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/export.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 <linux/posix_acl.h>
36 #include <asm/uaccess.h>
41 /* [Feb-1997 T. Schoebel-Theuer]
42 * Fundamental changes in the pathname lookup mechanisms (namei)
43 * were necessary because of omirr. The reason is that omirr needs
44 * to know the _real_ pathname, not the user-supplied one, in case
45 * of symlinks (and also when transname replacements occur).
47 * The new code replaces the old recursive symlink resolution with
48 * an iterative one (in case of non-nested symlink chains). It does
49 * this with calls to <fs>_follow_link().
50 * As a side effect, dir_namei(), _namei() and follow_link() are now
51 * replaced with a single function lookup_dentry() that can handle all
52 * the special cases of the former code.
54 * With the new dcache, the pathname is stored at each inode, at least as
55 * long as the refcount of the inode is positive. As a side effect, the
56 * size of the dcache depends on the inode cache and thus is dynamic.
58 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
59 * resolution to correspond with current state of the code.
61 * Note that the symlink resolution is not *completely* iterative.
62 * There is still a significant amount of tail- and mid- recursion in
63 * the algorithm. Also, note that <fs>_readlink() is not used in
64 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
65 * may return different results than <fs>_follow_link(). Many virtual
66 * filesystems (including /proc) exhibit this behavior.
69 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
70 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
71 * and the name already exists in form of a symlink, try to create the new
72 * name indicated by the symlink. The old code always complained that the
73 * name already exists, due to not following the symlink even if its target
74 * is nonexistent. The new semantics affects also mknod() and link() when
75 * the name is a symlink pointing to a non-existent name.
77 * I don't know which semantics is the right one, since I have no access
78 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
79 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
80 * "old" one. Personally, I think the new semantics is much more logical.
81 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
82 * file does succeed in both HP-UX and SunOs, but not in Solaris
83 * and in the old Linux semantics.
86 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
87 * semantics. See the comments in "open_namei" and "do_link" below.
89 * [10-Sep-98 Alan Modra] Another symlink change.
92 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
93 * inside the path - always follow.
94 * in the last component in creation/removal/renaming - never follow.
95 * if LOOKUP_FOLLOW passed - follow.
96 * if the pathname has trailing slashes - follow.
97 * otherwise - don't follow.
98 * (applied in that order).
100 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
101 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
102 * During the 2.4 we need to fix the userland stuff depending on it -
103 * hopefully we will be able to get rid of that wart in 2.5. So far only
104 * XEmacs seems to be relying on it...
107 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
108 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
109 * any extra contention...
112 /* In order to reduce some races, while at the same time doing additional
113 * checking and hopefully speeding things up, we copy filenames to the
114 * kernel data space before using them..
116 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
117 * PATH_MAX includes the nul terminator --RR.
119 static int do_getname(const char __user *filename, char *page)
122 unsigned long len = PATH_MAX;
124 if (!segment_eq(get_fs(), KERNEL_DS)) {
125 if ((unsigned long) filename >= TASK_SIZE)
127 if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
128 len = TASK_SIZE - (unsigned long) filename;
131 retval = strncpy_from_user(page, filename, len);
135 return -ENAMETOOLONG;
141 static char *getname_flags(const char __user *filename, int flags, int *empty)
143 char *result = __getname();
147 return ERR_PTR(-ENOMEM);
149 retval = do_getname(filename, result);
151 if (retval == -ENOENT && empty)
153 if (retval != -ENOENT || !(flags & LOOKUP_EMPTY)) {
155 return ERR_PTR(retval);
158 audit_getname(result);
162 char *getname(const char __user * filename)
164 return getname_flags(filename, 0, NULL);
167 #ifdef CONFIG_AUDITSYSCALL
168 void putname(const char *name)
170 if (unlikely(!audit_dummy_context()))
175 EXPORT_SYMBOL(putname);
178 static int check_acl(struct inode *inode, int mask)
180 #ifdef CONFIG_FS_POSIX_ACL
181 struct posix_acl *acl;
183 if (mask & MAY_NOT_BLOCK) {
184 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
187 /* no ->get_acl() calls in RCU mode... */
188 if (acl == ACL_NOT_CACHED)
190 return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
193 acl = get_cached_acl(inode, ACL_TYPE_ACCESS);
196 * A filesystem can force a ACL callback by just never filling the
197 * ACL cache. But normally you'd fill the cache either at inode
198 * instantiation time, or on the first ->get_acl call.
200 * If the filesystem doesn't have a get_acl() function at all, we'll
201 * just create the negative cache entry.
203 if (acl == ACL_NOT_CACHED) {
204 if (inode->i_op->get_acl) {
205 acl = inode->i_op->get_acl(inode, ACL_TYPE_ACCESS);
209 set_cached_acl(inode, ACL_TYPE_ACCESS, NULL);
215 int error = posix_acl_permission(inode, acl, mask);
216 posix_acl_release(acl);
225 * This does the basic permission checking
227 static int acl_permission_check(struct inode *inode, int mask)
229 unsigned int mode = inode->i_mode;
231 if (current_user_ns() != inode_userns(inode))
234 if (likely(current_fsuid() == inode->i_uid))
237 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
238 int error = check_acl(inode, mask);
239 if (error != -EAGAIN)
243 if (in_group_p(inode->i_gid))
249 * If the DACs are ok we don't need any capability check.
251 if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
257 * generic_permission - check for access rights on a Posix-like filesystem
258 * @inode: inode to check access rights for
259 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
261 * Used to check for read/write/execute permissions on a file.
262 * We use "fsuid" for this, letting us set arbitrary permissions
263 * for filesystem access without changing the "normal" uids which
264 * are used for other things.
266 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
267 * request cannot be satisfied (eg. requires blocking or too much complexity).
268 * It would then be called again in ref-walk mode.
270 int generic_permission(struct inode *inode, int mask)
275 * Do the basic permission checks.
277 ret = acl_permission_check(inode, mask);
281 if (S_ISDIR(inode->i_mode)) {
282 /* DACs are overridable for directories */
283 if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE))
285 if (!(mask & MAY_WRITE))
286 if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH))
291 * Read/write DACs are always overridable.
292 * Executable DACs are overridable when there is
293 * at least one exec bit set.
295 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
296 if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE))
300 * Searching includes executable on directories, else just read.
302 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
303 if (mask == MAY_READ)
304 if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH))
311 * We _really_ want to just do "generic_permission()" without
312 * even looking at the inode->i_op values. So we keep a cache
313 * flag in inode->i_opflags, that says "this has not special
314 * permission function, use the fast case".
316 static inline int do_inode_permission(struct inode *inode, int mask)
318 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
319 if (likely(inode->i_op->permission))
320 return inode->i_op->permission(inode, mask);
322 /* This gets set once for the inode lifetime */
323 spin_lock(&inode->i_lock);
324 inode->i_opflags |= IOP_FASTPERM;
325 spin_unlock(&inode->i_lock);
327 return generic_permission(inode, mask);
331 * inode_permission - check for access rights to a given inode
332 * @inode: inode to check permission on
333 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
335 * Used to check for read/write/execute permissions on an inode.
336 * We use "fsuid" for this, letting us set arbitrary permissions
337 * for filesystem access without changing the "normal" uids which
338 * are used for other things.
340 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
342 int inode_permission(struct inode *inode, int mask)
346 if (unlikely(mask & MAY_WRITE)) {
347 umode_t mode = inode->i_mode;
350 * Nobody gets write access to a read-only fs.
352 if (IS_RDONLY(inode) &&
353 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
357 * Nobody gets write access to an immutable file.
359 if (IS_IMMUTABLE(inode))
363 retval = do_inode_permission(inode, mask);
367 retval = devcgroup_inode_permission(inode, mask);
371 return security_inode_permission(inode, mask);
375 * path_get - get a reference to a path
376 * @path: path to get the reference to
378 * Given a path increment the reference count to the dentry and the vfsmount.
380 void path_get(struct path *path)
385 EXPORT_SYMBOL(path_get);
388 * path_put - put a reference to a path
389 * @path: path to put the reference to
391 * Given a path decrement the reference count to the dentry and the vfsmount.
393 void path_put(struct path *path)
398 EXPORT_SYMBOL(path_put);
401 * Path walking has 2 modes, rcu-walk and ref-walk (see
402 * Documentation/filesystems/path-lookup.txt). In situations when we can't
403 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
404 * normal reference counts on dentries and vfsmounts to transition to rcu-walk
405 * mode. Refcounts are grabbed at the last known good point before rcu-walk
406 * got stuck, so ref-walk may continue from there. If this is not successful
407 * (eg. a seqcount has changed), then failure is returned and it's up to caller
408 * to restart the path walk from the beginning in ref-walk mode.
412 * unlazy_walk - try to switch to ref-walk mode.
413 * @nd: nameidata pathwalk data
414 * @dentry: child of nd->path.dentry or NULL
415 * Returns: 0 on success, -ECHILD on failure
417 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
418 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
419 * @nd or NULL. Must be called from rcu-walk context.
421 static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
423 struct fs_struct *fs = current->fs;
424 struct dentry *parent = nd->path.dentry;
427 BUG_ON(!(nd->flags & LOOKUP_RCU));
428 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
430 spin_lock(&fs->lock);
431 if (nd->root.mnt != fs->root.mnt ||
432 nd->root.dentry != fs->root.dentry)
435 spin_lock(&parent->d_lock);
437 if (!__d_rcu_to_refcount(parent, nd->seq))
439 BUG_ON(nd->inode != parent->d_inode);
441 if (dentry->d_parent != parent)
443 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
444 if (!__d_rcu_to_refcount(dentry, nd->seq))
447 * If the sequence check on the child dentry passed, then
448 * the child has not been removed from its parent. This
449 * means the parent dentry must be valid and able to take
450 * a reference at this point.
