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/kernel.h>
20 #include <linux/slab.h>
22 #include <linux/namei.h>
23 #include <linux/pagemap.h>
24 #include <linux/fsnotify.h>
25 #include <linux/personality.h>
26 #include <linux/security.h>
27 #include <linux/ima.h>
28 #include <linux/syscalls.h>
29 #include <linux/mount.h>
30 #include <linux/audit.h>
31 #include <linux/capability.h>
32 #include <linux/file.h>
33 #include <linux/fcntl.h>
34 #include <linux/device_cgroup.h>
35 #include <linux/fs_struct.h>
36 #include <linux/posix_acl.h>
37 #include <asm/uaccess.h>
42 /* [Feb-1997 T. Schoebel-Theuer]
43 * Fundamental changes in the pathname lookup mechanisms (namei)
44 * were necessary because of omirr. The reason is that omirr needs
45 * to know the _real_ pathname, not the user-supplied one, in case
46 * of symlinks (and also when transname replacements occur).
48 * The new code replaces the old recursive symlink resolution with
49 * an iterative one (in case of non-nested symlink chains). It does
50 * this with calls to <fs>_follow_link().
51 * As a side effect, dir_namei(), _namei() and follow_link() are now
52 * replaced with a single function lookup_dentry() that can handle all
53 * the special cases of the former code.
55 * With the new dcache, the pathname is stored at each inode, at least as
56 * long as the refcount of the inode is positive. As a side effect, the
57 * size of the dcache depends on the inode cache and thus is dynamic.
59 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
60 * resolution to correspond with current state of the code.
62 * Note that the symlink resolution is not *completely* iterative.
63 * There is still a significant amount of tail- and mid- recursion in
64 * the algorithm. Also, note that <fs>_readlink() is not used in
65 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
66 * may return different results than <fs>_follow_link(). Many virtual
67 * filesystems (including /proc) exhibit this behavior.
70 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
71 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
72 * and the name already exists in form of a symlink, try to create the new
73 * name indicated by the symlink. The old code always complained that the
74 * name already exists, due to not following the symlink even if its target
75 * is nonexistent. The new semantics affects also mknod() and link() when
76 * the name is a symlink pointing to a non-existent name.
78 * I don't know which semantics is the right one, since I have no access
79 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
80 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
81 * "old" one. Personally, I think the new semantics is much more logical.
82 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
83 * file does succeed in both HP-UX and SunOs, but not in Solaris
84 * and in the old Linux semantics.
87 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
88 * semantics. See the comments in "open_namei" and "do_link" below.
90 * [10-Sep-98 Alan Modra] Another symlink change.
93 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
94 * inside the path - always follow.
95 * in the last component in creation/removal/renaming - never follow.
96 * if LOOKUP_FOLLOW passed - follow.
97 * if the pathname has trailing slashes - follow.
98 * otherwise - don't follow.
99 * (applied in that order).
101 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
102 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
103 * During the 2.4 we need to fix the userland stuff depending on it -
104 * hopefully we will be able to get rid of that wart in 2.5. So far only
105 * XEmacs seems to be relying on it...
108 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
109 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
110 * any extra contention...
113 /* In order to reduce some races, while at the same time doing additional
114 * checking and hopefully speeding things up, we copy filenames to the
115 * kernel data space before using them..
117 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
118 * PATH_MAX includes the nul terminator --RR.
120 static char *getname_flags(const char __user *filename, int flags, int *empty)
122 char *result = __getname(), *err;
125 if (unlikely(!result))
126 return ERR_PTR(-ENOMEM);
128 len = strncpy_from_user(result, filename, PATH_MAX);
130 if (unlikely(len < 0))
133 /* The empty path is special. */
134 if (unlikely(!len)) {
137 err = ERR_PTR(-ENOENT);
138 if (!(flags & LOOKUP_EMPTY))
142 err = ERR_PTR(-ENAMETOOLONG);
143 if (likely(len < PATH_MAX)) {
144 audit_getname(result);
153 char *getname(const char __user * filename)
155 return getname_flags(filename, 0, NULL);
158 #ifdef CONFIG_AUDITSYSCALL
159 void putname(const char *name)
161 if (unlikely(!audit_dummy_context()))
166 EXPORT_SYMBOL(putname);
169 static int check_acl(struct inode *inode, int mask)
171 #ifdef CONFIG_FS_POSIX_ACL
172 struct posix_acl *acl;
174 if (mask & MAY_NOT_BLOCK) {
175 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
178 /* no ->get_acl() calls in RCU mode... */
179 if (acl == ACL_NOT_CACHED)
181 return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
184 acl = get_cached_acl(inode, ACL_TYPE_ACCESS);
187 * A filesystem can force a ACL callback by just never filling the
188 * ACL cache. But normally you'd fill the cache either at inode
189 * instantiation time, or on the first ->get_acl call.
191 * If the filesystem doesn't have a get_acl() function at all, we'll
192 * just create the negative cache entry.
194 if (acl == ACL_NOT_CACHED) {
195 if (inode->i_op->get_acl) {
196 acl = inode->i_op->get_acl(inode, ACL_TYPE_ACCESS);
200 set_cached_acl(inode, ACL_TYPE_ACCESS, NULL);
206 int error = posix_acl_permission(inode, acl, mask);
207 posix_acl_release(acl);
216 * This does the basic permission checking
218 static int acl_permission_check(struct inode *inode, int mask)
220 unsigned int mode = inode->i_mode;
222 if (likely(uid_eq(current_fsuid(), inode->i_uid)))
225 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
226 int error = check_acl(inode, mask);
227 if (error != -EAGAIN)
231 if (in_group_p(inode->i_gid))
236 * If the DACs are ok we don't need any capability check.
238 if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
244 * generic_permission - check for access rights on a Posix-like filesystem
245 * @inode: inode to check access rights for
246 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
248 * Used to check for read/write/execute permissions on a file.
249 * We use "fsuid" for this, letting us set arbitrary permissions
250 * for filesystem access without changing the "normal" uids which
251 * are used for other things.
253 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
254 * request cannot be satisfied (eg. requires blocking or too much complexity).
255 * It would then be called again in ref-walk mode.
257 int generic_permission(struct inode *inode, int mask)
262 * Do the basic permission checks.
264 ret = acl_permission_check(inode, mask);
268 if (S_ISDIR(inode->i_mode)) {
269 /* DACs are overridable for directories */
270 if (inode_capable(inode, CAP_DAC_OVERRIDE))
272 if (!(mask & MAY_WRITE))
273 if (inode_capable(inode, CAP_DAC_READ_SEARCH))
278 * Read/write DACs are always overridable.
279 * Executable DACs are overridable when there is
280 * at least one exec bit set.
282 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
283 if (inode_capable(inode, CAP_DAC_OVERRIDE))
287 * Searching includes executable on directories, else just read.
289 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
290 if (mask == MAY_READ)
291 if (inode_capable(inode, CAP_DAC_READ_SEARCH))
298 * We _really_ want to just do "generic_permission()" without
299 * even looking at the inode->i_op values. So we keep a cache
300 * flag in inode->i_opflags, that says "this has not special
301 * permission function, use the fast case".
303 static inline int do_inode_permission(struct inode *inode, int mask)
305 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
306 if (likely(inode->i_op->permission))
307 return inode->i_op->permission(inode, mask);
309 /* This gets set once for the inode lifetime */
310 spin_lock(&inode->i_lock);
311 inode->i_opflags |= IOP_FASTPERM;
312 spin_unlock(&inode->i_lock);
314 return generic_permission(inode, mask);
318 * inode_permission - check for access rights to a given inode
319 * @inode: inode to check permission on
320 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
322 * Used to check for read/write/execute permissions on an inode.
323 * We use "fsuid" for this, letting us set arbitrary permissions
324 * for filesystem access without changing the "normal" uids which
325 * are used for other things.
327 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
329 int inode_permission(struct inode *inode, int mask)
333 if (unlikely(mask & MAY_WRITE)) {
334 umode_t mode = inode->i_mode;
337 * Nobody gets write access to a read-only fs.
339 if (IS_RDONLY(inode) &&
340 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
344 * Nobody gets write access to an immutable file.
346 if (IS_IMMUTABLE(inode))
350 retval = do_inode_permission(inode, mask);
354 retval = devcgroup_inode_permission(inode, mask);
358 return security_inode_permission(inode, mask);
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 * Path walking has 2 modes, rcu-walk and ref-walk (see
389 * Documentation/filesystems/path-lookup.txt). In situations when we can't
390 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
391 * normal reference counts on dentries and vfsmounts to transition to rcu-walk
392 * mode. Refcounts are grabbed at the last known good point before rcu-walk
393 * got stuck, so ref-walk may continue from there. If this is not successful
394 * (eg. a seqcount has changed), then failure is returned and it's up to caller
395 * to restart the path walk from the beginning in ref-walk mode.
399 * unlazy_walk - try to switch to ref-walk mode.
400 * @nd: nameidata pathwalk data
401 * @dentry: child of nd->path.dentry or NULL
402 * Returns: 0 on success, -ECHILD on failure
404 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
405 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
406 * @nd or NULL. Must be called from rcu-walk context.
