4 * Copyright (C) 1991, 1992 Linus Torvalds
8 * Some corrections by tytso.
11 /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
14 /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
17 #include <linux/init.h>
18 #include <linux/export.h>
19 #include <linux/kernel.h>
20 #include <linux/slab.h>
22 #include <linux/namei.h>
23 #include <linux/pagemap.h>
24 #include <linux/fsnotify.h>
25 #include <linux/personality.h>
26 #include <linux/security.h>
27 #include <linux/ima.h>
28 #include <linux/syscalls.h>
29 #include <linux/mount.h>
30 #include <linux/audit.h>
31 #include <linux/capability.h>
32 #include <linux/file.h>
33 #include <linux/fcntl.h>
34 #include <linux/device_cgroup.h>
35 #include <linux/fs_struct.h>
36 #include <linux/posix_acl.h>
37 #include <linux/hash.h>
38 #include <linux/bitops.h>
39 #include <linux/init_task.h>
40 #include <asm/uaccess.h>
45 /* [Feb-1997 T. Schoebel-Theuer]
46 * Fundamental changes in the pathname lookup mechanisms (namei)
47 * were necessary because of omirr. The reason is that omirr needs
48 * to know the _real_ pathname, not the user-supplied one, in case
49 * of symlinks (and also when transname replacements occur).
51 * The new code replaces the old recursive symlink resolution with
52 * an iterative one (in case of non-nested symlink chains). It does
53 * this with calls to <fs>_follow_link().
54 * As a side effect, dir_namei(), _namei() and follow_link() are now
55 * replaced with a single function lookup_dentry() that can handle all
56 * the special cases of the former code.
58 * With the new dcache, the pathname is stored at each inode, at least as
59 * long as the refcount of the inode is positive. As a side effect, the
60 * size of the dcache depends on the inode cache and thus is dynamic.
62 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
63 * resolution to correspond with current state of the code.
65 * Note that the symlink resolution is not *completely* iterative.
66 * There is still a significant amount of tail- and mid- recursion in
67 * the algorithm. Also, note that <fs>_readlink() is not used in
68 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
69 * may return different results than <fs>_follow_link(). Many virtual
70 * filesystems (including /proc) exhibit this behavior.
73 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
74 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
75 * and the name already exists in form of a symlink, try to create the new
76 * name indicated by the symlink. The old code always complained that the
77 * name already exists, due to not following the symlink even if its target
78 * is nonexistent. The new semantics affects also mknod() and link() when
79 * the name is a symlink pointing to a non-existent name.
81 * I don't know which semantics is the right one, since I have no access
82 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
83 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
84 * "old" one. Personally, I think the new semantics is much more logical.
85 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
86 * file does succeed in both HP-UX and SunOs, but not in Solaris
87 * and in the old Linux semantics.
90 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
91 * semantics. See the comments in "open_namei" and "do_link" below.
93 * [10-Sep-98 Alan Modra] Another symlink change.
96 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
97 * inside the path - always follow.
98 * in the last component in creation/removal/renaming - never follow.
99 * if LOOKUP_FOLLOW passed - follow.
100 * if the pathname has trailing slashes - follow.
101 * otherwise - don't follow.
102 * (applied in that order).
104 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
105 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
106 * During the 2.4 we need to fix the userland stuff depending on it -
107 * hopefully we will be able to get rid of that wart in 2.5. So far only
108 * XEmacs seems to be relying on it...
111 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
112 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
113 * any extra contention...
116 /* In order to reduce some races, while at the same time doing additional
117 * checking and hopefully speeding things up, we copy filenames to the
118 * kernel data space before using them..
120 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
121 * PATH_MAX includes the nul terminator --RR.
124 #define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname))
127 getname_flags(const char __user *filename, int flags, int *empty)
129 struct filename *result;
133 result = audit_reusename(filename);
137 result = __getname();
138 if (unlikely(!result))
139 return ERR_PTR(-ENOMEM);
142 * First, try to embed the struct filename inside the names_cache
145 kname = (char *)result->iname;
146 result->name = kname;
148 len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX);
149 if (unlikely(len < 0)) {
155 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
156 * separate struct filename so we can dedicate the entire
157 * names_cache allocation for the pathname, and re-do the copy from
160 if (unlikely(len == EMBEDDED_NAME_MAX)) {
161 const size_t size = offsetof(struct filename, iname[1]);
162 kname = (char *)result;
165 * size is chosen that way we to guarantee that
166 * result->iname[0] is within the same object and that
167 * kname can't be equal to result->iname, no matter what.
