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 <linux/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;
1105 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
1108 /* We don't want to mount if someone's just doing a stat -
1109 * unless they're stat'ing a directory and appended a '/' to
1112 * We do, however, want to mount if someone wants to open or
1113 * create a file of any type under the mountpoint, wants to
1114 * traverse through the mountpoint or wants to open the
1115 * mounted directory. Also, autofs may mark negative dentries
1116 * as being automount points. These will need the attentions
1117 * of the daemon to instantiate them before they can be used.
1119 if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
1120 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
1121 path->dentry->d_inode)
1124 if (path->dentry->d_sb->s_user_ns != &init_user_ns)
1127 nd->total_link_count++;
1128 if (nd->total_link_count >= 40)
1131 mnt = path->dentry->d_op->d_automount(path);
1134 * The filesystem is allowed to return -EISDIR here to indicate
1135 * it doesn't want to automount. For instance, autofs would do
1136 * this so that its userspace daemon can mount on this dentry.
1138 * However, we can only permit this if it's a terminal point in
1139 * the path being looked up; if it wasn't then the remainder of
1140 * the path is inaccessible and we should say so.
1142 if (PTR_ERR(mnt) == -EISDIR && (nd->flags & LOOKUP_PARENT))
1144 return PTR_ERR(mnt);
1147 if (!mnt) /* mount collision */
1150 if (!*need_mntput) {
1151 /* lock_mount() may release path->mnt on error */
1153 *need_mntput = true;
1155 err = finish_automount(mnt, path);
1159 /* Someone else made a mount here whilst we were busy */
1164 path->dentry = dget(mnt->mnt_root);
1173 * Handle a dentry that is managed in some way.
1174 * - Flagged for transit management (autofs)
1175 * - Flagged as mountpoint
1176 * - Flagged as automount point
1178 * This may only be called in refwalk mode.
1180 * Serialization is taken care of in namespace.c
1182 static int follow_managed(struct path *path, struct nameidata *nd)
1184 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
1186 bool need_mntput = false;
1189 /* Given that we're not holding a lock here, we retain the value in a
1190 * local variable for each dentry as we look at it so that we don't see
1191 * the components of that value change under us */
1192 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1193 managed &= DCACHE_MANAGED_DENTRY,
1194 unlikely(managed != 0)) {
1195 /* Allow the filesystem to manage the transit without i_mutex
1197 if (managed & DCACHE_MANAGE_TRANSIT) {
1198 BUG_ON(!path->dentry->d_op);
1199 BUG_ON(!path->dentry->d_op->d_manage);
1200 ret = path->dentry->d_op->d_manage(path, false);
1205 /* Transit to a mounted filesystem. */
1206 if (managed & DCACHE_MOUNTED) {
1207 struct vfsmount *mounted = lookup_mnt(path);
1212 path->mnt = mounted;
1213 path->dentry = dget(mounted->mnt_root);
1218 /* Something is mounted on this dentry in another
1219 * namespace and/or whatever was mounted there in this
1220 * namespace got unmounted before lookup_mnt() could
1224 /* Handle an automount point */
1225 if (managed & DCACHE_NEED_AUTOMOUNT) {
1226 ret = follow_automount(path, nd, &need_mntput);
1232 /* We didn't change the current path point */
1236 if (need_mntput && path->mnt == mnt)
1238 if (ret == -EISDIR || !ret)
1241 nd->flags |= LOOKUP_JUMPED;
1242 if (unlikely(ret < 0))
1243 path_put_conditional(path, nd);
1247 int follow_down_one(struct path *path)
1249 struct vfsmount *mounted;
1251 mounted = lookup_mnt(path);
1255 path->mnt = mounted;
1256 path->dentry = dget(mounted->mnt_root);
1261 EXPORT_SYMBOL(follow_down_one);
1263 static inline int managed_dentry_rcu(const struct path *path)
1265 return (path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) ?
1266 path->dentry->d_op->d_manage(path, true) : 0;
1270 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1271 * we meet a managed dentry that would need blocking.
1273 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
1274 struct inode **inode, unsigned *seqp)
1277 struct mount *mounted;
1279 * Don't forget we might have a non-mountpoint managed dentry
1280 * that wants to block transit.
1282 switch (managed_dentry_rcu(path)) {
1292 if (!d_mountpoint(path->dentry))
1293 return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
1295 mounted = __lookup_mnt(path->mnt, path->dentry);
1298 path->mnt = &mounted->mnt;
1299 path->dentry = mounted->mnt.mnt_root;
1300 nd->flags |= LOOKUP_JUMPED;
1301 *seqp = read_seqcount_begin(&path->dentry->d_seq);
1303 * Update the inode too. We don't need to re-check the
1304 * dentry sequence number here after this d_inode read,
1305 * because a mount-point is always pinned.
1307 *inode = path->dentry->d_inode;
1309 return !read_seqretry(&mount_lock, nd->m_seq) &&
1310 !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
1313 static int follow_dotdot_rcu(struct nameidata *nd)
1315 struct inode *inode = nd->inode;
1318 if (path_equal(&nd->path, &nd->root))
1320 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1321 struct dentry *old = nd->path.dentry;
1322 struct dentry *parent = old->d_parent;
1325 inode = parent->d_inode;
1326 seq = read_seqcount_begin(&parent->d_seq);
1327 if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq)))
1329 nd->path.dentry = parent;
1331 if (unlikely(!path_connected(&nd->path)))
1335 struct mount *mnt = real_mount(nd->path.mnt);
1336 struct mount *mparent = mnt->mnt_parent;
1337 struct dentry *mountpoint = mnt->mnt_mountpoint;
1338 struct inode *inode2 = mountpoint->d_inode;
1339 unsigned seq = read_seqcount_begin(&mountpoint->d_seq);
1340 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
1342 if (&mparent->mnt == nd->path.mnt)
1344 /* we know that mountpoint was pinned */
1345 nd->path.dentry = mountpoint;
1346 nd->path.mnt = &mparent->mnt;
1351 while (unlikely(d_mountpoint(nd->path.dentry))) {
1352 struct mount *mounted;
1353 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry);
1354 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
1358 nd->path.mnt = &mounted->mnt;
1359 nd->path.dentry = mounted->mnt.mnt_root;
1360 inode = nd->path.dentry->d_inode;
1361 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1368 * Follow down to the covering mount currently visible to userspace. At each
1369 * point, the filesystem owning that dentry may be queried as to whether the
1370 * caller is permitted to proceed or not.
1372 int follow_down(struct path *path)
1377 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1378 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
1379 /* Allow the filesystem to manage the transit without i_mutex
1382 * We indicate to the filesystem if someone is trying to mount
1383 * something here. This gives autofs the chance to deny anyone
1384 * other than its daemon the right to mount on its
1387 * The filesystem may sleep at this point.
1389 if (managed & DCACHE_MANAGE_TRANSIT) {
1390 BUG_ON(!path->dentry->d_op);
1391 BUG_ON(!path->dentry->d_op->d_manage);
1392 ret = path->dentry->d_op->d_manage(path, false);
1394 return ret == -EISDIR ? 0 : ret;
1397 /* Transit to a mounted filesystem. */
1398 if (managed & DCACHE_MOUNTED) {
1399 struct vfsmount *mounted = lookup_mnt(path);
1404 path->mnt = mounted;
1405 path->dentry = dget(mounted->mnt_root);
1409 /* Don't handle automount points here */
1414 EXPORT_SYMBOL(follow_down);
1417 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1419 static void follow_mount(struct path *path)
1421 while (d_mountpoint(path->dentry)) {
1422 struct vfsmount *mounted = lookup_mnt(path);
1427 path->mnt = mounted;
1428 path->dentry = dget(mounted->mnt_root);
1432 static int path_parent_directory(struct path *path)
1434 struct dentry *old = path->dentry;
1435 /* rare case of legitimate dget_parent()... */
1436 path->dentry = dget_parent(path->dentry);
1438 if (unlikely(!path_connected(path)))
1443 static int follow_dotdot(struct nameidata *nd)
1446 if (nd->path.dentry == nd->root.dentry &&
1447 nd->path.mnt == nd->root.mnt) {
1450 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1451 int ret = path_parent_directory(&nd->path);
1456 if (!follow_up(&nd->path))
1459 follow_mount(&nd->path);
1460 nd->inode = nd->path.dentry->d_inode;
1465 * This looks up the name in dcache and possibly revalidates the found dentry.
1466 * NULL is returned if the dentry does not exist in the cache.
1468 static struct dentry *lookup_dcache(const struct qstr *name,
1472 struct dentry *dentry;
1475 dentry = d_lookup(dir, name);
1477 if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
1478 error = d_revalidate(dentry, flags);
1479 if (unlikely(error <= 0)) {
1481 d_invalidate(dentry);
1483 return ERR_PTR(error);
1491 * Call i_op->lookup on the dentry. The dentry must be negative and
1494 * dir->d_inode->i_mutex must be held
1496 static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
1501 /* Don't create child dentry for a dead directory. */
1502 if (unlikely(IS_DEADDIR(dir))) {
1504 return ERR_PTR(-ENOENT);
1507 old = dir->i_op->lookup(dir, dentry, flags);
1508 if (unlikely(old)) {
1515 static struct dentry *__lookup_hash(const struct qstr *name,
1516 struct dentry *base, unsigned int flags)
1518 struct dentry *dentry = lookup_dcache(name, base, flags);
1523 dentry = d_alloc(base, name);
1524 if (unlikely(!dentry))
1525 return ERR_PTR(-ENOMEM);
1527 return lookup_real(base->d_inode, dentry, flags);
1530 static int lookup_fast(struct nameidata *nd,
1531 struct path *path, struct inode **inode,
1534 struct vfsmount *mnt = nd->path.mnt;
1535 struct dentry *dentry, *parent = nd->path.dentry;
1540 * Rename seqlock is not required here because in the off chance
1541 * of a false negative due to a concurrent rename, the caller is
1542 * going to fall back to non-racy lookup.
1544 if (nd->flags & LOOKUP_RCU) {
1547 dentry = __d_lookup_rcu(parent, &nd->last, &seq);
1548 if (unlikely(!dentry)) {
1549 if (unlazy_walk(nd, NULL, 0))
1555 * This sequence count validates that the inode matches
1556 * the dentry name information from lookup.
1558 *inode = d_backing_inode(dentry);
1559 negative = d_is_negative(dentry);
1560 if (unlikely(read_seqcount_retry(&dentry->d_seq, seq)))
1564 * This sequence count validates that the parent had no
1565 * changes while we did the lookup of the dentry above.