408 static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
410 struct fs_struct *fs = current->fs;
411 struct dentry *parent = nd->path.dentry;
414 BUG_ON(!(nd->flags & LOOKUP_RCU));
415 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
417 spin_lock(&fs->lock);
418 if (nd->root.mnt != fs->root.mnt ||
419 nd->root.dentry != fs->root.dentry)
422 spin_lock(&parent->d_lock);
424 if (!__d_rcu_to_refcount(parent, nd->seq))
426 BUG_ON(nd->inode != parent->d_inode);
428 if (dentry->d_parent != parent)
430 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
431 if (!__d_rcu_to_refcount(dentry, nd->seq))
434 * If the sequence check on the child dentry passed, then
435 * the child has not been removed from its parent. This
436 * means the parent dentry must be valid and able to take
437 * a reference at this point.
439 BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
440 BUG_ON(!parent->d_count);
442 spin_unlock(&dentry->d_lock);
444 spin_unlock(&parent->d_lock);
447 spin_unlock(&fs->lock);
449 mntget(nd->path.mnt);
452 br_read_unlock(vfsmount_lock);
453 nd->flags &= ~LOOKUP_RCU;
457 spin_unlock(&dentry->d_lock);
459 spin_unlock(&parent->d_lock);
462 spin_unlock(&fs->lock);
467 * release_open_intent - free up open intent resources
468 * @nd: pointer to nameidata
470 void release_open_intent(struct nameidata *nd)
472 struct file *file = nd->intent.open.file;
474 if (file && !IS_ERR(file)) {
475 if (file->f_path.dentry == NULL)
482 static inline int d_revalidate(struct dentry *dentry, struct nameidata *nd)
484 return dentry->d_op->d_revalidate(dentry, nd);
488 * complete_walk - successful completion of path walk
489 * @nd: pointer nameidata
491 * If we had been in RCU mode, drop out of it and legitimize nd->path.
492 * Revalidate the final result, unless we'd already done that during
493 * the path walk or the filesystem doesn't ask for it. Return 0 on
494 * success, -error on failure. In case of failure caller does not
495 * need to drop nd->path.
497 static int complete_walk(struct nameidata *nd)
499 struct dentry *dentry = nd->path.dentry;
502 if (nd->flags & LOOKUP_RCU) {
503 nd->flags &= ~LOOKUP_RCU;
504 if (!(nd->flags & LOOKUP_ROOT))
506 spin_lock(&dentry->d_lock);
507 if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) {
508 spin_unlock(&dentry->d_lock);
510 br_read_unlock(vfsmount_lock);
513 BUG_ON(nd->inode != dentry->d_inode);
514 spin_unlock(&dentry->d_lock);
515 mntget(nd->path.mnt);
517 br_read_unlock(vfsmount_lock);
520 if (likely(!(nd->flags & LOOKUP_JUMPED)))
523 if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
526 if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
529 /* Note: we do not d_invalidate() */
530 status = d_revalidate(dentry, nd);
541 static __always_inline void set_root(struct nameidata *nd)
544 get_fs_root(current->fs, &nd->root);
547 static int link_path_walk(const char *, struct nameidata *);
549 static __always_inline void set_root_rcu(struct nameidata *nd)
552 struct fs_struct *fs = current->fs;
556 seq = read_seqcount_begin(&fs->seq);
558 nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
559 } while (read_seqcount_retry(&fs->seq, seq));
563 static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
575 nd->flags |= LOOKUP_JUMPED;
577 nd->inode = nd->path.dentry->d_inode;
579 ret = link_path_walk(link, nd);
583 return PTR_ERR(link);
586 static void path_put_conditional(struct path *path, struct nameidata *nd)
589 if (path->mnt != nd->path.mnt)
593 static inline void path_to_nameidata(const struct path *path,
594 struct nameidata *nd)
596 if (!(nd->flags & LOOKUP_RCU)) {
597 dput(nd->path.dentry);
598 if (nd->path.mnt != path->mnt)
599 mntput(nd->path.mnt);
601 nd->path.mnt = path->mnt;
602 nd->path.dentry = path->dentry;
605 static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
607 struct inode *inode = link->dentry->d_inode;
608 if (!IS_ERR(cookie) && inode->i_op->put_link)
609 inode->i_op->put_link(link->dentry, nd, cookie);
613 static __always_inline int
614 follow_link(struct path *link, struct nameidata *nd, void **p)
617 struct dentry *dentry = link->dentry;
619 BUG_ON(nd->flags & LOOKUP_RCU);
621 if (link->mnt == nd->path.mnt)
624 if (unlikely(current->total_link_count >= 40)) {
625 *p = ERR_PTR(-ELOOP); /* no ->put_link(), please */
630 current->total_link_count++;
633 nd_set_link(nd, NULL);
635 error = security_inode_follow_link(link->dentry, nd);
637 *p = ERR_PTR(error); /* no ->put_link(), please */
642 nd->last_type = LAST_BIND;
643 *p = dentry->d_inode->i_op->follow_link(dentry, nd);
646 char *s = nd_get_link(nd);
649 error = __vfs_follow_link(nd, s);
650 else if (nd->last_type == LAST_BIND) {
651 nd->flags |= LOOKUP_JUMPED;
652 nd->inode = nd->path.dentry->d_inode;
653 if (nd->inode->i_op->follow_link) {
654 /* stepped on a _really_ weird one */
663 static int follow_up_rcu(struct path *path)
665 struct mount *mnt = real_mount(path->mnt);
666 struct mount *parent;
667 struct dentry *mountpoint;
669 parent = mnt->mnt_parent;
670 if (&parent->mnt == path->mnt)
672 mountpoint = mnt->mnt_mountpoint;
673 path->dentry = mountpoint;
674 path->mnt = &parent->mnt;
678 int follow_up(struct path *path)
680 struct mount *mnt = real_mount(path->mnt);
681 struct mount *parent;
682 struct dentry *mountpoint;
684 br_read_lock(vfsmount_lock);
685 parent = mnt->mnt_parent;
686 if (&parent->mnt == path->mnt) {
687 br_read_unlock(vfsmount_lock);
690 mntget(&parent->mnt);
691 mountpoint = dget(mnt->mnt_mountpoint);
692 br_read_unlock(vfsmount_lock);
694 path->dentry = mountpoint;
696 path->mnt = &parent->mnt;
701 * Perform an automount
702 * - return -EISDIR to tell follow_managed() to stop and return the path we
705 static int follow_automount(struct path *path, unsigned flags,
708 struct vfsmount *mnt;
711 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
714 /* We don't want to mount if someone's just doing a stat -
715 * unless they're stat'ing a directory and appended a '/' to
718 * We do, however, want to mount if someone wants to open or
719 * create a file of any type under the mountpoint, wants to
720 * traverse through the mountpoint or wants to open the
721 * mounted directory. Also, autofs may mark negative dentries
722 * as being automount points. These will need the attentions
723 * of the daemon to instantiate them before they can be used.
725 if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
726 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
727 path->dentry->d_inode)
730 current->total_link_count++;
731 if (current->total_link_count >= 40)
734 mnt = path->dentry->d_op->d_automount(path);
737 * The filesystem is allowed to return -EISDIR here to indicate
738 * it doesn't want to automount. For instance, autofs would do
739 * this so that its userspace daemon can mount on this dentry.
741 * However, we can only permit this if it's a terminal point in
742 * the path being looked up; if it wasn't then the remainder of
743 * the path is inaccessible and we should say so.
745 if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT))
750 if (!mnt) /* mount collision */
754 /* lock_mount() may release path->mnt on error */
758 err = finish_automount(mnt, path);
762 /* Someone else made a mount here whilst we were busy */
767 path->dentry = dget(mnt->mnt_root);
776 * Handle a dentry that is managed in some way.
777 * - Flagged for transit management (autofs)
778 * - Flagged as mountpoint
779 * - Flagged as automount point
781 * This may only be called in refwalk mode.
783 * Serialization is taken care of in namespace.c
785 static int follow_managed(struct path *path, unsigned flags)
787 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
789 bool need_mntput = false;
792 /* Given that we're not holding a lock here, we retain the value in a
793 * local variable for each dentry as we look at it so that we don't see
794 * the components of that value change under us */
795 while (managed = ACCESS_ONCE(path->dentry->d_flags),
796 managed &= DCACHE_MANAGED_DENTRY,
797 unlikely(managed != 0)) {
798 /* Allow the filesystem to manage the transit without i_mutex
800 if (managed & DCACHE_MANAGE_TRANSIT) {
801 BUG_ON(!path->dentry->d_op);
802 BUG_ON(!path->dentry->d_op->d_manage);
803 ret = path->dentry->d_op->d_manage(path->dentry, false);
808 /* Transit to a mounted filesystem. */
809 if (managed & DCACHE_MOUNTED) {
810 struct vfsmount *mounted = lookup_mnt(path);
816 path->dentry = dget(mounted->mnt_root);
821 /* Something is mounted on this dentry in another
822 * namespace and/or whatever was mounted there in this
823 * namespace got unmounted before we managed to get the
827 /* Handle an automount point */
828 if (managed & DCACHE_NEED_AUTOMOUNT) {
829 ret = follow_automount(path, flags, &need_mntput);
835 /* We didn't change the current path point */
839 if (need_mntput && path->mnt == mnt)
843 return ret < 0 ? ret : need_mntput;
846 int follow_down_one(struct path *path)
848 struct vfsmount *mounted;
850 mounted = lookup_mnt(path);
855 path->dentry = dget(mounted->mnt_root);
861 static inline bool managed_dentry_might_block(struct dentry *dentry)
863 return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
864 dentry->d_op->d_manage(dentry, true) < 0);
868 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
869 * we meet a managed dentry that would need blocking.
