may_create(dir, dentry);
2456 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
2459 if (!dir->i_op->mknod)
2462 error = devcgroup_inode_mknod(mode, dev);
2466 error = security_inode_mknod(dir, dentry, mode, dev);
2470 error = dir->i_op->mknod(dir, dentry, mode, dev);
2472 fsnotify_create(dir, dentry);
2476 static int may_mknod(mode_t mode)
2478 switch (mode & S_IFMT) {
2484 case 0: /* zero mode translates to S_IFREG */
2493 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, int, mode,
2498 struct dentry *dentry;
2499 struct nameidata nd;
2504 error = user_path_parent(dfd, filename, &nd, &tmp);
2508 dentry = lookup_create(&nd, 0);
2509 if (IS_ERR(dentry)) {
2510 error = PTR_ERR(dentry);
2513 if (!IS_POSIXACL(nd.path.dentry->d_inode))
2514 mode &= ~current_umask();
2515 error = may_mknod(mode);
2518 error = mnt_want_write(nd.path.mnt);
2521 error = security_path_mknod(&nd.path, dentry, mode, dev);
2523 goto out_drop_write;
2524 switch (mode & S_IFMT) {
2525 case 0: case S_IFREG:
2526 error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd);
2528 case S_IFCHR: case S_IFBLK:
2529 error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,
2530 new_decode_dev(dev));
2532 case S_IFIFO: case S_IFSOCK:
2533 error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);
2537 mnt_drop_write(nd.path.mnt);
2541 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2548 SYSCALL_DEFINE3(mknod, const char __user *, filename, int, mode, unsigned, dev)
2550 return sys_mknodat(AT_FDCWD, filename, mode, dev);
2553 int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
2555 int error = may_create(dir, dentry);
2560 if (!dir->i_op->mkdir)
2563 mode &= (S_IRWXUGO|S_ISVTX);
2564 error = security_inode_mkdir(dir, dentry, mode);
2568 error = dir->i_op->mkdir(dir, dentry, mode);
2570 fsnotify_mkdir(dir, dentry);
2574 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, int, mode)
2578 struct dentry *dentry;
2579 struct nameidata nd;
2581 error = user_path_parent(dfd, pathname, &nd, &tmp);
2585 dentry = lookup_create(&nd, 1);
2586 error = PTR_ERR(dentry);
2590 if (!IS_POSIXACL(nd.path.dentry->d_inode))
2591 mode &= ~current_umask();
2592 error = mnt_want_write(nd.path.mnt);
2595 error = security_path_mkdir(&nd.path, dentry, mode);
2597 goto out_drop_write;
2598 error = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
2600 mnt_drop_write(nd.path.mnt);
2604 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2611 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, int, mode)
2613 return sys_mkdirat(AT_FDCWD, pathname, mode);
2617 * We try to drop the dentry early: we should have
2618 * a usage count of 2 if we're the only user of this
2619 * dentry, and if that is true (possibly after pruning
2620 * the dcache), then we drop the dentry now.
2622 * A low-level filesystem can, if it choses, legally
2625 * if (!d_unhashed(dentry))
2628 * if it cannot handle the case of removing a directory
2629 * that is still in use by something else..
