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 <linux/hash.h>
38 #include <linux/bitops.h>
39 #include <linux/init_task.h>
40 #include <asm/uaccess.h>
45 /* [Feb-1997 T. Schoebel-Theuer]
46 * Fundamental changes in the pathname lookup mechanisms (namei)
47 * were necessary because of omirr. The reason is that omirr needs
48 * to know the _real_ pathname, not the user-supplied one, in case
49 * of symlinks (and also when transname replacements occur).
51 * The new code replaces the old recursive symlink resolution with
52 * an iterative one (in case of non-nested symlink chains). It does
53 * this with calls to <fs>_follow_link().
54 * As a side effect, dir_namei(), _namei() and follow_link() are now
55 * replaced with a single function lookup_dentry() that can handle all
56 * the special cases of the former code.
58 * With the new dcache, the pathname is stored at each inode, at least as
59 * long as the refcount of the inode is positive. As a side effect, the
60 * size of the dcache depends on the inode cache and thus is dynamic.
62 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
63 * resolution to correspond with current state of the code.
65 * Note that the symlink resolution is not *completely* iterative.
66 * There is still a significant amount of tail- and mid- recursion in
67 * the algorithm. Also, note that <fs>_readlink() is not used in
68 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
69 * may return different results than <fs>_follow_link(). Many virtual
70 * filesystems (including /proc) exhibit this behavior.
73 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
74 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
75 * and the name already exists in form of a symlink, try to create the new
76 * name indicated by the symlink. The old code always complained that the
77 * name already exists, due to not following the symlink even if its target
78 * is nonexistent. The new semantics affects also mknod() and link() when
79 * the name is a symlink pointing to a non-existent name.
81 * I don't know which semantics is the right one, since I have no access
82 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
83 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
84 * "old" one. Personally, I think the new semantics is much more logical.
85 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
86 * file does succeed in both HP-UX and SunOs, but not in Solaris
87 * and in the old Linux semantics.
90 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
91 * semantics. See the comments in "open_namei" and "do_link" below.
93 * [10-Sep-98 Alan Modra] Another symlink change.
96 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
97 * inside the path - always follow.
98 * in the last component in creation/removal/renaming - never follow.
99 * if LOOKUP_FOLLOW passed - follow.
100 * if the pathname has trailing slashes - follow.
101 * otherwise - don't follow.
102 * (applied in that order).
104 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
105 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
106 * During the 2.4 we need to fix the userland stuff depending on it -
107 * hopefully we will be able to get rid of that wart in 2.5. So far only
108 * XEmacs seems to be relying on it...
111 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
112 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
113 * any extra contention...
116 /* In order to reduce some races, while at the same time doing additional
117 * checking and hopefully speeding things up, we copy filenames to the
118 * kernel data space before using them..
120 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
121 * PATH_MAX includes the nul terminator --RR.
124 #define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname))
127 getname_flags(const char __user *filename, int flags, int *empty)
129 struct filename *result;
133 result = audit_reusename(filename);
137 result = __getname();
138 if (unlikely(!result))
139 return ERR_PTR(-ENOMEM);
142 * First, try to embed the struct filename inside the names_cache
145 kname = (char *)result->iname;
146 result->name = kname;
148 len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX);
149 if (unlikely(len < 0)) {
155 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
156 * separate struct filename so we can dedicate the entire
157 * names_cache allocation for the pathname, and re-do the copy from
160 if (unlikely(len == EMBEDDED_NAME_MAX)) {
161 const size_t size = offsetof(struct filename, iname[1]);
162 kname = (char *)result;
165 * size is chosen that way we to guarantee that
166 * result->iname[0] is within the same object and that
167 * kname can't be equal to result->iname, no matter what.
169 result = kzalloc(size, GFP_KERNEL);
170 if (unlikely(!result)) {
172 return ERR_PTR(-ENOMEM);
174 result->name = kname;
175 len = strncpy_from_user(kname, filename, PATH_MAX);
176 if (unlikely(len < 0)) {
181 if (unlikely(len == PATH_MAX)) {
184 return ERR_PTR(-ENAMETOOLONG);
189 /* The empty path is special. */
190 if (unlikely(!len)) {
193 if (!(flags & LOOKUP_EMPTY)) {
195 return ERR_PTR(-ENOENT);
199 result->uptr = filename;
200 result->aname = NULL;
201 audit_getname(result);
206 getname(const char __user * filename)
208 return getname_flags(filename, 0, NULL);
212 getname_kernel(const char * filename)
214 struct filename *result;
215 int len = strlen(filename) + 1;
217 result = __getname();
218 if (unlikely(!result))
219 return ERR_PTR(-ENOMEM);
221 if (len <= EMBEDDED_NAME_MAX) {
222 result->name = (char *)result->iname;
223 } else if (len <= PATH_MAX) {
224 struct filename *tmp;
226 tmp = kmalloc(sizeof(*tmp), GFP_KERNEL);
227 if (unlikely(!tmp)) {
229 return ERR_PTR(-ENOMEM);
231 tmp->name = (char *)result;
235 return ERR_PTR(-ENAMETOOLONG);
237 memcpy((char *)result->name, filename, len);
239 result->aname = NULL;
241 audit_getname(result);
246 void putname(struct filename *name)
248 BUG_ON(name->refcnt <= 0);
250 if (--name->refcnt > 0)
253 if (name->name != name->iname) {
254 __putname(name->name);
260 static int check_acl(struct inode *inode, int mask)
262 #ifdef CONFIG_FS_POSIX_ACL
263 struct posix_acl *acl;
265 if (mask & MAY_NOT_BLOCK) {
266 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
269 /* no ->get_acl() calls in RCU mode... */
270 if (is_uncached_acl(acl))
272 return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
275 acl = get_acl(inode, ACL_TYPE_ACCESS);
279 int error = posix_acl_permission(inode, acl, mask);
280 posix_acl_release(acl);
289 * This does the basic permission checking
291 static int acl_permission_check(struct inode *inode, int mask)
293 unsigned int mode = inode->i_mode;
295 if (likely(uid_eq(current_fsuid(), inode->i_uid)))
298 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
299 int error = check_acl(inode, mask);
300 if (error != -EAGAIN)
304 if (in_group_p(inode->i_gid))
309 * If the DACs are ok we don't need any capability check.
311 if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
317 * generic_permission - check for access rights on a Posix-like filesystem
318 * @inode: inode to check access rights for
319 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
321 * Used to check for read/write/execute permissions on a file.
322 * We use "fsuid" for this, letting us set arbitrary permissions
323 * for filesystem access without changing the "normal" uids which
324 * are used for other things.
326 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
327 * request cannot be satisfied (eg. requires blocking or too much complexity).
328 * It would then be called again in ref-walk mode.
330 int generic_permission(struct inode *inode, int mask)
335 * Do the basic permission checks.
337 ret = acl_permission_check(inode, mask);
341 if (S_ISDIR(inode->i_mode)) {
342 /* DACs are overridable for directories */
343 if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
345 if (!(mask & MAY_WRITE))
346 if (capable_wrt_inode_uidgid(inode,
347 CAP_DAC_READ_SEARCH))
352 * Read/write DACs are always overridable.
353 * Executable DACs are overridable when there is
354 * at least one exec bit set.
356 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
357 if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
361 * Searching includes executable on directories, else just read.
363 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
364 if (mask == MAY_READ)
365 if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH))
370 EXPORT_SYMBOL(generic_permission);
373 * We _really_ want to just do "generic_permission()" without
374 * even looking at the inode->i_op values. So we keep a cache
375 * flag in inode->i_opflags, that says "this has not special
376 * permission function, use the fast case".
378 static inline int do_inode_permission(struct inode *inode, int mask)
380 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
381 if (likely(inode->i_op->permission))
382 return inode->i_op->permission(inode, mask);
384 /* This gets set once for the inode lifetime */
385 spin_lock(&inode->i_lock);
386 inode->i_opflags |= IOP_FASTPERM;
387 spin_unlock(&inode->i_lock);
389 return generic_permission(inode, mask);
393 * __inode_permission - Check for access rights to a given inode
394 * @inode: Inode to check permission on
395 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
397 * Check for read/write/execute permissions on an inode.
399 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
401 * This does not check for a read-only file system. You probably want
402 * inode_permission().
404 int __inode_permission(struct inode *inode, int mask)
408 if (unlikely(mask & MAY_WRITE)) {
410 * Nobody gets write access to an immutable file.
412 if (IS_IMMUTABLE(inode))
416 * Updating mtime will likely cause i_uid and i_gid to be
417 * written back improperly if their true value is unknown
420 if (HAS_UNMAPPED_ID(inode))
424 retval = do_inode_permission(inode, mask);
428 retval = devcgroup_inode_permission(inode, mask);
432 return security_inode_permission(inode, mask);
434 EXPORT_SYMBOL(__inode_permission);
437 * sb_permission - Check superblock-level permissions
438 * @sb: Superblock of inode to check permission on
439 * @inode: Inode to check permission on
440 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
442 * Separate out file-system wide checks from inode-specific permission checks.
444 static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
446 if (unlikely(mask & MAY_WRITE)) {
447 umode_t mode = inode->i_mode;
449 /* Nobody gets write access to a read-only fs. */
450 if ((sb->s_flags & MS_RDONLY) &&
451 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
458 * inode_permission - Check for access rights to a given inode
459 * @inode: Inode to check permission on
460 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
462 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
463 * this, letting us set arbitrary permissions for filesystem access without
464 * changing the "normal" UIDs which are used for other things.
466 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
468 int inode_permission(struct inode *inode, int mask)
472 retval = sb_permission(inode->i_sb, inode, mask);
475 return __inode_permission(inode, mask);
477 EXPORT_SYMBOL(inode_permission);
480 * path_get - get a reference to a path
481 * @path: path to get the reference to
483 * Given a path increment the reference count to the dentry and the vfsmount.
485 void path_get(const struct path *path)
490 EXPORT_SYMBOL(path_get);
493 * path_put - put a reference to a path
494 * @path: path to put the reference to
496 * Given a path decrement the reference count to the dentry and the vfsmount.
498 void path_put(const struct path *path)
503 EXPORT_SYMBOL(path_put);
505 #define EMBEDDED_LEVELS 2
510 struct inode *inode; /* path.dentry.d_inode */
515 int total_link_count;
518 struct delayed_call done;
521 } *stack, internal[EMBEDDED_LEVELS];
522 struct filename *name;
523 struct nameidata *saved;
524 struct inode *link_inode;
529 static void set_nameidata(struct nameidata *p, int dfd, struct filename *name)
531 struct nameidata *old = current->nameidata;
532 p->stack = p->internal;
535 p->total_link_count = old ? old->total_link_count : 0;
537 current->nameidata = p;
540 static void restore_nameidata(void)
542 struct nameidata *now = current->nameidata, *old = now->saved;
544 current->nameidata = old;
546 old->total_link_count = now->total_link_count;
547 if (now->stack != now->internal)
551 static int __nd_alloc_stack(struct nameidata *nd)
555 if (nd->flags & LOOKUP_RCU) {
556 p= kmalloc(MAXSYMLINKS * sizeof(struct saved),
561 p= kmalloc(MAXSYMLINKS * sizeof(struct saved),
566 memcpy(p, nd->internal, sizeof(nd->internal));
572 * path_connected - Verify that a path->dentry is below path->mnt.mnt_root
573 * @path: nameidate to verify
575 * Rename can sometimes move a file or directory outside of a bind
576 * mount, path_connected allows those cases to be detected.
578 static bool path_connected(const struct path *path)
580 struct vfsmount *mnt = path->mnt;
582 /* Only bind mounts can have disconnected paths */
583 if (mnt->mnt_root == mnt->mnt_sb->s_root)
586 return is_subdir(path->dentry, mnt->mnt_root);
589 static inline int nd_alloc_stack(struct nameidata *nd)
591 if (likely(nd->depth != EMBEDDED_LEVELS))
593 if (likely(nd->stack != nd->internal))
595 return __nd_alloc_stack(nd);
598 static void drop_links(struct nameidata *nd)
602 struct saved *last = nd->stack + i;
603 do_delayed_call(&last->done);
604 clear_delayed_call(&last->done);
608 static void terminate_walk(struct nameidata *nd)
611 if (!(nd->flags & LOOKUP_RCU)) {
614 for (i = 0; i < nd->depth; i++)
615 path_put(&nd->stack[i].link);
616 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
621 nd->flags &= ~LOOKUP_RCU;
622 if (!(nd->flags & LOOKUP_ROOT))
629 /* path_put is needed afterwards regardless of success or failure */
630 static bool legitimize_path(struct nameidata *nd,
631 struct path *path, unsigned seq)
633 int res = __legitimize_mnt(path->mnt, nd->m_seq);
640 if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) {
644 return !read_seqcount_retry(&path->dentry->d_seq, seq);
647 static bool legitimize_links(struct nameidata *nd)
650 for (i = 0; i < nd->depth; i++) {
651 struct saved *last = nd->stack + i;
652 if (unlikely(!legitimize_path(nd, &last->link, last->seq))) {
662 * Path walking has 2 modes, rcu-walk and ref-walk (see
663 * Documentation/filesystems/path-lookup.txt). In situations when we can't
664 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
665 * normal reference counts on dentries and vfsmounts to transition to ref-walk
666 * mode. Refcounts are grabbed at the last known good point before rcu-walk
667 * got stuck, so ref-walk may continue from there. If this is not successful
668 * (eg. a seqcount has changed), then failure is returned and it's up to caller
669 * to restart the path walk from the beginning in ref-walk mode.