871 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
872 struct inode **inode)
875 struct mount *mounted;
877 * Don't forget we might have a non-mountpoint managed dentry
878 * that wants to block transit.
880 if (unlikely(managed_dentry_might_block(path->dentry)))
883 if (!d_mountpoint(path->dentry))
886 mounted = __lookup_mnt(path->mnt, path->dentry, 1);
889 path->mnt = &mounted->mnt;
890 path->dentry = mounted->mnt.mnt_root;
891 nd->flags |= LOOKUP_JUMPED;
892 nd->seq = read_seqcount_begin(&path->dentry->d_seq);
894 * Update the inode too. We don't need to re-check the
895 * dentry sequence number here after this d_inode read,
896 * because a mount-point is always pinned.
898 *inode = path->dentry->d_inode;
903 static void follow_mount_rcu(struct nameidata *nd)
905 while (d_mountpoint(nd->path.dentry)) {
906 struct mount *mounted;
907 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1);
910 nd->path.mnt = &mounted->mnt;
911 nd->path.dentry = mounted->mnt.mnt_root;
912 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
916 static int follow_dotdot_rcu(struct nameidata *nd)
921 if (nd->path.dentry == nd->root.dentry &&
922 nd->path.mnt == nd->root.mnt) {
925 if (nd->path.dentry != nd->path.mnt->mnt_root) {
926 struct dentry *old = nd->path.dentry;
927 struct dentry *parent = old->d_parent;
930 seq = read_seqcount_begin(&parent->d_seq);
931 if (read_seqcount_retry(&old->d_seq, nd->seq))
933 nd->path.dentry = parent;
937 if (!follow_up_rcu(&nd->path))
939 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
941 follow_mount_rcu(nd);
942 nd->inode = nd->path.dentry->d_inode;
946 nd->flags &= ~LOOKUP_RCU;
947 if (!(nd->flags & LOOKUP_ROOT))
950 br_read_unlock(vfsmount_lock);
955 * Follow down to the covering mount currently visible to userspace. At each
956 * point, the filesystem owning that dentry may be queried as to whether the
957 * caller is permitted to proceed or not.
959 int follow_down(struct path *path)
964 while (managed = ACCESS_ONCE(path->dentry->d_flags),
965 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
966 /* Allow the filesystem to manage the transit without i_mutex
969 * We indicate to the filesystem if someone is trying to mount
970 * something here. This gives autofs the chance to deny anyone
971 * other than its daemon the right to mount on its
974 * The filesystem may sleep at this point.
976 if (managed & DCACHE_MANAGE_TRANSIT) {
977 BUG_ON(!path->dentry->d_op);
978 BUG_ON(!path->dentry->d_op->d_manage);
979 ret = path->dentry->d_op->d_manage(
980 path->dentry, false);
982 return ret == -EISDIR ? 0 : ret;
985 /* Transit to a mounted filesystem. */
986 if (managed & DCACHE_MOUNTED) {
987 struct vfsmount *mounted = lookup_mnt(path);
993 path->dentry = dget(mounted->mnt_root);
997 /* Don't handle automount points here */
1004 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1006 static void follow_mount(struct path *path)
1008 while (d_mountpoint(path->dentry)) {
1009 struct vfsmount *mounted = lookup_mnt(path);
1014 path->mnt = mounted;
1015 path->dentry = dget(mounted->mnt_root);
1019 static void follow_dotdot(struct nameidata *nd)
1024 struct dentry *old = nd->path.dentry;
1026 if (nd->path.dentry == nd->root.dentry &&
1027 nd->path.mnt == nd->root.mnt) {
1030 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1031 /* rare case of legitimate dget_parent()... */
1032 nd->path.dentry = dget_parent(nd->path.dentry);
1036 if (!follow_up(&nd->path))
1039 follow_mount(&nd->path);
1040 nd->inode = nd->path.dentry->d_inode;
1044 * This looks up the name in dcache, possibly revalidates the old dentry and
1045 * allocates a new one if not found or not valid. In the need_lookup argument
1046 * returns whether i_op->lookup is necessary.
1048 * dir->d_inode->i_mutex must be held
1050 static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir,
1051 struct nameidata *nd, bool *need_lookup)
1053 struct dentry *dentry;
1056 *need_lookup = false;
1057 dentry = d_lookup(dir, name);
1059 if (d_need_lookup(dentry)) {
1060 *need_lookup = true;
1061 } else if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
1062 error = d_revalidate(dentry, nd);
1063 if (unlikely(error <= 0)) {
1066 return ERR_PTR(error);
1067 } else if (!d_invalidate(dentry)) {
1076 dentry = d_alloc(dir, name);
1077 if (unlikely(!dentry))
1078 return ERR_PTR(-ENOMEM);
1080 *need_lookup = true;
1086 * Call i_op->lookup on the dentry. The dentry must be negative but may be
1087 * hashed if it was pouplated with DCACHE_NEED_LOOKUP.
1089 * dir->d_inode->i_mutex must be held
1091 static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
1092 struct nameidata *nd)
1096 /* Don't create child dentry for a dead directory. */
1097 if (unlikely(IS_DEADDIR(dir))) {
1099 return ERR_PTR(-ENOENT);
1102 old = dir->i_op->lookup(dir, dentry, nd);
1103 if (unlikely(old)) {
1110 static struct dentry *__lookup_hash(struct qstr *name,
1111 struct dentry *base, struct nameidata *nd)
1114 struct dentry *dentry;
1116 dentry = lookup_dcache(name, base, nd, &need_lookup);
1120 return lookup_real(base->d_inode, dentry, nd);
1124 * It's more convoluted than I'd like it to be, but... it's still fairly
1125 * small and for now I'd prefer to have fast path as straight as possible.
1126 * It _is_ time-critical.
1128 static int do_lookup(struct nameidata *nd, struct qstr *name,
1129 struct path *path, struct inode **inode)
1131 struct vfsmount *mnt = nd->path.mnt;
1132 struct dentry *dentry, *parent = nd->path.dentry;
1138 * Rename seqlock is not required here because in the off chance
1139 * of a false negative due to a concurrent rename, we're going to
1140 * do the non-racy lookup, below.
1142 if (nd->flags & LOOKUP_RCU) {
1144 dentry = __d_lookup_rcu(parent, name, &seq, nd->inode);
1149 * This sequence count validates that the inode matches
1150 * the dentry name information from lookup.
1152 *inode = dentry->d_inode;
1153 if (read_seqcount_retry(&dentry->d_seq, seq))
1157 * This sequence count validates that the parent had no
1158 * changes while we did the lookup of the dentry above.
1160 * The memory barrier in read_seqcount_begin of child is
1161 * enough, we can use __read_seqcount_retry here.
1163 if (__read_seqcount_retry(&parent->d_seq, nd->seq))
1167 if (unlikely(d_need_lookup(dentry)))
1169 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1170 status = d_revalidate(dentry, nd);
1171 if (unlikely(status <= 0)) {
1172 if (status != -ECHILD)
1178 path->dentry = dentry;
1179 if (unlikely(!__follow_mount_rcu(nd, path, inode)))
1181 if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
1185 if (unlazy_walk(nd, dentry))
1188 dentry = __d_lookup(parent, name);
1191 if (unlikely(!dentry))
1194 if (unlikely(d_need_lookup(dentry))) {
1199 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
1200 status = d_revalidate(dentry, nd);
1201 if (unlikely(status <= 0)) {
1206 if (!d_invalidate(dentry)) {
1213 path->dentry = dentry;
1214 err = follow_managed(path, nd->flags);
1215 if (unlikely(err < 0)) {
1216 path_put_conditional(path, nd);
1220 nd->flags |= LOOKUP_JUMPED;
1221 *inode = path->dentry->d_inode;
1225 BUG_ON(nd->inode != parent->d_inode);
1227 mutex_lock(&parent->d_inode->i_mutex);
1228 dentry = __lookup_hash(name, parent, nd);
1229 mutex_unlock(&parent->d_inode->i_mutex);
1231 return PTR_ERR(dentry);
1235 static inline int may_lookup(struct nameidata *nd)
1237 if (nd->flags & LOOKUP_RCU) {
1238 int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1241 if (unlazy_walk(nd, NULL))
1244 return inode_permission(nd->inode, MAY_EXEC);
1247 static inline int handle_dots(struct nameidata *nd, int type)
1249 if (type == LAST_DOTDOT) {
1250 if (nd->flags & LOOKUP_RCU) {
1251 if (follow_dotdot_rcu(nd))
1259 static void terminate_walk(struct nameidata *nd)
1261 if (!(nd->flags & LOOKUP_RCU)) {
1262 path_put(&nd->path);
1264 nd->flags &= ~LOOKUP_RCU;
1265 if (!(nd->flags & LOOKUP_ROOT))
1266 nd->root.mnt = NULL;
1268 br_read_unlock(vfsmount_lock);
1273 * Do we need to follow links? We _really_ want to be able
1274 * to do this check without having to look at inode->i_op,
1275 * so we keep a cache of "no, this doesn't need follow_link"
1276 * for the common case.