2631 void dentry_unhash(struct dentry *dentry)
2634 shrink_dcache_parent(dentry);
2635 spin_lock(&dentry->d_lock);
2636 if (dentry->d_count == 2)
2638 spin_unlock(&dentry->d_lock);
2641 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
2643 int error = may_delete(dir, dentry, 1);
2648 if (!dir->i_op->rmdir)
2651 mutex_lock(&dentry->d_inode->i_mutex);
2652 dentry_unhash(dentry);
2653 if (d_mountpoint(dentry))
2656 error = security_inode_rmdir(dir, dentry);
2658 error = dir->i_op->rmdir(dir, dentry);
2660 dentry->d_inode->i_flags |= S_DEAD;
2665 mutex_unlock(&dentry->d_inode->i_mutex);
2674 static long do_rmdir(int dfd, const char __user *pathname)
2678 struct dentry *dentry;
2679 struct nameidata nd;
2681 error = user_path_parent(dfd, pathname, &nd, &name);
2685 switch(nd.last_type) {
2697 nd.flags &= ~LOOKUP_PARENT;
2699 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2700 dentry = lookup_hash(&nd);
2701 error = PTR_ERR(dentry);
2704 error = mnt_want_write(nd.path.mnt);
2707 error = security_path_rmdir(&nd.path, dentry);
2710 error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
2712 mnt_drop_write(nd.path.mnt);
2716 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2723 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
2725 return do_rmdir(AT_FDCWD, pathname);
2728 int vfs_unlink(struct inode *dir, struct dentry *dentry)
2730 int error = may_delete(dir, dentry, 0);
2735 if (!dir->i_op->unlink)
2738 mutex_lock(&dentry->d_inode->i_mutex);
2739 if (d_mountpoint(dentry))
2742 error = security_inode_unlink(dir, dentry);
2744 error = dir->i_op->unlink(dir, dentry);
2749 mutex_unlock(&dentry->d_inode->i_mutex);
2751 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
2752 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
2753 fsnotify_link_count(dentry->d_inode);
2761 * Make sure that the actual truncation of the file will occur outside its
2762 * directory's i_mutex. Truncate can take a long time if there is a lot of
2763 * writeout happening, and we don't want to prevent access to the directory
2764 * while waiting on the I/O.
2766 static long do_unlinkat(int dfd, const char __user *pathname)
2770 struct dentry *dentry;
2771 struct nameidata nd;
2772 struct inode *inode = NULL;
2774 error = user_path_parent(dfd, pathname, &nd, &name);
2779 if (nd.last_type != LAST_NORM)
2782 nd.flags &= ~LOOKUP_PARENT;
2784 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2785 dentry = lookup_hash(&nd);
2786 error = PTR_ERR(dentry);
2787 if (!IS_ERR(dentry)) {
2788 /* Why not before? Because we want correct error value */
2789 if (nd.last.name[nd.last.len])
2791 inode = dentry->d_inode;
2794 error = mnt_want_write(nd.path.mnt);
2797 error = security_path_unlink(&nd.path, dentry);
2800 error = vfs_unlink(nd.path.dentry->d_inode, dentry);
2802 mnt_drop_write(nd.path.mnt);
2806 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2808 iput(inode); /* truncate the inode here */
2815 error = !dentry->d_inode ? -ENOENT :
2816 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
2820 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
2822 if ((flag & ~AT_REMOVEDIR) != 0)
2825 if (flag & AT_REMOVEDIR)
2826 return do_rmdir(dfd, pathname);
2828 return do_unlinkat(dfd, pathname);
2831 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
2833 return do_unlinkat(AT_FDCWD, pathname);
2836 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
2838 int error = may_create(dir, dentry);
2843 if (!dir->i_op->symlink)
2846 error = security_inode_symlink(dir, dentry, oldname);
2850 error = dir->i_op->symlink(dir, dentry, oldname);
2852 fsnotify_create(dir, dentry);
2856 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
2857 int, newdfd, const char __user *, newname)
2862 struct dentry *dentry;
2863 struct nameidata nd;
2865 from = getname(oldname);
2867 return PTR_ERR(from);
2869 error = user_path_parent(newdfd, newname, &nd, &to);
2873 dentry = lookup_create(&nd, 0);
2874 error = PTR_ERR(dentry);
2878 error = mnt_want_write(nd.path.mnt);
2881 error = security_path_symlink(&nd.path, dentry, from);
2883 goto out_drop_write;
2884 error = vfs_symlink(nd.path.dentry->d_inode, dentry, from);
2886 mnt_drop_write(nd.path.mnt);
2890 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2898 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
2900 return sys_symlinkat(oldname, AT_FDCWD, newname);
2903 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
2905 struct inode *inode = old_dentry->d_inode;
2911 error = may_create(dir, new_dentry);
2915 if (dir->i_sb != inode->i_sb)
2919 * A link to an append-only or immutable file cannot be created.