452 BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
453 BUG_ON(!parent->d_count);
455 spin_unlock(&dentry->d_lock);
457 spin_unlock(&parent->d_lock);
460 spin_unlock(&fs->lock);
462 mntget(nd->path.mnt);
465 br_read_unlock(vfsmount_lock);
466 nd->flags &= ~LOOKUP_RCU;
470 spin_unlock(&dentry->d_lock);
472 spin_unlock(&parent->d_lock);
475 spin_unlock(&fs->lock);
480 * release_open_intent - free up open intent resources
481 * @nd: pointer to nameidata
483 void release_open_intent(struct nameidata *nd)
485 struct file *file = nd->intent.open.file;
487 if (file && !IS_ERR(file)) {
488 if (file->f_path.dentry == NULL)
495 static inline int d_revalidate(struct dentry *dentry, struct nameidata *nd)
497 return dentry->d_op->d_revalidate(dentry, nd);
501 * complete_walk - successful completion of path walk
502 * @nd: pointer nameidata
504 * If we had been in RCU mode, drop out of it and legitimize nd->path.
505 * Revalidate the final result, unless we'd already done that during
506 * the path walk or the filesystem doesn't ask for it. Return 0 on
507 * success, -error on failure. In case of failure caller does not
508 * need to drop nd->path.
510 static int complete_walk(struct nameidata *nd)
512 struct dentry *dentry = nd->path.dentry;
515 if (nd->flags & LOOKUP_RCU) {
516 nd->flags &= ~LOOKUP_RCU;
517 if (!(nd->flags & LOOKUP_ROOT))
519 spin_lock(&dentry->d_lock);
520 if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) {
521 spin_unlock(&dentry->d_lock);
523 br_read_unlock(vfsmount_lock);
526 BUG_ON(nd->inode != dentry->d_inode);
527 spin_unlock(&dentry->d_lock);
528 mntget(nd->path.mnt);
530 br_read_unlock(vfsmount_lock);
533 if (likely(!(nd->flags & LOOKUP_JUMPED)))
536 if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
539 if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
542 /* Note: we do not d_invalidate() */
543 status = d_revalidate(dentry, nd);
554 static __always_inline void set_root(struct nameidata *nd)
557 get_fs_root(current->fs, &nd->root);
560 static int link_path_walk(const char *, struct nameidata *);
562 static __always_inline void set_root_rcu(struct nameidata *nd)
565 struct fs_struct *fs = current->fs;
569 seq = read_seqcount_begin(&fs->seq);
571 nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
572 } while (read_seqcount_retry(&fs->seq, seq));
576 static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
588 nd->flags |= LOOKUP_JUMPED;
590 nd->inode = nd->path.dentry->d_inode;
592 ret = link_path_walk(link, nd);
596 return PTR_ERR(link);
599 static void path_put_conditional(struct path *path, struct nameidata *nd)
602 if (path->mnt != nd->path.mnt)
606 static inline void path_to_nameidata(const struct path *path,
607 struct nameidata *nd)
609 if (!(nd->flags & LOOKUP_RCU)) {
610 dput(nd->path.dentry);
611 if (nd->path.mnt != path->mnt)
612 mntput(nd->path.mnt);
614 nd->path.mnt = path->mnt;
615 nd->path.dentry = path->dentry;
618 static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
620 struct inode *inode = link->dentry->d_inode;
621 if (!IS_ERR(cookie) && inode->i_op->put_link)
622 inode->i_op->put_link(link->dentry, nd, cookie);
626 static __always_inline int
627 follow_link(struct path *link, struct nameidata *nd, void **p)
630 struct dentry *dentry = link->dentry;
632 BUG_ON(nd->flags & LOOKUP_RCU);
634 if (link->mnt == nd->path.mnt)
637 if (unlikely(current->total_link_count >= 40)) {
638 *p = ERR_PTR(-ELOOP); /* no ->put_link(), please */
643 current->total_link_count++;
646 nd_set_link(nd, NULL);
648 error = security_inode_follow_link(link->dentry, nd);
650 *p = ERR_PTR(error); /* no ->put_link(), please */
655 nd->last_type = LAST_BIND;
656 *p = dentry->d_inode->i_op->follow_link(dentry, nd);
659 char *s = nd_get_link(nd);
662 error = __vfs_follow_link(nd, s);
663 else if (nd->last_type == LAST_BIND) {
664 nd->flags |= LOOKUP_JUMPED;
665 nd->inode = nd->path.dentry->d_inode;
666 if (nd->inode->i_op->follow_link) {
667 /* stepped on a _really_ weird one */
676 static int follow_up_rcu(struct path *path)
678 struct mount *mnt = real_mount(path->mnt);
679 struct mount *parent;
680 struct dentry *mountpoint;
682 parent = mnt->mnt_parent;
683 if (&parent->mnt == path->mnt)
685 mountpoint = mnt->mnt_mountpoint;
686 path->dentry = mountpoint;
687 path->mnt = &parent->mnt;
691 int follow_up(struct path *path)
693 struct mount *mnt = real_mount(path->mnt);
694 struct mount *parent;
695 struct dentry *mountpoint;
697 br_read_lock(vfsmount_lock);
698 parent = mnt->mnt_parent;
699 if (&parent->mnt == path->mnt) {
700 br_read_unlock(vfsmount_lock);
703 mntget(&parent->mnt);
704 mountpoint = dget(mnt->mnt_mountpoint);
705 br_read_unlock(vfsmount_lock);
707 path->dentry = mountpoint;
709 path->mnt = &parent->mnt;
714 * Perform an automount
715 * - return -EISDIR to tell follow_managed() to stop and return the path we
718 static int follow_automount(struct path *path, unsigned flags,
721 struct vfsmount *mnt;
724 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
727 /* We don't want to mount if someone's just doing a stat -
728 * unless they're stat'ing a directory and appended a '/' to
731 * We do, however, want to mount if someone wants to open or
732 * create a file of any type under the mountpoint, wants to
733 * traverse through the mountpoint or wants to open the
734 * mounted directory. Also, autofs may mark negative dentries
735 * as being automount points. These will need the attentions
736 * of the daemon to instantiate them before they can be used.
738 if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
739 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
740 path->dentry->d_inode)
743 current->total_link_count++;
744 if (current->total_link_count >= 40)
747 mnt = path->dentry->d_op->d_automount(path);
750 * The filesystem is allowed to return -EISDIR here to indicate
751 * it doesn't want to automount. For instance, autofs would do
752 * this so that its userspace daemon can mount on this dentry.
754 * However, we can only permit this if it's a terminal point in
755 * the path being looked up; if it wasn't then the remainder of
756 * the path is inaccessible and we should say so.
758 if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT))
763 if (!mnt) /* mount collision */
767 /* lock_mount() may release path->mnt on error */
771 err = finish_automount(mnt, path);
775 /* Someone else made a mount here whilst we were busy */
780 path->dentry = dget(mnt->mnt_root);
789 * Handle a dentry that is managed in some way.
790 * - Flagged for transit management (autofs)
791 * - Flagged as mountpoint
792 * - Flagged as automount point
794 * This may only be called in refwalk mode.
796 * Serialization is taken care of in namespace.c
798 static int follow_managed(struct path *path, unsigned flags)
800 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
802 bool need_mntput = false;
805 /* Given that we're not holding a lock here, we retain the value in a
806 * local variable for each dentry as we look at it so that we don't see
807 * the components of that value change under us */
808 while (managed = ACCESS_ONCE(path->dentry->d_flags),
809 managed &= DCACHE_MANAGED_DENTRY,
810 unlikely(managed != 0)) {
811 /* Allow the filesystem to manage the transit without i_mutex
813 if (managed & DCACHE_MANAGE_TRANSIT) {
814 BUG_ON(!path->dentry->d_op);
815 BUG_ON(!path->dentry->d_op->d_manage);
816 ret = path->dentry->d_op->d_manage(path->dentry, false);
821 /* Transit to a mounted filesystem. */
822 if (managed & DCACHE_MOUNTED) {
823 struct vfsmount *mounted = lookup_mnt(path);
829 path->dentry = dget(mounted->mnt_root);
834 /* Something is mounted on this dentry in another
835 * namespace and/or whatever was mounted there in this
836 * namespace got unmounted before we managed to get the
840 /* Handle an automount point */
841 if (managed & DCACHE_NEED_AUTOMOUNT) {
842 ret = follow_automount(path, flags, &need_mntput);
848 /* We didn't change the current path point */
852 if (need_mntput && path->mnt == mnt)
856 return ret < 0 ? ret : need_mntput;
859 int follow_down_one(struct path *path)
861 struct vfsmount *mounted;
863 mounted = lookup_mnt(path);
868 path->dentry = dget(mounted->mnt_root);
874 static inline bool managed_dentry_might_block(struct dentry *dentry)
876 return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
877 dentry->d_op->d_manage(dentry, true) < 0);
881 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
882 * we meet a managed dentry that would need blocking.
884 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
885 struct inode **inode)
888 struct mount *mounted;
890 * Don't forget we might have a non-mountpoint managed dentry
891 * that wants to block transit.