1278 static inline int should_follow_link(struct inode *inode, int follow)
1280 if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1281 if (likely(inode->i_op->follow_link))
1284 /* This gets set once for the inode lifetime */
1285 spin_lock(&inode->i_lock);
1286 inode->i_opflags |= IOP_NOFOLLOW;
1287 spin_unlock(&inode->i_lock);
1292 static inline int walk_component(struct nameidata *nd, struct path *path,
1293 struct qstr *name, int type, int follow)
1295 struct inode *inode;
1298 * "." and ".." are special - ".." especially so because it has
1299 * to be able to know about the current root directory and
1300 * parent relationships.
1302 if (unlikely(type != LAST_NORM))
1303 return handle_dots(nd, type);
1304 err = do_lookup(nd, name, path, &inode);
1305 if (unlikely(err)) {
1310 path_to_nameidata(path, nd);
1314 if (should_follow_link(inode, follow)) {
1315 if (nd->flags & LOOKUP_RCU) {
1316 if (unlikely(unlazy_walk(nd, path->dentry))) {
1321 BUG_ON(inode != path->dentry->d_inode);
1324 path_to_nameidata(path, nd);
1330 * This limits recursive symlink follows to 8, while
1331 * limiting consecutive symlinks to 40.
1333 * Without that kind of total limit, nasty chains of consecutive
1334 * symlinks can cause almost arbitrarily long lookups.
1336 static inline int nested_symlink(struct path *path, struct nameidata *nd)
1340 if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
1341 path_put_conditional(path, nd);
1342 path_put(&nd->path);
1345 BUG_ON(nd->depth >= MAX_NESTED_LINKS);
1348 current->link_count++;
1351 struct path link = *path;
1354 res = follow_link(&link, nd, &cookie);
1356 res = walk_component(nd, path, &nd->last,
1357 nd->last_type, LOOKUP_FOLLOW);
1358 put_link(nd, &link, cookie);
1361 current->link_count--;
1367 * We really don't want to look at inode->i_op->lookup
1368 * when we don't have to. So we keep a cache bit in
1369 * the inode ->i_opflags field that says "yes, we can
1370 * do lookup on this inode".
1372 static inline int can_lookup(struct inode *inode)
1374 if (likely(inode->i_opflags & IOP_LOOKUP))
1376 if (likely(!inode->i_op->lookup))
1379 /* We do this once for the lifetime of the inode */
1380 spin_lock(&inode->i_lock);
1381 inode->i_opflags |= IOP_LOOKUP;
1382 spin_unlock(&inode->i_lock);
1387 * We can do the critical dentry name comparison and hashing
1388 * operations one word at a time, but we are limited to:
1390 * - Architectures with fast unaligned word accesses. We could
1391 * do a "get_unaligned()" if this helps and is sufficiently
1394 * - Little-endian machines (so that we can generate the mask
1395 * of low bytes efficiently). Again, we *could* do a byte
1396 * swapping load on big-endian architectures if that is not
1397 * expensive enough to make the optimization worthless.
1399 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1400 * do not trap on the (extremely unlikely) case of a page
1401 * crossing operation.
1403 * - Furthermore, we need an efficient 64-bit compile for the
1404 * 64-bit case in order to generate the "number of bytes in
1405 * the final mask". Again, that could be replaced with a
1406 * efficient population count instruction or similar.
1408 #ifdef CONFIG_DCACHE_WORD_ACCESS
1410 #include <asm/word-at-a-time.h>
1414 static inline unsigned int fold_hash(unsigned long hash)
1416 hash += hash >> (8*sizeof(int));
1420 #else /* 32-bit case */
1422 #define fold_hash(x) (x)
1426 unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1428 unsigned long a, mask;
1429 unsigned long hash = 0;
1432 a = load_unaligned_zeropad(name);
1433 if (len < sizeof(unsigned long))
1437 name += sizeof(unsigned long);
1438 len -= sizeof(unsigned long);
1442 mask = ~(~0ul << len*8);
1445 return fold_hash(hash);
1447 EXPORT_SYMBOL(full_name_hash);
1450 * Calculate the length and hash of the path component, and
1451 * return the length of the component;
1453 static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1455 unsigned long a, mask, hash, len;
1458 len = -sizeof(unsigned long);
1460 hash = (hash + a) * 9;
1461 len += sizeof(unsigned long);
1462 a = load_unaligned_zeropad(name+len);
1463 /* Do we have any NUL or '/' bytes in this word? */
1464 mask = has_zero(a) | has_zero(a ^ REPEAT_BYTE('/'));
1467 /* The mask *below* the first high bit set */
1468 mask = (mask - 1) & ~mask;
1471 *hashp = fold_hash(hash);
1473 return len + count_masked_bytes(mask);
1478 unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1480 unsigned long hash = init_name_hash();
1482 hash = partial_name_hash(*name++, hash);
1483 return end_name_hash(hash);
1485 EXPORT_SYMBOL(full_name_hash);
1488 * We know there's a real path component here of at least
1491 static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1493 unsigned long hash = init_name_hash();
1494 unsigned long len = 0, c;
1496 c = (unsigned char)*name;
1499 hash = partial_name_hash(c, hash);
1500 c = (unsigned char)name[len];
1501 } while (c && c != '/');
1502 *hashp = end_name_hash(hash);
1510 * This is the basic name resolution function, turning a pathname into
1511 * the final dentry. We expect 'base' to be positive and a directory.
1513 * Returns 0 and nd will have valid dentry and mnt on success.
1514 * Returns error and drops reference to input namei data on failure.
1516 static int link_path_walk(const char *name, struct nameidata *nd)
1526 /* At this point we know we have a real path component. */
1532 err = may_lookup(nd);
1536 len = hash_name(name, &this.hash);
1541 if (name[0] == '.') switch (len) {
1543 if (name[1] == '.') {
1545 nd->flags |= LOOKUP_JUMPED;
1551 if (likely(type == LAST_NORM)) {
1552 struct dentry *parent = nd->path.dentry;
1553 nd->flags &= ~LOOKUP_JUMPED;
1554 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
1555 err = parent->d_op->d_hash(parent, nd->inode,
1563 goto last_component;
1565 * If it wasn't NUL, we know it was '/'. Skip that
1566 * slash, and continue until no more slashes.
1570 } while (unlikely(name[len] == '/'));
1572 goto last_component;
1575 err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
1580 err = nested_symlink(&next, nd);
1584 if (can_lookup(nd->inode))
1588 /* here ends the main loop */
1592 nd->last_type = type;
1599 static int path_init(int dfd, const char *name, unsigned int flags,
1600 struct nameidata *nd, struct file **fp)
1606 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1607 nd->flags = flags | LOOKUP_JUMPED;
1609 if (flags & LOOKUP_ROOT) {
1610 struct inode *inode = nd->root.dentry->d_inode;
1612 if (!inode->i_op->lookup)
1614 retval = inode_permission(inode, MAY_EXEC);
1618 nd->path = nd->root;
1620 if (flags & LOOKUP_RCU) {
1621 br_read_lock(vfsmount_lock);
1623 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1625 path_get(&nd->path);
1630 nd->root.mnt = NULL;
1633 if (flags & LOOKUP_RCU) {
1634 br_read_lock(vfsmount_lock);
1639 path_get(&nd->root);
1641 nd->path = nd->root;
1642 } else if (dfd == AT_FDCWD) {
1643 if (flags & LOOKUP_RCU) {
1644 struct fs_struct *fs = current->fs;
1647 br_read_lock(vfsmount_lock);
1651 seq = read_seqcount_begin(&fs->seq);
1653 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1654 } while (read_seqcount_retry(&fs->seq, seq));
1656 get_fs_pwd(current->fs, &nd->path);
1659 struct dentry *dentry;
1661 file = fget_raw_light(dfd, &fput_needed);
1666 dentry = file->f_path.dentry;
1670 if (!S_ISDIR(dentry->d_inode->i_mode))
1673 retval = inode_permission(dentry->d_inode, MAY_EXEC);
1678 nd->path = file->f_path;
1679 if (flags & LOOKUP_RCU) {
1682 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1683 br_read_lock(vfsmount_lock);
1686 path_get(&file->f_path);
1687 fput_light(file, fput_needed);
1691 nd->inode = nd->path.dentry->d_inode;
1695 fput_light(file, fput_needed);
1700 static inline int lookup_last(struct nameidata *nd, struct path *path)
1702 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
1703 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
1705 nd->flags &= ~LOOKUP_PARENT;
1706 return walk_component(nd, path, &nd->last, nd->last_type,
1707 nd->flags & LOOKUP_FOLLOW);
1710 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1711 static int path_lookupat(int dfd, const char *name,
1712 unsigned int flags, struct nameidata *nd)
1714 struct file *base = NULL;
1719 * Path walking is largely split up into 2 different synchronisation
1720 * schemes, rcu-walk and ref-walk (explained in
1721 * Documentation/filesystems/path-lookup.txt). These share much of the
1722 * path walk code, but some things particularly setup, cleanup, and
1723 * following mounts are sufficiently divergent that functions are
1724 * duplicated. Typically there is a function foo(), and its RCU
1725 * analogue, foo_rcu().