673 * unlazy_walk - try to switch to ref-walk mode.
674 * @nd: nameidata pathwalk data
675 * @dentry: child of nd->path.dentry or NULL
676 * @seq: seq number to check dentry against
677 * Returns: 0 on success, -ECHILD on failure
679 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
680 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
681 * @nd or NULL. Must be called from rcu-walk context.
682 * Nothing should touch nameidata between unlazy_walk() failure and
685 static int unlazy_walk(struct nameidata *nd, struct dentry *dentry, unsigned seq)
687 struct dentry *parent = nd->path.dentry;
689 BUG_ON(!(nd->flags & LOOKUP_RCU));
691 nd->flags &= ~LOOKUP_RCU;
692 if (unlikely(!legitimize_links(nd)))
694 if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq)))
696 if (unlikely(!lockref_get_not_dead(&parent->d_lockref)))
700 * For a negative lookup, the lookup sequence point is the parents
701 * sequence point, and it only needs to revalidate the parent dentry.
703 * For a positive lookup, we need to move both the parent and the
704 * dentry from the RCU domain to be properly refcounted. And the
705 * sequence number in the dentry validates *both* dentry counters,
706 * since we checked the sequence number of the parent after we got
707 * the child sequence number. So we know the parent must still
708 * be valid if the child sequence number is still valid.
711 if (read_seqcount_retry(&parent->d_seq, nd->seq))
713 BUG_ON(nd->inode != parent->d_inode);
715 if (!lockref_get_not_dead(&dentry->d_lockref))
717 if (read_seqcount_retry(&dentry->d_seq, seq))
722 * Sequence counts matched. Now make sure that the root is
723 * still valid and get it if required.
725 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
726 if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq))) {
743 nd->path.dentry = NULL;
747 if (!(nd->flags & LOOKUP_ROOT))
752 static int unlazy_link(struct nameidata *nd, struct path *link, unsigned seq)
754 if (unlikely(!legitimize_path(nd, link, seq))) {
757 nd->flags &= ~LOOKUP_RCU;
759 nd->path.dentry = NULL;
760 if (!(nd->flags & LOOKUP_ROOT))
763 } else if (likely(unlazy_walk(nd, NULL, 0)) == 0) {
770 static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
772 return dentry->d_op->d_revalidate(dentry, flags);
776 * complete_walk - successful completion of path walk
777 * @nd: pointer nameidata
779 * If we had been in RCU mode, drop out of it and legitimize nd->path.
780 * Revalidate the final result, unless we'd already done that during
781 * the path walk or the filesystem doesn't ask for it. Return 0 on
782 * success, -error on failure. In case of failure caller does not
783 * need to drop nd->path.
785 static int complete_walk(struct nameidata *nd)
787 struct dentry *dentry = nd->path.dentry;
790 if (nd->flags & LOOKUP_RCU) {
791 if (!(nd->flags & LOOKUP_ROOT))
793 if (unlikely(unlazy_walk(nd, NULL, 0)))
797 if (likely(!(nd->flags & LOOKUP_JUMPED)))
800 if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
803 status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
813 static void set_root(struct nameidata *nd)
815 struct fs_struct *fs = current->fs;
817 if (nd->flags & LOOKUP_RCU) {
821 seq = read_seqcount_begin(&fs->seq);
823 nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
824 } while (read_seqcount_retry(&fs->seq, seq));
826 get_fs_root(fs, &nd->root);
830 static void path_put_conditional(struct path *path, struct nameidata *nd)
833 if (path->mnt != nd->path.mnt)
837 static inline void path_to_nameidata(const struct path *path,
838 struct nameidata *nd)
840 if (!(nd->flags & LOOKUP_RCU)) {
841 dput(nd->path.dentry);
842 if (nd->path.mnt != path->mnt)
843 mntput(nd->path.mnt);
845 nd->path.mnt = path->mnt;
846 nd->path.dentry = path->dentry;
849 static int nd_jump_root(struct nameidata *nd)
851 if (nd->flags & LOOKUP_RCU) {
855 nd->inode = d->d_inode;
856 nd->seq = nd->root_seq;
857 if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq)))
863 nd->inode = nd->path.dentry->d_inode;
865 nd->flags |= LOOKUP_JUMPED;
870 * Helper to directly jump to a known parsed path from ->get_link,
871 * caller must have taken a reference to path beforehand.
873 void nd_jump_link(struct path *path)
875 struct nameidata *nd = current->nameidata;
879 nd->inode = nd->path.dentry->d_inode;
880 nd->flags |= LOOKUP_JUMPED;
883 static inline void put_link(struct nameidata *nd)
885 struct saved *last = nd->stack + --nd->depth;
886 do_delayed_call(&last->done);
887 if (!(nd->flags & LOOKUP_RCU))
888 path_put(&last->link);
891 int sysctl_protected_symlinks __read_mostly = 0;
892 int sysctl_protected_hardlinks __read_mostly = 0;
895 * may_follow_link - Check symlink following for unsafe situations
896 * @nd: nameidata pathwalk data
898 * In the case of the sysctl_protected_symlinks sysctl being enabled,
899 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
900 * in a sticky world-writable directory. This is to protect privileged
901 * processes from failing races against path names that may change out
902 * from under them by way of other users creating malicious symlinks.
903 * It will permit symlinks to be followed only when outside a sticky
904 * world-writable directory, or when the uid of the symlink and follower
905 * match, or when the directory owner matches the symlink's owner.
907 * Returns 0 if following the symlink is allowed, -ve on error.
909 static inline int may_follow_link(struct nameidata *nd)
911 const struct inode *inode;
912 const struct inode *parent;
915 if (!sysctl_protected_symlinks)
918 /* Allowed if owner and follower match. */
919 inode = nd->link_inode;
920 if (uid_eq(current_cred()->fsuid, inode->i_uid))
923 /* Allowed if parent directory not sticky and world-writable. */
925 if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
928 /* Allowed if parent directory and link owner match. */
929 puid = parent->i_uid;
930 if (uid_valid(puid) && uid_eq(puid, inode->i_uid))
933 if (nd->flags & LOOKUP_RCU)
936 audit_log_link_denied("follow_link", &nd->stack[0].link);
941 * safe_hardlink_source - Check for safe hardlink conditions
942 * @inode: the source inode to hardlink from
944 * Return false if at least one of the following conditions:
945 * - inode is not a regular file
947 * - inode is setgid and group-exec
948 * - access failure for read and write
950 * Otherwise returns true.
952 static bool safe_hardlink_source(struct inode *inode)
954 umode_t mode = inode->i_mode;
956 /* Special files should not get pinned to the filesystem. */
960 /* Setuid files should not get pinned to the filesystem. */
964 /* Executable setgid files should not get pinned to the filesystem. */
965 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
968 /* Hardlinking to unreadable or unwritable sources is dangerous. */
969 if (inode_permission(inode, MAY_READ | MAY_WRITE))
976 * may_linkat - Check permissions for creating a hardlink
977 * @link: the source to hardlink from
979 * Block hardlink when all of:
980 * - sysctl_protected_hardlinks enabled
981 * - fsuid does not match inode
982 * - hardlink source is unsafe (see safe_hardlink_source() above)
983 * - not CAP_FOWNER in a namespace with the inode owner uid mapped
985 * Returns 0 if successful, -ve on error.
987 static int may_linkat(struct path *link)
991 if (!sysctl_protected_hardlinks)
994 inode = link->dentry->d_inode;
996 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
997 * otherwise, it must be a safe source.
999 if (inode_owner_or_capable(inode) || safe_hardlink_source(inode))
1002 audit_log_link_denied("linkat", link);
1006 static __always_inline
1007 const char *get_link(struct nameidata *nd)
1009 struct saved *last = nd->stack + nd->depth - 1;
1010 struct dentry *dentry = last->link.dentry;
1011 struct inode *inode = nd->link_inode;
1015 if (!(nd->flags & LOOKUP_RCU)) {
1016 touch_atime(&last->link);
1018 } else if (atime_needs_update_rcu(&last->link, inode)) {
1019 if (unlikely(unlazy_walk(nd, NULL, 0)))
1020 return ERR_PTR(-ECHILD);
1021 touch_atime(&last->link);
1024 error = security_inode_follow_link(dentry, inode,
1025 nd->flags & LOOKUP_RCU);
1026 if (unlikely(error))
1027 return ERR_PTR(error);
1029 nd->last_type = LAST_BIND;
1030 res = inode->i_link;
1032 const char * (*get)(struct dentry *, struct inode *,
1033 struct delayed_call *);
1034 get = inode->i_op->get_link;
1035 if (nd->flags & LOOKUP_RCU) {
1036 res = get(NULL, inode, &last->done);
1037 if (res == ERR_PTR(-ECHILD)) {
1038 if (unlikely(unlazy_walk(nd, NULL, 0)))
1039 return ERR_PTR(-ECHILD);
1040 res = get(dentry, inode, &last->done);
1043 res = get(dentry, inode, &last->done);
1045 if (IS_ERR_OR_NULL(res))
1051 if (unlikely(nd_jump_root(nd)))
1052 return ERR_PTR(-ECHILD);
1053 while (unlikely(*++res == '/'))
1062 * follow_up - Find the mountpoint of path's vfsmount
1064 * Given a path, find the mountpoint of its source file system.
1065 * Replace @path with the path of the mountpoint in the parent mount.
1068 * Return 1 if we went up a level and 0 if we were already at the
1071 int follow_up(struct path *path)
1073 struct mount *mnt = real_mount(path->mnt);
1074 struct mount *parent;
1075 struct dentry *mountpoint;
1077 read_seqlock_excl(&mount_lock);
1078 parent = mnt->mnt_parent;
1079 if (parent == mnt) {
1080 read_sequnlock_excl(&mount_lock);
1083 mntget(&parent->mnt);
1084 mountpoint = dget(mnt->mnt_mountpoint);
1085 read_sequnlock_excl(&mount_lock);
1087 path->dentry = mountpoint;
1089 path->mnt = &parent->mnt;
1092 EXPORT_SYMBOL(follow_up);
1095 * Perform an automount
1096 * - return -EISDIR to tell follow_managed() to stop and return the path we
1099 static int follow_automount(struct path *path, struct nameidata *nd,
1102 struct vfsmount *mnt;
1103 const struct cred *old_cred;
1106 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
1109 /* We don't want to mount if someone's just doing a stat -
1110 * unless they're stat'ing a directory and appended a '/' to
1113 * We do, however, want to mount if someone wants to open or
1114 * create a file of any type under the mountpoint, wants to
1115 * traverse through the mountpoint or wants to open the
1116 * mounted directory. Also, autofs may mark negative dentries
1117 * as being automount points. These will need the attentions
1118 * of the daemon to instantiate them before they can be used.
1120 if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
1121 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
1122 path->dentry->d_inode)
1125 if (path->dentry->d_sb->s_user_ns != &init_user_ns)
1128 nd->total_link_count++;
1129 if (nd->total_link_count >= 40)
1132 old_cred = override_creds(&init_cred);
1133 mnt = path->dentry->d_op->d_automount(path);
1134 revert_creds(old_cred);
1137 * The filesystem is allowed to return -EISDIR here to indicate
1138 * it doesn't want to automount. For instance, autofs would do
1139 * this so that its userspace daemon can mount on this dentry.
1141 * However, we can only permit this if it's a terminal point in
1142 * the path being looked up; if it wasn't then the remainder of
1143 * the path is inaccessible and we should say so.
1145 if (PTR_ERR(mnt) == -EISDIR && (nd->flags & LOOKUP_PARENT))
1147 return PTR_ERR(mnt);
1150 if (!mnt) /* mount collision */
1153 if (!*need_mntput) {
1154 /* lock_mount() may release path->mnt on error */
1156 *need_mntput = true;
1158 err = finish_automount(mnt, path);
1162 /* Someone else made a mount here whilst we were busy */
1167 path->dentry = dget(mnt->mnt_root);
1176 * Handle a dentry that is managed in some way.
1177 * - Flagged for transit management (autofs)
1178 * - Flagged as mountpoint
1179 * - Flagged as automount point
1181 * This may only be called in refwalk mode.
1183 * Serialization is taken care of in namespace.c
1185 static int follow_managed(struct path *path, struct nameidata *nd)
1187 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
1189 bool need_mntput = false;
1192 /* Given that we're not holding a lock here, we retain the value in a
1193 * local variable for each dentry as we look at it so that we don't see
1194 * the components of that value change under us */
1195 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1196 managed &= DCACHE_MANAGED_DENTRY,
1197 unlikely(managed != 0)) {
1198 /* Allow the filesystem to manage the transit without i_mutex
1200 if (managed & DCACHE_MANAGE_TRANSIT) {
1201 BUG_ON(!path->dentry->d_op);
1202 BUG_ON(!path->dentry->d_op->d_manage);
1203 ret = path->dentry->d_op->d_manage(path, false);
1208 /* Transit to a mounted filesystem. */
1209 if (managed & DCACHE_MOUNTED) {
1210 struct vfsmount *mounted = lookup_mnt(path);
1215 path->mnt = mounted;
1216 path->dentry = dget(mounted->mnt_root);
1221 /* Something is mounted on this dentry in another
1222 * namespace and/or whatever was mounted there in this
1223 * namespace got unmounted before lookup_mnt() could
1227 /* Handle an automount point */
1228 if (managed & DCACHE_NEED_AUTOMOUNT) {
1229 ret = follow_automount(path, nd, &need_mntput);
1235 /* We didn't change the current path point */
1239 if (need_mntput && path->mnt == mnt)
1241 if (ret == -EISDIR || !ret)
1244 nd->flags |= LOOKUP_JUMPED;
1245 if (unlikely(ret < 0))
1246 path_put_conditional(path, nd);
1250 int follow_down_one(struct path *path)
1252 struct vfsmount *mounted;
1254 mounted = lookup_mnt(path);
1258 path->mnt = mounted;
1259 path->dentry = dget(mounted->mnt_root);
1264 EXPORT_SYMBOL(follow_down_one);
1266 static inline int managed_dentry_rcu(const struct path *path)
1268 return (path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) ?