1567 * The memory barrier in read_seqcount_begin of child is
1568 * enough, we can use __read_seqcount_retry here.
1570 if (unlikely(__read_seqcount_retry(&parent->d_seq, nd->seq)))
1574 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
1575 status = d_revalidate(dentry, nd->flags);
1576 if (unlikely(status <= 0)) {
1577 if (unlazy_walk(nd, dentry, seq))
1579 if (status == -ECHILD)
1580 status = d_revalidate(dentry, nd->flags);
1583 * Note: do negative dentry check after revalidation in
1584 * case that drops it.
1586 if (unlikely(negative))
1589 path->dentry = dentry;
1590 if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
1592 if (unlazy_walk(nd, dentry, seq))
1596 dentry = __d_lookup(parent, &nd->last);
1597 if (unlikely(!dentry))
1599 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
1600 status = d_revalidate(dentry, nd->flags);
1602 if (unlikely(status <= 0)) {
1604 d_invalidate(dentry);
1608 if (unlikely(d_is_negative(dentry))) {
1614 path->dentry = dentry;
1615 err = follow_managed(path, nd);
1616 if (likely(err > 0))
1617 *inode = d_backing_inode(path->dentry);
1621 /* Fast lookup failed, do it the slow way */
1622 static struct dentry *lookup_slow(const struct qstr *name,
1626 struct dentry *dentry = ERR_PTR(-ENOENT), *old;
1627 struct inode *inode = dir->d_inode;
1628 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
1630 inode_lock_shared(inode);
1631 /* Don't go there if it's already dead */
1632 if (unlikely(IS_DEADDIR(inode)))
1635 dentry = d_alloc_parallel(dir, name, &wq);
1638 if (unlikely(!d_in_lookup(dentry))) {
1639 if ((dentry->d_flags & DCACHE_OP_REVALIDATE) &&
1640 !(flags & LOOKUP_NO_REVAL)) {
1641 int error = d_revalidate(dentry, flags);
1642 if (unlikely(error <= 0)) {
1644 d_invalidate(dentry);
1649 dentry = ERR_PTR(error);
1653 old = inode->i_op->lookup(inode, dentry, flags);
1654 d_lookup_done(dentry);
1655 if (unlikely(old)) {
1661 inode_unlock_shared(inode);
1665 static inline int may_lookup(struct nameidata *nd)
1667 if (nd->flags & LOOKUP_RCU) {
1668 int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1671 if (unlazy_walk(nd, NULL, 0))
1674 return inode_permission(nd->inode, MAY_EXEC);
1677 static inline int handle_dots(struct nameidata *nd, int type)
1679 if (type == LAST_DOTDOT) {
1682 if (nd->flags & LOOKUP_RCU) {
1683 return follow_dotdot_rcu(nd);
1685 return follow_dotdot(nd);
1690 static int pick_link(struct nameidata *nd, struct path *link,
1691 struct inode *inode, unsigned seq)
1695 if (unlikely(nd->total_link_count++ >= MAXSYMLINKS)) {
1696 path_to_nameidata(link, nd);
1699 if (!(nd->flags & LOOKUP_RCU)) {
1700 if (link->mnt == nd->path.mnt)
1703 error = nd_alloc_stack(nd);
1704 if (unlikely(error)) {
1705 if (error == -ECHILD) {
1706 if (unlikely(unlazy_link(nd, link, seq)))
1708 error = nd_alloc_stack(nd);
1716 last = nd->stack + nd->depth++;
1718 clear_delayed_call(&last->done);
1719 nd->link_inode = inode;
1724 enum {WALK_FOLLOW = 1, WALK_MORE = 2};
1727 * Do we need to follow links? We _really_ want to be able
1728 * to do this check without having to look at inode->i_op,
1729 * so we keep a cache of "no, this doesn't need follow_link"
1730 * for the common case.
1732 static inline int step_into(struct nameidata *nd, struct path *path,
1733 int flags, struct inode *inode, unsigned seq)
1735 if (!(flags & WALK_MORE) && nd->depth)
1737 if (likely(!d_is_symlink(path->dentry)) ||
1738 !(flags & WALK_FOLLOW || nd->flags & LOOKUP_FOLLOW)) {
1739 /* not a symlink or should not follow */
1740 path_to_nameidata(path, nd);
1745 /* make sure that d_is_symlink above matches inode */
1746 if (nd->flags & LOOKUP_RCU) {
1747 if (read_seqcount_retry(&path->dentry->d_seq, seq))
1750 return pick_link(nd, path, inode, seq);
1753 static int walk_component(struct nameidata *nd, int flags)
1756 struct inode *inode;
1760 * "." and ".." are special - ".." especially so because it has
1761 * to be able to know about the current root directory and
1762 * parent relationships.
1764 if (unlikely(nd->last_type != LAST_NORM)) {
1765 err = handle_dots(nd, nd->last_type);
1766 if (!(flags & WALK_MORE) && nd->depth)
1770 err = lookup_fast(nd, &path, &inode, &seq);
1771 if (unlikely(err <= 0)) {
1774 path.dentry = lookup_slow(&nd->last, nd->path.dentry,
1776 if (IS_ERR(path.dentry))
1777 return PTR_ERR(path.dentry);
1779 path.mnt = nd->path.mnt;
1780 err = follow_managed(&path, nd);
1781 if (unlikely(err < 0))
1784 if (unlikely(d_is_negative(path.dentry))) {
1785 path_to_nameidata(&path, nd);
1789 seq = 0; /* we are already out of RCU mode */
1790 inode = d_backing_inode(path.dentry);
1793 return step_into(nd, &path, flags, inode, seq);
1797 * We can do the critical dentry name comparison and hashing
1798 * operations one word at a time, but we are limited to:
1800 * - Architectures with fast unaligned word accesses. We could
1801 * do a "get_unaligned()" if this helps and is sufficiently
1804 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1805 * do not trap on the (extremely unlikely) case of a page
1806 * crossing operation.
1808 * - Furthermore, we need an efficient 64-bit compile for the
1809 * 64-bit case in order to generate the "number of bytes in
1810 * the final mask". Again, that could be replaced with a
1811 * efficient population count instruction or similar.
1813 #ifdef CONFIG_DCACHE_WORD_ACCESS
1815 #include <asm/word-at-a-time.h>
1819 /* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */
1821 #elif defined(CONFIG_64BIT)
1823 * Register pressure in the mixing function is an issue, particularly
1824 * on 32-bit x86, but almost any function requires one state value and
1825 * one temporary. Instead, use a function designed for two state values
1826 * and no temporaries.
1828 * This function cannot create a collision in only two iterations, so
1829 * we have two iterations to achieve avalanche. In those two iterations,
1830 * we have six layers of mixing, which is enough to spread one bit's
1831 * influence out to 2^6 = 64 state bits.
1833 * Rotate constants are scored by considering either 64 one-bit input
1834 * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the
1835 * probability of that delta causing a change to each of the 128 output
1836 * bits, using a sample of random initial states.
1838 * The Shannon entropy of the computed probabilities is then summed
1839 * to produce a score. Ideally, any input change has a 50% chance of
1840 * toggling any given output bit.
1842 * Mixing scores (in bits) for (12,45):
1843 * Input delta: 1-bit 2-bit
1844 * 1 round: 713.3 42542.6
1845 * 2 rounds: 2753.7 140389.8
1846 * 3 rounds: 5954.1 233458.2
1847 * 4 rounds: 7862.6 256672.2
1848 * Perfect: 8192 258048
1849 * (64*128) (64*63/2 * 128)
1851 #define HASH_MIX(x, y, a) \
1853 y ^= x, x = rol64(x,12),\
1854 x += y, y = rol64(y,45),\
1858 * Fold two longs into one 32-bit hash value. This must be fast, but
1859 * latency isn't quite as critical, as there is a fair bit of additional
1860 * work done before the hash value is used.
1862 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
1864 y ^= x * GOLDEN_RATIO_64;
1865 y *= GOLDEN_RATIO_64;
1869 #else /* 32-bit case */
1872 * Mixing scores (in bits) for (7,20):
1873 * Input delta: 1-bit 2-bit
1874 * 1 round: 330.3 9201.6
1875 * 2 rounds: 1246.4 25475.4
1876 * 3 rounds: 1907.1 31295.1
1877 * 4 rounds: 2042.3 31718.6
1878 * Perfect: 2048 31744
1879 * (32*64) (32*31/2 * 64)
1881 #define HASH_MIX(x, y, a) \
1883 y ^= x, x = rol32(x, 7),\
1884 x += y, y = rol32(y,20),\
1887 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
1889 /* Use arch-optimized multiply if one exists */
1890 return __hash_32(y ^ __hash_32(x));
1896 * Return the hash of a string of known length. This is carfully
1897 * designed to match hash_name(), which is the more critical function.
1898 * In particular, we must end by hashing a final word containing 0..7
1899 * payload bytes, to match the way that hash_name() iterates until it
1900 * finds the delimiter after the name.
1902 unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
1904 unsigned long a, x = 0, y = (unsigned long)salt;
1909 a = load_unaligned_zeropad(name);
1910 if (len < sizeof(unsigned long))
1913 name += sizeof(unsigned long);
1914 len -= sizeof(unsigned long);
1916 x ^= a & bytemask_from_count(len);
1918 return fold_hash(x, y);
1920 EXPORT_SYMBOL(full_name_hash);
1922 /* Return the "hash_len" (hash and length) of a null-terminated string */
1923 u64 hashlen_string(const void *salt, const char *name)
1925 unsigned long a = 0, x = 0, y = (unsigned long)salt;
1926 unsigned long adata, mask, len;
1927 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
1934 len += sizeof(unsigned long);
1936 a = load_unaligned_zeropad(name+len);
1937 } while (!has_zero(a, &adata, &constants));
1939 adata = prep_zero_mask(a, adata, &constants);
1940 mask = create_zero_mask(adata);
1941 x ^= a & zero_bytemask(mask);
1943 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
1945 EXPORT_SYMBOL(hashlen_string);
1948 * Calculate the length and hash of the path component, and
1949 * return the "hash_len" as the result.