1727 * -ECHILD is the error number of choice (just to avoid clashes) that
1728 * is returned if some aspect of an rcu-walk fails. Such an error must
1729 * be handled by restarting a traditional ref-walk (which will always
1730 * be able to complete).
1732 err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base);
1737 current->total_link_count = 0;
1738 err = link_path_walk(name, nd);
1740 if (!err && !(flags & LOOKUP_PARENT)) {
1741 err = lookup_last(nd, &path);
1744 struct path link = path;
1745 nd->flags |= LOOKUP_PARENT;
1746 err = follow_link(&link, nd, &cookie);
1748 err = lookup_last(nd, &path);
1749 put_link(nd, &link, cookie);
1754 err = complete_walk(nd);
1756 if (!err && nd->flags & LOOKUP_DIRECTORY) {
1757 if (!nd->inode->i_op->lookup) {
1758 path_put(&nd->path);
1766 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
1767 path_put(&nd->root);
1768 nd->root.mnt = NULL;
1773 static int do_path_lookup(int dfd, const char *name,
1774 unsigned int flags, struct nameidata *nd)
1776 int retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd);
1777 if (unlikely(retval == -ECHILD))
1778 retval = path_lookupat(dfd, name, flags, nd);
1779 if (unlikely(retval == -ESTALE))
1780 retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd);
1782 if (likely(!retval)) {
1783 if (unlikely(!audit_dummy_context())) {
1784 if (nd->path.dentry && nd->inode)
1785 audit_inode(name, nd->path.dentry);
1791 int kern_path_parent(const char *name, struct nameidata *nd)
1793 return do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, nd);
1796 int kern_path(const char *name, unsigned int flags, struct path *path)
1798 struct nameidata nd;
1799 int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
1806 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
1807 * @dentry: pointer to dentry of the base directory
1808 * @mnt: pointer to vfs mount of the base directory
1809 * @name: pointer to file name
1810 * @flags: lookup flags
1811 * @path: pointer to struct path to fill
1813 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
1814 const char *name, unsigned int flags,
1817 struct nameidata nd;
1819 nd.root.dentry = dentry;
1821 BUG_ON(flags & LOOKUP_PARENT);
1822 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
1823 err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd);
1830 * Restricted form of lookup. Doesn't follow links, single-component only,
1831 * needs parent already locked. Doesn't follow mounts.
1834 static struct dentry *lookup_hash(struct nameidata *nd)
1836 return __lookup_hash(&nd->last, nd->path.dentry, nd);
1840 * lookup_one_len - filesystem helper to lookup single pathname component
1841 * @name: pathname component to lookup
1842 * @base: base directory to lookup from
1843 * @len: maximum length @len should be interpreted to
1845 * Note that this routine is purely a helper for filesystem usage and should
1846 * not be called by generic code. Also note that by using this function the
1847 * nameidata argument is passed to the filesystem methods and a filesystem
1848 * using this helper needs to be prepared for that.
1850 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
1856 WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
1860 this.hash = full_name_hash(name, len);
1862 return ERR_PTR(-EACCES);
1865 c = *(const unsigned char *)name++;
1866 if (c == '/' || c == '\0')
1867 return ERR_PTR(-EACCES);
1870 * See if the low-level filesystem might want
1871 * to use its own hash..
1873 if (base->d_flags & DCACHE_OP_HASH) {
1874 int err = base->d_op->d_hash(base, base->d_inode, &this);
1876 return ERR_PTR(err);
1879 err = inode_permission(base->d_inode, MAY_EXEC);
1881 return ERR_PTR(err);
1883 return __lookup_hash(&this, base, NULL);
1886 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
1887 struct path *path, int *empty)
1889 struct nameidata nd;
1890 char *tmp = getname_flags(name, flags, empty);
1891 int err = PTR_ERR(tmp);
1894 BUG_ON(flags & LOOKUP_PARENT);
1896 err = do_path_lookup(dfd, tmp, flags, &nd);
1904 int user_path_at(int dfd, const char __user *name, unsigned flags,
1907 return user_path_at_empty(dfd, name, flags, path, NULL);
1910 static int user_path_parent(int dfd, const char __user *path,
1911 struct nameidata *nd, char **name)
1913 char *s = getname(path);
1919 error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd);
1929 * It's inline, so penalty for filesystems that don't use sticky bit is
1932 static inline int check_sticky(struct inode *dir, struct inode *inode)
1934 kuid_t fsuid = current_fsuid();
1936 if (!(dir->i_mode & S_ISVTX))
1938 if (uid_eq(inode->i_uid, fsuid))
1940 if (uid_eq(dir->i_uid, fsuid))
1942 return !inode_capable(inode, CAP_FOWNER);
1946 * Check whether we can remove a link victim from directory dir, check
1947 * whether the type of victim is right.
1948 * 1. We can't do it if dir is read-only (done in permission())
1949 * 2. We should have write and exec permissions on dir
1950 * 3. We can't remove anything from append-only dir
1951 * 4. We can't do anything with immutable dir (done in permission())
1952 * 5. If the sticky bit on dir is set we should either
1953 * a. be owner of dir, or
1954 * b. be owner of victim, or
1955 * c. have CAP_FOWNER capability
1956 * 6. If the victim is append-only or immutable we can't do antyhing with
1957 * links pointing to it.
1958 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
1959 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
1960 * 9. We can't remove a root or mountpoint.
1961 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
1962 * nfs_async_unlink().
1964 static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
1968 if (!victim->d_inode)
1971 BUG_ON(victim->d_parent->d_inode != dir);
1972 audit_inode_child(victim, dir);
1974 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
1979 if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
1980 IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
1983 if (!S_ISDIR(victim->d_inode->i_mode))
1985 if (IS_ROOT(victim))
1987 } else if (S_ISDIR(victim->d_inode->i_mode))
1989 if (IS_DEADDIR(dir))
1991 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
1996 /* Check whether we can create an object with dentry child in directory
1998 * 1. We can't do it if child already exists (open has special treatment for
1999 * this case, but since we are inlined it's OK)
2000 * 2. We can't do it if dir is read-only (done in permission())
2001 * 3. We should have write and exec permissions on dir
2002 * 4. We can't do it if dir is immutable (done in permission())
2004 static inline int may_create(struct inode *dir, struct dentry *child)
2008 if (IS_DEADDIR(dir))
2010 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
2014 * p1 and p2 should be directories on the same fs.
2016 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2021 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2025 mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2027 p = d_ancestor(p2, p1);
2029 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
2030 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
2034 p = d_ancestor(p1, p2);
2036 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2037 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2041 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2042 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2046 void unlock_rename(struct dentry *p1, struct dentry *p2)
2048 mutex_unlock(&p1->d_inode->i_mutex);
2050 mutex_unlock(&p2->d_inode->i_mutex);
2051 mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2055 int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2056 struct nameidata *nd)
2058 int error = may_create(dir, dentry);
2063 if (!dir->i_op->create)
2064 return -EACCES; /* shouldn't it be ENOSYS? */
2067 error = security_inode_create(dir, dentry, mode);
2070 error = dir->i_op->create(dir, dentry, mode, nd);
2072 fsnotify_create(dir, dentry);
2076 static int may_open(struct path *path, int acc_mode, int flag)
2078 struct dentry *dentry = path->dentry;
2079 struct inode *inode = dentry->d_inode;
2089 switch (inode->i_mode & S_IFMT) {
2093 if (acc_mode & MAY_WRITE)
2098 if (path->mnt->mnt_flags & MNT_NODEV)
2107 error = inode_permission(inode, acc_mode);
2112 * An append-only file must be opened in append mode for writing.
2114 if (IS_APPEND(inode)) {
2115 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
2121 /* O_NOATIME can only be set by the owner or superuser */
2122 if (flag & O_NOATIME && !inode_owner_or_capable(inode))
2128 static int handle_truncate(struct file *filp)
2130 struct path *path = &filp->f_path;
2131 struct inode *inode = path->dentry->d_inode;
2132 int error = get_write_access(inode);
2136 * Refuse to truncate files with mandatory locks held on them.