893 if (unlikely(managed_dentry_might_block(path->dentry)))
896 if (!d_mountpoint(path->dentry))
899 mounted = __lookup_mnt(path->mnt, path->dentry, 1);
902 path->mnt = &mounted->mnt;
903 path->dentry = mounted->mnt.mnt_root;
904 nd->flags |= LOOKUP_JUMPED;
905 nd->seq = read_seqcount_begin(&path->dentry->d_seq);
907 * Update the inode too. We don't need to re-check the
908 * dentry sequence number here after this d_inode read,
909 * because a mount-point is always pinned.
911 *inode = path->dentry->d_inode;
916 static void follow_mount_rcu(struct nameidata *nd)
918 while (d_mountpoint(nd->path.dentry)) {
919 struct mount *mounted;
920 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1);
923 nd->path.mnt = &mounted->mnt;
924 nd->path.dentry = mounted->mnt.mnt_root;
925 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
929 static int follow_dotdot_rcu(struct nameidata *nd)
934 if (nd->path.dentry == nd->root.dentry &&
935 nd->path.mnt == nd->root.mnt) {
938 if (nd->path.dentry != nd->path.mnt->mnt_root) {
939 struct dentry *old = nd->path.dentry;
940 struct dentry *parent = old->d_parent;
943 seq = read_seqcount_begin(&parent->d_seq);
944 if (read_seqcount_retry(&old->d_seq, nd->seq))
946 nd->path.dentry = parent;
950 if (!follow_up_rcu(&nd->path))
952 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
954 follow_mount_rcu(nd);
955 nd->inode = nd->path.dentry->d_inode;
959 nd->flags &= ~LOOKUP_RCU;
960 if (!(nd->flags & LOOKUP_ROOT))
963 br_read_unlock(vfsmount_lock);
968 * Follow down to the covering mount currently visible to userspace. At each
969 * point, the filesystem owning that dentry may be queried as to whether the
970 * caller is permitted to proceed or not.
972 int follow_down(struct path *path)
977 while (managed = ACCESS_ONCE(path->dentry->d_flags),
978 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
979 /* Allow the filesystem to manage the transit without i_mutex
982 * We indicate to the filesystem if someone is trying to mount
983 * something here. This gives autofs the chance to deny anyone
984 * other than its daemon the right to mount on its
987 * The filesystem may sleep at this point.
989 if (managed & DCACHE_MANAGE_TRANSIT) {
990 BUG_ON(!path->dentry->d_op);
991 BUG_ON(!path->dentry->d_op->d_manage);
992 ret = path->dentry->d_op->d_manage(
993 path->dentry, false);
995 return ret == -EISDIR ? 0 : ret;
998 /* Transit to a mounted filesystem. */
999 if (managed & DCACHE_MOUNTED) {
1000 struct vfsmount *mounted = lookup_mnt(path);
1005 path->mnt = mounted;
1006 path->dentry = dget(mounted->mnt_root);
1010 /* Don't handle automount points here */
1017 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1019 static void follow_mount(struct path *path)
1021 while (d_mountpoint(path->dentry)) {
1022 struct vfsmount *mounted = lookup_mnt(path);
1027 path->mnt = mounted;
1028 path->dentry = dget(mounted->mnt_root);
1032 static void follow_dotdot(struct nameidata *nd)
1037 struct dentry *old = nd->path.dentry;
1039 if (nd->path.dentry == nd->root.dentry &&
1040 nd->path.mnt == nd->root.mnt) {
1043 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1044 /* rare case of legitimate dget_parent()... */
1045 nd->path.dentry = dget_parent(nd->path.dentry);
1049 if (!follow_up(&nd->path))
1052 follow_mount(&nd->path);
1053 nd->inode = nd->path.dentry->d_inode;
1057 * Allocate a dentry with name and parent, and perform a parent
1058 * directory ->lookup on it. Returns the new dentry, or ERR_PTR
1059 * on error. parent->d_inode->i_mutex must be held. d_lookup must
1060 * have verified that no child exists while under i_mutex.
1062 static struct dentry *d_alloc_and_lookup(struct dentry *parent,
1063 struct qstr *name, struct nameidata *nd)
1065 struct inode *inode = parent->d_inode;
1066 struct dentry *dentry;
1069 /* Don't create child dentry for a dead directory. */
1070 if (unlikely(IS_DEADDIR(inode)))
1071 return ERR_PTR(-ENOENT);
1073 dentry = d_alloc(parent, name);
1074 if (unlikely(!dentry))
1075 return ERR_PTR(-ENOMEM);
1077 old = inode->i_op->lookup(inode, dentry, nd);
1078 if (unlikely(old)) {
1086 * We already have a dentry, but require a lookup to be performed on the parent
1087 * directory to fill in d_inode. Returns the new dentry, or ERR_PTR on error.
1088 * parent->d_inode->i_mutex must be held. d_lookup must have verified that no
1089 * child exists while under i_mutex.
1091 static struct dentry *d_inode_lookup(struct dentry *parent, struct dentry *dentry,
1092 struct nameidata *nd)
1094 struct inode *inode = parent->d_inode;
1097 /* Don't create child dentry for a dead directory. */
1098 if (unlikely(IS_DEADDIR(inode))) {
1100 return ERR_PTR(-ENOENT);
1103 old = inode->i_op->lookup(inode, dentry, nd);
1104 if (unlikely(old)) {
1112 * It's more convoluted than I'd like it to be, but... it's still fairly
1113 * small and for now I'd prefer to have fast path as straight as possible.
1114 * It _is_ time-critical.
1116 static int do_lookup(struct nameidata *nd, struct qstr *name,
1117 struct path *path, struct inode **inode)
1119 struct vfsmount *mnt = nd->path.mnt;
1120 struct dentry *dentry, *parent = nd->path.dentry;
1126 * Rename seqlock is not required here because in the off chance
1127 * of a false negative due to a concurrent rename, we're going to
1128 * do the non-racy lookup, below.
1130 if (nd->flags & LOOKUP_RCU) {
1133 dentry = __d_lookup_rcu(parent, name, &seq, inode);
1137 /* Memory barrier in read_seqcount_begin of child is enough */
1138 if (__read_seqcount_retry(&parent->d_seq, nd->seq))
1142 if (unlikely(d_need_lookup(dentry)))
1144 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1145 status = d_revalidate(dentry, nd);
1146 if (unlikely(status <= 0)) {
1147 if (status != -ECHILD)
1153 path->dentry = dentry;
1154 if (unlikely(!__follow_mount_rcu(nd, path, inode)))
1156 if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
1160 if (unlazy_walk(nd, dentry))
1163 dentry = __d_lookup(parent, name);
1166 if (dentry && unlikely(d_need_lookup(dentry))) {
1171 if (unlikely(!dentry)) {
1172 struct inode *dir = parent->d_inode;
1173 BUG_ON(nd->inode != dir);
1175 mutex_lock(&dir->i_mutex);
1176 dentry = d_lookup(parent, name);
1177 if (dentry && d_need_lookup(dentry)) {
1178 dentry = d_inode_lookup(parent, dentry, nd);
1181 if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1182 status = d_revalidate(dentry, nd);
1183 if (unlikely(status <= 0)) {
1186 dentry = ERR_PTR(status);
1189 if (!d_invalidate(dentry)) {
1191 dentry = d_alloc_and_lookup(parent, name, nd);
1194 } else if (!dentry) {
1195 dentry = d_alloc_and_lookup(parent, name, nd);
1198 mutex_unlock(&dir->i_mutex);
1200 return PTR_ERR(dentry);
1203 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
1204 status = d_revalidate(dentry, nd);
1205 if (unlikely(status <= 0)) {
1210 if (!d_invalidate(dentry)) {
1218 path->dentry = dentry;
1219 err = follow_managed(path, nd->flags);
1220 if (unlikely(err < 0)) {
1221 path_put_conditional(path, nd);
1225 nd->flags |= LOOKUP_JUMPED;
1226 *inode = path->dentry->d_inode;
1230 static inline int may_lookup(struct nameidata *nd)
1232 if (nd->flags & LOOKUP_RCU) {
1233 int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1236 if (unlazy_walk(nd, NULL))
1239 return inode_permission(nd->inode, MAY_EXEC);
1242 static inline int handle_dots(struct nameidata *nd, int type)
1244 if (type == LAST_DOTDOT) {
1245 if (nd->flags & LOOKUP_RCU) {
1246 if (follow_dotdot_rcu(nd))
1254 static void terminate_walk(struct nameidata *nd)
1256 if (!(nd->flags & LOOKUP_RCU)) {
1257 path_put(&nd->path);
1259 nd->flags &= ~LOOKUP_RCU;
1260 if (!(nd->flags & LOOKUP_ROOT))
1261 nd->root.mnt = NULL;
1263 br_read_unlock(vfsmount_lock);
1268 * Do we need to follow links? We _really_ want to be able
1269 * to do this check without having to look at inode->i_op,
1270 * so we keep a cache of "no, this doesn't need follow_link"
1271 * for the common case.
1273 static inline int should_follow_link(struct inode *inode, int follow)
1275 if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1276 if (likely(inode->i_op->follow_link))
1279 /* This gets set once for the inode lifetime */
1280 spin_lock(&inode->i_lock);
1281 inode->i_opflags |= IOP_NOFOLLOW;
1282 spin_unlock(&inode->i_lock);
1287 static inline int walk_component(struct nameidata *nd, struct path *path,
1288 struct qstr *name, int type, int follow)
1290 struct inode *inode;
1293 * "." and ".." are special - ".." especially so because it has
1294 * to be able to know about the current root directory and
1295 * parent relationships.