1951 static inline u64 hash_name(const void *salt, const char *name)
1953 unsigned long a = 0, b, x = 0, y = (unsigned long)salt;
1954 unsigned long adata, bdata, mask, len;
1955 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
1962 len += sizeof(unsigned long);
1964 a = load_unaligned_zeropad(name+len);
1965 b = a ^ REPEAT_BYTE('/');
1966 } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
1968 adata = prep_zero_mask(a, adata, &constants);
1969 bdata = prep_zero_mask(b, bdata, &constants);
1970 mask = create_zero_mask(adata | bdata);
1971 x ^= a & zero_bytemask(mask);
1973 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
1976 #else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */
1978 /* Return the hash of a string of known length */
1979 unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
1981 unsigned long hash = init_name_hash(salt);
1983 hash = partial_name_hash((unsigned char)*name++, hash);
1984 return end_name_hash(hash);
1986 EXPORT_SYMBOL(full_name_hash);
1988 /* Return the "hash_len" (hash and length) of a null-terminated string */
1989 u64 hashlen_string(const void *salt, const char *name)
1991 unsigned long hash = init_name_hash(salt);
1992 unsigned long len = 0, c;
1994 c = (unsigned char)*name;
1997 hash = partial_name_hash(c, hash);
1998 c = (unsigned char)name[len];
2000 return hashlen_create(end_name_hash(hash), len);
2002 EXPORT_SYMBOL(hashlen_string);
2005 * We know there's a real path component here of at least
2008 static inline u64 hash_name(const void *salt, const char *name)
2010 unsigned long hash = init_name_hash(salt);
2011 unsigned long len = 0, c;
2013 c = (unsigned char)*name;
2016 hash = partial_name_hash(c, hash);
2017 c = (unsigned char)name[len];
2018 } while (c && c != '/');
2019 return hashlen_create(end_name_hash(hash), len);
2026 * This is the basic name resolution function, turning a pathname into
2027 * the final dentry. We expect 'base' to be positive and a directory.
2029 * Returns 0 and nd will have valid dentry and mnt on success.
2030 * Returns error and drops reference to input namei data on failure.
2032 static int link_path_walk(const char *name, struct nameidata *nd)
2041 /* At this point we know we have a real path component. */
2046 err = may_lookup(nd);
2050 hash_len = hash_name(nd->path.dentry, name);
2053 if (name[0] == '.') switch (hashlen_len(hash_len)) {
2055 if (name[1] == '.') {
2057 nd->flags |= LOOKUP_JUMPED;
2063 if (likely(type == LAST_NORM)) {
2064 struct dentry *parent = nd->path.dentry;
2065 nd->flags &= ~LOOKUP_JUMPED;
2066 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
2067 struct qstr this = { { .hash_len = hash_len }, .name = name };
2068 err = parent->d_op->d_hash(parent, &this);
2071 hash_len = this.hash_len;
2076 nd->last.hash_len = hash_len;
2077 nd->last.name = name;
2078 nd->last_type = type;
2080 name += hashlen_len(hash_len);
2084 * If it wasn't NUL, we know it was '/'. Skip that
2085 * slash, and continue until no more slashes.
2089 } while (unlikely(*name == '/'));
2090 if (unlikely(!*name)) {
2092 /* pathname body, done */
2095 name = nd->stack[nd->depth - 1].name;
2096 /* trailing symlink, done */
2099 /* last component of nested symlink */
2100 err = walk_component(nd, WALK_FOLLOW);
2102 /* not the last component */
2103 err = walk_component(nd, WALK_FOLLOW | WALK_MORE);
2109 const char *s = get_link(nd);
2118 nd->stack[nd->depth - 1].name = name;
2123 if (unlikely(!d_can_lookup(nd->path.dentry))) {
2124 if (nd->flags & LOOKUP_RCU) {
2125 if (unlazy_walk(nd, NULL, 0))
2133 static const char *path_init(struct nameidata *nd, unsigned flags)
2136 const char *s = nd->name->name;
2138 nd->last_type = LAST_ROOT; /* if there are only slashes... */
2139 nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT;
2141 if (flags & LOOKUP_ROOT) {
2142 struct dentry *root = nd->root.dentry;
2143 struct inode *inode = root->d_inode;
2145 if (!d_can_lookup(root))
2146 return ERR_PTR(-ENOTDIR);
2147 retval = inode_permission(inode, MAY_EXEC);
2149 return ERR_PTR(retval);
2151 nd->path = nd->root;
2153 if (flags & LOOKUP_RCU) {
2155 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
2156 nd->root_seq = nd->seq;
2157 nd->m_seq = read_seqbegin(&mount_lock);
2159 path_get(&nd->path);
2164 nd->root.mnt = NULL;
2165 nd->path.mnt = NULL;
2166 nd->path.dentry = NULL;
2168 nd->m_seq = read_seqbegin(&mount_lock);
2170 if (flags & LOOKUP_RCU)
2173 if (likely(!nd_jump_root(nd)))
2175 nd->root.mnt = NULL;
2177 return ERR_PTR(-ECHILD);
2178 } else if (nd->dfd == AT_FDCWD) {
2179 if (flags & LOOKUP_RCU) {
2180 struct fs_struct *fs = current->fs;
2186 seq = read_seqcount_begin(&fs->seq);
2188 nd->inode = nd->path.dentry->d_inode;
2189 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
2190 } while (read_seqcount_retry(&fs->seq, seq));
2192 get_fs_pwd(current->fs, &nd->path);
2193 nd->inode = nd->path.dentry->d_inode;
2197 /* Caller must check execute permissions on the starting path component */
2198 struct fd f = fdget_raw(nd->dfd);
2199 struct dentry *dentry;
2202 return ERR_PTR(-EBADF);
2204 dentry = f.file->f_path.dentry;
2207 if (!d_can_lookup(dentry)) {
2209 return ERR_PTR(-ENOTDIR);
2213 nd->path = f.file->f_path;
2214 if (flags & LOOKUP_RCU) {
2216 nd->inode = nd->path.dentry->d_inode;
2217 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
2219 path_get(&nd->path);
2220 nd->inode = nd->path.dentry->d_inode;
2227 static const char *trailing_symlink(struct nameidata *nd)
2230 int error = may_follow_link(nd);
2231 if (unlikely(error))
2232 return ERR_PTR(error);
2233 nd->flags |= LOOKUP_PARENT;
2234 nd->stack[0].name = NULL;
2239 static inline int lookup_last(struct nameidata *nd)
2241 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
2242 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2244 nd->flags &= ~LOOKUP_PARENT;
2245 return walk_component(nd, 0);
2248 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2249 static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path)
2251 const char *s = path_init(nd, flags);
2256 while (!(err = link_path_walk(s, nd))
2257 && ((err = lookup_last(nd)) > 0)) {
2258 s = trailing_symlink(nd);
2265 err = complete_walk(nd);
2267 if (!err && nd->flags & LOOKUP_DIRECTORY)
2268 if (!d_can_lookup(nd->path.dentry))
2272 nd->path.mnt = NULL;
2273 nd->path.dentry = NULL;
2279 static int filename_lookup(int dfd, struct filename *name, unsigned flags,
2280 struct path *path, struct path *root)
2283 struct nameidata nd;
2285 return PTR_ERR(name);
2286 if (unlikely(root)) {
2288 flags |= LOOKUP_ROOT;
2290 set_nameidata(&nd, dfd, name);
2291 retval = path_lookupat(&nd, flags | LOOKUP_RCU, path);
2292 if (unlikely(retval == -ECHILD))
2293 retval = path_lookupat(&nd, flags, path);
2294 if (unlikely(retval == -ESTALE))
2295 retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path);
2297 if (likely(!retval))
2298 audit_inode(name, path->dentry, flags & LOOKUP_PARENT);
2299 restore_nameidata();
2304 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2305 static int path_parentat(struct nameidata *nd, unsigned flags,
2306 struct path *parent)
2308 const char *s = path_init(nd, flags);
2312 err = link_path_walk(s, nd);
2314 err = complete_walk(nd);
2317 nd->path.mnt = NULL;
2318 nd->path.dentry = NULL;
2324 static struct filename *filename_parentat(int dfd, struct filename *name,
2325 unsigned int flags, struct path *parent,
2326 struct qstr *last, int *type)
2329 struct nameidata nd;
2333 set_nameidata(&nd, dfd, name);
2334 retval = path_parentat(&nd, flags | LOOKUP_RCU, parent);
2335 if (unlikely(retval == -ECHILD))
2336 retval = path_parentat(&nd, flags, parent);
2337 if (unlikely(retval == -ESTALE))
2338 retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent);
2339 if (likely(!retval)) {
2341 *type = nd.last_type;
2342 audit_inode(name, parent->dentry, LOOKUP_PARENT);
2345 name = ERR_PTR(retval);
2347 restore_nameidata();
2351 /* does lookup, returns the object with parent locked */
2352 struct dentry *kern_path_locked(const char *name, struct path *path)
2354 struct filename *filename;
2359 filename = filename_parentat(AT_FDCWD, getname_kernel(name), 0, path,
2361 if (IS_ERR(filename))
2362 return ERR_CAST(filename);
2363 if (unlikely(type != LAST_NORM)) {
2366 return ERR_PTR(-EINVAL);
2368 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
2369 d = __lookup_hash(&last, path->dentry, 0);
2371 inode_unlock(path->dentry->d_inode);
2378 int kern_path(const char *name, unsigned int flags, struct path *path)
2380 return filename_lookup(AT_FDCWD, getname_kernel(name),
2383 EXPORT_SYMBOL(kern_path);
2386 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2387 * @dentry: pointer to dentry of the base directory
2388 * @mnt: pointer to vfs mount of the base directory
2389 * @name: pointer to file name
2390 * @flags: lookup flags
2391 * @path: pointer to struct path to fill
2393 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
2394 const char *name, unsigned int flags,
2397 struct path root = {.mnt = mnt, .dentry = dentry};
2398 /* the first argument of filename_lookup() is ignored with root */
2399 return filename_lookup(AT_FDCWD, getname_kernel(name),
2400 flags , path, &root);
2402 EXPORT_SYMBOL(vfs_path_lookup);
2405 * lookup_one_len - filesystem helper to lookup single pathname component
2406 * @name: pathname component to lookup
2407 * @base: base directory to lookup from
2408 * @len: maximum length @len should be interpreted to
2410 * Note that this routine is purely a helper for filesystem usage and should
2411 * not be called by generic code.
2413 * The caller must hold base->i_mutex.
2415 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
2421 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2425 this.hash = full_name_hash(base, name, len);
2427 return ERR_PTR(-EACCES);
2429 if (unlikely(name[0] == '.')) {
2430 if (len < 2 || (len == 2 && name[1] == '.'))
2431 return ERR_PTR(-EACCES);
2435 c = *(const unsigned char *)name++;
2436 if (c == '/' || c == '\0')
2437 return ERR_PTR(-EACCES);
2440 * See if the low-level filesystem might want
2441 * to use its own hash..