2921 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
2923 if (!dir->i_op->link)
2925 if (S_ISDIR(inode->i_mode))
2928 error = security_inode_link(old_dentry, dir, new_dentry);
2932 mutex_lock(&inode->i_mutex);
2933 error = dir->i_op->link(old_dentry, dir, new_dentry);
2934 mutex_unlock(&inode->i_mutex);
2936 fsnotify_link(dir, inode, new_dentry);
2941 * Hardlinks are often used in delicate situations. We avoid
2942 * security-related surprises by not following symlinks on the
2945 * We don't follow them on the oldname either to be compatible
2946 * with linux 2.0, and to avoid hard-linking to directories
2947 * and other special files. --ADM
2949 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
2950 int, newdfd, const char __user *, newname, int, flags)
2952 struct dentry *new_dentry;
2953 struct nameidata nd;
2954 struct path old_path;
2958 if ((flags & ~AT_SYMLINK_FOLLOW) != 0)
2961 error = user_path_at(olddfd, oldname,
2962 flags & AT_SYMLINK_FOLLOW ? LOOKUP_FOLLOW : 0,
2967 error = user_path_parent(newdfd, newname, &nd, &to);
2971 if (old_path.mnt != nd.path.mnt)
2973 new_dentry = lookup_create(&nd, 0);
2974 error = PTR_ERR(new_dentry);
2975 if (IS_ERR(new_dentry))
2977 error = mnt_want_write(nd.path.mnt);
2980 error = security_path_link(old_path.dentry, &nd.path, new_dentry);
2982 goto out_drop_write;
2983 error = vfs_link(old_path.dentry, nd.path.dentry->d_inode, new_dentry);
2985 mnt_drop_write(nd.path.mnt);
2989 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2994 path_put(&old_path);
2999 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
3001 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
3005 * The worst of all namespace operations - renaming directory. "Perverted"
3006 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3008 * a) we can get into loop creation. Check is done in is_subdir().
3009 * b) race potential - two innocent renames can create a loop together.
3010 * That's where 4.4 screws up. Current fix: serialization on
3011 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
3013 * c) we have to lock _three_ objects - parents and victim (if it exists).
3014 * And that - after we got ->i_mutex on parents (until then we don't know
3015 * whether the target exists). Solution: try to be smart with locking
3016 * order for inodes. We rely on the fact that tree topology may change
3017 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
3018 * move will be locked. Thus we can rank directories by the tree
3019 * (ancestors first) and rank all non-directories after them.
3020 * That works since everybody except rename does "lock parent, lookup,
3021 * lock child" and rename is under ->s_vfs_rename_mutex.
3022 * HOWEVER, it relies on the assumption that any object with ->lookup()
3023 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3024 * we'd better make sure that there's no link(2) for them.
3025 * d) some filesystems don't support opened-but-unlinked directories,
3026 * either because of layout or because they are not ready to deal with
3027 * all cases correctly. The latter will be fixed (taking this sort of
3028 * stuff into VFS), but the former is not going away. Solution: the same
3029 * trick as in rmdir().
3030 * e) conversion from fhandle to dentry may come in the wrong moment - when
3031 * we are removing the target. Solution: we will have to grab ->i_mutex
3032 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
3033 * ->i_mutex on parents, which works but leads to some truly excessive
3036 static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
3037 struct inode *new_dir, struct dentry *new_dentry)
3040 struct inode *target;
3043 * If we are going to change the parent - check write permissions,
3044 * we'll need to flip '..'.