1269 path->dentry->d_op->d_manage(path, true) : 0;
1273 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1274 * we meet a managed dentry that would need blocking.
1276 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
1277 struct inode **inode, unsigned *seqp)
1280 struct mount *mounted;
1282 * Don't forget we might have a non-mountpoint managed dentry
1283 * that wants to block transit.
1285 switch (managed_dentry_rcu(path)) {
1295 if (!d_mountpoint(path->dentry))
1296 return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
1298 mounted = __lookup_mnt(path->mnt, path->dentry);
1301 path->mnt = &mounted->mnt;
1302 path->dentry = mounted->mnt.mnt_root;
1303 nd->flags |= LOOKUP_JUMPED;
1304 *seqp = read_seqcount_begin(&path->dentry->d_seq);
1306 * Update the inode too. We don't need to re-check the
1307 * dentry sequence number here after this d_inode read,
1308 * because a mount-point is always pinned.
1310 *inode = path->dentry->d_inode;
1312 return !read_seqretry(&mount_lock, nd->m_seq) &&
1313 !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
1316 static int follow_dotdot_rcu(struct nameidata *nd)
1318 struct inode *inode = nd->inode;
1321 if (path_equal(&nd->path, &nd->root))
1323 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1324 struct dentry *old = nd->path.dentry;
1325 struct dentry *parent = old->d_parent;
1328 inode = parent->d_inode;
1329 seq = read_seqcount_begin(&parent->d_seq);
1330 if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq)))
1332 nd->path.dentry = parent;
1334 if (unlikely(!path_connected(&nd->path)))
1338 struct mount *mnt = real_mount(nd->path.mnt);
1339 struct mount *mparent = mnt->mnt_parent;
1340 struct dentry *mountpoint = mnt->mnt_mountpoint;
1341 struct inode *inode2 = mountpoint->d_inode;
1342 unsigned seq = read_seqcount_begin(&mountpoint->d_seq);
1343 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
1345 if (&mparent->mnt == nd->path.mnt)
1347 /* we know that mountpoint was pinned */
1348 nd->path.dentry = mountpoint;
1349 nd->path.mnt = &mparent->mnt;
1354 while (unlikely(d_mountpoint(nd->path.dentry))) {
1355 struct mount *mounted;
1356 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry);
1357 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
1361 nd->path.mnt = &mounted->mnt;
1362 nd->path.dentry = mounted->mnt.mnt_root;
1363 inode = nd->path.dentry->d_inode;
1364 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1371 * Follow down to the covering mount currently visible to userspace. At each
1372 * point, the filesystem owning that dentry may be queried as to whether the
1373 * caller is permitted to proceed or not.
1375 int follow_down(struct path *path)
1380 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1381 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
1382 /* Allow the filesystem to manage the transit without i_mutex
1385 * We indicate to the filesystem if someone is trying to mount
1386 * something here. This gives autofs the chance to deny anyone
1387 * other than its daemon the right to mount on its
1390 * The filesystem may sleep at this point.
1392 if (managed & DCACHE_MANAGE_TRANSIT) {
1393 BUG_ON(!path->dentry->d_op);
1394 BUG_ON(!path->dentry->d_op->d_manage);
1395 ret = path->dentry->d_op->d_manage(path, false);
1397 return ret == -EISDIR ? 0 : ret;
1400 /* Transit to a mounted filesystem. */
1401 if (managed & DCACHE_MOUNTED) {
1402 struct vfsmount *mounted = lookup_mnt(path);
1407 path->mnt = mounted;
1408 path->dentry = dget(mounted->mnt_root);
1412 /* Don't handle automount points here */
1417 EXPORT_SYMBOL(follow_down);
1420 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1422 static void follow_mount(struct path *path)
1424 while (d_mountpoint(path->dentry)) {
1425 struct vfsmount *mounted = lookup_mnt(path);
1430 path->mnt = mounted;
1431 path->dentry = dget(mounted->mnt_root);
1435 static int path_parent_directory(struct path *path)
1437 struct dentry *old = path->dentry;
1438 /* rare case of legitimate dget_parent()... */
1439 path->dentry = dget_parent(path->dentry);
1441 if (unlikely(!path_connected(path)))
1446 static int follow_dotdot(struct nameidata *nd)
1449 if (nd->path.dentry == nd->root.dentry &&
1450 nd->path.mnt == nd->root.mnt) {
1453 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1454 int ret = path_parent_directory(&nd->path);
1459 if (!follow_up(&nd->path))
1462 follow_mount(&nd->path);
1463 nd->inode = nd->path.dentry->d_inode;
1468 * This looks up the name in dcache and possibly revalidates the found dentry.
1469 * NULL is returned if the dentry does not exist in the cache.
1471 static struct dentry *lookup_dcache(const struct qstr *name,
1475 struct dentry *dentry;
1478 dentry = d_lookup(dir, name);
1480 if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
1481 error = d_revalidate(dentry, flags);
1482 if (unlikely(error <= 0)) {
1484 d_invalidate(dentry);
1486 return ERR_PTR(error);
1494 * Call i_op->lookup on the dentry. The dentry must be negative and
1497 * dir->d_inode->i_mutex must be held
1499 static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
1504 /* Don't create child dentry for a dead directory. */
1505 if (unlikely(IS_DEADDIR(dir))) {
1507 return ERR_PTR(-ENOENT);
1510 old = dir->i_op->lookup(dir, dentry, flags);
1511 if (unlikely(old)) {
1518 static struct dentry *__lookup_hash(const struct qstr *name,
1519 struct dentry *base, unsigned int flags)
1521 struct dentry *dentry = lookup_dcache(name, base, flags);
1526 dentry = d_alloc(base, name);
1527 if (unlikely(!dentry))
1528 return ERR_PTR(-ENOMEM);
1530 return lookup_real(base->d_inode, dentry, flags);
1533 static int lookup_fast(struct nameidata *nd,
1534 struct path *path, struct inode **inode,
1537 struct vfsmount *mnt = nd->path.mnt;
1538 struct dentry *dentry, *parent = nd->path.dentry;
1543 * Rename seqlock is not required here because in the off chance
1544 * of a false negative due to a concurrent rename, the caller is
1545 * going to fall back to non-racy lookup.
1547 if (nd->flags & LOOKUP_RCU) {
1550 dentry = __d_lookup_rcu(parent, &nd->last, &seq);
1551 if (unlikely(!dentry)) {
1552 if (unlazy_walk(nd, NULL, 0))
1558 * This sequence count validates that the inode matches
1559 * the dentry name information from lookup.
1561 *inode = d_backing_inode(dentry);
1562 negative = d_is_negative(dentry);
1563 if (unlikely(read_seqcount_retry(&dentry->d_seq, seq)))
1567 * This sequence count validates that the parent had no
1568 * changes while we did the lookup of the dentry above.
1570 * The memory barrier in read_seqcount_begin of child is
1571 * enough, we can use __read_seqcount_retry here.
1573 if (unlikely(__read_seqcount_retry(&parent->d_seq, nd->seq)))
1577 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
1578 status = d_revalidate(dentry, nd->flags);
1579 if (unlikely(status <= 0)) {
1580 if (unlazy_walk(nd, dentry, seq))
1582 if (status == -ECHILD)
1583 status = d_revalidate(dentry, nd->flags);
1586 * Note: do negative dentry check after revalidation in
1587 * case that drops it.
1589 if (unlikely(negative))
1592 path->dentry = dentry;
1593 if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
1595 if (unlazy_walk(nd, dentry, seq))
1599 dentry = __d_lookup(parent, &nd->last);
1600 if (unlikely(!dentry))
1602 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
1603 status = d_revalidate(dentry, nd->flags);
1605 if (unlikely(status <= 0)) {
1607 d_invalidate(dentry);
1611 if (unlikely(d_is_negative(dentry))) {
1617 path->dentry = dentry;
1618 err = follow_managed(path, nd);
1619 if (likely(err > 0))
1620 *inode = d_backing_inode(path->dentry);
1624 /* Fast lookup failed, do it the slow way */
1625 static struct dentry *lookup_slow(const struct qstr *name,
1629 struct dentry *dentry = ERR_PTR(-ENOENT), *old;
1630 struct inode *inode = dir->d_inode;
1631 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
1633 inode_lock_shared(inode);
1634 /* Don't go there if it's already dead */
1635 if (unlikely(IS_DEADDIR(inode)))
1638 dentry = d_alloc_parallel(dir, name, &wq);
1641 if (unlikely(!d_in_lookup(dentry))) {
1642 if ((dentry->d_flags & DCACHE_OP_REVALIDATE) &&
1643 !(flags & LOOKUP_NO_REVAL)) {
1644 int error = d_revalidate(dentry, flags);
1645 if (unlikely(error <= 0)) {
1647 d_invalidate(dentry);
1652 dentry = ERR_PTR(error);
1656 old = inode->i_op->lookup(inode, dentry, flags);
1657 d_lookup_done(dentry);
1658 if (unlikely(old)) {
1664 inode_unlock_shared(inode);
1668 static inline int may_lookup(struct nameidata *nd)
1670 if (nd->flags & LOOKUP_RCU) {
1671 int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1674 if (unlazy_walk(nd, NULL, 0))
1677 return inode_permission(nd->inode, MAY_EXEC);
1680 static inline int handle_dots(struct nameidata *nd, int type)
1682 if (type == LAST_DOTDOT) {
1685 if (nd->flags & LOOKUP_RCU) {
1686 return follow_dotdot_rcu(nd);
1688 return follow_dotdot(nd);
1693 static int pick_link(struct nameidata *nd, struct path *link,
1694 struct inode *inode, unsigned seq)
1698 if (unlikely(nd->total_link_count++ >= MAXSYMLINKS)) {
1699 path_to_nameidata(link, nd);
1702 if (!(nd->flags & LOOKUP_RCU)) {
1703 if (link->mnt == nd->path.mnt)
1706 error = nd_alloc_stack(nd);
1707 if (unlikely(error)) {
1708 if (error == -ECHILD) {
1709 if (unlikely(unlazy_link(nd, link, seq)))
1711 error = nd_alloc_stack(nd);
1719 last = nd->stack + nd->depth++;
1721 clear_delayed_call(&last->done);
1722 nd->link_inode = inode;
1728 * Do we need to follow links? We _really_ want to be able
1729 * to do this check without having to look at inode->i_op,
1730 * so we keep a cache of "no, this doesn't need follow_link"
1731 * for the common case.
1733 static inline int should_follow_link(struct nameidata *nd, struct path *link,
1735 struct inode *inode, unsigned seq)
1737 if (likely(!d_is_symlink(link->dentry)))
1741 /* make sure that d_is_symlink above matches inode */
1742 if (nd->flags & LOOKUP_RCU) {
1743 if (read_seqcount_retry(&link->dentry->d_seq, seq))
1746 return pick_link(nd, link, inode, seq);
1749 enum {WALK_GET = 1, WALK_PUT = 2};
1751 static int walk_component(struct nameidata *nd, int flags)
1754 struct inode *inode;
1758 * "." and ".." are special - ".." especially so because it has
1759 * to be able to know about the current root directory and
1760 * parent relationships.
1762 if (unlikely(nd->last_type != LAST_NORM)) {
1763 err = handle_dots(nd, nd->last_type);
1764 if (flags & WALK_PUT)
1768 err = lookup_fast(nd, &path, &inode, &seq);
1769 if (unlikely(err <= 0)) {
1772 path.dentry = lookup_slow(&nd->last, nd->path.dentry,
1774 if (IS_ERR(path.dentry))
1775 return PTR_ERR(path.dentry);
1777 path.mnt = nd->path.mnt;
1778 err = follow_managed(&path, nd);
1779 if (unlikely(err < 0))
1782 if (unlikely(d_is_negative(path.dentry))) {
1783 path_to_nameidata(&path, nd);
1787 seq = 0; /* we are already out of RCU mode */
1788 inode = d_backing_inode(path.dentry);
1791 if (flags & WALK_PUT)
1793 err = should_follow_link(nd, &path, flags & WALK_GET, inode, seq);
1796 path_to_nameidata(&path, nd);
1803 * We can do the critical dentry name comparison and hashing
1804 * operations one word at a time, but we are limited to:
1806 * - Architectures with fast unaligned word accesses. We could
1807 * do a "get_unaligned()" if this helps and is sufficiently
1810 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1811 * do not trap on the (extremely unlikely) case of a page
1812 * crossing operation.
1814 * - Furthermore, we need an efficient 64-bit compile for the
1815 * 64-bit case in order to generate the "number of bytes in
1816 * the final mask". Again, that could be replaced with a
1817 * efficient population count instruction or similar.