2443 if (base->d_flags & DCACHE_OP_HASH) {
2444 int err = base->d_op->d_hash(base, &this);
2446 return ERR_PTR(err);
2449 err = inode_permission(base->d_inode, MAY_EXEC);
2451 return ERR_PTR(err);
2453 return __lookup_hash(&this, base, 0);
2455 EXPORT_SYMBOL(lookup_one_len);
2458 * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
2459 * @name: pathname component to lookup
2460 * @base: base directory to lookup from
2461 * @len: maximum length @len should be interpreted to
2463 * Note that this routine is purely a helper for filesystem usage and should
2464 * not be called by generic code.
2466 * Unlike lookup_one_len, it should be called without the parent
2467 * i_mutex held, and will take the i_mutex itself if necessary.
2469 struct dentry *lookup_one_len_unlocked(const char *name,
2470 struct dentry *base, int len)
2479 this.hash = full_name_hash(base, name, len);
2481 return ERR_PTR(-EACCES);
2483 if (unlikely(name[0] == '.')) {
2484 if (len < 2 || (len == 2 && name[1] == '.'))
2485 return ERR_PTR(-EACCES);
2489 c = *(const unsigned char *)name++;
2490 if (c == '/' || c == '\0')
2491 return ERR_PTR(-EACCES);
2494 * See if the low-level filesystem might want
2495 * to use its own hash..
2497 if (base->d_flags & DCACHE_OP_HASH) {
2498 int err = base->d_op->d_hash(base, &this);
2500 return ERR_PTR(err);
2503 err = inode_permission(base->d_inode, MAY_EXEC);
2505 return ERR_PTR(err);
2507 ret = lookup_dcache(&this, base, 0);
2509 ret = lookup_slow(&this, base, 0);
2512 EXPORT_SYMBOL(lookup_one_len_unlocked);
2514 #ifdef CONFIG_UNIX98_PTYS
2515 int path_pts(struct path *path)
2517 /* Find something mounted on "pts" in the same directory as
2520 struct dentry *child, *parent;
2524 ret = path_parent_directory(path);
2528 parent = path->dentry;
2531 child = d_hash_and_lookup(parent, &this);
2535 path->dentry = child;
2542 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
2543 struct path *path, int *empty)
2545 return filename_lookup(dfd, getname_flags(name, flags, empty),
2548 EXPORT_SYMBOL(user_path_at_empty);
2551 * mountpoint_last - look up last component for umount
2552 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2554 * This is a special lookup_last function just for umount. In this case, we
2555 * need to resolve the path without doing any revalidation.
2557 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2558 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2559 * in almost all cases, this lookup will be served out of the dcache. The only
2560 * cases where it won't are if nd->last refers to a symlink or the path is
2561 * bogus and it doesn't exist.
2564 * -error: if there was an error during lookup. This includes -ENOENT if the
2565 * lookup found a negative dentry.
2567 * 0: if we successfully resolved nd->last and found it to not to be a
2568 * symlink that needs to be followed.
2570 * 1: if we successfully resolved nd->last and found it to be a symlink
2571 * that needs to be followed.
2574 mountpoint_last(struct nameidata *nd)
2577 struct dentry *dir = nd->path.dentry;
2580 /* If we're in rcuwalk, drop out of it to handle last component */
2581 if (nd->flags & LOOKUP_RCU) {
2582 if (unlazy_walk(nd, NULL, 0))
2586 nd->flags &= ~LOOKUP_PARENT;
2588 if (unlikely(nd->last_type != LAST_NORM)) {
2589 error = handle_dots(nd, nd->last_type);
2592 path.dentry = dget(nd->path.dentry);
2594 path.dentry = d_lookup(dir, &nd->last);
2597 * No cached dentry. Mounted dentries are pinned in the
2598 * cache, so that means that this dentry is probably
2599 * a symlink or the path doesn't actually point
2600 * to a mounted dentry.
2602 path.dentry = lookup_slow(&nd->last, dir,
2603 nd->flags | LOOKUP_NO_REVAL);
2604 if (IS_ERR(path.dentry))
2605 return PTR_ERR(path.dentry);
2608 if (d_is_negative(path.dentry)) {
2612 path.mnt = nd->path.mnt;
2613 return step_into(nd, &path, 0, d_backing_inode(path.dentry), 0);
2617 * path_mountpoint - look up a path to be umounted
2618 * @nd: lookup context
2619 * @flags: lookup flags
2620 * @path: pointer to container for result
2622 * Look up the given name, but don't attempt to revalidate the last component.
2623 * Returns 0 and "path" will be valid on success; Returns error otherwise.
2626 path_mountpoint(struct nameidata *nd, unsigned flags, struct path *path)
2628 const char *s = path_init(nd, flags);
2632 while (!(err = link_path_walk(s, nd)) &&
2633 (err = mountpoint_last(nd)) > 0) {
2634 s = trailing_symlink(nd);
2642 nd->path.mnt = NULL;
2643 nd->path.dentry = NULL;
2651 filename_mountpoint(int dfd, struct filename *name, struct path *path,
2654 struct nameidata nd;
2657 return PTR_ERR(name);
2658 set_nameidata(&nd, dfd, name);
2659 error = path_mountpoint(&nd, flags | LOOKUP_RCU, path);
2660 if (unlikely(error == -ECHILD))
2661 error = path_mountpoint(&nd, flags, path);
2662 if (unlikely(error == -ESTALE))
2663 error = path_mountpoint(&nd, flags | LOOKUP_REVAL, path);
2665 audit_inode(name, path->dentry, 0);
2666 restore_nameidata();
2672 * user_path_mountpoint_at - lookup a path from userland in order to umount it
2673 * @dfd: directory file descriptor
2674 * @name: pathname from userland
2675 * @flags: lookup flags
2676 * @path: pointer to container to hold result
2678 * A umount is a special case for path walking. We're not actually interested
2679 * in the inode in this situation, and ESTALE errors can be a problem. We
2680 * simply want track down the dentry and vfsmount attached at the mountpoint
2681 * and avoid revalidating the last component.
2683 * Returns 0 and populates "path" on success.
2686 user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags,
2689 return filename_mountpoint(dfd, getname(name), path, flags);
2693 kern_path_mountpoint(int dfd, const char *name, struct path *path,
2696 return filename_mountpoint(dfd, getname_kernel(name), path, flags);
2698 EXPORT_SYMBOL(kern_path_mountpoint);
2700 int __check_sticky(struct inode *dir, struct inode *inode)
2702 kuid_t fsuid = current_fsuid();
2704 if (uid_eq(inode->i_uid, fsuid))
2706 if (uid_eq(dir->i_uid, fsuid))
2708 return !capable_wrt_inode_uidgid(inode, CAP_FOWNER);
2710 EXPORT_SYMBOL(__check_sticky);
2713 * Check whether we can remove a link victim from directory dir, check
2714 * whether the type of victim is right.
2715 * 1. We can't do it if dir is read-only (done in permission())
2716 * 2. We should have write and exec permissions on dir
2717 * 3. We can't remove anything from append-only dir
2718 * 4. We can't do anything with immutable dir (done in permission())
2719 * 5. If the sticky bit on dir is set we should either
2720 * a. be owner of dir, or
2721 * b. be owner of victim, or
2722 * c. have CAP_FOWNER capability
2723 * 6. If the victim is append-only or immutable we can't do antyhing with
2724 * links pointing to it.
2725 * 7. If the victim has an unknown uid or gid we can't change the inode.
2726 * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2727 * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2728 * 10. We can't remove a root or mountpoint.
2729 * 11. We don't allow removal of NFS sillyrenamed files; it's handled by
2730 * nfs_async_unlink().
2732 static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
2734 struct inode *inode = d_backing_inode(victim);
2737 if (d_is_negative(victim))
2741 BUG_ON(victim->d_parent->d_inode != dir);
2742 audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
2744 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
2750 if (check_sticky(dir, inode) || IS_APPEND(inode) ||
2751 IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) || HAS_UNMAPPED_ID(inode))
2754 if (!d_is_dir(victim))
2756 if (IS_ROOT(victim))
2758 } else if (d_is_dir(victim))
2760 if (IS_DEADDIR(dir))
2762 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2767 /* Check whether we can create an object with dentry child in directory
2769 * 1. We can't do it if child already exists (open has special treatment for
2770 * this case, but since we are inlined it's OK)
2771 * 2. We can't do it if dir is read-only (done in permission())
2772 * 3. We can't do it if the fs can't represent the fsuid or fsgid.
2773 * 4. We should have write and exec permissions on dir
2774 * 5. We can't do it if dir is immutable (done in permission())
2776 static inline int may_create(struct inode *dir, struct dentry *child)
2778 struct user_namespace *s_user_ns;
2779 audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
2782 if (IS_DEADDIR(dir))
2784 s_user_ns = dir->i_sb->s_user_ns;
2785 if (!kuid_has_mapping(s_user_ns, current_fsuid()) ||
2786 !kgid_has_mapping(s_user_ns, current_fsgid()))
2788 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
2792 * p1 and p2 should be directories on the same fs.
2794 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2799 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2803 mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
2805 p = d_ancestor(p2, p1);
2807 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
2808 inode_lock_nested(p1->d_inode, I_MUTEX_CHILD);
2812 p = d_ancestor(p1, p2);
2814 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2815 inode_lock_nested(p2->d_inode, I_MUTEX_CHILD);
2819 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2820 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
2823 EXPORT_SYMBOL(lock_rename);
2825 void unlock_rename(struct dentry *p1, struct dentry *p2)
2827 inode_unlock(p1->d_inode);
2829 inode_unlock(p2->d_inode);
2830 mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
2833 EXPORT_SYMBOL(unlock_rename);
2835 int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2838 int error = may_create(dir, dentry);
2842 if (!dir->i_op->create)
2843 return -EACCES; /* shouldn't it be ENOSYS? */
2846 error = security_inode_create(dir, dentry, mode);
2849 error = dir->i_op->create(dir, dentry, mode, want_excl);
2851 fsnotify_create(dir, dentry);
2854 EXPORT_SYMBOL(vfs_create);
2856 bool may_open_dev(const struct path *path)
2858 return !(path->mnt->mnt_flags & MNT_NODEV) &&
2859 !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV);
2862 static int may_open(const struct path *path, int acc_mode, int flag)
2864 struct dentry *dentry = path->dentry;
2865 struct inode *inode = dentry->d_inode;
2871 switch (inode->i_mode & S_IFMT) {
2875 if (acc_mode & MAY_WRITE)
2880 if (!may_open_dev(path))
2889 error = inode_permission(inode, MAY_OPEN | acc_mode);
2894 * An append-only file must be opened in append mode for writing.