169 result = kzalloc(size, GFP_KERNEL);
170 if (unlikely(!result)) {
172 return ERR_PTR(-ENOMEM);
174 result->name = kname;
175 len = strncpy_from_user(kname, filename, PATH_MAX);
176 if (unlikely(len < 0)) {
181 if (unlikely(len == PATH_MAX)) {
184 return ERR_PTR(-ENAMETOOLONG);
189 /* The empty path is special. */
190 if (unlikely(!len)) {
193 if (!(flags & LOOKUP_EMPTY)) {
195 return ERR_PTR(-ENOENT);
199 result->uptr = filename;
200 result->aname = NULL;
201 audit_getname(result);
206 getname(const char __user * filename)
208 return getname_flags(filename, 0, NULL);
212 getname_kernel(const char * filename)
214 struct filename *result;
215 int len = strlen(filename) + 1;
217 result = __getname();
218 if (unlikely(!result))
219 return ERR_PTR(-ENOMEM);
221 if (len <= EMBEDDED_NAME_MAX) {
222 result->name = (char *)result->iname;
223 } else if (len <= PATH_MAX) {
224 struct filename *tmp;
226 tmp = kmalloc(sizeof(*tmp), GFP_KERNEL);
227 if (unlikely(!tmp)) {
229 return ERR_PTR(-ENOMEM);
231 tmp->name = (char *)result;
235 return ERR_PTR(-ENAMETOOLONG);
237 memcpy((char *)result->name, filename, len);
239 result->aname = NULL;
241 audit_getname(result);
246 void putname(struct filename *name)
248 BUG_ON(name->refcnt <= 0);
250 if (--name->refcnt > 0)
253 if (name->name != name->iname) {
254 __putname(name->name);
260 static int check_acl(struct inode *inode, int mask)
262 #ifdef CONFIG_FS_POSIX_ACL
263 struct posix_acl *acl;
265 if (mask & MAY_NOT_BLOCK) {
266 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
269 /* no ->get_acl() calls in RCU mode... */
270 if (is_uncached_acl(acl))
272 return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
275 acl = get_acl(inode, ACL_TYPE_ACCESS);
279 int error = posix_acl_permission(inode, acl, mask);
280 posix_acl_release(acl);
289 * This does the basic permission checking
291 static int acl_permission_check(struct inode *inode, int mask)
293 unsigned int mode = inode->i_mode;
295 if (likely(uid_eq(current_fsuid(), inode->i_uid)))
298 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
299 int error = check_acl(inode, mask);
300 if (error != -EAGAIN)
304 if (in_group_p(inode->i_gid))
309 * If the DACs are ok we don't need any capability check.
311 if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
317 * generic_permission - check for access rights on a Posix-like filesystem
318 * @inode: inode to check access rights for
319 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
321 * Used to check for read/write/execute permissions on a file.
322 * We use "fsuid" for this, letting us set arbitrary permissions
323 * for filesystem access without changing the "normal" uids which
324 * are used for other things.
326 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
327 * request cannot be satisfied (eg. requires blocking or too much complexity).
328 * It would then be called again in ref-walk mode.
330 int generic_permission(struct inode *inode, int mask)
335 * Do the basic permission checks.
337 ret = acl_permission_check(inode, mask);
341 if (S_ISDIR(inode->i_mode)) {
342 /* DACs are overridable for directories */
343 if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
345 if (!(mask & MAY_WRITE))
346 if (capable_wrt_inode_uidgid(inode,
347 CAP_DAC_READ_SEARCH))
352 * Read/write DACs are always overridable.
353 * Executable DACs are overridable when there is
354 * at least one exec bit set.
356 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
357 if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
361 * Searching includes executable on directories, else just read.
363 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
364 if (mask == MAY_READ)
365 if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH))
370 EXPORT_SYMBOL(generic_permission);
373 * We _really_ want to just do "generic_permission()" without
374 * even looking at the inode->i_op values. So we keep a cache
375 * flag in inode->i_opflags, that says "this has not special
376 * permission function, use the fast case".
378 static inline int do_inode_permission(struct inode *inode, int mask)
380 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
381 if (likely(inode->i_op->permission))
382 return inode->i_op->permission(inode, mask);
384 /* This gets set once for the inode lifetime */
385 spin_lock(&inode->i_lock);
386 inode->i_opflags |= IOP_FASTPERM;
387 spin_unlock(&inode->i_lock);
389 return generic_permission(inode, mask);
393 * __inode_permission - Check for access rights to a given inode
394 * @inode: Inode to check permission on
395 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
397 * Check for read/write/execute permissions on an inode.
399 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
401 * This does not check for a read-only file system. You probably want
402 * inode_permission().
404 int __inode_permission(struct inode *inode, int mask)
408 if (unlikely(mask & MAY_WRITE)) {
410 * Nobody gets write access to an immutable file.
412 if (IS_IMMUTABLE(inode))
416 * Updating mtime will likely cause i_uid and i_gid to be
417 * written back improperly if their true value is unknown
420 if (HAS_UNMAPPED_ID(inode))
424 retval = do_inode_permission(inode, mask);
428 retval = devcgroup_inode_permission(inode, mask);
432 return security_inode_permission(inode, mask);
434 EXPORT_SYMBOL(__inode_permission);
437 * sb_permission - Check superblock-level permissions
438 * @sb: Superblock of inode to check permission on
439 * @inode: Inode to check permission on
440 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
442 * Separate out file-system wide checks from inode-specific permission checks.