3046 if (new_dir != old_dir) {
3047 error = inode_permission(old_dentry->d_inode, MAY_WRITE);
3052 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3056 target = new_dentry->d_inode;
3058 mutex_lock(&target->i_mutex);
3059 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
3063 dentry_unhash(new_dentry);
3064 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3068 target->i_flags |= S_DEAD;
3069 dont_mount(new_dentry);
3071 mutex_unlock(&target->i_mutex);
3072 if (d_unhashed(new_dentry))
3073 d_rehash(new_dentry);
3077 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3078 d_move(old_dentry,new_dentry);
3082 static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
3083 struct inode *new_dir, struct dentry *new_dentry)
3085 struct inode *target;
3088 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3093 target = new_dentry->d_inode;
3095 mutex_lock(&target->i_mutex);
3096 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
3099 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3102 dont_mount(new_dentry);
3103 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3104 d_move(old_dentry, new_dentry);
3107 mutex_unlock(&target->i_mutex);
3112 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
3113 struct inode *new_dir, struct dentry *new_dentry)
3116 int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
3117 const unsigned char *old_name;
3119 if (old_dentry->d_inode == new_dentry->d_inode)
3122 error = may_delete(old_dir, old_dentry, is_dir);
3126 if (!new_dentry->d_inode)
3127 error = may_create(new_dir, new_dentry);
3129 error = may_delete(new_dir, new_dentry, is_dir);
3133 if (!old_dir->i_op->rename)
3136 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
3139 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
3141 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
3143 fsnotify_move(old_dir, new_dir, old_name, is_dir,
3144 new_dentry->d_inode, old_dentry);
3145 fsnotify_oldname_free(old_name);
3150 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
3151 int, newdfd, const char __user *, newname)
3153 struct dentry *old_dir, *new_dir;
3154 struct dentry *old_dentry, *new_dentry;
3155 struct dentry *trap;
3156 struct nameidata oldnd, newnd;
3161 error = user_path_parent(olddfd, oldname, &oldnd, &from);
3165 error = user_path_parent(newdfd, newname, &newnd, &to);
3170 if (oldnd.path.mnt != newnd.path.mnt)
3173 old_dir = oldnd.path.dentry;
3175 if (oldnd.last_type != LAST_NORM)
3178 new_dir = newnd.path.dentry;
3179 if (newnd.last_type != LAST_NORM)
3182 oldnd.flags &= ~LOOKUP_PARENT;
3183 newnd.flags &= ~LOOKUP_PARENT;
3184 newnd.flags |= LOOKUP_RENAME_TARGET;
3186 trap = lock_rename(new_dir, old_dir);
3188 old_dentry = lookup_hash(&oldnd);
3189 error = PTR_ERR(old_dentry);
3190 if (IS_ERR(old_dentry))
3192 /* source must exist */
3194 if (!old_dentry->d_inode)
3196 /* unless the source is a directory trailing slashes give -ENOTDIR */
3197 if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
3199 if (oldnd.last.name[oldnd.last.len])
3201 if (newnd.last.name[newnd.last.len])
3204 /* source should not be ancestor of target */
3206 if (old_dentry == trap)
3208 new_dentry = lookup_hash(&newnd);
3209 error = PTR_ERR(new_dentry);
3210 if (IS_ERR(new_dentry))
3212 /* target should not be an ancestor of source */
3214 if (new_dentry == trap)
3217 error = mnt_want_write(oldnd.path.mnt);
3220 error = security_path_rename(&oldnd.path, old_dentry,
3221 &newnd.path, new_dentry);
3224 error = vfs_rename(old_dir->d_inode, old_dentry,
3225 new_dir->d_inode, new_dentry);
3227 mnt_drop_write(oldnd.path.mnt);
3233 unlock_rename(new_dir, old_dir);
3235 path_put(&newnd.path);
3238 path_put(&oldnd.path);
3244 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
3246 return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
3249 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
3253 len = PTR_ERR(link);
3258 if (len > (unsigned) buflen)
3260 if (copy_to_user(buffer, link, len))
3267 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
3268 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
3269 * using) it for any given inode is up to filesystem.