2896 if (IS_APPEND(inode)) {
2897 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
2903 /* O_NOATIME can only be set by the owner or superuser */
2904 if (flag & O_NOATIME && !inode_owner_or_capable(inode))
2910 static int handle_truncate(struct file *filp)
2912 const struct path *path = &filp->f_path;
2913 struct inode *inode = path->dentry->d_inode;
2914 int error = get_write_access(inode);
2918 * Refuse to truncate files with mandatory locks held on them.
2920 error = locks_verify_locked(filp);
2922 error = security_path_truncate(path);
2924 error = do_truncate(path->dentry, 0,
2925 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
2928 put_write_access(inode);
2932 static inline int open_to_namei_flags(int flag)
2934 if ((flag & O_ACCMODE) == 3)
2939 static int may_o_create(const struct path *dir, struct dentry *dentry, umode_t mode)
2941 struct user_namespace *s_user_ns;
2942 int error = security_path_mknod(dir, dentry, mode, 0);
2946 s_user_ns = dir->dentry->d_sb->s_user_ns;
2947 if (!kuid_has_mapping(s_user_ns, current_fsuid()) ||
2948 !kgid_has_mapping(s_user_ns, current_fsgid()))
2951 error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
2955 return security_inode_create(dir->dentry->d_inode, dentry, mode);
2959 * Attempt to atomically look up, create and open a file from a negative
2962 * Returns 0 if successful. The file will have been created and attached to
2963 * @file by the filesystem calling finish_open().
2965 * Returns 1 if the file was looked up only or didn't need creating. The
2966 * caller will need to perform the open themselves. @path will have been
2967 * updated to point to the new dentry. This may be negative.
2969 * Returns an error code otherwise.
2971 static int atomic_open(struct nameidata *nd, struct dentry *dentry,
2972 struct path *path, struct file *file,
2973 const struct open_flags *op,
2974 int open_flag, umode_t mode,
2977 struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
2978 struct inode *dir = nd->path.dentry->d_inode;
2981 if (!(~open_flag & (O_EXCL | O_CREAT))) /* both O_EXCL and O_CREAT */
2982 open_flag &= ~O_TRUNC;
2984 if (nd->flags & LOOKUP_DIRECTORY)
2985 open_flag |= O_DIRECTORY;
2987 file->f_path.dentry = DENTRY_NOT_SET;
2988 file->f_path.mnt = nd->path.mnt;
2989 error = dir->i_op->atomic_open(dir, dentry, file,
2990 open_to_namei_flags(open_flag),
2992 d_lookup_done(dentry);
2995 * We didn't have the inode before the open, so check open
2998 int acc_mode = op->acc_mode;
2999 if (*opened & FILE_CREATED) {
3000 WARN_ON(!(open_flag & O_CREAT));
3001 fsnotify_create(dir, dentry);
3004 error = may_open(&file->f_path, acc_mode, open_flag);
3005 if (WARN_ON(error > 0))
3007 } else if (error > 0) {
3008 if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
3011 if (file->f_path.dentry) {
3013 dentry = file->f_path.dentry;
3015 if (*opened & FILE_CREATED)
3016 fsnotify_create(dir, dentry);
3017 if (unlikely(d_is_negative(dentry))) {
3020 path->dentry = dentry;
3021 path->mnt = nd->path.mnt;
3031 * Look up and maybe create and open the last component.
3033 * Must be called with i_mutex held on parent.
3035 * Returns 0 if the file was successfully atomically created (if necessary) and
3036 * opened. In this case the file will be returned attached to @file.
3038 * Returns 1 if the file was not completely opened at this time, though lookups
3039 * and creations will have been performed and the dentry returned in @path will
3040 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
3041 * specified then a negative dentry may be returned.
3043 * An error code is returned otherwise.
3045 * FILE_CREATE will be set in @*opened if the dentry was created and will be
3046 * cleared otherwise prior to returning.
3048 static int lookup_open(struct nameidata *nd, struct path *path,
3050 const struct open_flags *op,
3051 bool got_write, int *opened)
3053 struct dentry *dir = nd->path.dentry;
3054 struct inode *dir_inode = dir->d_inode;
3055 int open_flag = op->open_flag;
3056 struct dentry *dentry;
3057 int error, create_error = 0;
3058 umode_t mode = op->mode;
3059 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
3061 if (unlikely(IS_DEADDIR(dir_inode)))
3064 *opened &= ~FILE_CREATED;
3065 dentry = d_lookup(dir, &nd->last);
3068 dentry = d_alloc_parallel(dir, &nd->last, &wq);
3070 return PTR_ERR(dentry);
3072 if (d_in_lookup(dentry))
3075 if (!(dentry->d_flags & DCACHE_OP_REVALIDATE))
3078 error = d_revalidate(dentry, nd->flags);
3079 if (likely(error > 0))
3083 d_invalidate(dentry);
3087 if (dentry->d_inode) {
3088 /* Cached positive dentry: will open in f_op->open */
3093 * Checking write permission is tricky, bacuse we don't know if we are
3094 * going to actually need it: O_CREAT opens should work as long as the
3095 * file exists. But checking existence breaks atomicity. The trick is
3096 * to check access and if not granted clear O_CREAT from the flags.
3098 * Another problem is returing the "right" error value (e.g. for an
3099 * O_EXCL open we want to return EEXIST not EROFS).
3101 if (open_flag & O_CREAT) {
3102 if (!IS_POSIXACL(dir->d_inode))
3103 mode &= ~current_umask();
3104 if (unlikely(!got_write)) {
3105 create_error = -EROFS;
3106 open_flag &= ~O_CREAT;
3107 if (open_flag & (O_EXCL | O_TRUNC))
3109 /* No side effects, safe to clear O_CREAT */
3111 create_error = may_o_create(&nd->path, dentry, mode);
3113 open_flag &= ~O_CREAT;
3114 if (open_flag & O_EXCL)
3118 } else if ((open_flag & (O_TRUNC|O_WRONLY|O_RDWR)) &&
3119 unlikely(!got_write)) {
3121 * No O_CREATE -> atomicity not a requirement -> fall
3122 * back to lookup + open
3127 if (dir_inode->i_op->atomic_open) {
3128 error = atomic_open(nd, dentry, path, file, op, open_flag,
3130 if (unlikely(error == -ENOENT) && create_error)
3131 error = create_error;
3136 if (d_in_lookup(dentry)) {
3137 struct dentry *res = dir_inode->i_op->lookup(dir_inode, dentry,
3139 d_lookup_done(dentry);
3140 if (unlikely(res)) {
3142 error = PTR_ERR(res);
3150 /* Negative dentry, just create the file */
3151 if (!dentry->d_inode && (open_flag & O_CREAT)) {
3152 *opened |= FILE_CREATED;
3153 audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);
3154 if (!dir_inode->i_op->create) {
3158 error = dir_inode->i_op->create(dir_inode, dentry, mode,
3159 open_flag & O_EXCL);
3162 fsnotify_create(dir_inode, dentry);
3164 if (unlikely(create_error) && !dentry->d_inode) {
3165 error = create_error;
3169 path->dentry = dentry;
3170 path->mnt = nd->path.mnt;
3179 * Handle the last step of open()
3181 static int do_last(struct nameidata *nd,
3182 struct file *file, const struct open_flags *op,
3185 struct dentry *dir = nd->path.dentry;
3186 int open_flag = op->open_flag;
3187 bool will_truncate = (open_flag & O_TRUNC) != 0;
3188 bool got_write = false;
3189 int acc_mode = op->acc_mode;
3191 struct inode *inode;
3195 nd->flags &= ~LOOKUP_PARENT;
3196 nd->flags |= op->intent;
3198 if (nd->last_type != LAST_NORM) {
3199 error = handle_dots(nd, nd->last_type);
3200 if (unlikely(error))
3205 if (!(open_flag & O_CREAT)) {
3206 if (nd->last.name[nd->last.len])
3207 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
3208 /* we _can_ be in RCU mode here */
3209 error = lookup_fast(nd, &path, &inode, &seq);
3210 if (likely(error > 0))
3216 BUG_ON(nd->inode != dir->d_inode);
3217 BUG_ON(nd->flags & LOOKUP_RCU);
3219 /* create side of things */
3221 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
3222 * has been cleared when we got to the last component we are
3225 error = complete_walk(nd);
3229 audit_inode(nd->name, dir, LOOKUP_PARENT);
3230 /* trailing slashes? */
3231 if (unlikely(nd->last.name[nd->last.len]))
3235 if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
3236 error = mnt_want_write(nd->path.mnt);
3240 * do _not_ fail yet - we might not need that or fail with
3241 * a different error; let lookup_open() decide; we'll be
3242 * dropping this one anyway.
3245 if (open_flag & O_CREAT)
3246 inode_lock(dir->d_inode);
3248 inode_lock_shared(dir->d_inode);
3249 error = lookup_open(nd, &path, file, op, got_write, opened);
3250 if (open_flag & O_CREAT)
3251 inode_unlock(dir->d_inode);
3253 inode_unlock_shared(dir->d_inode);
3259 if ((*opened & FILE_CREATED) ||
3260 !S_ISREG(file_inode(file)->i_mode))
3261 will_truncate = false;
3263 audit_inode(nd->name, file->f_path.dentry, 0);
3267 if (*opened & FILE_CREATED) {
3268 /* Don't check for write permission, don't truncate */
3269 open_flag &= ~O_TRUNC;
3270 will_truncate = false;
3272 path_to_nameidata(&path, nd);
3273 goto finish_open_created;
3277 * If atomic_open() acquired write access it is dropped now due to
3278 * possible mount and symlink following (this might be optimized away if
3282 mnt_drop_write(nd->path.mnt);
3286 error = follow_managed(&path, nd);
3287 if (unlikely(error < 0))
3290 if (unlikely(d_is_negative(path.dentry))) {
3291 path_to_nameidata(&path, nd);
3296 * create/update audit record if it already exists.