1819 #ifdef CONFIG_DCACHE_WORD_ACCESS
1821 #include <asm/word-at-a-time.h>
1825 /* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */
1827 #elif defined(CONFIG_64BIT)
1829 * Register pressure in the mixing function is an issue, particularly
1830 * on 32-bit x86, but almost any function requires one state value and
1831 * one temporary. Instead, use a function designed for two state values
1832 * and no temporaries.
1834 * This function cannot create a collision in only two iterations, so
1835 * we have two iterations to achieve avalanche. In those two iterations,
1836 * we have six layers of mixing, which is enough to spread one bit's
1837 * influence out to 2^6 = 64 state bits.
1839 * Rotate constants are scored by considering either 64 one-bit input
1840 * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the
1841 * probability of that delta causing a change to each of the 128 output
1842 * bits, using a sample of random initial states.
1844 * The Shannon entropy of the computed probabilities is then summed
1845 * to produce a score. Ideally, any input change has a 50% chance of
1846 * toggling any given output bit.
1848 * Mixing scores (in bits) for (12,45):
1849 * Input delta: 1-bit 2-bit
1850 * 1 round: 713.3 42542.6
1851 * 2 rounds: 2753.7 140389.8
1852 * 3 rounds: 5954.1 233458.2
1853 * 4 rounds: 7862.6 256672.2
1854 * Perfect: 8192 258048
1855 * (64*128) (64*63/2 * 128)
1857 #define HASH_MIX(x, y, a) \
1859 y ^= x, x = rol64(x,12),\
1860 x += y, y = rol64(y,45),\
1864 * Fold two longs into one 32-bit hash value. This must be fast, but
1865 * latency isn't quite as critical, as there is a fair bit of additional
1866 * work done before the hash value is used.
1868 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
1870 y ^= x * GOLDEN_RATIO_64;
1871 y *= GOLDEN_RATIO_64;
1875 #else /* 32-bit case */
1878 * Mixing scores (in bits) for (7,20):
1879 * Input delta: 1-bit 2-bit
1880 * 1 round: 330.3 9201.6
1881 * 2 rounds: 1246.4 25475.4
1882 * 3 rounds: 1907.1 31295.1
1883 * 4 rounds: 2042.3 31718.6
1884 * Perfect: 2048 31744
1885 * (32*64) (32*31/2 * 64)
1887 #define HASH_MIX(x, y, a) \
1889 y ^= x, x = rol32(x, 7),\
1890 x += y, y = rol32(y,20),\
1893 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
1895 /* Use arch-optimized multiply if one exists */
1896 return __hash_32(y ^ __hash_32(x));
1902 * Return the hash of a string of known length. This is carfully
1903 * designed to match hash_name(), which is the more critical function.
1904 * In particular, we must end by hashing a final word containing 0..7
1905 * payload bytes, to match the way that hash_name() iterates until it
1906 * finds the delimiter after the name.
1908 unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
1910 unsigned long a, x = 0, y = (unsigned long)salt;
1915 a = load_unaligned_zeropad(name);
1916 if (len < sizeof(unsigned long))
1919 name += sizeof(unsigned long);
1920 len -= sizeof(unsigned long);
1922 x ^= a & bytemask_from_count(len);
1924 return fold_hash(x, y);
1926 EXPORT_SYMBOL(full_name_hash);
1928 /* Return the "hash_len" (hash and length) of a null-terminated string */
1929 u64 hashlen_string(const void *salt, const char *name)
1931 unsigned long a = 0, x = 0, y = (unsigned long)salt;
1932 unsigned long adata, mask, len;
1933 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
1940 len += sizeof(unsigned long);
1942 a = load_unaligned_zeropad(name+len);
1943 } while (!has_zero(a, &adata, &constants));
1945 adata = prep_zero_mask(a, adata, &constants);
1946 mask = create_zero_mask(adata);
1947 x ^= a & zero_bytemask(mask);
1949 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
1951 EXPORT_SYMBOL(hashlen_string);
1954 * Calculate the length and hash of the path component, and
1955 * return the "hash_len" as the result.
1957 static inline u64 hash_name(const void *salt, const char *name)
1959 unsigned long a = 0, b, x = 0, y = (unsigned long)salt;
1960 unsigned long adata, bdata, mask, len;
1961 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
1968 len += sizeof(unsigned long);
1970 a = load_unaligned_zeropad(name+len);
1971 b = a ^ REPEAT_BYTE('/');
1972 } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
1974 adata = prep_zero_mask(a, adata, &constants);
1975 bdata = prep_zero_mask(b, bdata, &constants);
1976 mask = create_zero_mask(adata | bdata);
1977 x ^= a & zero_bytemask(mask);
1979 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
1982 #else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */
1984 /* Return the hash of a string of known length */
1985 unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
1987 unsigned long hash = init_name_hash(salt);
1989 hash = partial_name_hash((unsigned char)*name++, hash);
1990 return end_name_hash(hash);
1992 EXPORT_SYMBOL(full_name_hash);
1994 /* Return the "hash_len" (hash and length) of a null-terminated string */
1995 u64 hashlen_string(const void *salt, const char *name)
1997 unsigned long hash = init_name_hash(salt);
1998 unsigned long len = 0, c;
2000 c = (unsigned char)*name;
2003 hash = partial_name_hash(c, hash);
2004 c = (unsigned char)name[len];
2006 return hashlen_create(end_name_hash(hash), len);
2008 EXPORT_SYMBOL(hashlen_string);
2011 * We know there's a real path component here of at least
2014 static inline u64 hash_name(const void *salt, const char *name)
2016 unsigned long hash = init_name_hash(salt);
2017 unsigned long len = 0, c;
2019 c = (unsigned char)*name;
2022 hash = partial_name_hash(c, hash);
2023 c = (unsigned char)name[len];
2024 } while (c && c != '/');
2025 return hashlen_create(end_name_hash(hash), len);
2032 * This is the basic name resolution function, turning a pathname into
2033 * the final dentry. We expect 'base' to be positive and a directory.
2035 * Returns 0 and nd will have valid dentry and mnt on success.
2036 * Returns error and drops reference to input namei data on failure.
2038 static int link_path_walk(const char *name, struct nameidata *nd)
2047 /* At this point we know we have a real path component. */
2052 err = may_lookup(nd);
2056 hash_len = hash_name(nd->path.dentry, name);
2059 if (name[0] == '.') switch (hashlen_len(hash_len)) {
2061 if (name[1] == '.') {
2063 nd->flags |= LOOKUP_JUMPED;
2069 if (likely(type == LAST_NORM)) {
2070 struct dentry *parent = nd->path.dentry;
2071 nd->flags &= ~LOOKUP_JUMPED;
2072 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
2073 struct qstr this = { { .hash_len = hash_len }, .name = name };
2074 err = parent->d_op->d_hash(parent, &this);
2077 hash_len = this.hash_len;
2082 nd->last.hash_len = hash_len;
2083 nd->last.name = name;
2084 nd->last_type = type;
2086 name += hashlen_len(hash_len);
2090 * If it wasn't NUL, we know it was '/'. Skip that
2091 * slash, and continue until no more slashes.
2095 } while (unlikely(*name == '/'));
2096 if (unlikely(!*name)) {
2098 /* pathname body, done */
2101 name = nd->stack[nd->depth - 1].name;
2102 /* trailing symlink, done */
2105 /* last component of nested symlink */
2106 err = walk_component(nd, WALK_GET | WALK_PUT);
2108 err = walk_component(nd, WALK_GET);
2114 const char *s = get_link(nd);
2123 nd->stack[nd->depth - 1].name = name;
2128 if (unlikely(!d_can_lookup(nd->path.dentry))) {
2129 if (nd->flags & LOOKUP_RCU) {
2130 if (unlazy_walk(nd, NULL, 0))
2138 static const char *path_init(struct nameidata *nd, unsigned flags)
2141 const char *s = nd->name->name;
2143 nd->last_type = LAST_ROOT; /* if there are only slashes... */
2144 nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT;
2146 if (flags & LOOKUP_ROOT) {
2147 struct dentry *root = nd->root.dentry;
2148 struct inode *inode = root->d_inode;
2150 if (!d_can_lookup(root))
2151 return ERR_PTR(-ENOTDIR);
2152 retval = inode_permission(inode, MAY_EXEC);
2154 return ERR_PTR(retval);
2156 nd->path = nd->root;
2158 if (flags & LOOKUP_RCU) {
2160 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
2161 nd->root_seq = nd->seq;
2162 nd->m_seq = read_seqbegin(&mount_lock);
2164 path_get(&nd->path);
2169 nd->root.mnt = NULL;
2170 nd->path.mnt = NULL;
2171 nd->path.dentry = NULL;
2173 nd->m_seq = read_seqbegin(&mount_lock);
2175 if (flags & LOOKUP_RCU)
2178 if (likely(!nd_jump_root(nd)))
2180 nd->root.mnt = NULL;
2182 return ERR_PTR(-ECHILD);
2183 } else if (nd->dfd == AT_FDCWD) {
2184 if (flags & LOOKUP_RCU) {
2185 struct fs_struct *fs = current->fs;
2191 seq = read_seqcount_begin(&fs->seq);
2193 nd->inode = nd->path.dentry->d_inode;
2194 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
2195 } while (read_seqcount_retry(&fs->seq, seq));
2197 get_fs_pwd(current->fs, &nd->path);
2198 nd->inode = nd->path.dentry->d_inode;
2202 /* Caller must check execute permissions on the starting path component */
2203 struct fd f = fdget_raw(nd->dfd);
2204 struct dentry *dentry;
2207 return ERR_PTR(-EBADF);
2209 dentry = f.file->f_path.dentry;
2212 if (!d_can_lookup(dentry)) {
2214 return ERR_PTR(-ENOTDIR);
2218 nd->path = f.file->f_path;
2219 if (flags & LOOKUP_RCU) {
2221 nd->inode = nd->path.dentry->d_inode;
2222 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
2224 path_get(&nd->path);
2225 nd->inode = nd->path.dentry->d_inode;
2232 static const char *trailing_symlink(struct nameidata *nd)
2235 int error = may_follow_link(nd);
2236 if (unlikely(error))
2237 return ERR_PTR(error);
2238 nd->flags |= LOOKUP_PARENT;
2239 nd->stack[0].name = NULL;
2244 static inline int lookup_last(struct nameidata *nd)
2246 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
2247 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2249 nd->flags &= ~LOOKUP_PARENT;
2250 return walk_component(nd,
2251 nd->flags & LOOKUP_FOLLOW
2253 ? WALK_PUT | WALK_GET
2258 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2259 static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path)
2261 const char *s = path_init(nd, flags);
2266 while (!(err = link_path_walk(s, nd))
2267 && ((err = lookup_last(nd)) > 0)) {
2268 s = trailing_symlink(nd);
2275 err = complete_walk(nd);
2277 if (!err && nd->flags & LOOKUP_DIRECTORY)
2278 if (!d_can_lookup(nd->path.dentry))
2282 nd->path.mnt = NULL;
2283 nd->path.dentry = NULL;
2289 static int filename_lookup(int dfd, struct filename *name, unsigned flags,
2290 struct path *path, struct path *root)
2293 struct nameidata nd;
2295 return PTR_ERR(name);
2296 if (unlikely(root)) {
2298 flags |= LOOKUP_ROOT;
2300 set_nameidata(&nd, dfd, name);
2301 retval = path_lookupat(&nd, flags | LOOKUP_RCU, path);
2302 if (unlikely(retval == -ECHILD))
2303 retval = path_lookupat(&nd, flags, path);
2304 if (unlikely(retval == -ESTALE))
2305 retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path);
2307 if (likely(!retval))
2308 audit_inode(name, path->dentry, flags & LOOKUP_PARENT);
2309 restore_nameidata();
2314 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2315 static int path_parentat(struct nameidata *nd, unsigned flags,
2316 struct path *parent)
2318 const char *s = path_init(nd, flags);
2322 err = link_path_walk(s, nd);
2324 err = complete_walk(nd);
2327 nd->path.mnt = NULL;
2328 nd->path.dentry = NULL;
2334 static struct filename *filename_parentat(int dfd, struct filename *name,
2335 unsigned int flags, struct path *parent,
2336 struct qstr *last, int *type)
2339 struct nameidata nd;
2343 set_nameidata(&nd, dfd, name);
2344 retval = path_parentat(&nd, flags | LOOKUP_RCU, parent);
2345 if (unlikely(retval == -ECHILD))
2346 retval = path_parentat(&nd, flags, parent);
2347 if (unlikely(retval == -ESTALE))
2348 retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent);
2349 if (likely(!retval)) {
2351 *type = nd.last_type;
2352 audit_inode(name, parent->dentry, LOOKUP_PARENT);
2355 name = ERR_PTR(retval);
2357 restore_nameidata();
2361 /* does lookup, returns the object with parent locked */
2362 struct dentry *kern_path_locked(const char *name, struct path *path)
2364 struct filename *filename;
2369 filename = filename_parentat(AT_FDCWD, getname_kernel(name), 0, path,
2371 if (IS_ERR(filename))
2372 return ERR_CAST(filename);
2373 if (unlikely(type != LAST_NORM)) {
2376 return ERR_PTR(-EINVAL);
2378 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
2379 d = __lookup_hash(&last, path->dentry, 0);
2381 inode_unlock(path->dentry->d_inode);
2388 int kern_path(const char *name, unsigned int flags, struct path *path)
2390 return filename_lookup(AT_FDCWD, getname_kernel(name),
2393 EXPORT_SYMBOL(kern_path);
2396 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2397 * @dentry: pointer to dentry of the base directory
2398 * @mnt: pointer to vfs mount of the base directory
2399 * @name: pointer to file name
2400 * @flags: lookup flags
2401 * @path: pointer to struct path to fill
2403 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
2404 const char *name, unsigned int flags,
2407 struct path root = {.mnt = mnt, .dentry = dentry};
2408 /* the first argument of filename_lookup() is ignored with root */
2409 return filename_lookup(AT_FDCWD, getname_kernel(name),
2410 flags , path, &root);
2412 EXPORT_SYMBOL(vfs_path_lookup);
2415 * lookup_one_len - filesystem helper to lookup single pathname component
2416 * @name: pathname component to lookup
2417 * @base: base directory to lookup from
2418 * @len: maximum length @len should be interpreted to
2420 * Note that this routine is purely a helper for filesystem usage and should
2421 * not be called by generic code.