444 static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
446 if (unlikely(mask & MAY_WRITE)) {
447 umode_t mode = inode->i_mode;
449 /* Nobody gets write access to a read-only fs. */
450 if ((sb->s_flags & MS_RDONLY) &&
451 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
458 * inode_permission - Check for access rights to a given inode
459 * @inode: Inode to check permission on
460 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
462 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
463 * this, letting us set arbitrary permissions for filesystem access without
464 * changing the "normal" UIDs which are used for other things.
466 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
468 int inode_permission(struct inode *inode, int mask)
472 retval = sb_permission(inode->i_sb, inode, mask);
475 return __inode_permission(inode, mask);
477 EXPORT_SYMBOL(inode_permission);
480 * path_get - get a reference to a path
481 * @path: path to get the reference to
483 * Given a path increment the reference count to the dentry and the vfsmount.
485 void path_get(const struct path *path)
490 EXPORT_SYMBOL(path_get);
493 * path_put - put a reference to a path
494 * @path: path to put the reference to
496 * Given a path decrement the reference count to the dentry and the vfsmount.
498 void path_put(const struct path *path)
503 EXPORT_SYMBOL(path_put);
505 #define EMBEDDED_LEVELS 2
510 struct inode *inode; /* path.dentry.d_inode */
515 int total_link_count;
518 struct delayed_call done;
521 } *stack, internal[EMBEDDED_LEVELS];
522 struct filename *name;
523 struct nameidata *saved;
524 struct inode *link_inode;
529 static void set_nameidata(struct nameidata *p, int dfd, struct filename *name)
531 struct nameidata *old = current->nameidata;
532 p->stack = p->internal;
535 p->total_link_count = old ? old->total_link_count : 0;
537 current->nameidata = p;
540 static void restore_nameidata(void)
542 struct nameidata *now = current->nameidata, *old = now->saved;
544 current->nameidata = old;
546 old->total_link_count = now->total_link_count;
547 if (now->stack != now->internal)
551 static int __nd_alloc_stack(struct nameidata *nd)
555 if (nd->flags & LOOKUP_RCU) {
556 p= kmalloc(MAXSYMLINKS * sizeof(struct saved),
561 p= kmalloc(MAXSYMLINKS * sizeof(struct saved),
566 memcpy(p, nd->internal, sizeof(nd->internal));
572 * path_connected - Verify that a path->dentry is below path->mnt.mnt_root
573 * @path: nameidate to verify
575 * Rename can sometimes move a file or directory outside of a bind
576 * mount, path_connected allows those cases to be detected.
578 static bool path_connected(const struct path *path)
580 struct vfsmount *mnt = path->mnt;
582 /* Only bind mounts can have disconnected paths */
583 if (mnt->mnt_root == mnt->mnt_sb->s_root)
586 return is_subdir(path->dentry, mnt->mnt_root);
589 static inline int nd_alloc_stack(struct nameidata *nd)
591 if (likely(nd->depth != EMBEDDED_LEVELS))
593 if (likely(nd->stack != nd->internal))
595 return __nd_alloc_stack(nd);
598 static void drop_links(struct nameidata *nd)
602 struct saved *last = nd->stack + i;
603 do_delayed_call(&last->done);
604 clear_delayed_call(&last->done);
608 static void terminate_walk(struct nameidata *nd)
611 if (!(nd->flags & LOOKUP_RCU)) {
614 for (i = 0; i < nd->depth; i++)
615 path_put(&nd->stack[i].link);
616 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
621 nd->flags &= ~LOOKUP_RCU;
622 if (!(nd->flags & LOOKUP_ROOT))
629 /* path_put is needed afterwards regardless of success or failure */
630 static bool legitimize_path(struct nameidata *nd,
631 struct path *path, unsigned seq)
633 int res = __legitimize_mnt(path->mnt, nd->m_seq);
640 if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) {
644 return !read_seqcount_retry(&path->dentry->d_seq, seq);
647 static bool legitimize_links(struct nameidata *nd)
650 for (i = 0; i < nd->depth; i++) {
651 struct saved *last = nd->stack + i;
652 if (unlikely(!legitimize_path(nd, &last->link, last->seq))) {
662 * Path walking has 2 modes, rcu-walk and ref-walk (see
663 * Documentation/filesystems/path-lookup.txt). In situations when we can't
664 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
665 * normal reference counts on dentries and vfsmounts to transition to ref-walk
666 * mode. Refcounts are grabbed at the last known good point before rcu-walk
667 * got stuck, so ref-walk may continue from there. If this is not successful
668 * (eg. a seqcount has changed), then failure is returned and it's up to caller
669 * to restart the path walk from the beginning in ref-walk mode.
673 * unlazy_walk - try to switch to ref-walk mode.