1297 if (unlikely(type != LAST_NORM))
1298 return handle_dots(nd, type);
1299 err = do_lookup(nd, name, path, &inode);
1300 if (unlikely(err)) {
1305 path_to_nameidata(path, nd);
1309 if (should_follow_link(inode, follow)) {
1310 if (nd->flags & LOOKUP_RCU) {
1311 if (unlikely(unlazy_walk(nd, path->dentry))) {
1316 BUG_ON(inode != path->dentry->d_inode);
1319 path_to_nameidata(path, nd);
1325 * This limits recursive symlink follows to 8, while
1326 * limiting consecutive symlinks to 40.
1328 * Without that kind of total limit, nasty chains of consecutive
1329 * symlinks can cause almost arbitrarily long lookups.
1331 static inline int nested_symlink(struct path *path, struct nameidata *nd)
1335 if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
1336 path_put_conditional(path, nd);
1337 path_put(&nd->path);
1340 BUG_ON(nd->depth >= MAX_NESTED_LINKS);
1343 current->link_count++;
1346 struct path link = *path;
1349 res = follow_link(&link, nd, &cookie);
1351 res = walk_component(nd, path, &nd->last,
1352 nd->last_type, LOOKUP_FOLLOW);
1353 put_link(nd, &link, cookie);
1356 current->link_count--;
1362 * We really don't want to look at inode->i_op->lookup
1363 * when we don't have to. So we keep a cache bit in
1364 * the inode ->i_opflags field that says "yes, we can
1365 * do lookup on this inode".
1367 static inline int can_lookup(struct inode *inode)
1369 if (likely(inode->i_opflags & IOP_LOOKUP))
1371 if (likely(!inode->i_op->lookup))
1374 /* We do this once for the lifetime of the inode */
1375 spin_lock(&inode->i_lock);
1376 inode->i_opflags |= IOP_LOOKUP;
1377 spin_unlock(&inode->i_lock);
1382 * We can do the critical dentry name comparison and hashing
1383 * operations one word at a time, but we are limited to:
1385 * - Architectures with fast unaligned word accesses. We could
1386 * do a "get_unaligned()" if this helps and is sufficiently
1389 * - Little-endian machines (so that we can generate the mask
1390 * of low bytes efficiently). Again, we *could* do a byte
1391 * swapping load on big-endian architectures if that is not
1392 * expensive enough to make the optimization worthless.
1394 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1395 * do not trap on the (extremely unlikely) case of a page
1396 * crossing operation.
1398 * - Furthermore, we need an efficient 64-bit compile for the
1399 * 64-bit case in order to generate the "number of bytes in
1400 * the final mask". Again, that could be replaced with a
1401 * efficient population count instruction or similar.
1403 #ifdef CONFIG_DCACHE_WORD_ACCESS
1408 * Jan Achrenius on G+: microoptimized version of
1409 * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
1410 * that works for the bytemasks without having to
1413 static inline long count_masked_bytes(unsigned long mask)
1415 return mask*0x0001020304050608ul >> 56;
1418 static inline unsigned int fold_hash(unsigned long hash)
1420 hash += hash >> (8*sizeof(int));
1424 #else /* 32-bit case */
1426 /* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
1427 static inline long count_masked_bytes(long mask)
1429 /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
1430 long a = (0x0ff0001+mask) >> 23;
1431 /* Fix the 1 for 00 case */
1435 #define fold_hash(x) (x)
1439 unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1441 unsigned long a, mask;
1442 unsigned long hash = 0;
1445 a = *(unsigned long *)name;
1446 if (len < sizeof(unsigned long))
1450 name += sizeof(unsigned long);
1451 len -= sizeof(unsigned long);
1455 mask = ~(~0ul << len*8);
1458 return fold_hash(hash);
1460 EXPORT_SYMBOL(full_name_hash);
1462 #define REPEAT_BYTE(x) ((~0ul / 0xff) * (x))
1463 #define ONEBYTES REPEAT_BYTE(0x01)
1464 #define SLASHBYTES REPEAT_BYTE('/')
1465 #define HIGHBITS REPEAT_BYTE(0x80)
1467 /* Return the high bit set in the first byte that is a zero */
1468 static inline unsigned long has_zero(unsigned long a)
1470 return ((a - ONEBYTES) & ~a) & HIGHBITS;
1474 * Calculate the length and hash of the path component, and
1475 * return the length of the component;
1477 static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1479 unsigned long a, mask, hash, len;
1482 len = -sizeof(unsigned long);
1484 hash = (hash + a) * 9;
1485 len += sizeof(unsigned long);
1486 a = *(unsigned long *)(name+len);
1487 /* Do we have any NUL or '/' bytes in this word? */
1488 mask = has_zero(a) | has_zero(a ^ SLASHBYTES);
1491 /* The mask *below* the first high bit set */
1492 mask = (mask - 1) & ~mask;
1495 *hashp = fold_hash(hash);
1497 return len + count_masked_bytes(mask);
1502 unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1504 unsigned long hash = init_name_hash();
1506 hash = partial_name_hash(*name++, hash);
1507 return end_name_hash(hash);
1509 EXPORT_SYMBOL(full_name_hash);
1512 * We know there's a real path component here of at least
1515 static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1517 unsigned long hash = init_name_hash();
1518 unsigned long len = 0, c;
1520 c = (unsigned char)*name;
1523 hash = partial_name_hash(c, hash);
1524 c = (unsigned char)name[len];
1525 } while (c && c != '/');
1526 *hashp = end_name_hash(hash);
1534 * This is the basic name resolution function, turning a pathname into
1535 * the final dentry. We expect 'base' to be positive and a directory.
1537 * Returns 0 and nd will have valid dentry and mnt on success.
1538 * Returns error and drops reference to input namei data on failure.
1540 static int link_path_walk(const char *name, struct nameidata *nd)
1550 /* At this point we know we have a real path component. */
1556 err = may_lookup(nd);
1560 len = hash_name(name, &this.hash);
1565 if (name[0] == '.') switch (len) {
1567 if (name[1] == '.') {
1569 nd->flags |= LOOKUP_JUMPED;
1575 if (likely(type == LAST_NORM)) {
1576 struct dentry *parent = nd->path.dentry;
1577 nd->flags &= ~LOOKUP_JUMPED;
1578 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
1579 err = parent->d_op->d_hash(parent, nd->inode,
1587 goto last_component;
1589 * If it wasn't NUL, we know it was '/'. Skip that
1590 * slash, and continue until no more slashes.
1594 } while (unlikely(name[len] == '/'));
1596 goto last_component;
1599 err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
1604 err = nested_symlink(&next, nd);
1608 if (can_lookup(nd->inode))
1612 /* here ends the main loop */
1616 nd->last_type = type;
1623 static int path_init(int dfd, const char *name, unsigned int flags,
1624 struct nameidata *nd, struct file **fp)
1630 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1631 nd->flags = flags | LOOKUP_JUMPED;
1633 if (flags & LOOKUP_ROOT) {
1634 struct inode *inode = nd->root.dentry->d_inode;
1636 if (!inode->i_op->lookup)
1638 retval = inode_permission(inode, MAY_EXEC);
1642 nd->path = nd->root;
1644 if (flags & LOOKUP_RCU) {
1645 br_read_lock(vfsmount_lock);
1647 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1649 path_get(&nd->path);
1654 nd->root.mnt = NULL;
1657 if (flags & LOOKUP_RCU) {
1658 br_read_lock(vfsmount_lock);
1663 path_get(&nd->root);
1665 nd->path = nd->root;
1666 } else if (dfd == AT_FDCWD) {
1667 if (flags & LOOKUP_RCU) {
1668 struct fs_struct *fs = current->fs;
1671 br_read_lock(vfsmount_lock);
1675 seq = read_seqcount_begin(&fs->seq);
1677 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1678 } while (read_seqcount_retry(&fs->seq, seq));
1680 get_fs_pwd(current->fs, &nd->path);
1683 struct dentry *dentry;
1685 file = fget_raw_light(dfd, &fput_needed);
1690 dentry = file->f_path.dentry;
1694 if (!S_ISDIR(dentry->d_inode->i_mode))
1697 retval = inode_permission(dentry->d_inode, MAY_EXEC);
1702 nd->path = file->f_path;
1703 if (flags & LOOKUP_RCU) {
1706 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1707 br_read_lock(vfsmount_lock);
1710 path_get(&file->f_path);
1711 fput_light(file, fput_needed);
1715 nd->inode = nd->path.dentry->d_inode;
1719 fput_light(file, fput_needed);
1724 static inline int lookup_last(struct nameidata *nd, struct path *path)
1726 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
1727 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
1729 nd->flags &= ~LOOKUP_PARENT;
1730 return walk_component(nd, path, &nd->last, nd->last_type,
1731 nd->flags & LOOKUP_FOLLOW);
1734 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1735 static int path_lookupat(int dfd, const char *name,
1736 unsigned int flags, struct nameidata *nd)
1738 struct file *base = NULL;
1743 * Path walking is largely split up into 2 different synchronisation
1744 * schemes, rcu-walk and ref-walk (explained in
1745 * Documentation/filesystems/path-lookup.txt). These share much of the
1746 * path walk code, but some things particularly setup, cleanup, and
1747 * following mounts are sufficiently divergent that functions are
1748 * duplicated. Typically there is a function foo(), and its RCU
1749 * analogue, foo_rcu().