2423 * The caller must hold base->i_mutex.
2425 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
2431 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2435 this.hash = full_name_hash(base, name, len);
2437 return ERR_PTR(-EACCES);
2439 if (unlikely(name[0] == '.')) {
2440 if (len < 2 || (len == 2 && name[1] == '.'))
2441 return ERR_PTR(-EACCES);
2445 c = *(const unsigned char *)name++;
2446 if (c == '/' || c == '\0')
2447 return ERR_PTR(-EACCES);
2450 * See if the low-level filesystem might want
2451 * to use its own hash..
2453 if (base->d_flags & DCACHE_OP_HASH) {
2454 int err = base->d_op->d_hash(base, &this);
2456 return ERR_PTR(err);
2459 err = inode_permission(base->d_inode, MAY_EXEC);
2461 return ERR_PTR(err);
2463 return __lookup_hash(&this, base, 0);
2465 EXPORT_SYMBOL(lookup_one_len);
2468 * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
2469 * @name: pathname component to lookup
2470 * @base: base directory to lookup from
2471 * @len: maximum length @len should be interpreted to
2473 * Note that this routine is purely a helper for filesystem usage and should
2474 * not be called by generic code.
2476 * Unlike lookup_one_len, it should be called without the parent
2477 * i_mutex held, and will take the i_mutex itself if necessary.
2479 struct dentry *lookup_one_len_unlocked(const char *name,
2480 struct dentry *base, int len)
2489 this.hash = full_name_hash(base, name, len);
2491 return ERR_PTR(-EACCES);
2493 if (unlikely(name[0] == '.')) {
2494 if (len < 2 || (len == 2 && name[1] == '.'))
2495 return ERR_PTR(-EACCES);
2499 c = *(const unsigned char *)name++;
2500 if (c == '/' || c == '\0')
2501 return ERR_PTR(-EACCES);
2504 * See if the low-level filesystem might want
2505 * to use its own hash..
2507 if (base->d_flags & DCACHE_OP_HASH) {
2508 int err = base->d_op->d_hash(base, &this);
2510 return ERR_PTR(err);
2513 err = inode_permission(base->d_inode, MAY_EXEC);
2515 return ERR_PTR(err);
2517 ret = lookup_dcache(&this, base, 0);
2519 ret = lookup_slow(&this, base, 0);
2522 EXPORT_SYMBOL(lookup_one_len_unlocked);
2524 #ifdef CONFIG_UNIX98_PTYS
2525 int path_pts(struct path *path)
2527 /* Find something mounted on "pts" in the same directory as
2530 struct dentry *child, *parent;
2534 ret = path_parent_directory(path);
2538 parent = path->dentry;
2541 child = d_hash_and_lookup(parent, &this);
2545 path->dentry = child;
2552 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
2553 struct path *path, int *empty)
2555 return filename_lookup(dfd, getname_flags(name, flags, empty),
2558 EXPORT_SYMBOL(user_path_at_empty);
2561 * NB: most callers don't do anything directly with the reference to the
2562 * to struct filename, but the nd->last pointer points into the name string
2563 * allocated by getname. So we must hold the reference to it until all
2564 * path-walking is complete.
2566 static inline struct filename *
2567 user_path_parent(int dfd, const char __user *path,
2568 struct path *parent,
2573 /* only LOOKUP_REVAL is allowed in extra flags */
2574 return filename_parentat(dfd, getname(path), flags & LOOKUP_REVAL,
2575 parent, last, type);
2579 * mountpoint_last - look up last component for umount
2580 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2581 * @path: pointer to container for result
2583 * This is a special lookup_last function just for umount. In this case, we
2584 * need to resolve the path without doing any revalidation.
2586 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2587 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2588 * in almost all cases, this lookup will be served out of the dcache. The only
2589 * cases where it won't are if nd->last refers to a symlink or the path is
2590 * bogus and it doesn't exist.
2593 * -error: if there was an error during lookup. This includes -ENOENT if the
2594 * lookup found a negative dentry. The nd->path reference will also be
2597 * 0: if we successfully resolved nd->path and found it to not to be a
2598 * symlink that needs to be followed. "path" will also be populated.
2599 * The nd->path reference will also be put.
2601 * 1: if we successfully resolved nd->last and found it to be a symlink
2602 * that needs to be followed. "path" will be populated with the path
2603 * to the link, and nd->path will *not* be put.
2606 mountpoint_last(struct nameidata *nd, struct path *path)
2609 struct dentry *dentry;
2610 struct dentry *dir = nd->path.dentry;
2612 /* If we're in rcuwalk, drop out of it to handle last component */
2613 if (nd->flags & LOOKUP_RCU) {
2614 if (unlazy_walk(nd, NULL, 0))
2618 nd->flags &= ~LOOKUP_PARENT;
2620 if (unlikely(nd->last_type != LAST_NORM)) {
2621 error = handle_dots(nd, nd->last_type);
2624 dentry = dget(nd->path.dentry);
2626 dentry = d_lookup(dir, &nd->last);
2629 * No cached dentry. Mounted dentries are pinned in the
2630 * cache, so that means that this dentry is probably
2631 * a symlink or the path doesn't actually point
2632 * to a mounted dentry.
2634 dentry = lookup_slow(&nd->last, dir,
2635 nd->flags | LOOKUP_NO_REVAL);
2637 return PTR_ERR(dentry);
2640 if (d_is_negative(dentry)) {
2646 path->dentry = dentry;
2647 path->mnt = nd->path.mnt;
2648 error = should_follow_link(nd, path, nd->flags & LOOKUP_FOLLOW,
2649 d_backing_inode(dentry), 0);
2650 if (unlikely(error))
2658 * path_mountpoint - look up a path to be umounted
2659 * @nd: lookup context
2660 * @flags: lookup flags
2661 * @path: pointer to container for result
2663 * Look up the given name, but don't attempt to revalidate the last component.
2664 * Returns 0 and "path" will be valid on success; Returns error otherwise.
2667 path_mountpoint(struct nameidata *nd, unsigned flags, struct path *path)
2669 const char *s = path_init(nd, flags);
2673 while (!(err = link_path_walk(s, nd)) &&
2674 (err = mountpoint_last(nd, path)) > 0) {
2675 s = trailing_symlink(nd);
2686 filename_mountpoint(int dfd, struct filename *name, struct path *path,
2689 struct nameidata nd;
2692 return PTR_ERR(name);
2693 set_nameidata(&nd, dfd, name);
2694 error = path_mountpoint(&nd, flags | LOOKUP_RCU, path);
2695 if (unlikely(error == -ECHILD))
2696 error = path_mountpoint(&nd, flags, path);
2697 if (unlikely(error == -ESTALE))
2698 error = path_mountpoint(&nd, flags | LOOKUP_REVAL, path);
2700 audit_inode(name, path->dentry, 0);
2701 restore_nameidata();
2707 * user_path_mountpoint_at - lookup a path from userland in order to umount it
2708 * @dfd: directory file descriptor
2709 * @name: pathname from userland
2710 * @flags: lookup flags
2711 * @path: pointer to container to hold result
2713 * A umount is a special case for path walking. We're not actually interested
2714 * in the inode in this situation, and ESTALE errors can be a problem. We
2715 * simply want track down the dentry and vfsmount attached at the mountpoint
2716 * and avoid revalidating the last component.
2718 * Returns 0 and populates "path" on success.
2721 user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags,
2724 return filename_mountpoint(dfd, getname(name), path, flags);
2728 kern_path_mountpoint(int dfd, const char *name, struct path *path,
2731 return filename_mountpoint(dfd, getname_kernel(name), path, flags);
2733 EXPORT_SYMBOL(kern_path_mountpoint);
2735 int __check_sticky(struct inode *dir, struct inode *inode)
2737 kuid_t fsuid = current_fsuid();
2739 if (uid_eq(inode->i_uid, fsuid))
2741 if (uid_eq(dir->i_uid, fsuid))
2743 return !capable_wrt_inode_uidgid(inode, CAP_FOWNER);
2745 EXPORT_SYMBOL(__check_sticky);
2748 * Check whether we can remove a link victim from directory dir, check
2749 * whether the type of victim is right.
2750 * 1. We can't do it if dir is read-only (done in permission())
2751 * 2. We should have write and exec permissions on dir
2752 * 3. We can't remove anything from append-only dir
2753 * 4. We can't do anything with immutable dir (done in permission())
2754 * 5. If the sticky bit on dir is set we should either
2755 * a. be owner of dir, or
2756 * b. be owner of victim, or
2757 * c. have CAP_FOWNER capability
2758 * 6. If the victim is append-only or immutable we can't do antyhing with
2759 * links pointing to it.
2760 * 7. If the victim has an unknown uid or gid we can't change the inode.
2761 * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2762 * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2763 * 10. We can't remove a root or mountpoint.
2764 * 11. We don't allow removal of NFS sillyrenamed files; it's handled by
2765 * nfs_async_unlink().
2767 static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
2769 struct inode *inode = d_backing_inode(victim);
2772 if (d_is_negative(victim))
2776 BUG_ON(victim->d_parent->d_inode != dir);
2777 audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
2779 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
2785 if (check_sticky(dir, inode) || IS_APPEND(inode) ||
2786 IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) || HAS_UNMAPPED_ID(inode))
2789 if (!d_is_dir(victim))
2791 if (IS_ROOT(victim))
2793 } else if (d_is_dir(victim))
2795 if (IS_DEADDIR(dir))
2797 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2802 /* Check whether we can create an object with dentry child in directory
2804 * 1. We can't do it if child already exists (open has special treatment for
2805 * this case, but since we are inlined it's OK)
2806 * 2. We can't do it if dir is read-only (done in permission())
2807 * 3. We can't do it if the fs can't represent the fsuid or fsgid.
2808 * 4. We should have write and exec permissions on dir
2809 * 5. We can't do it if dir is immutable (done in permission())
2811 static inline int may_create(struct inode *dir, struct dentry *child)
2813 struct user_namespace *s_user_ns;
2814 audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
2817 if (IS_DEADDIR(dir))
2819 s_user_ns = dir->i_sb->s_user_ns;
2820 if (!kuid_has_mapping(s_user_ns, current_fsuid()) ||
2821 !kgid_has_mapping(s_user_ns, current_fsgid()))
2823 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
2827 * p1 and p2 should be directories on the same fs.
2829 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2834 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2838 mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
2840 p = d_ancestor(p2, p1);
2842 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
2843 inode_lock_nested(p1->d_inode, I_MUTEX_CHILD);
2847 p = d_ancestor(p1, p2);
2849 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2850 inode_lock_nested(p2->d_inode, I_MUTEX_CHILD);
2854 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2855 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
2858 EXPORT_SYMBOL(lock_rename);
2860 void unlock_rename(struct dentry *p1, struct dentry *p2)
2862 inode_unlock(p1->d_inode);
2864 inode_unlock(p2->d_inode);
2865 mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
2868 EXPORT_SYMBOL(unlock_rename);
2870 int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2873 int error = may_create(dir, dentry);
2877 if (!dir->i_op->create)
2878 return -EACCES; /* shouldn't it be ENOSYS? */
2881 error = security_inode_create(dir, dentry, mode);
2884 error = dir->i_op->create(dir, dentry, mode, want_excl);
2886 fsnotify_create(dir, dentry);
2889 EXPORT_SYMBOL(vfs_create);
2891 bool may_open_dev(const struct path *path)
2893 return !(path->mnt->mnt_flags & MNT_NODEV) &&
2894 !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV);
2897 static int may_open(const struct path *path, int acc_mode, int flag)
2899 struct dentry *dentry = path->dentry;
2900 struct inode *inode = dentry->d_inode;
2906 switch (inode->i_mode & S_IFMT) {
2910 if (acc_mode & MAY_WRITE)
2915 if (!may_open_dev(path))
2924 error = inode_permission(inode, MAY_OPEN | acc_mode);
2929 * An append-only file must be opened in append mode for writing.
2931 if (IS_APPEND(inode)) {
2932 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
2938 /* O_NOATIME can only be set by the owner or superuser */
2939 if (flag & O_NOATIME && !inode_owner_or_capable(inode))
2945 static int handle_truncate(struct file *filp)
2947 const struct path *path = &filp->f_path;
2948 struct inode *inode = path->dentry->d_inode;
2949 int error = get_write_access(inode);
2953 * Refuse to truncate files with mandatory locks held on them.
2955 error = locks_verify_locked(filp);
2957 error = security_path_truncate(path);
2959 error = do_truncate(path->dentry, 0,
2960 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
2963 put_write_access(inode);
2967 static inline int open_to_namei_flags(int flag)
2969 if ((flag & O_ACCMODE) == 3)
2974 static int may_o_create(const struct path *dir, struct dentry *dentry, umode_t mode)
2976 int error = security_path_mknod(dir, dentry, mode, 0);
2980 error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
2984 return security_inode_create(dir->dentry->d_inode, dentry, mode);
2988 * Attempt to atomically look up, create and open a file from a negative
2991 * Returns 0 if successful. The file will have been created and attached to
2992 * @file by the filesystem calling finish_open().