674 * @nd: nameidata pathwalk data
675 * @dentry: child of nd->path.dentry or NULL
676 * @seq: seq number to check dentry against
677 * Returns: 0 on success, -ECHILD on failure
679 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
680 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
681 * @nd or NULL. Must be called from rcu-walk context.
682 * Nothing should touch nameidata between unlazy_walk() failure and
685 static int unlazy_walk(struct nameidata *nd, struct dentry *dentry, unsigned seq)
687 struct dentry *parent = nd->path.dentry;
689 BUG_ON(!(nd->flags & LOOKUP_RCU));
691 nd->flags &= ~LOOKUP_RCU;
692 if (unlikely(!legitimize_links(nd)))
694 if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq)))
696 if (unlikely(!lockref_get_not_dead(&parent->d_lockref)))
700 * For a negative lookup, the lookup sequence point is the parents
701 * sequence point, and it only needs to revalidate the parent dentry.
703 * For a positive lookup, we need to move both the parent and the
704 * dentry from the RCU domain to be properly refcounted. And the
705 * sequence number in the dentry validates *both* dentry counters,
706 * since we checked the sequence number of the parent after we got
707 * the child sequence number. So we know the parent must still
708 * be valid if the child sequence number is still valid.
711 if (read_seqcount_retry(&parent->d_seq, nd->seq))
713 BUG_ON(nd->inode != parent->d_inode);
715 if (!lockref_get_not_dead(&dentry->d_lockref))
717 if (read_seqcount_retry(&dentry->d_seq, seq))
722 * Sequence counts matched. Now make sure that the root is
723 * still valid and get it if required.
725 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
726 if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq))) {
743 nd->path.dentry = NULL;
747 if (!(nd->flags & LOOKUP_ROOT))
752 static int unlazy_link(struct nameidata *nd, struct path *link, unsigned seq)
754 if (unlikely(!legitimize_path(nd, link, seq))) {
757 nd->flags &= ~LOOKUP_RCU;
759 nd->path.dentry = NULL;
760 if (!(nd->flags & LOOKUP_ROOT))
763 } else if (likely(unlazy_walk(nd, NULL, 0)) == 0) {
770 static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
772 return dentry->d_op->d_revalidate(dentry, flags);
776 * complete_walk - successful completion of path walk
777 * @nd: pointer nameidata
779 * If we had been in RCU mode, drop out of it and legitimize nd->path.
780 * Revalidate the final result, unless we'd already done that during
781 * the path walk or the filesystem doesn't ask for it. Return 0 on
782 * success, -error on failure. In case of failure caller does not
783 * need to drop nd->path.
785 static int complete_walk(struct nameidata *nd)
787 struct dentry *dentry = nd->path.dentry;
790 if (nd->flags & LOOKUP_RCU) {
791 if (!(nd->flags & LOOKUP_ROOT))
793 if (unlikely(unlazy_walk(nd, NULL, 0)))
797 if (likely(!(nd->flags & LOOKUP_JUMPED)))
800 if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
803 status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
813 static void set_root(struct nameidata *nd)
815 struct fs_struct *fs = current->fs;
817 if (nd->flags & LOOKUP_RCU) {
821 seq = read_seqcount_begin(&fs->seq);
823 nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
824 } while (read_seqcount_retry(&fs->seq, seq));
826 get_fs_root(fs, &nd->root);
830 static void path_put_conditional(struct path *path, struct nameidata *nd)
833 if (path->mnt != nd->path.mnt)
837 static inline void path_to_nameidata(const struct path *path,
838 struct nameidata *nd)
840 if (!(nd->flags & LOOKUP_RCU)) {
841 dput(nd->path.dentry);
842 if (nd->path.mnt != path->mnt)
843 mntput(nd->path.mnt);
845 nd->path.mnt = path->mnt;
846 nd->path.dentry = path->dentry;
849 static int nd_jump_root(struct nameidata *nd)
851 if (nd->flags & LOOKUP_RCU) {
855 nd->inode = d->d_inode;
856 nd->seq = nd->root_seq;
857 if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq)))
863 nd->inode = nd->path.dentry->d_inode;
865 nd->flags |= LOOKUP_JUMPED;
870 * Helper to directly jump to a known parsed path from ->get_link,
871 * caller must have taken a reference to path beforehand.
873 void nd_jump_link(struct path *path)
875 struct nameidata *nd = current->nameidata;
879 nd->inode = nd->path.dentry->d_inode;
880 nd->flags |= LOOKUP_JUMPED;
883 static inline void put_link(struct nameidata *nd)
885 struct saved *last = nd->stack + --nd->depth;
886 do_delayed_call(&last->done);
887 if (!(nd->flags & LOOKUP_RCU))
888 path_put(&last->link);
891 int sysctl_protected_symlinks __read_mostly = 0;
892 int sysctl_protected_hardlinks __read_mostly = 0;
895 * may_follow_link - Check symlink following for unsafe situations
896 * @nd: nameidata pathwalk data
898 * In the case of the sysctl_protected_symlinks sysctl being enabled,
899 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
900 * in a sticky world-writable directory. This is to protect privileged
901 * processes from failing races against path names that may change out
902 * from under them by way of other users creating malicious symlinks.