1751 * -ECHILD is the error number of choice (just to avoid clashes) that
1752 * is returned if some aspect of an rcu-walk fails. Such an error must
1753 * be handled by restarting a traditional ref-walk (which will always
1754 * be able to complete).
1756 err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base);
1761 current->total_link_count = 0;
1762 err = link_path_walk(name, nd);
1764 if (!err && !(flags & LOOKUP_PARENT)) {
1765 err = lookup_last(nd, &path);
1768 struct path link = path;
1769 nd->flags |= LOOKUP_PARENT;
1770 err = follow_link(&link, nd, &cookie);
1772 err = lookup_last(nd, &path);
1773 put_link(nd, &link, cookie);
1778 err = complete_walk(nd);
1780 if (!err && nd->flags & LOOKUP_DIRECTORY) {
1781 if (!nd->inode->i_op->lookup) {
1782 path_put(&nd->path);
1790 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
1791 path_put(&nd->root);
1792 nd->root.mnt = NULL;
1797 static int do_path_lookup(int dfd, const char *name,
1798 unsigned int flags, struct nameidata *nd)
1800 int retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd);
1801 if (unlikely(retval == -ECHILD))
1802 retval = path_lookupat(dfd, name, flags, nd);
1803 if (unlikely(retval == -ESTALE))
1804 retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd);
1806 if (likely(!retval)) {
1807 if (unlikely(!audit_dummy_context())) {
1808 if (nd->path.dentry && nd->inode)
1809 audit_inode(name, nd->path.dentry);
1815 int kern_path_parent(const char *name, struct nameidata *nd)
1817 return do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, nd);
1820 int kern_path(const char *name, unsigned int flags, struct path *path)
1822 struct nameidata nd;
1823 int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
1830 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
1831 * @dentry: pointer to dentry of the base directory
1832 * @mnt: pointer to vfs mount of the base directory
1833 * @name: pointer to file name
1834 * @flags: lookup flags
1835 * @path: pointer to struct path to fill
1837 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
1838 const char *name, unsigned int flags,
1841 struct nameidata nd;
1843 nd.root.dentry = dentry;
1845 BUG_ON(flags & LOOKUP_PARENT);
1846 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
1847 err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd);
1853 static struct dentry *__lookup_hash(struct qstr *name,
1854 struct dentry *base, struct nameidata *nd)
1856 struct dentry *dentry;
1859 * Don't bother with __d_lookup: callers are for creat as
1860 * well as unlink, so a lot of the time it would cost
1863 dentry = d_lookup(base, name);
1865 if (dentry && d_need_lookup(dentry)) {
1867 * __lookup_hash is called with the parent dir's i_mutex already
1868 * held, so we are good to go here.
1870 return d_inode_lookup(base, dentry, nd);
1873 if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1874 int status = d_revalidate(dentry, nd);
1875 if (unlikely(status <= 0)) {
1877 * The dentry failed validation.
1878 * If d_revalidate returned 0 attempt to invalidate
1879 * the dentry otherwise d_revalidate is asking us
1880 * to return a fail status.
1884 return ERR_PTR(status);
1885 } else if (!d_invalidate(dentry)) {
1893 dentry = d_alloc_and_lookup(base, name, nd);
1899 * Restricted form of lookup. Doesn't follow links, single-component only,
1900 * needs parent already locked. Doesn't follow mounts.
1903 static struct dentry *lookup_hash(struct nameidata *nd)
1905 return __lookup_hash(&nd->last, nd->path.dentry, nd);
1909 * lookup_one_len - filesystem helper to lookup single pathname component
1910 * @name: pathname component to lookup
1911 * @base: base directory to lookup from
1912 * @len: maximum length @len should be interpreted to
1914 * Note that this routine is purely a helper for filesystem usage and should
1915 * not be called by generic code. Also note that by using this function the
1916 * nameidata argument is passed to the filesystem methods and a filesystem
1917 * using this helper needs to be prepared for that.
1919 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
1925 WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
1929 this.hash = full_name_hash(name, len);
1931 return ERR_PTR(-EACCES);
1934 c = *(const unsigned char *)name++;
1935 if (c == '/' || c == '\0')
1936 return ERR_PTR(-EACCES);
1939 * See if the low-level filesystem might want
1940 * to use its own hash..
1942 if (base->d_flags & DCACHE_OP_HASH) {
1943 int err = base->d_op->d_hash(base, base->d_inode, &this);
1945 return ERR_PTR(err);
1948 err = inode_permission(base->d_inode, MAY_EXEC);
1950 return ERR_PTR(err);
1952 return __lookup_hash(&this, base, NULL);
1955 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
1956 struct path *path, int *empty)
1958 struct nameidata nd;
1959 char *tmp = getname_flags(name, flags, empty);
1960 int err = PTR_ERR(tmp);
1963 BUG_ON(flags & LOOKUP_PARENT);
1965 err = do_path_lookup(dfd, tmp, flags, &nd);
1973 int user_path_at(int dfd, const char __user *name, unsigned flags,
1976 return user_path_at_empty(dfd, name, flags, path, NULL);
1979 static int user_path_parent(int dfd, const char __user *path,
1980 struct nameidata *nd, char **name)
1982 char *s = getname(path);
1988 error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd);
1998 * It's inline, so penalty for filesystems that don't use sticky bit is
2001 static inline int check_sticky(struct inode *dir, struct inode *inode)
2003 uid_t fsuid = current_fsuid();
2005 if (!(dir->i_mode & S_ISVTX))
2007 if (current_user_ns() != inode_userns(inode))
2009 if (inode->i_uid == fsuid)
2011 if (dir->i_uid == fsuid)
2015 return !ns_capable(inode_userns(inode), CAP_FOWNER);
2019 * Check whether we can remove a link victim from directory dir, check
2020 * whether the type of victim is right.
2021 * 1. We can't do it if dir is read-only (done in permission())
2022 * 2. We should have write and exec permissions on dir
2023 * 3. We can't remove anything from append-only dir
2024 * 4. We can't do anything with immutable dir (done in permission())
2025 * 5. If the sticky bit on dir is set we should either
2026 * a. be owner of dir, or
2027 * b. be owner of victim, or
2028 * c. have CAP_FOWNER capability
2029 * 6. If the victim is append-only or immutable we can't do antyhing with
2030 * links pointing to it.
2031 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2032 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2033 * 9. We can't remove a root or mountpoint.
2034 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2035 * nfs_async_unlink().
2037 static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
2041 if (!victim->d_inode)
2044 BUG_ON(victim->d_parent->d_inode != dir);
2045 audit_inode_child(victim, dir);
2047 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
2052 if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
2053 IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
2056 if (!S_ISDIR(victim->d_inode->i_mode))
2058 if (IS_ROOT(victim))
2060 } else if (S_ISDIR(victim->d_inode->i_mode))
2062 if (IS_DEADDIR(dir))
2064 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2069 /* Check whether we can create an object with dentry child in directory
2071 * 1. We can't do it if child already exists (open has special treatment for
2072 * this case, but since we are inlined it's OK)
2073 * 2. We can't do it if dir is read-only (done in permission())
2074 * 3. We should have write and exec permissions on dir
2075 * 4. We can't do it if dir is immutable (done in permission())
2077 static inline int may_create(struct inode *dir, struct dentry *child)
2081 if (IS_DEADDIR(dir))
2083 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
2087 * p1 and p2 should be directories on the same fs.
2089 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2094 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2098 mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2100 p = d_ancestor(p2, p1);
2102 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
2103 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
2107 p = d_ancestor(p1, p2);
2109 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2110 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2114 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2115 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2119 void unlock_rename(struct dentry *p1, struct dentry *p2)
2121 mutex_unlock(&p1->d_inode->i_mutex);
2123 mutex_unlock(&p2->d_inode->i_mutex);
2124 mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2128 int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2129 struct nameidata *nd)
2131 int error = may_create(dir, dentry);
2136 if (!dir->i_op->create)
2137 return -EACCES; /* shouldn't it be ENOSYS? */
2140 error = security_inode_create(dir, dentry, mode);
2143 error = dir->i_op->create(dir, dentry, mode, nd);
2145 fsnotify_create(dir, dentry);
2149 static int may_open(struct path *path, int acc_mode, int flag)
2151 struct dentry *dentry = path->dentry;
2152 struct inode *inode = dentry->d_inode;
2162 switch (inode->i_mode & S_IFMT) {
2166 if (acc_mode & MAY_WRITE)
2171 if (path->mnt->mnt_flags & MNT_NODEV)
2180 error = inode_permission(inode, acc_mode);
2185 * An append-only file must be opened in append mode for writing.
2187 if (IS_APPEND(inode)) {
2188 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
2194 /* O_NOATIME can only be set by the owner or superuser */
2195 if (flag & O_NOATIME && !inode_owner_or_capable(inode))
2201 static int handle_truncate(struct file *filp)
2203 struct path *path = &filp->f_path;
2204 struct inode *inode = path->dentry->d_inode;
2205 int error = get_write_access(inode);
2209 * Refuse to truncate files with mandatory locks held on them.