2994 * Returns 1 if the file was looked up only or didn't need creating. The
2995 * caller will need to perform the open themselves. @path will have been
2996 * updated to point to the new dentry. This may be negative.
2998 * Returns an error code otherwise.
3000 static int atomic_open(struct nameidata *nd, struct dentry *dentry,
3001 struct path *path, struct file *file,
3002 const struct open_flags *op,
3003 int open_flag, umode_t mode,
3006 struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
3007 struct inode *dir = nd->path.dentry->d_inode;
3010 if (!(~open_flag & (O_EXCL | O_CREAT))) /* both O_EXCL and O_CREAT */
3011 open_flag &= ~O_TRUNC;
3013 if (nd->flags & LOOKUP_DIRECTORY)
3014 open_flag |= O_DIRECTORY;
3016 file->f_path.dentry = DENTRY_NOT_SET;
3017 file->f_path.mnt = nd->path.mnt;
3018 error = dir->i_op->atomic_open(dir, dentry, file,
3019 open_to_namei_flags(open_flag),
3021 d_lookup_done(dentry);
3024 * We didn't have the inode before the open, so check open
3027 int acc_mode = op->acc_mode;
3028 if (*opened & FILE_CREATED) {
3029 WARN_ON(!(open_flag & O_CREAT));
3030 fsnotify_create(dir, dentry);
3033 error = may_open(&file->f_path, acc_mode, open_flag);
3034 if (WARN_ON(error > 0))
3036 } else if (error > 0) {
3037 if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
3040 if (file->f_path.dentry) {
3042 dentry = file->f_path.dentry;
3044 if (*opened & FILE_CREATED)
3045 fsnotify_create(dir, dentry);
3046 if (unlikely(d_is_negative(dentry))) {
3049 path->dentry = dentry;
3050 path->mnt = nd->path.mnt;
3060 * Look up and maybe create and open the last component.
3062 * Must be called with i_mutex held on parent.
3064 * Returns 0 if the file was successfully atomically created (if necessary) and
3065 * opened. In this case the file will be returned attached to @file.
3067 * Returns 1 if the file was not completely opened at this time, though lookups
3068 * and creations will have been performed and the dentry returned in @path will
3069 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
3070 * specified then a negative dentry may be returned.
3072 * An error code is returned otherwise.
3074 * FILE_CREATE will be set in @*opened if the dentry was created and will be
3075 * cleared otherwise prior to returning.
3077 static int lookup_open(struct nameidata *nd, struct path *path,
3079 const struct open_flags *op,
3080 bool got_write, int *opened)
3082 struct dentry *dir = nd->path.dentry;
3083 struct inode *dir_inode = dir->d_inode;
3084 int open_flag = op->open_flag;
3085 struct dentry *dentry;
3086 int error, create_error = 0;
3087 umode_t mode = op->mode;
3088 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
3090 if (unlikely(IS_DEADDIR(dir_inode)))
3093 *opened &= ~FILE_CREATED;
3094 dentry = d_lookup(dir, &nd->last);
3097 dentry = d_alloc_parallel(dir, &nd->last, &wq);
3099 return PTR_ERR(dentry);
3101 if (d_in_lookup(dentry))
3104 if (!(dentry->d_flags & DCACHE_OP_REVALIDATE))
3107 error = d_revalidate(dentry, nd->flags);
3108 if (likely(error > 0))
3112 d_invalidate(dentry);
3116 if (dentry->d_inode) {
3117 /* Cached positive dentry: will open in f_op->open */
3122 * Checking write permission is tricky, bacuse we don't know if we are
3123 * going to actually need it: O_CREAT opens should work as long as the
3124 * file exists. But checking existence breaks atomicity. The trick is
3125 * to check access and if not granted clear O_CREAT from the flags.
3127 * Another problem is returing the "right" error value (e.g. for an
3128 * O_EXCL open we want to return EEXIST not EROFS).
3130 if (open_flag & O_CREAT) {
3131 if (!IS_POSIXACL(dir->d_inode))
3132 mode &= ~current_umask();
3133 if (unlikely(!got_write)) {
3134 create_error = -EROFS;
3135 open_flag &= ~O_CREAT;
3136 if (open_flag & (O_EXCL | O_TRUNC))
3138 /* No side effects, safe to clear O_CREAT */
3140 create_error = may_o_create(&nd->path, dentry, mode);
3142 open_flag &= ~O_CREAT;
3143 if (open_flag & O_EXCL)
3147 } else if ((open_flag & (O_TRUNC|O_WRONLY|O_RDWR)) &&
3148 unlikely(!got_write)) {
3150 * No O_CREATE -> atomicity not a requirement -> fall
3151 * back to lookup + open
3156 if (dir_inode->i_op->atomic_open) {
3157 error = atomic_open(nd, dentry, path, file, op, open_flag,
3159 if (unlikely(error == -ENOENT) && create_error)
3160 error = create_error;
3165 if (d_in_lookup(dentry)) {
3166 struct dentry *res = dir_inode->i_op->lookup(dir_inode, dentry,
3168 d_lookup_done(dentry);
3169 if (unlikely(res)) {
3171 error = PTR_ERR(res);
3179 /* Negative dentry, just create the file */
3180 if (!dentry->d_inode && (open_flag & O_CREAT)) {
3181 *opened |= FILE_CREATED;
3182 audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);
3183 if (!dir_inode->i_op->create) {
3187 error = dir_inode->i_op->create(dir_inode, dentry, mode,
3188 open_flag & O_EXCL);
3191 fsnotify_create(dir_inode, dentry);
3193 if (unlikely(create_error) && !dentry->d_inode) {
3194 error = create_error;
3198 path->dentry = dentry;
3199 path->mnt = nd->path.mnt;
3208 * Handle the last step of open()
3210 static int do_last(struct nameidata *nd,
3211 struct file *file, const struct open_flags *op,
3214 struct dentry *dir = nd->path.dentry;
3215 int open_flag = op->open_flag;
3216 bool will_truncate = (open_flag & O_TRUNC) != 0;
3217 bool got_write = false;
3218 int acc_mode = op->acc_mode;
3220 struct inode *inode;
3224 nd->flags &= ~LOOKUP_PARENT;
3225 nd->flags |= op->intent;
3227 if (nd->last_type != LAST_NORM) {
3228 error = handle_dots(nd, nd->last_type);
3229 if (unlikely(error))
3234 if (!(open_flag & O_CREAT)) {
3235 if (nd->last.name[nd->last.len])
3236 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
3237 /* we _can_ be in RCU mode here */
3238 error = lookup_fast(nd, &path, &inode, &seq);
3239 if (likely(error > 0))
3245 BUG_ON(nd->inode != dir->d_inode);
3246 BUG_ON(nd->flags & LOOKUP_RCU);
3248 /* create side of things */
3250 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
3251 * has been cleared when we got to the last component we are
3254 error = complete_walk(nd);
3258 audit_inode(nd->name, dir, LOOKUP_PARENT);
3259 /* trailing slashes? */
3260 if (unlikely(nd->last.name[nd->last.len]))
3264 if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
3265 error = mnt_want_write(nd->path.mnt);
3269 * do _not_ fail yet - we might not need that or fail with
3270 * a different error; let lookup_open() decide; we'll be
3271 * dropping this one anyway.
3274 if (open_flag & O_CREAT)
3275 inode_lock(dir->d_inode);
3277 inode_lock_shared(dir->d_inode);
3278 error = lookup_open(nd, &path, file, op, got_write, opened);
3279 if (open_flag & O_CREAT)
3280 inode_unlock(dir->d_inode);
3282 inode_unlock_shared(dir->d_inode);
3288 if ((*opened & FILE_CREATED) ||
3289 !S_ISREG(file_inode(file)->i_mode))
3290 will_truncate = false;
3292 audit_inode(nd->name, file->f_path.dentry, 0);
3296 if (*opened & FILE_CREATED) {
3297 /* Don't check for write permission, don't truncate */
3298 open_flag &= ~O_TRUNC;
3299 will_truncate = false;
3301 path_to_nameidata(&path, nd);
3302 goto finish_open_created;
3306 * If atomic_open() acquired write access it is dropped now due to
3307 * possible mount and symlink following (this might be optimized away if
3311 mnt_drop_write(nd->path.mnt);
3315 error = follow_managed(&path, nd);
3316 if (unlikely(error < 0))
3319 if (unlikely(d_is_negative(path.dentry))) {
3320 path_to_nameidata(&path, nd);
3325 * create/update audit record if it already exists.
3327 audit_inode(nd->name, path.dentry, 0);
3329 if (unlikely((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))) {
3330 path_to_nameidata(&path, nd);
3334 seq = 0; /* out of RCU mode, so the value doesn't matter */
3335 inode = d_backing_inode(path.dentry);
3339 error = should_follow_link(nd, &path, nd->flags & LOOKUP_FOLLOW,
3341 if (unlikely(error))
3344 path_to_nameidata(&path, nd);
3347 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3349 error = complete_walk(nd);
3352 audit_inode(nd->name, nd->path.dentry, 0);
3354 if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry))
3357 if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
3359 if (!d_is_reg(nd->path.dentry))
3360 will_truncate = false;
3362 if (will_truncate) {
3363 error = mnt_want_write(nd->path.mnt);
3368 finish_open_created:
3369 error = may_open(&nd->path, acc_mode, open_flag);
3372 BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
3373 error = vfs_open(&nd->path, file, current_cred());
3376 *opened |= FILE_OPENED;
3378 error = open_check_o_direct(file);
3380 error = ima_file_check(file, op->acc_mode, *opened);
3381 if (!error && will_truncate)
3382 error = handle_truncate(file);
3384 if (unlikely(error) && (*opened & FILE_OPENED))
3386 if (unlikely(error > 0)) {
3391 mnt_drop_write(nd->path.mnt);
3395 static int do_tmpfile(struct nameidata *nd, unsigned flags,
3396 const struct open_flags *op,
3397 struct file *file, int *opened)
3399 static const struct qstr name = QSTR_INIT("/", 1);
3400 struct dentry *child;
3403 int error = path_lookupat(nd, flags | LOOKUP_DIRECTORY, &path);
3404 if (unlikely(error))
3406 error = mnt_want_write(path.mnt);
3407 if (unlikely(error))
3409 dir = path.dentry->d_inode;
3410 /* we want directory to be writable */
3411 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
3414 if (!dir->i_op->tmpfile) {
3415 error = -EOPNOTSUPP;
3418 child = d_alloc(path.dentry, &name);
3419 if (unlikely(!child)) {
3424 path.dentry = child;
3425 error = dir->i_op->tmpfile(dir, child, op->mode);
3428 audit_inode(nd->name, child, 0);
3429 /* Don't check for other permissions, the inode was just created */
3430 error = may_open(&path, 0, op->open_flag);
3433 file->f_path.mnt = path.mnt;
3434 error = finish_open(file, child, NULL, opened);
3437 error = open_check_o_direct(file);
3440 } else if (!(op->open_flag & O_EXCL)) {
3441 struct inode *inode = file_inode(file);
3442 spin_lock(&inode->i_lock);
3443 inode->i_state |= I_LINKABLE;
3444 spin_unlock(&inode->i_lock);
3447 mnt_drop_write(path.mnt);
3453 static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file)
3456 int error = path_lookupat(nd, flags, &path);
3458 audit_inode(nd->name, path.dentry, 0);
3459 error = vfs_open(&path, file, current_cred());
3465 static struct file *path_openat(struct nameidata *nd,
3466 const struct open_flags *op, unsigned flags)
3473 file = get_empty_filp();
3477 file->f_flags = op->open_flag;
3479 if (unlikely(file->f_flags & __O_TMPFILE)) {
3480 error = do_tmpfile(nd, flags, op, file, &opened);
3484 if (unlikely(file->f_flags & O_PATH)) {
3485 error = do_o_path(nd, flags, file);
3487 opened |= FILE_OPENED;
3491 s = path_init(nd, flags);
3496 while (!(error = link_path_walk(s, nd)) &&
3497 (error = do_last(nd, file, op, &opened)) > 0) {
3498 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
3499 s = trailing_symlink(nd);
3507 if (!(opened & FILE_OPENED)) {
3511 if (unlikely(error)) {
3512 if (error == -EOPENSTALE) {
3513 if (flags & LOOKUP_RCU)
3518 file = ERR_PTR(error);
3523 struct file *do_filp_open(int dfd, struct filename *pathname,
3524 const struct open_flags *op)
3526 struct nameidata nd;
3527 int flags = op->lookup_flags;
3530 set_nameidata(&nd, dfd, pathname);
3531 filp = path_openat(&nd, op, flags | LOOKUP_RCU);
3532 if (unlikely(filp == ERR_PTR(-ECHILD)))
3533 filp = path_openat(&nd, op, flags);
3534 if (unlikely(filp == ERR_PTR(-ESTALE)))
3535 filp = path_openat(&nd, op, flags | LOOKUP_REVAL);
3536 restore_nameidata();
3540 struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
3541 const char *name, const struct open_flags *op)
3543 struct nameidata nd;
3545 struct filename *filename;
3546 int flags = op->lookup_flags | LOOKUP_ROOT;
3549 nd.root.dentry = dentry;
3551 if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN)
3552 return ERR_PTR(-ELOOP);
3554 filename = getname_kernel(name);
3555 if (IS_ERR(filename))
3556 return ERR_CAST(filename);
3558 set_nameidata(&nd, -1, filename);
3559 file = path_openat(&nd, op, flags | LOOKUP_RCU);
3560 if (unlikely(file == ERR_PTR(-ECHILD)))
3561 file = path_openat(&nd, op, flags);
3562 if (unlikely(file == ERR_PTR(-ESTALE)))
3563 file = path_openat(&nd, op, flags | LOOKUP_REVAL);
3564 restore_nameidata();
3569 static struct dentry *filename_create(int dfd, struct filename *name,
3570 struct path *path, unsigned int lookup_flags)
3572 struct dentry *dentry = ERR_PTR(-EEXIST);
3577 bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
3580 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3581 * other flags passed in are ignored!