903 * It will permit symlinks to be followed only when outside a sticky
904 * world-writable directory, or when the uid of the symlink and follower
905 * match, or when the directory owner matches the symlink's owner.
907 * Returns 0 if following the symlink is allowed, -ve on error.
909 static inline int may_follow_link(struct nameidata *nd)
911 const struct inode *inode;
912 const struct inode *parent;
915 if (!sysctl_protected_symlinks)
918 /* Allowed if owner and follower match. */
919 inode = nd->link_inode;
920 if (uid_eq(current_cred()->fsuid, inode->i_uid))
923 /* Allowed if parent directory not sticky and world-writable. */
925 if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
928 /* Allowed if parent directory and link owner match. */
929 puid = parent->i_uid;
930 if (uid_valid(puid) && uid_eq(puid, inode->i_uid))
933 if (nd->flags & LOOKUP_RCU)
936 audit_log_link_denied("follow_link", &nd->stack[0].link);
941 * safe_hardlink_source - Check for safe hardlink conditions
942 * @inode: the source inode to hardlink from
944 * Return false if at least one of the following conditions:
945 * - inode is not a regular file
947 * - inode is setgid and group-exec
948 * - access failure for read and write
950 * Otherwise returns true.
952 static bool safe_hardlink_source(struct inode *inode)
954 umode_t mode = inode->i_mode;
956 /* Special files should not get pinned to the filesystem. */
960 /* Setuid files should not get pinned to the filesystem. */
964 /* Executable setgid files should not get pinned to the filesystem. */
965 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
968 /* Hardlinking to unreadable or unwritable sources is dangerous. */
969 if (inode_permission(inode, MAY_READ | MAY_WRITE))
976 * may_linkat - Check permissions for creating a hardlink
977 * @link: the source to hardlink from
979 * Block hardlink when all of:
980 * - sysctl_protected_hardlinks enabled
981 * - fsuid does not match inode
982 * - hardlink source is unsafe (see safe_hardlink_source() above)
983 * - not CAP_FOWNER in a namespace with the inode owner uid mapped
985 * Returns 0 if successful, -ve on error.
987 static int may_linkat(struct path *link)
991 if (!sysctl_protected_hardlinks)
994 inode = link->dentry->d_inode;
996 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
997 * otherwise, it must be a safe source.
999 if (inode_owner_or_capable(inode) || safe_hardlink_source(inode))
1002 audit_log_link_denied("linkat", link);
1006 static __always_inline
1007 const char *get_link(struct nameidata *nd)
1009 struct saved *last = nd->stack + nd->depth - 1;
1010 struct dentry *dentry = last->link.dentry;
1011 struct inode *inode = nd->link_inode;
1015 if (!(nd->flags & LOOKUP_RCU)) {
1016 touch_atime(&last->link);
1018 } else if (atime_needs_update(&last->link, inode)) {
1019 if (unlikely(unlazy_walk(nd, NULL, 0)))
1020 return ERR_PTR(-ECHILD);
1021 touch_atime(&last->link);
1024 error = security_inode_follow_link(dentry, inode,
1025 nd->flags & LOOKUP_RCU);
1026 if (unlikely(error))
1027 return ERR_PTR(error);
1029 nd->last_type = LAST_BIND;
1030 res = inode->i_link;
1032 const char * (*get)(struct dentry *, struct inode *,
1033 struct delayed_call *);
1034 get = inode->i_op->get_link;
1035 if (nd->flags & LOOKUP_RCU) {
1036 res = get(NULL, inode, &last->done);
1037 if (res == ERR_PTR(-ECHILD)) {
1038 if (unlikely(unlazy_walk(nd, NULL, 0)))
1039 return ERR_PTR(-ECHILD);
1040 res = get(dentry, inode, &last->done);
1043 res = get(dentry, inode, &last->done);
1045 if (IS_ERR_OR_NULL(res))
1051 if (unlikely(nd_jump_root(nd)))
1052 return ERR_PTR(-ECHILD);
1053 while (unlikely(*++res == '/'))
1062 * follow_up - Find the mountpoint of path's vfsmount
1064 * Given a path, find the mountpoint of its source file system.
1065 * Replace @path with the path of the mountpoint in the parent mount.