2138 error = locks_verify_locked(inode);
2140 error = security_path_truncate(path);
2142 error = do_truncate(path->dentry, 0,
2143 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
2146 put_write_access(inode);
2150 static inline int open_to_namei_flags(int flag)
2152 if ((flag & O_ACCMODE) == 3)
2158 * Handle the last step of open()
2160 static struct file *do_last(struct nameidata *nd, struct path *path,
2161 const struct open_flags *op, const char *pathname)
2163 struct dentry *dir = nd->path.dentry;
2164 struct dentry *dentry;
2165 int open_flag = op->open_flag;
2166 int will_truncate = open_flag & O_TRUNC;
2168 int acc_mode = op->acc_mode;
2172 nd->flags &= ~LOOKUP_PARENT;
2173 nd->flags |= op->intent;
2175 switch (nd->last_type) {
2178 error = handle_dots(nd, nd->last_type);
2180 return ERR_PTR(error);
2183 error = complete_walk(nd);
2185 return ERR_PTR(error);
2186 audit_inode(pathname, nd->path.dentry);
2187 if (open_flag & O_CREAT) {
2193 error = complete_walk(nd);
2195 return ERR_PTR(error);
2196 audit_inode(pathname, dir);
2200 if (!(open_flag & O_CREAT)) {
2202 if (nd->last.name[nd->last.len])
2203 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2204 if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
2206 /* we _can_ be in RCU mode here */
2207 error = walk_component(nd, path, &nd->last, LAST_NORM,
2210 return ERR_PTR(error);
2211 if (error) /* symlink */
2214 error = complete_walk(nd);
2216 return ERR_PTR(error);
2219 if (nd->flags & LOOKUP_DIRECTORY) {
2220 if (!nd->inode->i_op->lookup)
2223 audit_inode(pathname, nd->path.dentry);
2227 /* create side of things */
2229 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED has been
2230 * cleared when we got to the last component we are about to look up
2232 error = complete_walk(nd);
2234 return ERR_PTR(error);
2236 audit_inode(pathname, dir);
2238 /* trailing slashes? */
2239 if (nd->last.name[nd->last.len])
2242 mutex_lock(&dir->d_inode->i_mutex);
2244 dentry = lookup_hash(nd);
2245 error = PTR_ERR(dentry);
2246 if (IS_ERR(dentry)) {
2247 mutex_unlock(&dir->d_inode->i_mutex);
2251 path->dentry = dentry;
2252 path->mnt = nd->path.mnt;
2254 /* Negative dentry, just create the file */
2255 if (!dentry->d_inode) {
2256 umode_t mode = op->mode;
2257 if (!IS_POSIXACL(dir->d_inode))
2258 mode &= ~current_umask();
2260 * This write is needed to ensure that a
2261 * rw->ro transition does not occur between
2262 * the time when the file is created and when
2263 * a permanent write count is taken through
2264 * the 'struct file' in nameidata_to_filp().
2266 error = mnt_want_write(nd->path.mnt);
2268 goto exit_mutex_unlock;
2270 /* Don't check for write permission, don't truncate */
2271 open_flag &= ~O_TRUNC;
2273 acc_mode = MAY_OPEN;
2274 error = security_path_mknod(&nd->path, dentry, mode, 0);
2276 goto exit_mutex_unlock;
2277 error = vfs_create(dir->d_inode, dentry, mode, nd);
2279 goto exit_mutex_unlock;
2280 mutex_unlock(&dir->d_inode->i_mutex);
2281 dput(nd->path.dentry);
2282 nd->path.dentry = dentry;
2287 * It already exists.
2289 mutex_unlock(&dir->d_inode->i_mutex);
2290 audit_inode(pathname, path->dentry);
2293 if (open_flag & O_EXCL)
2296 error = follow_managed(path, nd->flags);
2301 nd->flags |= LOOKUP_JUMPED;
2304 if (!path->dentry->d_inode)
2307 if (path->dentry->d_inode->i_op->follow_link)
2310 path_to_nameidata(path, nd);
2311 nd->inode = path->dentry->d_inode;
2312 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
2313 error = complete_walk(nd);
2315 return ERR_PTR(error);
2317 if (S_ISDIR(nd->inode->i_mode))
2320 if (!S_ISREG(nd->inode->i_mode))
2323 if (will_truncate) {
2324 error = mnt_want_write(nd->path.mnt);
2330 error = may_open(&nd->path, acc_mode, open_flag);
2333 filp = nameidata_to_filp(nd);
2334 if (!IS_ERR(filp)) {
2335 error = ima_file_check(filp, op->acc_mode);
2338 filp = ERR_PTR(error);
2341 if (!IS_ERR(filp)) {
2342 if (will_truncate) {
2343 error = handle_truncate(filp);
2346 filp = ERR_PTR(error);
2352 mnt_drop_write(nd->path.mnt);
2353 path_put(&nd->path);
2357 mutex_unlock(&dir->d_inode->i_mutex);
2359 path_put_conditional(path, nd);
2361 filp = ERR_PTR(error);
2365 static struct file *path_openat(int dfd, const char *pathname,
2366 struct nameidata *nd, const struct open_flags *op, int flags)
2368 struct file *base = NULL;
2373 filp = get_empty_filp();
2375 return ERR_PTR(-ENFILE);
2377 filp->f_flags = op->open_flag;
2378 nd->intent.open.file = filp;
2379 nd->intent.open.flags = open_to_namei_flags(op->open_flag);
2380 nd->intent.open.create_mode = op->mode;
2382 error = path_init(dfd, pathname, flags | LOOKUP_PARENT, nd, &base);
2383 if (unlikely(error))
2386 current->total_link_count = 0;
2387 error = link_path_walk(pathname, nd);
2388 if (unlikely(error))
2391 filp = do_last(nd, &path, op, pathname);
2392 while (unlikely(!filp)) { /* trailing symlink */
2393 struct path link = path;
2395 if (!(nd->flags & LOOKUP_FOLLOW)) {
2396 path_put_conditional(&path, nd);
2397 path_put(&nd->path);
2398 filp = ERR_PTR(-ELOOP);
2401 nd->flags |= LOOKUP_PARENT;
2402 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
2403 error = follow_link(&link, nd, &cookie);
2404 if (unlikely(error))
2405 filp = ERR_PTR(error);
2407 filp = do_last(nd, &path, op, pathname);
2408 put_link(nd, &link, cookie);
2411 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
2412 path_put(&nd->root);
2415 release_open_intent(nd);
2419 filp = ERR_PTR(error);
2423 struct file *do_filp_open(int dfd, const char *pathname,
2424 const struct open_flags *op, int flags)
2426 struct nameidata nd;
2429 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
2430 if (unlikely(filp == ERR_PTR(-ECHILD)))
2431 filp = path_openat(dfd, pathname, &nd, op, flags);
2432 if (unlikely(filp == ERR_PTR(-ESTALE)))
2433 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
2437 struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
2438 const char *name, const struct open_flags *op, int flags)
2440 struct nameidata nd;
2444 nd.root.dentry = dentry;
2446 flags |= LOOKUP_ROOT;
2448 if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
2449 return ERR_PTR(-ELOOP);
2451 file = path_openat(-1, name, &nd, op, flags | LOOKUP_RCU);
2452 if (unlikely(file == ERR_PTR(-ECHILD)))
2453 file = path_openat(-1, name, &nd, op, flags);
2454 if (unlikely(file == ERR_PTR(-ESTALE)))
2455 file = path_openat(-1, name, &nd, op, flags | LOOKUP_REVAL);
2459 struct dentry *kern_path_create(int dfd, const char *pathname, struct path *path, int is_dir)
2461 struct dentry *dentry = ERR_PTR(-EEXIST);
2462 struct nameidata nd;
2463 int error = do_path_lookup(dfd, pathname, LOOKUP_PARENT, &nd);
2465 return ERR_PTR(error);
2468 * Yucky last component or no last component at all?
2469 * (foo/., foo/.., /////)
2471 if (nd.last_type != LAST_NORM)
2473 nd.flags &= ~LOOKUP_PARENT;
2474 nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL;
2475 nd.intent.open.flags = O_EXCL;
2478 * Do the final lookup.
2480 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2481 dentry = lookup_hash(&nd);
2485 if (dentry->d_inode)
2488 * Special case - lookup gave negative, but... we had foo/bar/
2489 * From the vfs_mknod() POV we just have a negative dentry -
2490 * all is fine. Let's be bastards - you had / on the end, you've
2491 * been asking for (non-existent) directory. -ENOENT for you.