3298 audit_inode(nd->name, path.dentry, 0);
3300 if (unlikely((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))) {
3301 path_to_nameidata(&path, nd);
3305 seq = 0; /* out of RCU mode, so the value doesn't matter */
3306 inode = d_backing_inode(path.dentry);
3308 error = step_into(nd, &path, 0, inode, seq);
3309 if (unlikely(error))
3312 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3313 error = complete_walk(nd);
3316 audit_inode(nd->name, nd->path.dentry, 0);
3318 if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry))
3321 if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
3323 if (!d_is_reg(nd->path.dentry))
3324 will_truncate = false;
3326 if (will_truncate) {
3327 error = mnt_want_write(nd->path.mnt);
3332 finish_open_created:
3333 error = may_open(&nd->path, acc_mode, open_flag);
3336 BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
3337 error = vfs_open(&nd->path, file, current_cred());
3340 *opened |= FILE_OPENED;
3342 error = open_check_o_direct(file);
3344 error = ima_file_check(file, op->acc_mode, *opened);
3345 if (!error && will_truncate)
3346 error = handle_truncate(file);
3348 if (unlikely(error) && (*opened & FILE_OPENED))
3350 if (unlikely(error > 0)) {
3355 mnt_drop_write(nd->path.mnt);
3359 static int do_tmpfile(struct nameidata *nd, unsigned flags,
3360 const struct open_flags *op,
3361 struct file *file, int *opened)
3363 static const struct qstr name = QSTR_INIT("/", 1);
3364 struct dentry *child;
3367 int error = path_lookupat(nd, flags | LOOKUP_DIRECTORY, &path);
3368 if (unlikely(error))
3370 error = mnt_want_write(path.mnt);
3371 if (unlikely(error))
3373 dir = path.dentry->d_inode;
3374 /* we want directory to be writable */
3375 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
3378 if (!dir->i_op->tmpfile) {
3379 error = -EOPNOTSUPP;
3382 child = d_alloc(path.dentry, &name);
3383 if (unlikely(!child)) {
3388 path.dentry = child;
3389 error = dir->i_op->tmpfile(dir, child, op->mode);
3392 audit_inode(nd->name, child, 0);
3393 /* Don't check for other permissions, the inode was just created */
3394 error = may_open(&path, 0, op->open_flag);
3397 file->f_path.mnt = path.mnt;
3398 error = finish_open(file, child, NULL, opened);
3401 error = open_check_o_direct(file);
3404 } else if (!(op->open_flag & O_EXCL)) {
3405 struct inode *inode = file_inode(file);
3406 spin_lock(&inode->i_lock);
3407 inode->i_state |= I_LINKABLE;
3408 spin_unlock(&inode->i_lock);
3411 mnt_drop_write(path.mnt);
3417 static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file)
3420 int error = path_lookupat(nd, flags, &path);
3422 audit_inode(nd->name, path.dentry, 0);
3423 error = vfs_open(&path, file, current_cred());
3429 static struct file *path_openat(struct nameidata *nd,
3430 const struct open_flags *op, unsigned flags)
3437 file = get_empty_filp();
3441 file->f_flags = op->open_flag;
3443 if (unlikely(file->f_flags & __O_TMPFILE)) {
3444 error = do_tmpfile(nd, flags, op, file, &opened);
3448 if (unlikely(file->f_flags & O_PATH)) {
3449 error = do_o_path(nd, flags, file);
3451 opened |= FILE_OPENED;
3455 s = path_init(nd, flags);
3460 while (!(error = link_path_walk(s, nd)) &&
3461 (error = do_last(nd, file, op, &opened)) > 0) {
3462 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
3463 s = trailing_symlink(nd);
3471 if (!(opened & FILE_OPENED)) {
3475 if (unlikely(error)) {
3476 if (error == -EOPENSTALE) {
3477 if (flags & LOOKUP_RCU)
3482 file = ERR_PTR(error);
3487 struct file *do_filp_open(int dfd, struct filename *pathname,
3488 const struct open_flags *op)
3490 struct nameidata nd;
3491 int flags = op->lookup_flags;
3494 set_nameidata(&nd, dfd, pathname);
3495 filp = path_openat(&nd, op, flags | LOOKUP_RCU);
3496 if (unlikely(filp == ERR_PTR(-ECHILD)))
3497 filp = path_openat(&nd, op, flags);
3498 if (unlikely(filp == ERR_PTR(-ESTALE)))
3499 filp = path_openat(&nd, op, flags | LOOKUP_REVAL);
3500 restore_nameidata();
3504 struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
3505 const char *name, const struct open_flags *op)
3507 struct nameidata nd;
3509 struct filename *filename;
3510 int flags = op->lookup_flags | LOOKUP_ROOT;
3513 nd.root.dentry = dentry;
3515 if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN)
3516 return ERR_PTR(-ELOOP);
3518 filename = getname_kernel(name);
3519 if (IS_ERR(filename))
3520 return ERR_CAST(filename);
3522 set_nameidata(&nd, -1, filename);
3523 file = path_openat(&nd, op, flags | LOOKUP_RCU);
3524 if (unlikely(file == ERR_PTR(-ECHILD)))
3525 file = path_openat(&nd, op, flags);
3526 if (unlikely(file == ERR_PTR(-ESTALE)))
3527 file = path_openat(&nd, op, flags | LOOKUP_REVAL);
3528 restore_nameidata();
3533 static struct dentry *filename_create(int dfd, struct filename *name,
3534 struct path *path, unsigned int lookup_flags)
3536 struct dentry *dentry = ERR_PTR(-EEXIST);
3541 bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
3544 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3545 * other flags passed in are ignored!
3547 lookup_flags &= LOOKUP_REVAL;
3549 name = filename_parentat(dfd, name, lookup_flags, path, &last, &type);
3551 return ERR_CAST(name);
3554 * Yucky last component or no last component at all?
3555 * (foo/., foo/.., /////)
3557 if (unlikely(type != LAST_NORM))
3560 /* don't fail immediately if it's r/o, at least try to report other errors */
3561 err2 = mnt_want_write(path->mnt);
3563 * Do the final lookup.
3565 lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL;
3566 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
3567 dentry = __lookup_hash(&last, path->dentry, lookup_flags);
3572 if (d_is_positive(dentry))
3576 * Special case - lookup gave negative, but... we had foo/bar/
3577 * From the vfs_mknod() POV we just have a negative dentry -
3578 * all is fine. Let's be bastards - you had / on the end, you've
3579 * been asking for (non-existent) directory. -ENOENT for you.
3581 if (unlikely(!is_dir && last.name[last.len])) {
3585 if (unlikely(err2)) {
3593 dentry = ERR_PTR(error);
3595 inode_unlock(path->dentry->d_inode);
3597 mnt_drop_write(path->mnt);
3604 struct dentry *kern_path_create(int dfd, const char *pathname,
3605 struct path *path, unsigned int lookup_flags)
3607 return filename_create(dfd, getname_kernel(pathname),
3608 path, lookup_flags);
3610 EXPORT_SYMBOL(kern_path_create);
3612 void done_path_create(struct path *path, struct dentry *dentry)
3615 inode_unlock(path->dentry->d_inode);
3616 mnt_drop_write(path->mnt);
3619 EXPORT_SYMBOL(done_path_create);
3621 inline struct dentry *user_path_create(int dfd, const char __user *pathname,
3622 struct path *path, unsigned int lookup_flags)
3624 return filename_create(dfd, getname(pathname), path, lookup_flags);
3626 EXPORT_SYMBOL(user_path_create);
3628 int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
3630 int error = may_create(dir, dentry);
3635 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
3638 if (!dir->i_op->mknod)
3641 error = devcgroup_inode_mknod(mode, dev);
3645 error = security_inode_mknod(dir, dentry, mode, dev);
3649 error = dir->i_op->mknod(dir, dentry, mode, dev);
3651 fsnotify_create(dir, dentry);
3654 EXPORT_SYMBOL(vfs_mknod);
3656 static int may_mknod(umode_t mode)
3658 switch (mode & S_IFMT) {
3664 case 0: /* zero mode translates to S_IFREG */
3673 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
3676 struct dentry *dentry;
3679 unsigned int lookup_flags = 0;
3681 error = may_mknod(mode);
3685 dentry = user_path_create(dfd, filename, &path, lookup_flags);
3687 return PTR_ERR(dentry);
3689 if (!IS_POSIXACL(path.dentry->d_inode))
3690 mode &= ~current_umask();
3691 error = security_path_mknod(&path, dentry, mode, dev);
3694 switch (mode & S_IFMT) {
3695 case 0: case S_IFREG:
3696 error = vfs_create(path.dentry->d_inode,dentry,mode,true);
3698 ima_post_path_mknod(dentry);
3700 case S_IFCHR: case S_IFBLK:
3701 error = vfs_mknod(path.dentry->d_inode,dentry,mode,
3702 new_decode_dev(dev));
3704 case S_IFIFO: case S_IFSOCK:
3705 error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
3709 done_path_create(&path, dentry);
3710 if (retry_estale(error, lookup_flags)) {
3711 lookup_flags |= LOOKUP_REVAL;
3717 SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
3719 return sys_mknodat(AT_FDCWD, filename, mode, dev);
3722 int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
3724 int error = may_create(dir, dentry);
3725 unsigned max_links = dir->i_sb->s_max_links;
3730 if (!dir->i_op->mkdir)
3733 mode &= (S_IRWXUGO|S_ISVTX);
3734 error = security_inode_mkdir(dir, dentry, mode);
3738 if (max_links && dir->i_nlink >= max_links)
3741 error = dir->i_op->mkdir(dir, dentry, mode);
3743 fsnotify_mkdir(dir, dentry);
3746 EXPORT_SYMBOL(vfs_mkdir);
3748 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
3750 struct dentry *dentry;
3753 unsigned int lookup_flags = LOOKUP_DIRECTORY;
3756 dentry = user_path_create(dfd, pathname, &path, lookup_flags);
3758 return PTR_ERR(dentry);
3760 if (!IS_POSIXACL(path.dentry->d_inode))
3761 mode &= ~current_umask();
3762 error = security_path_mkdir(&path, dentry, mode);
3764 error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
3765 done_path_create(&path, dentry);
3766 if (retry_estale(error, lookup_flags)) {
3767 lookup_flags |= LOOKUP_REVAL;
3773 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
3775 return sys_mkdirat(AT_FDCWD, pathname, mode);
3778 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
3780 int error = may_delete(dir, dentry, 1);
3785 if (!dir->i_op->rmdir)
3789 inode_lock(dentry->d_inode);
3792 if (is_local_mountpoint(dentry))
3795 error = security_inode_rmdir(dir, dentry);
3799 shrink_dcache_parent(dentry);
3800 error = dir->i_op->rmdir(dir, dentry);
3804 dentry->d_inode->i_flags |= S_DEAD;
3806 detach_mounts(dentry);
3809 inode_unlock(dentry->d_inode);
3815 EXPORT_SYMBOL(vfs_rmdir);
3817 static long do_rmdir(int dfd, const char __user *pathname)
3820 struct filename *name;
3821 struct dentry *dentry;
3825 unsigned int lookup_flags = 0;
3827 name = filename_parentat(dfd, getname(pathname), lookup_flags,
3828 &path, &last, &type);
3830 return PTR_ERR(name);
3844 error = mnt_want_write(path.mnt);
3848 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
3849 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
3850 error = PTR_ERR(dentry);
3853 if (!dentry->d_inode) {
3857 error = security_path_rmdir(&path, dentry);
3860 error = vfs_rmdir(path.dentry->d_inode, dentry);
3864 inode_unlock(path.dentry->d_inode);
3865 mnt_drop_write(path.mnt);
3869 if (retry_estale(error, lookup_flags)) {
3870 lookup_flags |= LOOKUP_REVAL;
3876 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
3878 return do_rmdir(AT_FDCWD, pathname);
3882 * vfs_unlink - unlink a filesystem object
3883 * @dir: parent directory
3885 * @delegated_inode: returns victim inode, if the inode is delegated.