1068 * Return 1 if we went up a level and 0 if we were already at the
1071 int follow_up(struct path *path)
1073 struct mount *mnt = real_mount(path->mnt);
1074 struct mount *parent;
1075 struct dentry *mountpoint;
1077 read_seqlock_excl(&mount_lock);
1078 parent = mnt->mnt_parent;
1079 if (parent == mnt) {
1080 read_sequnlock_excl(&mount_lock);
1083 mntget(&parent->mnt);
1084 mountpoint = dget(mnt->mnt_mountpoint);
1085 read_sequnlock_excl(&mount_lock);
1087 path->dentry = mountpoint;
1089 path->mnt = &parent->mnt;
1092 EXPORT_SYMBOL(follow_up);
1095 * Perform an automount
1096 * - return -EISDIR to tell follow_managed() to stop and return the path we
1099 static int follow_automount(struct path *path, struct nameidata *nd,
1102 struct vfsmount *mnt;
1103 const struct cred *old_cred;
1106 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
1109 /* We don't want to mount if someone's just doing a stat -
1110 * unless they're stat'ing a directory and appended a '/' to
1113 * We do, however, want to mount if someone wants to open or
1114 * create a file of any type under the mountpoint, wants to
1115 * traverse through the mountpoint or wants to open the
1116 * mounted directory. Also, autofs may mark negative dentries
1117 * as being automount points. These will need the attentions
1118 * of the daemon to instantiate them before they can be used.
1120 if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
1121 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
1122 path->dentry->d_inode)
1125 if (path->dentry->d_sb->s_user_ns != &init_user_ns)
1128 nd->total_link_count++;
1129 if (nd->total_link_count >= 40)
1132 old_cred = override_creds(&init_cred);
1133 mnt = path->dentry->d_op->d_automount(path);
1134 revert_creds(old_cred);
1137 * The filesystem is allowed to return -EISDIR here to indicate
1138 * it doesn't want to automount. For instance, autofs would do
1139 * this so that its userspace daemon can mount on this dentry.
1141 * However, we can only permit this if it's a terminal point in
1142 * the path being looked up; if it wasn't then the remainder of
1143 * the path is inaccessible and we should say so.
1145 if (PTR_ERR(mnt) == -EISDIR && (nd->flags & LOOKUP_PARENT))
1147 return PTR_ERR(mnt);
1150 if (!mnt) /* mount collision */
1153 if (!*need_mntput) {
1154 /* lock_mount() may release path->mnt on error */
1156 *need_mntput = true;
1158 err = finish_automount(mnt, path);
1162 /* Someone else made a mount here whilst we were busy */
1167 path->dentry = dget(mnt->mnt_root);
1176 * Handle a dentry that is managed in some way.
1177 * - Flagged for transit management (autofs)
1178 * - Flagged as mountpoint
1179 * - Flagged as automount point
1181 * This may only be called in refwalk mode.
1183 * Serialization is taken care of in namespace.c
1185 static int follow_managed(struct path *path, struct nameidata *nd)
1187 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
1189 bool need_mntput = false;
1192 /* Given that we're not holding a lock here, we retain the value in a
1193 * local variable for each dentry as we look at it so that we don't see
1194 * the components of that value change under us */
1195 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1196 managed &= DCACHE_MANAGED_DENTRY,
1197 unlikely(managed != 0)) {
1198 /* Allow the filesystem to manage the transit without i_mutex
1200 if (managed & DCACHE_MANAGE_TRANSIT) {
1201 BUG_ON(!path->dentry->d_op);
1202 BUG_ON(!path->dentry->d_op->d_manage);
1203 ret = path->dentry->d_op->d_manage(path->dentry, false);
1208 /* Transit to a mounted filesystem. */
1209 if (managed & DCACHE_MOUNTED) {
1210 struct vfsmount *mounted = lookup_mnt(path);
1215 path->mnt = mounted;
1216 path->dentry = dget(mounted->mnt_root);
1221 /* Something is mounted on this dentry in another
1222 * namespace and/or whatever was mounted there in this
1223 * namespace got unmounted before lookup_mnt() could
1227 /* Handle an automount point */
1228 if (managed & DCACHE_NEED_AUTOMOUNT) {
1229 ret = follow_automount(path, nd, &need_mntput);
1235 /* We didn't change the current path point */
1239 if (need_mntput && path->mnt == mnt)
1241 if (ret == -EISDIR || !ret)
1244 nd->flags |= LOOKUP_JUMPED;
1245 if (unlikely(ret < 0))
1246 path_put_conditional(path, nd);
1250 int follow_down_one(struct path *path)
1252 struct vfsmount *mounted;
1254 mounted = lookup_mnt(path);
1258 path->mnt = mounted;
1259 path->dentry = dget(mounted->mnt_root);
1264 EXPORT_SYMBOL(follow_down_one);
1266 static inline int managed_dentry_rcu(struct dentry *dentry)
1268 return (dentry->d_flags & DCACHE_MANAGE_TRANSIT) ?
1269 dentry->d_op->d_manage(dentry, true) : 0;
1273 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1274 * we meet a managed dentry that would need blocking.
1276 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
1277 struct inode **inode, unsigned *seqp)
1280 struct mount *mounted;
1282 * Don't forget we might have a non-mountpoint managed dentry
1283 * that wants to block transit.