3583 lookup_flags &= LOOKUP_REVAL;
3585 name = filename_parentat(dfd, name, lookup_flags, path, &last, &type);
3587 return ERR_CAST(name);
3590 * Yucky last component or no last component at all?
3591 * (foo/., foo/.., /////)
3593 if (unlikely(type != LAST_NORM))
3596 /* don't fail immediately if it's r/o, at least try to report other errors */
3597 err2 = mnt_want_write(path->mnt);
3599 * Do the final lookup.
3601 lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL;
3602 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
3603 dentry = __lookup_hash(&last, path->dentry, lookup_flags);
3608 if (d_is_positive(dentry))
3612 * Special case - lookup gave negative, but... we had foo/bar/
3613 * From the vfs_mknod() POV we just have a negative dentry -
3614 * all is fine. Let's be bastards - you had / on the end, you've
3615 * been asking for (non-existent) directory. -ENOENT for you.
3617 if (unlikely(!is_dir && last.name[last.len])) {
3621 if (unlikely(err2)) {
3629 dentry = ERR_PTR(error);
3631 inode_unlock(path->dentry->d_inode);
3633 mnt_drop_write(path->mnt);
3640 struct dentry *kern_path_create(int dfd, const char *pathname,
3641 struct path *path, unsigned int lookup_flags)
3643 return filename_create(dfd, getname_kernel(pathname),
3644 path, lookup_flags);
3646 EXPORT_SYMBOL(kern_path_create);
3648 void done_path_create(struct path *path, struct dentry *dentry)
3651 inode_unlock(path->dentry->d_inode);
3652 mnt_drop_write(path->mnt);
3655 EXPORT_SYMBOL(done_path_create);
3657 inline struct dentry *user_path_create(int dfd, const char __user *pathname,
3658 struct path *path, unsigned int lookup_flags)
3660 return filename_create(dfd, getname(pathname), path, lookup_flags);
3662 EXPORT_SYMBOL(user_path_create);
3664 int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
3666 int error = may_create(dir, dentry);
3671 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
3674 if (!dir->i_op->mknod)
3677 error = devcgroup_inode_mknod(mode, dev);
3681 error = security_inode_mknod(dir, dentry, mode, dev);
3685 error = dir->i_op->mknod(dir, dentry, mode, dev);
3687 fsnotify_create(dir, dentry);
3690 EXPORT_SYMBOL(vfs_mknod);
3692 static int may_mknod(umode_t mode)
3694 switch (mode & S_IFMT) {
3700 case 0: /* zero mode translates to S_IFREG */
3709 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
3712 struct dentry *dentry;
3715 unsigned int lookup_flags = 0;
3717 error = may_mknod(mode);
3721 dentry = user_path_create(dfd, filename, &path, lookup_flags);
3723 return PTR_ERR(dentry);
3725 if (!IS_POSIXACL(path.dentry->d_inode))
3726 mode &= ~current_umask();
3727 error = security_path_mknod(&path, dentry, mode, dev);
3730 switch (mode & S_IFMT) {
3731 case 0: case S_IFREG:
3732 error = vfs_create(path.dentry->d_inode,dentry,mode,true);
3734 ima_post_path_mknod(dentry);
3736 case S_IFCHR: case S_IFBLK:
3737 error = vfs_mknod(path.dentry->d_inode,dentry,mode,
3738 new_decode_dev(dev));
3740 case S_IFIFO: case S_IFSOCK:
3741 error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
3745 done_path_create(&path, dentry);
3746 if (retry_estale(error, lookup_flags)) {
3747 lookup_flags |= LOOKUP_REVAL;
3753 SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
3755 return sys_mknodat(AT_FDCWD, filename, mode, dev);
3758 int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
3760 int error = may_create(dir, dentry);
3761 unsigned max_links = dir->i_sb->s_max_links;
3766 if (!dir->i_op->mkdir)
3769 mode &= (S_IRWXUGO|S_ISVTX);
3770 error = security_inode_mkdir(dir, dentry, mode);
3774 if (max_links && dir->i_nlink >= max_links)
3777 error = dir->i_op->mkdir(dir, dentry, mode);
3779 fsnotify_mkdir(dir, dentry);
3782 EXPORT_SYMBOL(vfs_mkdir);
3784 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
3786 struct dentry *dentry;
3789 unsigned int lookup_flags = LOOKUP_DIRECTORY;
3792 dentry = user_path_create(dfd, pathname, &path, lookup_flags);
3794 return PTR_ERR(dentry);
3796 if (!IS_POSIXACL(path.dentry->d_inode))
3797 mode &= ~current_umask();
3798 error = security_path_mkdir(&path, dentry, mode);
3800 error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
3801 done_path_create(&path, dentry);
3802 if (retry_estale(error, lookup_flags)) {
3803 lookup_flags |= LOOKUP_REVAL;
3809 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
3811 return sys_mkdirat(AT_FDCWD, pathname, mode);
3814 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
3816 int error = may_delete(dir, dentry, 1);
3821 if (!dir->i_op->rmdir)
3825 inode_lock(dentry->d_inode);
3828 if (is_local_mountpoint(dentry))
3831 error = security_inode_rmdir(dir, dentry);
3835 shrink_dcache_parent(dentry);
3836 error = dir->i_op->rmdir(dir, dentry);
3840 dentry->d_inode->i_flags |= S_DEAD;
3842 detach_mounts(dentry);
3845 inode_unlock(dentry->d_inode);
3851 EXPORT_SYMBOL(vfs_rmdir);
3853 static long do_rmdir(int dfd, const char __user *pathname)
3856 struct filename *name;
3857 struct dentry *dentry;
3861 unsigned int lookup_flags = 0;
3863 name = user_path_parent(dfd, pathname,
3864 &path, &last, &type, lookup_flags);
3866 return PTR_ERR(name);
3880 error = mnt_want_write(path.mnt);
3884 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
3885 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
3886 error = PTR_ERR(dentry);
3889 if (!dentry->d_inode) {
3893 error = security_path_rmdir(&path, dentry);
3896 error = vfs_rmdir(path.dentry->d_inode, dentry);
3900 inode_unlock(path.dentry->d_inode);
3901 mnt_drop_write(path.mnt);
3905 if (retry_estale(error, lookup_flags)) {
3906 lookup_flags |= LOOKUP_REVAL;
3912 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
3914 return do_rmdir(AT_FDCWD, pathname);
3918 * vfs_unlink - unlink a filesystem object
3919 * @dir: parent directory
3921 * @delegated_inode: returns victim inode, if the inode is delegated.
3923 * The caller must hold dir->i_mutex.
3925 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
3926 * return a reference to the inode in delegated_inode. The caller
3927 * should then break the delegation on that inode and retry. Because
3928 * breaking a delegation may take a long time, the caller should drop
3929 * dir->i_mutex before doing so.
3931 * Alternatively, a caller may pass NULL for delegated_inode. This may
3932 * be appropriate for callers that expect the underlying filesystem not
3933 * to be NFS exported.
3935 int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode)
3937 struct inode *target = dentry->d_inode;
3938 int error = may_delete(dir, dentry, 0);
3943 if (!dir->i_op->unlink)
3947 if (is_local_mountpoint(dentry))
3950 error = security_inode_unlink(dir, dentry);
3952 error = try_break_deleg(target, delegated_inode);
3955 error = dir->i_op->unlink(dir, dentry);
3958 detach_mounts(dentry);
3963 inode_unlock(target);
3965 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3966 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
3967 fsnotify_link_count(target);
3973 EXPORT_SYMBOL(vfs_unlink);
3976 * Make sure that the actual truncation of the file will occur outside its
3977 * directory's i_mutex. Truncate can take a long time if there is a lot of
3978 * writeout happening, and we don't want to prevent access to the directory
3979 * while waiting on the I/O.
3981 static long do_unlinkat(int dfd, const char __user *pathname)
3984 struct filename *name;
3985 struct dentry *dentry;
3989 struct inode *inode = NULL;
3990 struct inode *delegated_inode = NULL;
3991 unsigned int lookup_flags = 0;
3993 name = user_path_parent(dfd, pathname,
3994 &path, &last, &type, lookup_flags);
3996 return PTR_ERR(name);
3999 if (type != LAST_NORM)
4002 error = mnt_want_write(path.mnt);
4006 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
4007 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
4008 error = PTR_ERR(dentry);
4009 if (!IS_ERR(dentry)) {
4010 /* Why not before? Because we want correct error value */
4011 if (last.name[last.len])
4013 inode = dentry->d_inode;
4014 if (d_is_negative(dentry))
4017 error = security_path_unlink(&path, dentry);
4020 error = vfs_unlink(path.dentry->d_inode, dentry, &delegated_inode);
4024 inode_unlock(path.dentry->d_inode);
4026 iput(inode); /* truncate the inode here */
4028 if (delegated_inode) {
4029 error = break_deleg_wait(&delegated_inode);
4033 mnt_drop_write(path.mnt);
4037 if (retry_estale(error, lookup_flags)) {
4038 lookup_flags |= LOOKUP_REVAL;
4045 if (d_is_negative(dentry))
4047 else if (d_is_dir(dentry))
4054 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
4056 if ((flag & ~AT_REMOVEDIR) != 0)
4059 if (flag & AT_REMOVEDIR)
4060 return do_rmdir(dfd, pathname);
4062 return do_unlinkat(dfd, pathname);
4065 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
4067 return do_unlinkat(AT_FDCWD, pathname);
4070 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
4072 int error = may_create(dir, dentry);
4077 if (!dir->i_op->symlink)
4080 error = security_inode_symlink(dir, dentry, oldname);
4084 error = dir->i_op->symlink(dir, dentry, oldname);
4086 fsnotify_create(dir, dentry);
4089 EXPORT_SYMBOL(vfs_symlink);
4091 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
4092 int, newdfd, const char __user *, newname)
4095 struct filename *from;
4096 struct dentry *dentry;
4098 unsigned int lookup_flags = 0;
4100 from = getname(oldname);
4102 return PTR_ERR(from);
4104 dentry = user_path_create(newdfd, newname, &path, lookup_flags);
4105 error = PTR_ERR(dentry);
4109 error = security_path_symlink(&path, dentry, from->name);
4111 error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
4112 done_path_create(&path, dentry);
4113 if (retry_estale(error, lookup_flags)) {
4114 lookup_flags |= LOOKUP_REVAL;
4122 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
4124 return sys_symlinkat(oldname, AT_FDCWD, newname);
4128 * vfs_link - create a new link
4129 * @old_dentry: object to be linked
4131 * @new_dentry: where to create the new link
4132 * @delegated_inode: returns inode needing a delegation break
4134 * The caller must hold dir->i_mutex
4136 * If vfs_link discovers a delegation on the to-be-linked file in need
4137 * of breaking, it will return -EWOULDBLOCK and return a reference to the
4138 * inode in delegated_inode. The caller should then break the delegation
4139 * and retry. Because breaking a delegation may take a long time, the
4140 * caller should drop the i_mutex before doing so.
4142 * Alternatively, a caller may pass NULL for delegated_inode. This may
4143 * be appropriate for callers that expect the underlying filesystem not
4144 * to be NFS exported.
4146 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode)
4148 struct inode *inode = old_dentry->d_inode;
4149 unsigned max_links = dir->i_sb->s_max_links;
4155 error = may_create(dir, new_dentry);
4159 if (dir->i_sb != inode->i_sb)
4163 * A link to an append-only or immutable file cannot be created.
4165 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
4168 * Updating the link count will likely cause i_uid and i_gid to
4169 * be writen back improperly if their true value is unknown to
4172 if (HAS_UNMAPPED_ID(inode))
4174 if (!dir->i_op->link)
4176 if (S_ISDIR(inode->i_mode))
4179 error = security_inode_link(old_dentry, dir, new_dentry);
4184 /* Make sure we don't allow creating hardlink to an unlinked file */
4185 if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
4187 else if (max_links && inode->i_nlink >= max_links)
4190 error = try_break_deleg(inode, delegated_inode);
4192 error = dir->i_op->link(old_dentry, dir, new_dentry);
4195 if (!error && (inode->i_state & I_LINKABLE)) {
4196 spin_lock(&inode->i_lock);
4197 inode->i_state &= ~I_LINKABLE;
4198 spin_unlock(&inode->i_lock);
4200 inode_unlock(inode);
4202 fsnotify_link(dir, inode, new_dentry);
4205 EXPORT_SYMBOL(vfs_link);
4208 * Hardlinks are often used in delicate situations. We avoid
4209 * security-related surprises by not following symlinks on the
4212 * We don't follow them on the oldname either to be compatible
4213 * with linux 2.0, and to avoid hard-linking to directories
4214 * and other special files. --ADM
4216 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
4217 int, newdfd, const char __user *, newname, int, flags)
4219 struct dentry *new_dentry;
4220 struct path old_path, new_path;
4221 struct inode *delegated_inode = NULL;
4225 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
4228 * To use null names we require CAP_DAC_READ_SEARCH
4229 * This ensures that not everyone will be able to create
4230 * handlink using the passed filedescriptor.