2493 if (unlikely(!is_dir && nd.last.name[nd.last.len])) {
2495 dentry = ERR_PTR(-ENOENT);
2502 dentry = ERR_PTR(-EEXIST);
2504 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2509 EXPORT_SYMBOL(kern_path_create);
2511 struct dentry *user_path_create(int dfd, const char __user *pathname, struct path *path, int is_dir)
2513 char *tmp = getname(pathname);
2516 return ERR_CAST(tmp);
2517 res = kern_path_create(dfd, tmp, path, is_dir);
2521 EXPORT_SYMBOL(user_path_create);
2523 int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
2525 int error = may_create(dir, dentry);
2530 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
2533 if (!dir->i_op->mknod)
2536 error = devcgroup_inode_mknod(mode, dev);
2540 error = security_inode_mknod(dir, dentry, mode, dev);
2544 error = dir->i_op->mknod(dir, dentry, mode, dev);
2546 fsnotify_create(dir, dentry);
2550 static int may_mknod(umode_t mode)
2552 switch (mode & S_IFMT) {
2558 case 0: /* zero mode translates to S_IFREG */
2567 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
2570 struct dentry *dentry;
2577 dentry = user_path_create(dfd, filename, &path, 0);
2579 return PTR_ERR(dentry);
2581 if (!IS_POSIXACL(path.dentry->d_inode))
2582 mode &= ~current_umask();
2583 error = may_mknod(mode);
2586 error = mnt_want_write(path.mnt);
2589 error = security_path_mknod(&path, dentry, mode, dev);
2591 goto out_drop_write;
2592 switch (mode & S_IFMT) {
2593 case 0: case S_IFREG:
2594 error = vfs_create(path.dentry->d_inode,dentry,mode,NULL);
2596 case S_IFCHR: case S_IFBLK:
2597 error = vfs_mknod(path.dentry->d_inode,dentry,mode,
2598 new_decode_dev(dev));
2600 case S_IFIFO: case S_IFSOCK:
2601 error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
2605 mnt_drop_write(path.mnt);
2608 mutex_unlock(&path.dentry->d_inode->i_mutex);
2614 SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
2616 return sys_mknodat(AT_FDCWD, filename, mode, dev);
2619 int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
2621 int error = may_create(dir, dentry);
2622 unsigned max_links = dir->i_sb->s_max_links;
2627 if (!dir->i_op->mkdir)
2630 mode &= (S_IRWXUGO|S_ISVTX);
2631 error = security_inode_mkdir(dir, dentry, mode);
2635 if (max_links && dir->i_nlink >= max_links)
2638 error = dir->i_op->mkdir(dir, dentry, mode);
2640 fsnotify_mkdir(dir, dentry);
2644 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
2646 struct dentry *dentry;
2650 dentry = user_path_create(dfd, pathname, &path, 1);
2652 return PTR_ERR(dentry);
2654 if (!IS_POSIXACL(path.dentry->d_inode))
2655 mode &= ~current_umask();
2656 error = mnt_want_write(path.mnt);
2659 error = security_path_mkdir(&path, dentry, mode);
2661 goto out_drop_write;
2662 error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
2664 mnt_drop_write(path.mnt);
2667 mutex_unlock(&path.dentry->d_inode->i_mutex);
2672 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
2674 return sys_mkdirat(AT_FDCWD, pathname, mode);
2678 * The dentry_unhash() helper will try to drop the dentry early: we
2679 * should have a usage count of 1 if we're the only user of this
2680 * dentry, and if that is true (possibly after pruning the dcache),
2681 * then we drop the dentry now.
2683 * A low-level filesystem can, if it choses, legally
2686 * if (!d_unhashed(dentry))
2689 * if it cannot handle the case of removing a directory
2690 * that is still in use by something else..
2692 void dentry_unhash(struct dentry *dentry)
2694 shrink_dcache_parent(dentry);
2695 spin_lock(&dentry->d_lock);
2696 if (dentry->d_count == 1)
2698 spin_unlock(&dentry->d_lock);
2701 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
2703 int error = may_delete(dir, dentry, 1);
2708 if (!dir->i_op->rmdir)
2712 mutex_lock(&dentry->d_inode->i_mutex);
2715 if (d_mountpoint(dentry))
2718 error = security_inode_rmdir(dir, dentry);
2722 shrink_dcache_parent(dentry);
2723 error = dir->i_op->rmdir(dir, dentry);
2727 dentry->d_inode->i_flags |= S_DEAD;
2731 mutex_unlock(&dentry->d_inode->i_mutex);
2738 static long do_rmdir(int dfd, const char __user *pathname)
2742 struct dentry *dentry;
2743 struct nameidata nd;
2745 error = user_path_parent(dfd, pathname, &nd, &name);
2749 switch(nd.last_type) {
2761 nd.flags &= ~LOOKUP_PARENT;
2763 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2764 dentry = lookup_hash(&nd);
2765 error = PTR_ERR(dentry);
2768 if (!dentry->d_inode) {
2772 error = mnt_want_write(nd.path.mnt);
2775 error = security_path_rmdir(&nd.path, dentry);
2778 error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
2780 mnt_drop_write(nd.path.mnt);
2784 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2791 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
2793 return do_rmdir(AT_FDCWD, pathname);
2796 int vfs_unlink(struct inode *dir, struct dentry *dentry)
2798 int error = may_delete(dir, dentry, 0);
2803 if (!dir->i_op->unlink)
2806 mutex_lock(&dentry->d_inode->i_mutex);
2807 if (d_mountpoint(dentry))
2810 error = security_inode_unlink(dir, dentry);
2812 error = dir->i_op->unlink(dir, dentry);
2817 mutex_unlock(&dentry->d_inode->i_mutex);
2819 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
2820 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
2821 fsnotify_link_count(dentry->d_inode);
2829 * Make sure that the actual truncation of the file will occur outside its
2830 * directory's i_mutex. Truncate can take a long time if there is a lot of
2831 * writeout happening, and we don't want to prevent access to the directory
2832 * while waiting on the I/O.
2834 static long do_unlinkat(int dfd, const char __user *pathname)
2838 struct dentry *dentry;
2839 struct nameidata nd;
2840 struct inode *inode = NULL;
2842 error = user_path_parent(dfd, pathname, &nd, &name);
2847 if (nd.last_type != LAST_NORM)
2850 nd.flags &= ~LOOKUP_PARENT;
2852 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2853 dentry = lookup_hash(&nd);
2854 error = PTR_ERR(dentry);
2855 if (!IS_ERR(dentry)) {
2856 /* Why not before? Because we want correct error value */
2857 if (nd.last.name[nd.last.len])
2859 inode = dentry->d_inode;
2863 error = mnt_want_write(nd.path.mnt);
2866 error = security_path_unlink(&nd.path, dentry);
2869 error = vfs_unlink(nd.path.dentry->d_inode, dentry);
2871 mnt_drop_write(nd.path.mnt);
2875 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2877 iput(inode); /* truncate the inode here */
2884 error = !dentry->d_inode ? -ENOENT :
2885 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
2889 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
2891 if ((flag & ~AT_REMOVEDIR) != 0)
2894 if (flag & AT_REMOVEDIR)
2895 return do_rmdir(dfd, pathname);
2897 return do_unlinkat(dfd, pathname);
2900 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
2902 return do_unlinkat(AT_FDCWD, pathname);
2905 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
2907 int error = may_create(dir, dentry);
2912 if (!dir->i_op->symlink)
2915 error = security_inode_symlink(dir, dentry, oldname);
2919 error = dir->i_op->symlink(dir, dentry, oldname);
2921 fsnotify_create(dir, dentry);
2925 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
2926 int, newdfd, const char __user *, newname)
2930 struct dentry *dentry;
2933 from = getname(oldname);
2935 return PTR_ERR(from);
2937 dentry = user_path_create(newdfd, newname, &path, 0);
2938 error = PTR_ERR(dentry);
2942 error = mnt_want_write(path.mnt);
2945 error = security_path_symlink(&path, dentry, from);
2947 goto out_drop_write;
2948 error = vfs_symlink(path.dentry->d_inode, dentry, from);
2950 mnt_drop_write(path.mnt);
2953 mutex_unlock(&path.dentry->d_inode->i_mutex);
2960 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
2962 return sys_symlinkat(oldname, AT_FDCWD, newname);
2965 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
2967 struct inode *inode = old_dentry->d_inode;
2968 unsigned max_links = dir->i_sb->s_max_links;
2974 error = may_create(dir, new_dentry);
2978 if (dir->i_sb != inode->i_sb)
2982 * A link to an append-only or immutable file cannot be created.
2984 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
2986 if (!dir->i_op->link)
2988 if (S_ISDIR(inode->i_mode))
2991 error = security_inode_link(old_dentry, dir, new_dentry);
2995 mutex_lock(&inode->i_mutex);
2996 /* Make sure we don't allow creating hardlink to an unlinked file */
2997 if (inode->i_nlink == 0)
2999 else if (max_links && inode->i_nlink >= max_links)
3002 error = dir->i_op->link(old_dentry, dir, new_dentry);
3003 mutex_unlock(&inode->i_mutex);
3005 fsnotify_link(dir, inode, new_dentry);
3010 * Hardlinks are often used in delicate situations. We avoid
3011 * security-related surprises by not following symlinks on the
3014 * We don't follow them on the oldname either to be compatible
3015 * with linux 2.0, and to avoid hard-linking to directories
3016 * and other special files. --ADM
3018 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
3019 int, newdfd, const char __user *, newname, int, flags)
3021 struct dentry *new_dentry;
3022 struct path old_path, new_path;
3026 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
3029 * To use null names we require CAP_DAC_READ_SEARCH
3030 * This ensures that not everyone will be able to create
3031 * handlink using the passed filedescriptor.
3033 if (flags & AT_EMPTY_PATH) {
3034 if (!capable(CAP_DAC_READ_SEARCH))
3039 if (flags & AT_SYMLINK_FOLLOW)
3040 how |= LOOKUP_FOLLOW;
3042 error = user_path_at(olddfd, oldname, how, &old_path);
3046 new_dentry = user_path_create(newdfd, newname, &new_path, 0);
3047 error = PTR_ERR(new_dentry);
3048 if (IS_ERR(new_dentry))
3052 if (old_path.mnt != new_path.mnt)
3054 error = mnt_want_write(new_path.mnt);
3057 error = security_path_link(old_path.dentry, &new_path, new_dentry);
3059 goto out_drop_write;
3060 error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry);
3062 mnt_drop_write(new_path.mnt);
3065 mutex_unlock(&new_path.dentry->d_inode->i_mutex);
3066 path_put(&new_path);
3068 path_put(&old_path);
3073 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
3075 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
3079 * The worst of all namespace operations - renaming directory. "Perverted"
3080 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3082 * a) we can get into loop creation. Check is done in is_subdir().