1285 switch (managed_dentry_rcu(path->dentry)) {
1295 if (!d_mountpoint(path->dentry))
1296 return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
1298 mounted = __lookup_mnt(path->mnt, path->dentry);
1301 path->mnt = &mounted->mnt;
1302 path->dentry = mounted->mnt.mnt_root;
1303 nd->flags |= LOOKUP_JUMPED;
1304 *seqp = read_seqcount_begin(&path->dentry->d_seq);
1306 * Update the inode too. We don't need to re-check the
1307 * dentry sequence number here after this d_inode read,
1308 * because a mount-point is always pinned.
1310 *inode = path->dentry->d_inode;
1312 return !read_seqretry(&mount_lock, nd->m_seq) &&
1313 !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
1316 static int follow_dotdot_rcu(struct nameidata *nd)
1318 struct inode *inode = nd->inode;
1321 if (path_equal(&nd->path, &nd->root))
1323 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1324 struct dentry *old = nd->path.dentry;
1325 struct dentry *parent = old->d_parent;
1328 inode = parent->d_inode;
1329 seq = read_seqcount_begin(&parent->d_seq);
1330 if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq)))
1332 nd->path.dentry = parent;
1334 if (unlikely(!path_connected(&nd->path)))
1338 struct mount *mnt = real_mount(nd->path.mnt);
1339 struct mount *mparent = mnt->mnt_parent;
1340 struct dentry *mountpoint = mnt->mnt_mountpoint;
1341 struct inode *inode2 = mountpoint->d_inode;
1342 unsigned seq = read_seqcount_begin(&mountpoint->d_seq);
1343 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
1345 if (&mparent->mnt == nd->path.mnt)
1347 /* we know that mountpoint was pinned */
1348 nd->path.dentry = mountpoint;
1349 nd->path.mnt = &mparent->mnt;
1354 while (unlikely(d_mountpoint(nd->path.dentry))) {
1355 struct mount *mounted;
1356 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry);
1357 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
1361 nd->path.mnt = &mounted->mnt;
1362 nd->path.dentry = mounted->mnt.mnt_root;
1363 inode = nd->path.dentry->d_inode;
1364 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1371 * Follow down to the covering mount currently visible to userspace. At each
1372 * point, the filesystem owning that dentry may be queried as to whether the
1373 * caller is permitted to proceed or not.
1375 int follow_down(struct path *path)
1380 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1381 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
1382 /* Allow the filesystem to manage the transit without i_mutex
1385 * We indicate to the filesystem if someone is trying to mount
1386 * something here. This gives autofs the chance to deny anyone
1387 * other than its daemon the right to mount on its
1390 * The filesystem may sleep at this point.
1392 if (managed & DCACHE_MANAGE_TRANSIT) {
1393 BUG_ON(!path->dentry->d_op);
1394 BUG_ON(!path->dentry->d_op->d_manage);
1395 ret = path->dentry->d_op->d_manage(
1396 path->dentry, false);
1398 return ret == -EISDIR ? 0 : ret;
1401 /* Transit to a mounted filesystem. */
1402 if (managed & DCACHE_MOUNTED) {
1403 struct vfsmount *mounted = lookup_mnt(path);
1408 path->mnt = mounted;
1409 path->dentry = dget(mounted->mnt_root);
1413 /* Don't handle automount points here */
1418 EXPORT_SYMBOL(follow_down);
1421 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1423 static void follow_mount(struct path *path)
1425 while (d_mountpoint(path->dentry)) {
1426 struct vfsmount *mounted = lookup_mnt(path);
1431 path->mnt = mounted;
1432 path->dentry = dget(mounted->mnt_root);
1436 static int path_parent_directory(struct path *path)
1438 struct dentry *old = path->dentry;
1439 /* rare case of legitimate dget_parent()... */
1440 path->dentry = dget_parent(path->dentry);
1442 if (unlikely(!path_connected(path)))
1447 static int follow_dotdot(struct nameidata *nd)
1450 if (nd->path.dentry == nd->root.dentry &&
1451 nd->path.mnt == nd->root.mnt) {
1454 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1455 int ret = path_parent_directory(&nd->path);
1460 if (!follow_up(&nd->path))
1463 follow_mount(&nd->path);
1464 nd->inode = nd->path.dentry->d_inode;
1469 * This looks up the name in dcache, possibly revalidates the old dentry and
1470 * allocates a new one if not found or not valid. In the need_lookup argument
1471 * returns whether i_op->lookup is necessary.