3887 * The caller must hold dir->i_mutex.
3889 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
3890 * return a reference to the inode in delegated_inode. The caller
3891 * should then break the delegation on that inode and retry. Because
3892 * breaking a delegation may take a long time, the caller should drop
3893 * dir->i_mutex before doing so.
3895 * Alternatively, a caller may pass NULL for delegated_inode. This may
3896 * be appropriate for callers that expect the underlying filesystem not
3897 * to be NFS exported.
3899 int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode)
3901 struct inode *target = dentry->d_inode;
3902 int error = may_delete(dir, dentry, 0);
3907 if (!dir->i_op->unlink)
3911 if (is_local_mountpoint(dentry))
3914 error = security_inode_unlink(dir, dentry);
3916 error = try_break_deleg(target, delegated_inode);
3919 error = dir->i_op->unlink(dir, dentry);
3922 detach_mounts(dentry);
3927 inode_unlock(target);
3929 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3930 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
3931 fsnotify_link_count(target);
3937 EXPORT_SYMBOL(vfs_unlink);
3940 * Make sure that the actual truncation of the file will occur outside its
3941 * directory's i_mutex. Truncate can take a long time if there is a lot of
3942 * writeout happening, and we don't want to prevent access to the directory
3943 * while waiting on the I/O.
3945 static long do_unlinkat(int dfd, const char __user *pathname)
3948 struct filename *name;
3949 struct dentry *dentry;
3953 struct inode *inode = NULL;
3954 struct inode *delegated_inode = NULL;
3955 unsigned int lookup_flags = 0;
3957 name = filename_parentat(dfd, getname(pathname), lookup_flags,
3958 &path, &last, &type);
3960 return PTR_ERR(name);
3963 if (type != LAST_NORM)
3966 error = mnt_want_write(path.mnt);
3970 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
3971 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
3972 error = PTR_ERR(dentry);
3973 if (!IS_ERR(dentry)) {
3974 /* Why not before? Because we want correct error value */
3975 if (last.name[last.len])
3977 inode = dentry->d_inode;
3978 if (d_is_negative(dentry))
3981 error = security_path_unlink(&path, dentry);
3984 error = vfs_unlink(path.dentry->d_inode, dentry, &delegated_inode);
3988 inode_unlock(path.dentry->d_inode);
3990 iput(inode); /* truncate the inode here */
3992 if (delegated_inode) {
3993 error = break_deleg_wait(&delegated_inode);
3997 mnt_drop_write(path.mnt);
4001 if (retry_estale(error, lookup_flags)) {
4002 lookup_flags |= LOOKUP_REVAL;
4009 if (d_is_negative(dentry))
4011 else if (d_is_dir(dentry))
4018 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
4020 if ((flag & ~AT_REMOVEDIR) != 0)
4023 if (flag & AT_REMOVEDIR)
4024 return do_rmdir(dfd, pathname);
4026 return do_unlinkat(dfd, pathname);
4029 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
4031 return do_unlinkat(AT_FDCWD, pathname);
4034 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
4036 int error = may_create(dir, dentry);
4041 if (!dir->i_op->symlink)
4044 error = security_inode_symlink(dir, dentry, oldname);
4048 error = dir->i_op->symlink(dir, dentry, oldname);
4050 fsnotify_create(dir, dentry);
4053 EXPORT_SYMBOL(vfs_symlink);
4055 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
4056 int, newdfd, const char __user *, newname)
4059 struct filename *from;
4060 struct dentry *dentry;
4062 unsigned int lookup_flags = 0;
4064 from = getname(oldname);
4066 return PTR_ERR(from);
4068 dentry = user_path_create(newdfd, newname, &path, lookup_flags);
4069 error = PTR_ERR(dentry);
4073 error = security_path_symlink(&path, dentry, from->name);
4075 error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
4076 done_path_create(&path, dentry);
4077 if (retry_estale(error, lookup_flags)) {
4078 lookup_flags |= LOOKUP_REVAL;
4086 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
4088 return sys_symlinkat(oldname, AT_FDCWD, newname);
4092 * vfs_link - create a new link
4093 * @old_dentry: object to be linked
4095 * @new_dentry: where to create the new link
4096 * @delegated_inode: returns inode needing a delegation break
4098 * The caller must hold dir->i_mutex
4100 * If vfs_link discovers a delegation on the to-be-linked file in need
4101 * of breaking, it will return -EWOULDBLOCK and return a reference to the
4102 * inode in delegated_inode. The caller should then break the delegation
4103 * and retry. Because breaking a delegation may take a long time, the
4104 * caller should drop the i_mutex before doing so.
4106 * Alternatively, a caller may pass NULL for delegated_inode. This may
4107 * be appropriate for callers that expect the underlying filesystem not
4108 * to be NFS exported.
4110 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode)
4112 struct inode *inode = old_dentry->d_inode;
4113 unsigned max_links = dir->i_sb->s_max_links;
4119 error = may_create(dir, new_dentry);
4123 if (dir->i_sb != inode->i_sb)
4127 * A link to an append-only or immutable file cannot be created.
4129 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
4132 * Updating the link count will likely cause i_uid and i_gid to
4133 * be writen back improperly if their true value is unknown to
4136 if (HAS_UNMAPPED_ID(inode))
4138 if (!dir->i_op->link)
4140 if (S_ISDIR(inode->i_mode))
4143 error = security_inode_link(old_dentry, dir, new_dentry);
4148 /* Make sure we don't allow creating hardlink to an unlinked file */
4149 if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
4151 else if (max_links && inode->i_nlink >= max_links)
4154 error = try_break_deleg(inode, delegated_inode);
4156 error = dir->i_op->link(old_dentry, dir, new_dentry);
4159 if (!error && (inode->i_state & I_LINKABLE)) {
4160 spin_lock(&inode->i_lock);
4161 inode->i_state &= ~I_LINKABLE;
4162 spin_unlock(&inode->i_lock);
4164 inode_unlock(inode);
4166 fsnotify_link(dir, inode, new_dentry);
4169 EXPORT_SYMBOL(vfs_link);
4172 * Hardlinks are often used in delicate situations. We avoid
4173 * security-related surprises by not following symlinks on the
4176 * We don't follow them on the oldname either to be compatible
4177 * with linux 2.0, and to avoid hard-linking to directories
4178 * and other special files. --ADM
4180 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
4181 int, newdfd, const char __user *, newname, int, flags)
4183 struct dentry *new_dentry;
4184 struct path old_path, new_path;
4185 struct inode *delegated_inode = NULL;
4189 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
4192 * To use null names we require CAP_DAC_READ_SEARCH
4193 * This ensures that not everyone will be able to create
4194 * handlink using the passed filedescriptor.
4196 if (flags & AT_EMPTY_PATH) {
4197 if (!capable(CAP_DAC_READ_SEARCH))
4202 if (flags & AT_SYMLINK_FOLLOW)
4203 how |= LOOKUP_FOLLOW;
4205 error = user_path_at(olddfd, oldname, how, &old_path);
4209 new_dentry = user_path_create(newdfd, newname, &new_path,
4210 (how & LOOKUP_REVAL));
4211 error = PTR_ERR(new_dentry);
4212 if (IS_ERR(new_dentry))
4216 if (old_path.mnt != new_path.mnt)
4218 error = may_linkat(&old_path);
4219 if (unlikely(error))
4221 error = security_path_link(old_path.dentry, &new_path, new_dentry);
4224 error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, &delegated_inode);
4226 done_path_create(&new_path, new_dentry);
4227 if (delegated_inode) {
4228 error = break_deleg_wait(&delegated_inode);
4230 path_put(&old_path);
4234 if (retry_estale(error, how)) {
4235 path_put(&old_path);
4236 how |= LOOKUP_REVAL;
4240 path_put(&old_path);
4245 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
4247 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
4251 * vfs_rename - rename a filesystem object
4252 * @old_dir: parent of source
4253 * @old_dentry: source
4254 * @new_dir: parent of destination
4255 * @new_dentry: destination
4256 * @delegated_inode: returns an inode needing a delegation break
4257 * @flags: rename flags
4259 * The caller must hold multiple mutexes--see lock_rename()).
4261 * If vfs_rename discovers a delegation in need of breaking at either
4262 * the source or destination, it will return -EWOULDBLOCK and return a
4263 * reference to the inode in delegated_inode. The caller should then
4264 * break the delegation and retry. Because breaking a delegation may
4265 * take a long time, the caller should drop all locks before doing
4268 * Alternatively, a caller may pass NULL for delegated_inode. This may
4269 * be appropriate for callers that expect the underlying filesystem not
4270 * to be NFS exported.
4272 * The worst of all namespace operations - renaming directory. "Perverted"
4273 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4275 * a) we can get into loop creation.
4276 * b) race potential - two innocent renames can create a loop together.
4277 * That's where 4.4 screws up. Current fix: serialization on
4278 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4280 * c) we have to lock _four_ objects - parents and victim (if it exists),
4281 * and source (if it is not a directory).
4282 * And that - after we got ->i_mutex on parents (until then we don't know
4283 * whether the target exists). Solution: try to be smart with locking
4284 * order for inodes. We rely on the fact that tree topology may change
4285 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4286 * move will be locked. Thus we can rank directories by the tree
4287 * (ancestors first) and rank all non-directories after them.
4288 * That works since everybody except rename does "lock parent, lookup,
4289 * lock child" and rename is under ->s_vfs_rename_mutex.
4290 * HOWEVER, it relies on the assumption that any object with ->lookup()
4291 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4292 * we'd better make sure that there's no link(2) for them.