2211 error = locks_verify_locked(inode);
2213 error = security_path_truncate(path);
2215 error = do_truncate(path->dentry, 0,
2216 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
2219 put_write_access(inode);
2223 static inline int open_to_namei_flags(int flag)
2225 if ((flag & O_ACCMODE) == 3)
2231 * Handle the last step of open()
2233 static struct file *do_last(struct nameidata *nd, struct path *path,
2234 const struct open_flags *op, const char *pathname)
2236 struct dentry *dir = nd->path.dentry;
2237 struct dentry *dentry;
2238 int open_flag = op->open_flag;
2239 int will_truncate = open_flag & O_TRUNC;
2241 int acc_mode = op->acc_mode;
2245 nd->flags &= ~LOOKUP_PARENT;
2246 nd->flags |= op->intent;
2248 switch (nd->last_type) {
2251 error = handle_dots(nd, nd->last_type);
2253 return ERR_PTR(error);
2256 error = complete_walk(nd);
2258 return ERR_PTR(error);
2259 audit_inode(pathname, nd->path.dentry);
2260 if (open_flag & O_CREAT) {
2266 error = complete_walk(nd);
2268 return ERR_PTR(error);
2269 audit_inode(pathname, dir);
2273 if (!(open_flag & O_CREAT)) {
2275 if (nd->last.name[nd->last.len])
2276 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2277 if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
2279 /* we _can_ be in RCU mode here */
2280 error = walk_component(nd, path, &nd->last, LAST_NORM,
2283 return ERR_PTR(error);
2284 if (error) /* symlink */
2287 error = complete_walk(nd);
2289 return ERR_PTR(error);
2292 if (nd->flags & LOOKUP_DIRECTORY) {
2293 if (!nd->inode->i_op->lookup)
2296 audit_inode(pathname, nd->path.dentry);
2300 /* create side of things */
2302 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED has been
2303 * cleared when we got to the last component we are about to look up
2305 error = complete_walk(nd);
2307 return ERR_PTR(error);
2309 audit_inode(pathname, dir);
2311 /* trailing slashes? */
2312 if (nd->last.name[nd->last.len])
2315 mutex_lock(&dir->d_inode->i_mutex);
2317 dentry = lookup_hash(nd);
2318 error = PTR_ERR(dentry);
2319 if (IS_ERR(dentry)) {
2320 mutex_unlock(&dir->d_inode->i_mutex);
2324 path->dentry = dentry;
2325 path->mnt = nd->path.mnt;
2327 /* Negative dentry, just create the file */
2328 if (!dentry->d_inode) {
2329 umode_t mode = op->mode;
2330 if (!IS_POSIXACL(dir->d_inode))
2331 mode &= ~current_umask();
2333 * This write is needed to ensure that a
2334 * rw->ro transition does not occur between
2335 * the time when the file is created and when
2336 * a permanent write count is taken through
2337 * the 'struct file' in nameidata_to_filp().
2339 error = mnt_want_write(nd->path.mnt);
2341 goto exit_mutex_unlock;
2343 /* Don't check for write permission, don't truncate */
2344 open_flag &= ~O_TRUNC;
2346 acc_mode = MAY_OPEN;
2347 error = security_path_mknod(&nd->path, dentry, mode, 0);
2349 goto exit_mutex_unlock;
2350 error = vfs_create(dir->d_inode, dentry, mode, nd);
2352 goto exit_mutex_unlock;
2353 mutex_unlock(&dir->d_inode->i_mutex);
2354 dput(nd->path.dentry);
2355 nd->path.dentry = dentry;
2360 * It already exists.
2362 mutex_unlock(&dir->d_inode->i_mutex);
2363 audit_inode(pathname, path->dentry);
2366 if (open_flag & O_EXCL)
2369 error = follow_managed(path, nd->flags);
2374 nd->flags |= LOOKUP_JUMPED;
2377 if (!path->dentry->d_inode)
2380 if (path->dentry->d_inode->i_op->follow_link)
2383 path_to_nameidata(path, nd);
2384 nd->inode = path->dentry->d_inode;
2385 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
2386 error = complete_walk(nd);
2388 return ERR_PTR(error);
2390 if (S_ISDIR(nd->inode->i_mode))
2393 if (!S_ISREG(nd->inode->i_mode))
2396 if (will_truncate) {
2397 error = mnt_want_write(nd->path.mnt);
2403 error = may_open(&nd->path, acc_mode, open_flag);
2406 filp = nameidata_to_filp(nd);
2407 if (!IS_ERR(filp)) {
2408 error = ima_file_check(filp, op->acc_mode);
2411 filp = ERR_PTR(error);
2414 if (!IS_ERR(filp)) {
2415 if (will_truncate) {
2416 error = handle_truncate(filp);
2419 filp = ERR_PTR(error);
2425 mnt_drop_write(nd->path.mnt);
2426 path_put(&nd->path);
2430 mutex_unlock(&dir->d_inode->i_mutex);
2432 path_put_conditional(path, nd);
2434 filp = ERR_PTR(error);
2438 static struct file *path_openat(int dfd, const char *pathname,
2439 struct nameidata *nd, const struct open_flags *op, int flags)
2441 struct file *base = NULL;
2446 filp = get_empty_filp();
2448 return ERR_PTR(-ENFILE);
2450 filp->f_flags = op->open_flag;
2451 nd->intent.open.file = filp;
2452 nd->intent.open.flags = open_to_namei_flags(op->open_flag);
2453 nd->intent.open.create_mode = op->mode;
2455 error = path_init(dfd, pathname, flags | LOOKUP_PARENT, nd, &base);
2456 if (unlikely(error))
2459 current->total_link_count = 0;
2460 error = link_path_walk(pathname, nd);
2461 if (unlikely(error))
2464 filp = do_last(nd, &path, op, pathname);
2465 while (unlikely(!filp)) { /* trailing symlink */
2466 struct path link = path;
2468 if (!(nd->flags & LOOKUP_FOLLOW)) {
2469 path_put_conditional(&path, nd);
2470 path_put(&nd->path);
2471 filp = ERR_PTR(-ELOOP);
2474 nd->flags |= LOOKUP_PARENT;
2475 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
2476 error = follow_link(&link, nd, &cookie);
2477 if (unlikely(error))
2478 filp = ERR_PTR(error);
2480 filp = do_last(nd, &path, op, pathname);
2481 put_link(nd, &link, cookie);
2484 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
2485 path_put(&nd->root);
2488 release_open_intent(nd);
2492 filp = ERR_PTR(error);
2496 struct file *do_filp_open(int dfd, const char *pathname,
2497 const struct open_flags *op, int flags)
2499 struct nameidata nd;
2502 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
2503 if (unlikely(filp == ERR_PTR(-ECHILD)))
2504 filp = path_openat(dfd, pathname, &nd, op, flags);
2505 if (unlikely(filp == ERR_PTR(-ESTALE)))
2506 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
2510 struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
2511 const char *name, const struct open_flags *op, int flags)
2513 struct nameidata nd;
2517 nd.root.dentry = dentry;
2519 flags |= LOOKUP_ROOT;
2521 if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
2522 return ERR_PTR(-ELOOP);
2524 file = path_openat(-1, name, &nd, op, flags | LOOKUP_RCU);
2525 if (unlikely(file == ERR_PTR(-ECHILD)))
2526 file = path_openat(-1, name, &nd, op, flags);
2527 if (unlikely(file == ERR_PTR(-ESTALE)))
2528 file = path_openat(-1, name, &nd, op, flags | LOOKUP_REVAL);
2532 struct dentry *kern_path_create(int dfd, const char *pathname, struct path *path, int is_dir)
2534 struct dentry *dentry = ERR_PTR(-EEXIST);
2535 struct nameidata nd;
2536 int error = do_path_lookup(dfd, pathname, LOOKUP_PARENT, &nd);
2538 return ERR_PTR(error);
2541 * Yucky last component or no last component at all?
2542 * (foo/., foo/.., /////)
2544 if (nd.last_type != LAST_NORM)
2546 nd.flags &= ~LOOKUP_PARENT;
2547 nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL;
2548 nd.intent.open.flags = O_EXCL;
2551 * Do the final lookup.
2553 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2554 dentry = lookup_hash(&nd);
2558 if (dentry->d_inode)
2561 * Special case - lookup gave negative, but... we had foo/bar/
2562 * From the vfs_mknod() POV we just have a negative dentry -
2563 * all is fine. Let's be bastards - you had / on the end, you've
2564 * been asking for (non-existent) directory. -ENOENT for you.