3271 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3273 struct nameidata nd;
3278 cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
3280 return PTR_ERR(cookie);
3282 res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
3283 if (dentry->d_inode->i_op->put_link)
3284 dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
3288 int vfs_follow_link(struct nameidata *nd, const char *link)
3290 return __vfs_follow_link(nd, link);
3293 /* get the link contents into pagecache */
3294 static char *page_getlink(struct dentry * dentry, struct page **ppage)
3298 struct address_space *mapping = dentry->d_inode->i_mapping;
3299 page = read_mapping_page(mapping, 0, NULL);
3304 nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
3308 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3310 struct page *page = NULL;
3311 char *s = page_getlink(dentry, &page);
3312 int res = vfs_readlink(dentry,buffer,buflen,s);
3315 page_cache_release(page);
3320 void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
3322 struct page *page = NULL;
3323 nd_set_link(nd, page_getlink(dentry, &page));
3327 void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
3329 struct page *page = cookie;
3333 page_cache_release(page);
3338 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
3340 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
3342 struct address_space *mapping = inode->i_mapping;
3347 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
3349 flags |= AOP_FLAG_NOFS;
3352 err = pagecache_write_begin(NULL, mapping, 0, len-1,
3353 flags, &page, &fsdata);
3357 kaddr = kmap_atomic(page, KM_USER0);
3358 memcpy(kaddr, symname, len-1);
3359 kunmap_atomic(kaddr, KM_USER0);
3361 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
3368 mark_inode_dirty(inode);
3374 int page_symlink(struct inode *inode, const char *symname, int len)
3376 return __page_symlink(inode, symname, len,
3377 !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
3380 const struct inode_operations page_symlink_inode_operations = {
3381 .readlink = generic_readlink,
3382 .follow_link = page_follow_link_light,
3383 .put_link = page_put_link,
3386 EXPORT_SYMBOL(user_path_at);
3387 EXPORT_SYMBOL(follow_down);
3388 EXPORT_SYMBOL(follow_up);
3389 EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
3390 EXPORT_SYMBOL(getname);
3391 EXPORT_SYMBOL(lock_rename);
3392 EXPORT_SYMBOL(lookup_one_len);
3393 EXPORT_SYMBOL(page_follow_link_light);
3394 EXPORT_SYMBOL(page_put_link);
3395 EXPORT_SYMBOL(page_readlink);
3396 EXPORT_SYMBOL(__page_symlink);
3397 EXPORT_SYMBOL(page_symlink);
3398 EXPORT_SYMBOL(page_symlink_inode_operations);
3399 EXPORT_SYMBOL(path_lookup);
3400 EXPORT_SYMBOL(kern_path);
3401 EXPORT_SYMBOL(vfs_path_lookup);
3402 EXPORT_SYMBOL(inode_permission);
3403 EXPORT_SYMBOL(file_permission);
3404 EXPORT_SYMBOL(unlock_rename);
3405 EXPORT_SYMBOL(vfs_create);
3406 EXPORT_SYMBOL(vfs_follow_link);
3407 EXPORT_SYMBOL(vfs_link);
3408 EXPORT_SYMBOL(vfs_mkdir);
3409 EXPORT_SYMBOL(vfs_mknod);
3410 EXPORT_SYMBOL(generic_permission);
3411 EXPORT_SYMBOL(vfs_readlink);
3412 EXPORT_SYMBOL(vfs_rename);
3413 EXPORT_SYMBOL(vfs_rmdir);
3414 EXPORT_SYMBOL(vfs_symlink);
3415 EXPORT_SYMBOL(vfs_unlink);
3416 EXPORT_SYMBOL(dentry_unhash);
3417 EXPORT_SYMBOL(generic_readlink);