4232 if (flags & AT_EMPTY_PATH) {
4233 if (!capable(CAP_DAC_READ_SEARCH))
4238 if (flags & AT_SYMLINK_FOLLOW)
4239 how |= LOOKUP_FOLLOW;
4241 error = user_path_at(olddfd, oldname, how, &old_path);
4245 new_dentry = user_path_create(newdfd, newname, &new_path,
4246 (how & LOOKUP_REVAL));
4247 error = PTR_ERR(new_dentry);
4248 if (IS_ERR(new_dentry))
4252 if (old_path.mnt != new_path.mnt)
4254 error = may_linkat(&old_path);
4255 if (unlikely(error))
4257 error = security_path_link(old_path.dentry, &new_path, new_dentry);
4260 error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, &delegated_inode);
4262 done_path_create(&new_path, new_dentry);
4263 if (delegated_inode) {
4264 error = break_deleg_wait(&delegated_inode);
4266 path_put(&old_path);
4270 if (retry_estale(error, how)) {
4271 path_put(&old_path);
4272 how |= LOOKUP_REVAL;
4276 path_put(&old_path);
4281 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
4283 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
4287 * vfs_rename - rename a filesystem object
4288 * @old_dir: parent of source
4289 * @old_dentry: source
4290 * @new_dir: parent of destination
4291 * @new_dentry: destination
4292 * @delegated_inode: returns an inode needing a delegation break
4293 * @flags: rename flags
4295 * The caller must hold multiple mutexes--see lock_rename()).
4297 * If vfs_rename discovers a delegation in need of breaking at either
4298 * the source or destination, it will return -EWOULDBLOCK and return a
4299 * reference to the inode in delegated_inode. The caller should then
4300 * break the delegation and retry. Because breaking a delegation may
4301 * take a long time, the caller should drop all locks before doing
4304 * Alternatively, a caller may pass NULL for delegated_inode. This may
4305 * be appropriate for callers that expect the underlying filesystem not
4306 * to be NFS exported.
4308 * The worst of all namespace operations - renaming directory. "Perverted"
4309 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4311 * a) we can get into loop creation.
4312 * b) race potential - two innocent renames can create a loop together.
4313 * That's where 4.4 screws up. Current fix: serialization on
4314 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4316 * c) we have to lock _four_ objects - parents and victim (if it exists),
4317 * and source (if it is not a directory).
4318 * And that - after we got ->i_mutex on parents (until then we don't know
4319 * whether the target exists). Solution: try to be smart with locking
4320 * order for inodes. We rely on the fact that tree topology may change
4321 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4322 * move will be locked. Thus we can rank directories by the tree
4323 * (ancestors first) and rank all non-directories after them.
4324 * That works since everybody except rename does "lock parent, lookup,
4325 * lock child" and rename is under ->s_vfs_rename_mutex.
4326 * HOWEVER, it relies on the assumption that any object with ->lookup()
4327 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4328 * we'd better make sure that there's no link(2) for them.
4329 * d) conversion from fhandle to dentry may come in the wrong moment - when
4330 * we are removing the target. Solution: we will have to grab ->i_mutex
4331 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4332 * ->i_mutex on parents, which works but leads to some truly excessive
4335 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
4336 struct inode *new_dir, struct dentry *new_dentry,
4337 struct inode **delegated_inode, unsigned int flags)
4340 bool is_dir = d_is_dir(old_dentry);
4341 const unsigned char *old_name;
4342 struct inode *source = old_dentry->d_inode;
4343 struct inode *target = new_dentry->d_inode;
4344 bool new_is_dir = false;
4345 unsigned max_links = new_dir->i_sb->s_max_links;
4348 * Check source == target.
4349 * On overlayfs need to look at underlying inodes.
4351 if (d_real_inode(old_dentry) == d_real_inode(new_dentry))
4354 error = may_delete(old_dir, old_dentry, is_dir);
4359 error = may_create(new_dir, new_dentry);
4361 new_is_dir = d_is_dir(new_dentry);
4363 if (!(flags & RENAME_EXCHANGE))
4364 error = may_delete(new_dir, new_dentry, is_dir);
4366 error = may_delete(new_dir, new_dentry, new_is_dir);
4371 if (!old_dir->i_op->rename)
4375 * If we are going to change the parent - check write permissions,
4376 * we'll need to flip '..'.
4378 if (new_dir != old_dir) {
4380 error = inode_permission(source, MAY_WRITE);
4384 if ((flags & RENAME_EXCHANGE) && new_is_dir) {
4385 error = inode_permission(target, MAY_WRITE);
4391 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
4396 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
4398 if (!is_dir || (flags & RENAME_EXCHANGE))
4399 lock_two_nondirectories(source, target);
4404 if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry))
4407 if (max_links && new_dir != old_dir) {
4409 if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
4411 if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
4412 old_dir->i_nlink >= max_links)
4415 if (is_dir && !(flags & RENAME_EXCHANGE) && target)
4416 shrink_dcache_parent(new_dentry);
4418 error = try_break_deleg(source, delegated_inode);
4422 if (target && !new_is_dir) {
4423 error = try_break_deleg(target, delegated_inode);
4427 error = old_dir->i_op->rename(old_dir, old_dentry,
4428 new_dir, new_dentry, flags);
4432 if (!(flags & RENAME_EXCHANGE) && target) {
4434 target->i_flags |= S_DEAD;
4435 dont_mount(new_dentry);
4436 detach_mounts(new_dentry);
4438 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
4439 if (!(flags & RENAME_EXCHANGE))
4440 d_move(old_dentry, new_dentry);
4442 d_exchange(old_dentry, new_dentry);
4445 if (!is_dir || (flags & RENAME_EXCHANGE))
4446 unlock_two_nondirectories(source, target);
4448 inode_unlock(target);
4451 fsnotify_move(old_dir, new_dir, old_name, is_dir,
4452 !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
4453 if (flags & RENAME_EXCHANGE) {
4454 fsnotify_move(new_dir, old_dir, old_dentry->d_name.name,
4455 new_is_dir, NULL, new_dentry);
4458 fsnotify_oldname_free(old_name);
4462 EXPORT_SYMBOL(vfs_rename);
4464 SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
4465 int, newdfd, const char __user *, newname, unsigned int, flags)
4467 struct dentry *old_dentry, *new_dentry;
4468 struct dentry *trap;
4469 struct path old_path, new_path;
4470 struct qstr old_last, new_last;
4471 int old_type, new_type;
4472 struct inode *delegated_inode = NULL;
4473 struct filename *from;
4474 struct filename *to;
4475 unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET;
4476 bool should_retry = false;
4479 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
4482 if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
4483 (flags & RENAME_EXCHANGE))
4486 if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD))
4489 if (flags & RENAME_EXCHANGE)
4493 from = user_path_parent(olddfd, oldname,
4494 &old_path, &old_last, &old_type, lookup_flags);
4496 error = PTR_ERR(from);
4500 to = user_path_parent(newdfd, newname,
4501 &new_path, &new_last, &new_type, lookup_flags);
4503 error = PTR_ERR(to);
4508 if (old_path.mnt != new_path.mnt)
4512 if (old_type != LAST_NORM)
4515 if (flags & RENAME_NOREPLACE)
4517 if (new_type != LAST_NORM)
4520 error = mnt_want_write(old_path.mnt);
4525 trap = lock_rename(new_path.dentry, old_path.dentry);
4527 old_dentry = __lookup_hash(&old_last, old_path.dentry, lookup_flags);
4528 error = PTR_ERR(old_dentry);
4529 if (IS_ERR(old_dentry))
4531 /* source must exist */
4533 if (d_is_negative(old_dentry))
4535 new_dentry = __lookup_hash(&new_last, new_path.dentry, lookup_flags | target_flags);
4536 error = PTR_ERR(new_dentry);
4537 if (IS_ERR(new_dentry))
4540 if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
4542 if (flags & RENAME_EXCHANGE) {
4544 if (d_is_negative(new_dentry))
4547 if (!d_is_dir(new_dentry)) {
4549 if (new_last.name[new_last.len])
4553 /* unless the source is a directory trailing slashes give -ENOTDIR */
4554 if (!d_is_dir(old_dentry)) {
4556 if (old_last.name[old_last.len])
4558 if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len])
4561 /* source should not be ancestor of target */
4563 if (old_dentry == trap)
4565 /* target should not be an ancestor of source */
4566 if (!(flags & RENAME_EXCHANGE))
4568 if (new_dentry == trap)
4571 error = security_path_rename(&old_path, old_dentry,
4572 &new_path, new_dentry, flags);
4575 error = vfs_rename(old_path.dentry->d_inode, old_dentry,
4576 new_path.dentry->d_inode, new_dentry,
4577 &delegated_inode, flags);
4583 unlock_rename(new_path.dentry, old_path.dentry);
4584 if (delegated_inode) {
4585 error = break_deleg_wait(&delegated_inode);
4589 mnt_drop_write(old_path.mnt);
4591 if (retry_estale(error, lookup_flags))
4592 should_retry = true;
4593 path_put(&new_path);
4596 path_put(&old_path);
4599 should_retry = false;
4600 lookup_flags |= LOOKUP_REVAL;
4607 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
4608 int, newdfd, const char __user *, newname)
4610 return sys_renameat2(olddfd, oldname, newdfd, newname, 0);
4613 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
4615 return sys_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
4618 int vfs_whiteout(struct inode *dir, struct dentry *dentry)
4620 int error = may_create(dir, dentry);
4624 if (!dir->i_op->mknod)
4627 return dir->i_op->mknod(dir, dentry,
4628 S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
4630 EXPORT_SYMBOL(vfs_whiteout);
4632 int readlink_copy(char __user *buffer, int buflen, const char *link)
4634 int len = PTR_ERR(link);
4639 if (len > (unsigned) buflen)
4641 if (copy_to_user(buffer, link, len))
4648 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
4649 * have ->get_link() not calling nd_jump_link(). Using (or not using) it
4650 * for any given inode is up to filesystem.
4652 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4654 DEFINE_DELAYED_CALL(done);
4655 struct inode *inode = d_inode(dentry);
4656 const char *link = inode->i_link;
4660 link = inode->i_op->get_link(dentry, inode, &done);
4662 return PTR_ERR(link);
4664 res = readlink_copy(buffer, buflen, link);
4665 do_delayed_call(&done);
4668 EXPORT_SYMBOL(generic_readlink);
4671 * vfs_get_link - get symlink body
4672 * @dentry: dentry on which to get symbolic link
4673 * @done: caller needs to free returned data with this
4675 * Calls security hook and i_op->get_link() on the supplied inode.
4677 * It does not touch atime. That's up to the caller if necessary.
4679 * Does not work on "special" symlinks like /proc/$$/fd/N
4681 const char *vfs_get_link(struct dentry *dentry, struct delayed_call *done)
4683 const char *res = ERR_PTR(-EINVAL);
4684 struct inode *inode = d_inode(dentry);
4686 if (d_is_symlink(dentry)) {
4687 res = ERR_PTR(security_inode_readlink(dentry));
4689 res = inode->i_op->get_link(dentry, inode, done);
4693 EXPORT_SYMBOL(vfs_get_link);
4695 /* get the link contents into pagecache */
4696 const char *page_get_link(struct dentry *dentry, struct inode *inode,
4697 struct delayed_call *callback)
4701 struct address_space *mapping = inode->i_mapping;
4704 page = find_get_page(mapping, 0);
4706 return ERR_PTR(-ECHILD);
4707 if (!PageUptodate(page)) {
4709 return ERR_PTR(-ECHILD);
4712 page = read_mapping_page(mapping, 0, NULL);
4716 set_delayed_call(callback, page_put_link, page);
4717 BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
4718 kaddr = page_address(page);
4719 nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1);
4723 EXPORT_SYMBOL(page_get_link);
4725 void page_put_link(void *arg)
4729 EXPORT_SYMBOL(page_put_link);
4731 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4733 DEFINE_DELAYED_CALL(done);
4734 int res = readlink_copy(buffer, buflen,
4735 page_get_link(dentry, d_inode(dentry),
4737 do_delayed_call(&done);
4740 EXPORT_SYMBOL(page_readlink);
4743 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4745 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
4747 struct address_space *mapping = inode->i_mapping;
4751 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
4753 flags |= AOP_FLAG_NOFS;
4756 err = pagecache_write_begin(NULL, mapping, 0, len-1,
4757 flags, &page, &fsdata);
4761 memcpy(page_address(page), symname, len-1);
4763 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
4770 mark_inode_dirty(inode);
4775 EXPORT_SYMBOL(__page_symlink);
4777 int page_symlink(struct inode *inode, const char *symname, int len)
4779 return __page_symlink(inode, symname, len,
4780 !mapping_gfp_constraint(inode->i_mapping, __GFP_FS));
4782 EXPORT_SYMBOL(page_symlink);
4784 const struct inode_operations page_symlink_inode_operations = {
4785 .readlink = generic_readlink,
4786 .get_link = page_get_link,
4788 EXPORT_SYMBOL(page_symlink_inode_operations);