2566 if (unlikely(!is_dir && nd.last.name[nd.last.len])) {
2568 dentry = ERR_PTR(-ENOENT);
2575 dentry = ERR_PTR(-EEXIST);
2577 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2582 EXPORT_SYMBOL(kern_path_create);
2584 struct dentry *user_path_create(int dfd, const char __user *pathname, struct path *path, int is_dir)
2586 char *tmp = getname(pathname);
2589 return ERR_CAST(tmp);
2590 res = kern_path_create(dfd, tmp, path, is_dir);
2594 EXPORT_SYMBOL(user_path_create);
2596 int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
2598 int error = may_create(dir, dentry);
2603 if ((S_ISCHR(mode) || S_ISBLK(mode)) &&
2604 !ns_capable(inode_userns(dir), CAP_MKNOD))
2607 if (!dir->i_op->mknod)
2610 error = devcgroup_inode_mknod(mode, dev);
2614 error = security_inode_mknod(dir, dentry, mode, dev);
2618 error = dir->i_op->mknod(dir, dentry, mode, dev);
2620 fsnotify_create(dir, dentry);
2624 static int may_mknod(umode_t mode)
2626 switch (mode & S_IFMT) {
2632 case 0: /* zero mode translates to S_IFREG */
2641 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
2644 struct dentry *dentry;
2651 dentry = user_path_create(dfd, filename, &path, 0);
2653 return PTR_ERR(dentry);
2655 if (!IS_POSIXACL(path.dentry->d_inode))
2656 mode &= ~current_umask();
2657 error = may_mknod(mode);
2660 error = mnt_want_write(path.mnt);
2663 error = security_path_mknod(&path, dentry, mode, dev);
2665 goto out_drop_write;
2666 switch (mode & S_IFMT) {
2667 case 0: case S_IFREG:
2668 error = vfs_create(path.dentry->d_inode,dentry,mode,NULL);
2670 case S_IFCHR: case S_IFBLK:
2671 error = vfs_mknod(path.dentry->d_inode,dentry,mode,
2672 new_decode_dev(dev));
2674 case S_IFIFO: case S_IFSOCK:
2675 error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
2679 mnt_drop_write(path.mnt);
2682 mutex_unlock(&path.dentry->d_inode->i_mutex);
2688 SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
2690 return sys_mknodat(AT_FDCWD, filename, mode, dev);
2693 int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
2695 int error = may_create(dir, dentry);
2696 unsigned max_links = dir->i_sb->s_max_links;
2701 if (!dir->i_op->mkdir)
2704 mode &= (S_IRWXUGO|S_ISVTX);
2705 error = security_inode_mkdir(dir, dentry, mode);
2709 if (max_links && dir->i_nlink >= max_links)
2712 error = dir->i_op->mkdir(dir, dentry, mode);
2714 fsnotify_mkdir(dir, dentry);
2718 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
2720 struct dentry *dentry;
2724 dentry = user_path_create(dfd, pathname, &path, 1);
2726 return PTR_ERR(dentry);
2728 if (!IS_POSIXACL(path.dentry->d_inode))
2729 mode &= ~current_umask();
2730 error = mnt_want_write(path.mnt);
2733 error = security_path_mkdir(&path, dentry, mode);
2735 goto out_drop_write;
2736 error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
2738 mnt_drop_write(path.mnt);
2741 mutex_unlock(&path.dentry->d_inode->i_mutex);
2746 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
2748 return sys_mkdirat(AT_FDCWD, pathname, mode);
2752 * The dentry_unhash() helper will try to drop the dentry early: we
2753 * should have a usage count of 2 if we're the only user of this
2754 * dentry, and if that is true (possibly after pruning the dcache),
2755 * then we drop the dentry now.
2757 * A low-level filesystem can, if it choses, legally
2760 * if (!d_unhashed(dentry))
2763 * if it cannot handle the case of removing a directory
2764 * that is still in use by something else..
2766 void dentry_unhash(struct dentry *dentry)
2768 shrink_dcache_parent(dentry);
2769 spin_lock(&dentry->d_lock);
2770 if (dentry->d_count == 1)
2772 spin_unlock(&dentry->d_lock);
2775 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
2777 int error = may_delete(dir, dentry, 1);
2782 if (!dir->i_op->rmdir)
2786 mutex_lock(&dentry->d_inode->i_mutex);
2789 if (d_mountpoint(dentry))
2792 error = security_inode_rmdir(dir, dentry);
2796 shrink_dcache_parent(dentry);
2797 error = dir->i_op->rmdir(dir, dentry);
2801 dentry->d_inode->i_flags |= S_DEAD;
2805 mutex_unlock(&dentry->d_inode->i_mutex);
2812 static long do_rmdir(int dfd, const char __user *pathname)
2816 struct dentry *dentry;
2817 struct nameidata nd;
2819 error = user_path_parent(dfd, pathname, &nd, &name);
2823 switch(nd.last_type) {
2835 nd.flags &= ~LOOKUP_PARENT;
2837 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2838 dentry = lookup_hash(&nd);
2839 error = PTR_ERR(dentry);
2842 if (!dentry->d_inode) {
2846 error = mnt_want_write(nd.path.mnt);
2849 error = security_path_rmdir(&nd.path, dentry);
2852 error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
2854 mnt_drop_write(nd.path.mnt);
2858 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2865 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
2867 return do_rmdir(AT_FDCWD, pathname);
2870 int vfs_unlink(struct inode *dir, struct dentry *dentry)
2872 int error = may_delete(dir, dentry, 0);
2877 if (!dir->i_op->unlink)
2880 mutex_lock(&dentry->d_inode->i_mutex);
2881 if (d_mountpoint(dentry))
2884 error = security_inode_unlink(dir, dentry);
2886 error = dir->i_op->unlink(dir, dentry);
2891 mutex_unlock(&dentry->d_inode->i_mutex);
2893 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
2894 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
2895 fsnotify_link_count(dentry->d_inode);
2903 * Make sure that the actual truncation of the file will occur outside its
2904 * directory's i_mutex. Truncate can take a long time if there is a lot of
2905 * writeout happening, and we don't want to prevent access to the directory
2906 * while waiting on the I/O.
2908 static long do_unlinkat(int dfd, const char __user *pathname)
2912 struct dentry *dentry;
2913 struct nameidata nd;
2914 struct inode *inode = NULL;
2916 error = user_path_parent(dfd, pathname, &nd, &name);
2921 if (nd.last_type != LAST_NORM)
2924 nd.flags &= ~LOOKUP_PARENT;
2926 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2927 dentry = lookup_hash(&nd);
2928 error = PTR_ERR(dentry);
2929 if (!IS_ERR(dentry)) {
2930 /* Why not before? Because we want correct error value */
2931 if (nd.last.name[nd.last.len])
2933 inode = dentry->d_inode;
2937 error = mnt_want_write(nd.path.mnt);
2940 error = security_path_unlink(&nd.path, dentry);
2943 error = vfs_unlink(nd.path.dentry->d_inode, dentry);
2945 mnt_drop_write(nd.path.mnt);
2949 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2951 iput(inode); /* truncate the inode here */
2958 error = !dentry->d_inode ? -ENOENT :
2959 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
2963 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
2965 if ((flag & ~AT_REMOVEDIR) != 0)
2968 if (flag & AT_REMOVEDIR)
2969 return do_rmdir(dfd, pathname);
2971 return do_unlinkat(dfd, pathname);
2974 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
2976 return do_unlinkat(AT_FDCWD, pathname);
2979 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
2981 int error = may_create(dir, dentry);
2986 if (!dir->i_op->symlink)
2989 error = security_inode_symlink(dir, dentry, oldname);
2993 error = dir->i_op->symlink(dir, dentry, oldname);
2995 fsnotify_create(dir, dentry);
2999 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
3000 int, newdfd, const char __user *, newname)
3004 struct dentry *dentry;
3007 from = getname(oldname);
3009 return PTR_ERR(from);
3011 dentry = user_path_create(newdfd, newname, &path, 0);
3012 error = PTR_ERR(dentry);
3016 error = mnt_want_write(path.mnt);
3019 error = security_path_symlink(&path, dentry, from);
3021 goto out_drop_write;
3022 error = vfs_symlink(path.dentry->d_inode, dentry, from);
3024 mnt_drop_write(path.mnt);
3027 mutex_unlock(&path.dentry->d_inode->i_mutex);
3034 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
3036 return sys_symlinkat(oldname, AT_FDCWD, newname);
3039 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
3041 struct inode *inode = old_dentry->d_inode;
3042 unsigned max_links = dir->i_sb->s_max_links;
3048 error = may_create(dir, new_dentry);
3052 if (dir->i_sb != inode->i_sb)
3056 * A link to an append-only or immutable file cannot be created.
3058 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
3060 if (!dir->i_op->link)
3062 if (S_ISDIR(inode->i_mode))
3065 error = security_inode_link(old_dentry, dir, new_dentry);
3069 mutex_lock(&inode->i_mutex);
3070 /* Make sure we don't allow creating hardlink to an unlinked file */
3071 if (inode->i_nlink == 0)
3073 else if (max_links && inode->i_nlink >= max_links)
3076 error = dir->i_op->link(old_dentry, dir, new_dentry);
3077 mutex_unlock(&inode->i_mutex);
3079 fsnotify_link(dir, inode, new_dentry);
3084 * Hardlinks are often used in delicate situations. We avoid
3085 * security-related surprises by not following symlinks on the
3088 * We don't follow them on the oldname either to be compatible
3089 * with linux 2.0, and to avoid hard-linking to directories
3090 * and other special files. --ADM
3092 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
3093 int, newdfd, const char __user *, newname, int, flags)
3095 struct dentry *new_dentry;
3096 struct path old_path, new_path;
3100 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
3103 * To use null names we require CAP_DAC_READ_SEARCH
3104 * This ensures that not everyone will be able to create
3105 * handlink using the passed filedescriptor.
3107 if (flags & AT_EMPTY_PATH) {
3108 if (!capable(CAP_DAC_READ_SEARCH))
3113 if (flags & AT_SYMLINK_FOLLOW)
3114 how |= LOOKUP_FOLLOW;
3116 error = user_path_at(olddfd, oldname, how, &old_path);
3120 new_dentry = user_path_create(newdfd, newname, &new_path, 0);
3121 error = PTR_ERR(new_dentry);
3122 if (IS_ERR(new_dentry))
3126 if (old_path.mnt != new_path.mnt)
3128 error = mnt_want_write(new_path.mnt);
3131 error = security_path_link(old_path.dentry, &new_path, new_dentry);
3133 goto out_drop_write;
3134 error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry);
3136 mnt_drop_write(new_path.mnt);
3139 mutex_unlock(&new_path.dentry->d_inode->i_mutex);
3140 path_put(&new_path);
3142 path_put(&old_path);
3147 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
3149 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
3153 * The worst of all namespace operations - renaming directory. "Perverted"
3154 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3156 * a) we can get into loop creation. Check is done in is_subdir().