3083 * b) race potential - two innocent renames can create a loop together.
3084 * That's where 4.4 screws up. Current fix: serialization on
3085 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
3087 * c) we have to lock _three_ objects - parents and victim (if it exists).
3088 * And that - after we got ->i_mutex on parents (until then we don't know
3089 * whether the target exists). Solution: try to be smart with locking
3090 * order for inodes. We rely on the fact that tree topology may change
3091 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
3092 * move will be locked. Thus we can rank directories by the tree
3093 * (ancestors first) and rank all non-directories after them.
3094 * That works since everybody except rename does "lock parent, lookup,
3095 * lock child" and rename is under ->s_vfs_rename_mutex.
3096 * HOWEVER, it relies on the assumption that any object with ->lookup()
3097 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3098 * we'd better make sure that there's no link(2) for them.
3099 * d) conversion from fhandle to dentry may come in the wrong moment - when
3100 * we are removing the target. Solution: we will have to grab ->i_mutex
3101 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
3102 * ->i_mutex on parents, which works but leads to some truly excessive
3105 static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
3106 struct inode *new_dir, struct dentry *new_dentry)
3109 struct inode *target = new_dentry->d_inode;
3110 unsigned max_links = new_dir->i_sb->s_max_links;
3113 * If we are going to change the parent - check write permissions,
3114 * we'll need to flip '..'.
3116 if (new_dir != old_dir) {
3117 error = inode_permission(old_dentry->d_inode, MAY_WRITE);
3122 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3128 mutex_lock(&target->i_mutex);
3131 if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
3135 if (max_links && !target && new_dir != old_dir &&
3136 new_dir->i_nlink >= max_links)
3140 shrink_dcache_parent(new_dentry);
3141 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3146 target->i_flags |= S_DEAD;
3147 dont_mount(new_dentry);
3151 mutex_unlock(&target->i_mutex);
3154 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3155 d_move(old_dentry,new_dentry);
3159 static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
3160 struct inode *new_dir, struct dentry *new_dentry)
3162 struct inode *target = new_dentry->d_inode;
3165 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3171 mutex_lock(&target->i_mutex);
3174 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
3177 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3182 dont_mount(new_dentry);
3183 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3184 d_move(old_dentry, new_dentry);
3187 mutex_unlock(&target->i_mutex);
3192 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
3193 struct inode *new_dir, struct dentry *new_dentry)
3196 int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
3197 const unsigned char *old_name;
3199 if (old_dentry->d_inode == new_dentry->d_inode)
3202 error = may_delete(old_dir, old_dentry, is_dir);
3206 if (!new_dentry->d_inode)
3207 error = may_create(new_dir, new_dentry);
3209 error = may_delete(new_dir, new_dentry, is_dir);
3213 if (!old_dir->i_op->rename)
3216 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
3219 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
3221 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
3223 fsnotify_move(old_dir, new_dir, old_name, is_dir,
3224 new_dentry->d_inode, old_dentry);
3225 fsnotify_oldname_free(old_name);
3230 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
3231 int, newdfd, const char __user *, newname)
3233 struct dentry *old_dir, *new_dir;
3234 struct dentry *old_dentry, *new_dentry;
3235 struct dentry *trap;
3236 struct nameidata oldnd, newnd;
3241 error = user_path_parent(olddfd, oldname, &oldnd, &from);
3245 error = user_path_parent(newdfd, newname, &newnd, &to);
3250 if (oldnd.path.mnt != newnd.path.mnt)
3253 old_dir = oldnd.path.dentry;
3255 if (oldnd.last_type != LAST_NORM)
3258 new_dir = newnd.path.dentry;
3259 if (newnd.last_type != LAST_NORM)
3262 oldnd.flags &= ~LOOKUP_PARENT;
3263 newnd.flags &= ~LOOKUP_PARENT;
3264 newnd.flags |= LOOKUP_RENAME_TARGET;
3266 trap = lock_rename(new_dir, old_dir);
3268 old_dentry = lookup_hash(&oldnd);
3269 error = PTR_ERR(old_dentry);
3270 if (IS_ERR(old_dentry))
3272 /* source must exist */
3274 if (!old_dentry->d_inode)
3276 /* unless the source is a directory trailing slashes give -ENOTDIR */
3277 if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
3279 if (oldnd.last.name[oldnd.last.len])
3281 if (newnd.last.name[newnd.last.len])
3284 /* source should not be ancestor of target */
3286 if (old_dentry == trap)
3288 new_dentry = lookup_hash(&newnd);
3289 error = PTR_ERR(new_dentry);
3290 if (IS_ERR(new_dentry))
3292 /* target should not be an ancestor of source */
3294 if (new_dentry == trap)
3297 error = mnt_want_write(oldnd.path.mnt);
3300 error = security_path_rename(&oldnd.path, old_dentry,
3301 &newnd.path, new_dentry);
3304 error = vfs_rename(old_dir->d_inode, old_dentry,
3305 new_dir->d_inode, new_dentry);
3307 mnt_drop_write(oldnd.path.mnt);
3313 unlock_rename(new_dir, old_dir);
3315 path_put(&newnd.path);
3318 path_put(&oldnd.path);
3324 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
3326 return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
3329 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
3333 len = PTR_ERR(link);
3338 if (len > (unsigned) buflen)
3340 if (copy_to_user(buffer, link, len))
3347 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
3348 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
3349 * using) it for any given inode is up to filesystem.
3351 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3353 struct nameidata nd;
3358 cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
3360 return PTR_ERR(cookie);
3362 res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
3363 if (dentry->d_inode->i_op->put_link)
3364 dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
3368 int vfs_follow_link(struct nameidata *nd, const char *link)
3370 return __vfs_follow_link(nd, link);
3373 /* get the link contents into pagecache */
3374 static char *page_getlink(struct dentry * dentry, struct page **ppage)
3378 struct address_space *mapping = dentry->d_inode->i_mapping;
3379 page = read_mapping_page(mapping, 0, NULL);
3384 nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
3388 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3390 struct page *page = NULL;
3391 char *s = page_getlink(dentry, &page);
3392 int res = vfs_readlink(dentry,buffer,buflen,s);
3395 page_cache_release(page);
3400 void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
3402 struct page *page = NULL;
3403 nd_set_link(nd, page_getlink(dentry, &page));
3407 void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
3409 struct page *page = cookie;
3413 page_cache_release(page);
3418 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
3420 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
3422 struct address_space *mapping = inode->i_mapping;
3427 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
3429 flags |= AOP_FLAG_NOFS;
3432 err = pagecache_write_begin(NULL, mapping, 0, len-1,
3433 flags, &page, &fsdata);
3437 kaddr = kmap_atomic(page);
3438 memcpy(kaddr, symname, len-1);
3439 kunmap_atomic(kaddr);
3441 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
3448 mark_inode_dirty(inode);
3454 int page_symlink(struct inode *inode, const char *symname, int len)
3456 return __page_symlink(inode, symname, len,
3457 !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
3460 const struct inode_operations page_symlink_inode_operations = {
3461 .readlink = generic_readlink,
3462 .follow_link = page_follow_link_light,
3463 .put_link = page_put_link,
3466 EXPORT_SYMBOL(user_path_at);
3467 EXPORT_SYMBOL(follow_down_one);
3468 EXPORT_SYMBOL(follow_down);
3469 EXPORT_SYMBOL(follow_up);
3470 EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
3471 EXPORT_SYMBOL(getname);
3472 EXPORT_SYMBOL(lock_rename);
3473 EXPORT_SYMBOL(lookup_one_len);
3474 EXPORT_SYMBOL(page_follow_link_light);
3475 EXPORT_SYMBOL(page_put_link);
3476 EXPORT_SYMBOL(page_readlink);
3477 EXPORT_SYMBOL(__page_symlink);
3478 EXPORT_SYMBOL(page_symlink);
3479 EXPORT_SYMBOL(page_symlink_inode_operations);
3480 EXPORT_SYMBOL(kern_path);
3481 EXPORT_SYMBOL(vfs_path_lookup);
3482 EXPORT_SYMBOL(inode_permission);
3483 EXPORT_SYMBOL(unlock_rename);
3484 EXPORT_SYMBOL(vfs_create);
3485 EXPORT_SYMBOL(vfs_follow_link);
3486 EXPORT_SYMBOL(vfs_link);
3487 EXPORT_SYMBOL(vfs_mkdir);
3488 EXPORT_SYMBOL(vfs_mknod);
3489 EXPORT_SYMBOL(generic_permission);
3490 EXPORT_SYMBOL(vfs_readlink);
3491 EXPORT_SYMBOL(vfs_rename);
3492 EXPORT_SYMBOL(vfs_rmdir);
3493 EXPORT_SYMBOL(vfs_symlink);
3494 EXPORT_SYMBOL(vfs_unlink);
3495 EXPORT_SYMBOL(dentry_unhash);
3496 EXPORT_SYMBOL(generic_readlink);