4293 * d) conversion from fhandle to dentry may come in the wrong moment - when
4294 * we are removing the target. Solution: we will have to grab ->i_mutex
4295 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4296 * ->i_mutex on parents, which works but leads to some truly excessive
4299 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
4300 struct inode *new_dir, struct dentry *new_dentry,
4301 struct inode **delegated_inode, unsigned int flags)
4304 bool is_dir = d_is_dir(old_dentry);
4305 const unsigned char *old_name;
4306 struct inode *source = old_dentry->d_inode;
4307 struct inode *target = new_dentry->d_inode;
4308 bool new_is_dir = false;
4309 unsigned max_links = new_dir->i_sb->s_max_links;
4311 if (source == target)
4314 error = may_delete(old_dir, old_dentry, is_dir);
4319 error = may_create(new_dir, new_dentry);
4321 new_is_dir = d_is_dir(new_dentry);
4323 if (!(flags & RENAME_EXCHANGE))
4324 error = may_delete(new_dir, new_dentry, is_dir);
4326 error = may_delete(new_dir, new_dentry, new_is_dir);
4331 if (!old_dir->i_op->rename)
4335 * If we are going to change the parent - check write permissions,
4336 * we'll need to flip '..'.
4338 if (new_dir != old_dir) {
4340 error = inode_permission(source, MAY_WRITE);
4344 if ((flags & RENAME_EXCHANGE) && new_is_dir) {
4345 error = inode_permission(target, MAY_WRITE);
4351 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
4356 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
4358 if (!is_dir || (flags & RENAME_EXCHANGE))
4359 lock_two_nondirectories(source, target);
4364 if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry))
4367 if (max_links && new_dir != old_dir) {
4369 if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
4371 if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
4372 old_dir->i_nlink >= max_links)
4375 if (is_dir && !(flags & RENAME_EXCHANGE) && target)
4376 shrink_dcache_parent(new_dentry);
4378 error = try_break_deleg(source, delegated_inode);
4382 if (target && !new_is_dir) {
4383 error = try_break_deleg(target, delegated_inode);
4387 error = old_dir->i_op->rename(old_dir, old_dentry,
4388 new_dir, new_dentry, flags);
4392 if (!(flags & RENAME_EXCHANGE) && target) {
4394 target->i_flags |= S_DEAD;
4395 dont_mount(new_dentry);
4396 detach_mounts(new_dentry);
4398 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
4399 if (!(flags & RENAME_EXCHANGE))
4400 d_move(old_dentry, new_dentry);
4402 d_exchange(old_dentry, new_dentry);
4405 if (!is_dir || (flags & RENAME_EXCHANGE))
4406 unlock_two_nondirectories(source, target);
4408 inode_unlock(target);
4411 fsnotify_move(old_dir, new_dir, old_name, is_dir,
4412 !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
4413 if (flags & RENAME_EXCHANGE) {
4414 fsnotify_move(new_dir, old_dir, old_dentry->d_name.name,
4415 new_is_dir, NULL, new_dentry);
4418 fsnotify_oldname_free(old_name);
4422 EXPORT_SYMBOL(vfs_rename);
4424 SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
4425 int, newdfd, const char __user *, newname, unsigned int, flags)
4427 struct dentry *old_dentry, *new_dentry;
4428 struct dentry *trap;
4429 struct path old_path, new_path;
4430 struct qstr old_last, new_last;
4431 int old_type, new_type;
4432 struct inode *delegated_inode = NULL;
4433 struct filename *from;
4434 struct filename *to;
4435 unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET;
4436 bool should_retry = false;
4439 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
4442 if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
4443 (flags & RENAME_EXCHANGE))
4446 if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD))
4449 if (flags & RENAME_EXCHANGE)
4453 from = filename_parentat(olddfd, getname(oldname), lookup_flags,
4454 &old_path, &old_last, &old_type);
4456 error = PTR_ERR(from);
4460 to = filename_parentat(newdfd, getname(newname), lookup_flags,
4461 &new_path, &new_last, &new_type);
4463 error = PTR_ERR(to);
4468 if (old_path.mnt != new_path.mnt)
4472 if (old_type != LAST_NORM)
4475 if (flags & RENAME_NOREPLACE)
4477 if (new_type != LAST_NORM)
4480 error = mnt_want_write(old_path.mnt);
4485 trap = lock_rename(new_path.dentry, old_path.dentry);
4487 old_dentry = __lookup_hash(&old_last, old_path.dentry, lookup_flags);
4488 error = PTR_ERR(old_dentry);
4489 if (IS_ERR(old_dentry))
4491 /* source must exist */
4493 if (d_is_negative(old_dentry))
4495 new_dentry = __lookup_hash(&new_last, new_path.dentry, lookup_flags | target_flags);
4496 error = PTR_ERR(new_dentry);
4497 if (IS_ERR(new_dentry))
4500 if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
4502 if (flags & RENAME_EXCHANGE) {
4504 if (d_is_negative(new_dentry))
4507 if (!d_is_dir(new_dentry)) {
4509 if (new_last.name[new_last.len])
4513 /* unless the source is a directory trailing slashes give -ENOTDIR */
4514 if (!d_is_dir(old_dentry)) {
4516 if (old_last.name[old_last.len])
4518 if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len])
4521 /* source should not be ancestor of target */
4523 if (old_dentry == trap)
4525 /* target should not be an ancestor of source */
4526 if (!(flags & RENAME_EXCHANGE))
4528 if (new_dentry == trap)
4531 error = security_path_rename(&old_path, old_dentry,
4532 &new_path, new_dentry, flags);
4535 error = vfs_rename(old_path.dentry->d_inode, old_dentry,
4536 new_path.dentry->d_inode, new_dentry,
4537 &delegated_inode, flags);
4543 unlock_rename(new_path.dentry, old_path.dentry);
4544 if (delegated_inode) {
4545 error = break_deleg_wait(&delegated_inode);
4549 mnt_drop_write(old_path.mnt);
4551 if (retry_estale(error, lookup_flags))
4552 should_retry = true;
4553 path_put(&new_path);
4556 path_put(&old_path);
4559 should_retry = false;
4560 lookup_flags |= LOOKUP_REVAL;
4567 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
4568 int, newdfd, const char __user *, newname)
4570 return sys_renameat2(olddfd, oldname, newdfd, newname, 0);
4573 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
4575 return sys_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
4578 int vfs_whiteout(struct inode *dir, struct dentry *dentry)
4580 int error = may_create(dir, dentry);
4584 if (!dir->i_op->mknod)
4587 return dir->i_op->mknod(dir, dentry,
4588 S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
4590 EXPORT_SYMBOL(vfs_whiteout);
4592 int readlink_copy(char __user *buffer, int buflen, const char *link)
4594 int len = PTR_ERR(link);
4599 if (len > (unsigned) buflen)
4601 if (copy_to_user(buffer, link, len))
4608 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
4609 * have ->get_link() not calling nd_jump_link(). Using (or not using) it
4610 * for any given inode is up to filesystem.
4612 static int generic_readlink(struct dentry *dentry, char __user *buffer,
4615 DEFINE_DELAYED_CALL(done);
4616 struct inode *inode = d_inode(dentry);
4617 const char *link = inode->i_link;
4621 link = inode->i_op->get_link(dentry, inode, &done);
4623 return PTR_ERR(link);
4625 res = readlink_copy(buffer, buflen, link);
4626 do_delayed_call(&done);
4631 * vfs_readlink - copy symlink body into userspace buffer
4632 * @dentry: dentry on which to get symbolic link
4633 * @buffer: user memory pointer
4634 * @buflen: size of buffer
4636 * Does not touch atime. That's up to the caller if necessary
4638 * Does not call security hook.
4640 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4642 struct inode *inode = d_inode(dentry);
4644 if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) {
4645 if (unlikely(inode->i_op->readlink))
4646 return inode->i_op->readlink(dentry, buffer, buflen);
4648 if (!d_is_symlink(dentry))
4651 spin_lock(&inode->i_lock);
4652 inode->i_opflags |= IOP_DEFAULT_READLINK;
4653 spin_unlock(&inode->i_lock);
4656 return generic_readlink(dentry, buffer, buflen);
4658 EXPORT_SYMBOL(vfs_readlink);
4661 * vfs_get_link - get symlink body
4662 * @dentry: dentry on which to get symbolic link
4663 * @done: caller needs to free returned data with this
4665 * Calls security hook and i_op->get_link() on the supplied inode.
4667 * It does not touch atime. That's up to the caller if necessary.
4669 * Does not work on "special" symlinks like /proc/$$/fd/N
4671 const char *vfs_get_link(struct dentry *dentry, struct delayed_call *done)
4673 const char *res = ERR_PTR(-EINVAL);
4674 struct inode *inode = d_inode(dentry);
4676 if (d_is_symlink(dentry)) {
4677 res = ERR_PTR(security_inode_readlink(dentry));
4679 res = inode->i_op->get_link(dentry, inode, done);
4683 EXPORT_SYMBOL(vfs_get_link);
4685 /* get the link contents into pagecache */
4686 const char *page_get_link(struct dentry *dentry, struct inode *inode,
4687 struct delayed_call *callback)
4691 struct address_space *mapping = inode->i_mapping;
4694 page = find_get_page(mapping, 0);
4696 return ERR_PTR(-ECHILD);
4697 if (!PageUptodate(page)) {
4699 return ERR_PTR(-ECHILD);
4702 page = read_mapping_page(mapping, 0, NULL);
4706 set_delayed_call(callback, page_put_link, page);
4707 BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
4708 kaddr = page_address(page);
4709 nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1);
4713 EXPORT_SYMBOL(page_get_link);
4715 void page_put_link(void *arg)
4719 EXPORT_SYMBOL(page_put_link);
4721 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4723 DEFINE_DELAYED_CALL(done);
4724 int res = readlink_copy(buffer, buflen,
4725 page_get_link(dentry, d_inode(dentry),
4727 do_delayed_call(&done);
4730 EXPORT_SYMBOL(page_readlink);
4733 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4735 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
4737 struct address_space *mapping = inode->i_mapping;
4741 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
4743 flags |= AOP_FLAG_NOFS;
4746 err = pagecache_write_begin(NULL, mapping, 0, len-1,
4747 flags, &page, &fsdata);
4751 memcpy(page_address(page), symname, len-1);
4753 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
4760 mark_inode_dirty(inode);
4765 EXPORT_SYMBOL(__page_symlink);
4767 int page_symlink(struct inode *inode, const char *symname, int len)
4769 return __page_symlink(inode, symname, len,
4770 !mapping_gfp_constraint(inode->i_mapping, __GFP_FS));
4772 EXPORT_SYMBOL(page_symlink);
4774 const struct inode_operations page_symlink_inode_operations = {
4775 .get_link = page_get_link,
4777 EXPORT_SYMBOL(page_symlink_inode_operations);