3157 * b) race potential - two innocent renames can create a loop together.
3158 * That's where 4.4 screws up. Current fix: serialization on
3159 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
3161 * c) we have to lock _three_ objects - parents and victim (if it exists).
3162 * And that - after we got ->i_mutex on parents (until then we don't know
3163 * whether the target exists). Solution: try to be smart with locking
3164 * order for inodes. We rely on the fact that tree topology may change
3165 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
3166 * move will be locked. Thus we can rank directories by the tree
3167 * (ancestors first) and rank all non-directories after them.
3168 * That works since everybody except rename does "lock parent, lookup,
3169 * lock child" and rename is under ->s_vfs_rename_mutex.
3170 * HOWEVER, it relies on the assumption that any object with ->lookup()
3171 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3172 * we'd better make sure that there's no link(2) for them.
3173 * d) conversion from fhandle to dentry may come in the wrong moment - when
3174 * we are removing the target. Solution: we will have to grab ->i_mutex
3175 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
3176 * ->i_mutex on parents, which works but leads to some truly excessive
3179 static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
3180 struct inode *new_dir, struct dentry *new_dentry)
3183 struct inode *target = new_dentry->d_inode;
3184 unsigned max_links = new_dir->i_sb->s_max_links;
3187 * If we are going to change the parent - check write permissions,
3188 * we'll need to flip '..'.
3190 if (new_dir != old_dir) {
3191 error = inode_permission(old_dentry->d_inode, MAY_WRITE);
3196 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3202 mutex_lock(&target->i_mutex);
3205 if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
3209 if (max_links && !target && new_dir != old_dir &&
3210 new_dir->i_nlink >= max_links)
3214 shrink_dcache_parent(new_dentry);
3215 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3220 target->i_flags |= S_DEAD;
3221 dont_mount(new_dentry);
3225 mutex_unlock(&target->i_mutex);
3228 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3229 d_move(old_dentry,new_dentry);
3233 static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
3234 struct inode *new_dir, struct dentry *new_dentry)
3236 struct inode *target = new_dentry->d_inode;
3239 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3245 mutex_lock(&target->i_mutex);
3248 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
3251 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3256 dont_mount(new_dentry);
3257 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3258 d_move(old_dentry, new_dentry);
3261 mutex_unlock(&target->i_mutex);
3266 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
3267 struct inode *new_dir, struct dentry *new_dentry)
3270 int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
3271 const unsigned char *old_name;
3273 if (old_dentry->d_inode == new_dentry->d_inode)
3276 error = may_delete(old_dir, old_dentry, is_dir);
3280 if (!new_dentry->d_inode)
3281 error = may_create(new_dir, new_dentry);
3283 error = may_delete(new_dir, new_dentry, is_dir);
3287 if (!old_dir->i_op->rename)
3290 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
3293 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
3295 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
3297 fsnotify_move(old_dir, new_dir, old_name, is_dir,
3298 new_dentry->d_inode, old_dentry);
3299 fsnotify_oldname_free(old_name);
3304 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
3305 int, newdfd, const char __user *, newname)
3307 struct dentry *old_dir, *new_dir;
3308 struct dentry *old_dentry, *new_dentry;
3309 struct dentry *trap;
3310 struct nameidata oldnd, newnd;
3315 error = user_path_parent(olddfd, oldname, &oldnd, &from);
3319 error = user_path_parent(newdfd, newname, &newnd, &to);
3324 if (oldnd.path.mnt != newnd.path.mnt)
3327 old_dir = oldnd.path.dentry;
3329 if (oldnd.last_type != LAST_NORM)
3332 new_dir = newnd.path.dentry;
3333 if (newnd.last_type != LAST_NORM)
3336 oldnd.flags &= ~LOOKUP_PARENT;
3337 newnd.flags &= ~LOOKUP_PARENT;
3338 newnd.flags |= LOOKUP_RENAME_TARGET;
3340 trap = lock_rename(new_dir, old_dir);
3342 old_dentry = lookup_hash(&oldnd);
3343 error = PTR_ERR(old_dentry);
3344 if (IS_ERR(old_dentry))
3346 /* source must exist */
3348 if (!old_dentry->d_inode)
3350 /* unless the source is a directory trailing slashes give -ENOTDIR */
3351 if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
3353 if (oldnd.last.name[oldnd.last.len])
3355 if (newnd.last.name[newnd.last.len])
3358 /* source should not be ancestor of target */
3360 if (old_dentry == trap)
3362 new_dentry = lookup_hash(&newnd);
3363 error = PTR_ERR(new_dentry);
3364 if (IS_ERR(new_dentry))
3366 /* target should not be an ancestor of source */
3368 if (new_dentry == trap)
3371 error = mnt_want_write(oldnd.path.mnt);
3374 error = security_path_rename(&oldnd.path, old_dentry,
3375 &newnd.path, new_dentry);
3378 error = vfs_rename(old_dir->d_inode, old_dentry,
3379 new_dir->d_inode, new_dentry);
3381 mnt_drop_write(oldnd.path.mnt);
3387 unlock_rename(new_dir, old_dir);
3389 path_put(&newnd.path);
3392 path_put(&oldnd.path);
3398 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
3400 return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
3403 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
3407 len = PTR_ERR(link);
3412 if (len > (unsigned) buflen)
3414 if (copy_to_user(buffer, link, len))
3421 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
3422 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
3423 * using) it for any given inode is up to filesystem.
3425 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3427 struct nameidata nd;
3432 cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
3434 return PTR_ERR(cookie);
3436 res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
3437 if (dentry->d_inode->i_op->put_link)
3438 dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
3442 int vfs_follow_link(struct nameidata *nd, const char *link)
3444 return __vfs_follow_link(nd, link);
3447 /* get the link contents into pagecache */
3448 static char *page_getlink(struct dentry * dentry, struct page **ppage)
3452 struct address_space *mapping = dentry->d_inode->i_mapping;
3453 page = read_mapping_page(mapping, 0, NULL);
3458 nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
3462 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3464 struct page *page = NULL;
3465 char *s = page_getlink(dentry, &page);
3466 int res = vfs_readlink(dentry,buffer,buflen,s);
3469 page_cache_release(page);
3474 void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
3476 struct page *page = NULL;
3477 nd_set_link(nd, page_getlink(dentry, &page));
3481 void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
3483 struct page *page = cookie;
3487 page_cache_release(page);
3492 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
3494 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
3496 struct address_space *mapping = inode->i_mapping;
3501 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
3503 flags |= AOP_FLAG_NOFS;
3506 err = pagecache_write_begin(NULL, mapping, 0, len-1,
3507 flags, &page, &fsdata);
3511 kaddr = kmap_atomic(page);
3512 memcpy(kaddr, symname, len-1);
3513 kunmap_atomic(kaddr);
3515 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
3522 mark_inode_dirty(inode);
3528 int page_symlink(struct inode *inode, const char *symname, int len)
3530 return __page_symlink(inode, symname, len,
3531 !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
3534 const struct inode_operations page_symlink_inode_operations = {
3535 .readlink = generic_readlink,
3536 .follow_link = page_follow_link_light,
3537 .put_link = page_put_link,
3540 EXPORT_SYMBOL(user_path_at);
3541 EXPORT_SYMBOL(follow_down_one);
3542 EXPORT_SYMBOL(follow_down);
3543 EXPORT_SYMBOL(follow_up);
3544 EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
3545 EXPORT_SYMBOL(getname);
3546 EXPORT_SYMBOL(lock_rename);
3547 EXPORT_SYMBOL(lookup_one_len);
3548 EXPORT_SYMBOL(page_follow_link_light);
3549 EXPORT_SYMBOL(page_put_link);
3550 EXPORT_SYMBOL(page_readlink);
3551 EXPORT_SYMBOL(__page_symlink);
3552 EXPORT_SYMBOL(page_symlink);
3553 EXPORT_SYMBOL(page_symlink_inode_operations);
3554 EXPORT_SYMBOL(kern_path);
3555 EXPORT_SYMBOL(vfs_path_lookup);
3556 EXPORT_SYMBOL(inode_permission);
3557 EXPORT_SYMBOL(unlock_rename);
3558 EXPORT_SYMBOL(vfs_create);
3559 EXPORT_SYMBOL(vfs_follow_link);
3560 EXPORT_SYMBOL(vfs_link);
3561 EXPORT_SYMBOL(vfs_mkdir);
3562 EXPORT_SYMBOL(vfs_mknod);
3563 EXPORT_SYMBOL(generic_permission);
3564 EXPORT_SYMBOL(vfs_readlink);
3565 EXPORT_SYMBOL(vfs_rename);
3566 EXPORT_SYMBOL(vfs_rmdir);
3567 EXPORT_SYMBOL(vfs_symlink);
3568 EXPORT_SYMBOL(vfs_unlink);
3569 EXPORT_SYMBOL(dentry_unhash);
3570 EXPORT_SYMBOL(generic_readlink);