1473 static struct dentry *lookup_dcache(const struct qstr *name,
1477 struct dentry *dentry;
1480 dentry = d_lookup(dir, name);
1482 if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
1483 error = d_revalidate(dentry, flags);
1484 if (unlikely(error <= 0)) {
1486 d_invalidate(dentry);
1488 return ERR_PTR(error);
1496 * Call i_op->lookup on the dentry. The dentry must be negative and
1499 * dir->d_inode->i_mutex must be held
1501 static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
1506 /* Don't create child dentry for a dead directory. */
1507 if (unlikely(IS_DEADDIR(dir))) {
1509 return ERR_PTR(-ENOENT);
1512 old = dir->i_op->lookup(dir, dentry, flags);
1513 if (unlikely(old)) {
1520 static struct dentry *__lookup_hash(const struct qstr *name,
1521 struct dentry *base, unsigned int flags)
1523 struct dentry *dentry = lookup_dcache(name, base, flags);
1528 dentry = d_alloc(base, name);
1529 if (unlikely(!dentry))
1530 return ERR_PTR(-ENOMEM);
1532 return lookup_real(base->d_inode, dentry, flags);
1535 static int lookup_fast(struct nameidata *nd,
1536 struct path *path, struct inode **inode,
1539 struct vfsmount *mnt = nd->path.mnt;
1540 struct dentry *dentry, *parent = nd->path.dentry;
1545 * Rename seqlock is not required here because in the off chance
1546 * of a false negative due to a concurrent rename, the caller is
1547 * going to fall back to non-racy lookup.
1549 if (nd->flags & LOOKUP_RCU) {
1552 dentry = __d_lookup_rcu(parent, &nd->last, &seq);
1553 if (unlikely(!dentry)) {
1554 if (unlazy_walk(nd, NULL, 0))
1560 * This sequence count validates that the inode matches
1561 * the dentry name information from lookup.
1563 *inode = d_backing_inode(dentry);
1564 negative = d_is_negative(dentry);
1565 if (unlikely(read_seqcount_retry(&dentry->d_seq, seq)))
1569 * This sequence count validates that the parent had no
1570 * changes while we did the lookup of the dentry above.
1572 * The memory barrier in read_seqcount_begin of child is
1573 * enough, we can use __read_seqcount_retry here.
1575 if (unlikely(__read_seqcount_retry(&parent->d_seq, nd->seq)))
1579 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
1580 status = d_revalidate(dentry, nd->flags);
1581 if (unlikely(status <= 0)) {
1582 if (unlazy_walk(nd, dentry, seq))
1584 if (status == -ECHILD)
1585 status = d_revalidate(dentry, nd->flags);
1588 * Note: do negative dentry check after revalidation in
1589 * case that drops it.
1591 if (unlikely(negative))
1594 path->dentry = dentry;
1595 if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
1597 if (unlazy_walk(nd, dentry, seq))
1601 dentry = __d_lookup(parent, &nd->last);
1602 if (unlikely(!dentry))
1604 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
1605 status = d_revalidate(dentry, nd->flags);
1607 if (unlikely(status <= 0)) {
1609 d_invalidate(dentry);
1613 if (unlikely(d_is_negative(dentry))) {
1619 path->dentry = dentry;
1620 err = follow_managed(path, nd);
1621 if (likely(err > 0))
1622 *inode = d_backing_inode(path->dentry);
1626 /* Fast lookup failed, do it the slow way */
1627 static struct dentry *lookup_slow(const struct qstr *name,
1631 struct dentry *dentry = ERR_PTR(-ENOENT), *old;
1632 struct inode *inode = dir->d_inode;
1633 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
1635 inode_lock_shared(inode);
1636 /* Don't go there if it's already dead */
1637 if (unlikely(IS_DEADDIR(inode)))
1640 dentry = d_alloc_parallel(dir, name, &wq);
1643 if (unlikely(!d_in_lookup(dentry))) {
1644 if ((dentry->d_flags & DCACHE_OP_REVALIDATE) &&
1645 !(flags & LOOKUP_NO_REVAL)) {
1646 int error = d_revalidate(dentry, flags);
1647 if (unlikely(error <= 0)) {
1649 d_invalidate(dentry);
1654 dentry = ERR_PTR(error);
1658 old = inode->i_op->lookup(inode, dentry, flags);
1659 d_lookup_done(dentry);
1660 if (unlikely(old)) {
1666 inode_unlock_shared(inode);
1670 static inline int may_lookup(struct nameidata *nd)
1672 if (nd->flags & LOOKUP_RCU) {
1673 int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1676 if (unlazy_walk(nd, NULL, 0))
1679 return inode_permission(nd->inode, MAY_EXEC);
1682 static inline int handle_dots(struct nameidata *nd, int type)
1684 if (type == LAST_DOTDOT) {
1687 if (nd->flags & LOOKUP_RCU) {
1688 return follow_dotdot_rcu(nd);
1690 return follow_dotdot(nd);
1695 static int pick_link(struct nameidata *nd, struct path *link,
1696 struct inode *inode, unsigned seq)
1700 if (unlikely(nd->total_link_count++ >= MAXSYMLINKS)) {
1701 path_to_nameidata(link, nd);
1704 if (!(nd->flags & LOOKUP_RCU)) {
1705 if (link->mnt == nd->path.mnt)
1708 error = nd_alloc_stack(nd);
1709 if (unlikely(error)) {
1710 if (error == -ECHILD) {
1711 if (unlikely(unlazy_link(nd, link, seq)))
1713 error = nd_alloc_stack(nd);
1721 last = nd->stack + nd->depth++;
1723 clear_delayed_call(&last->done);
1724 nd->link_inode = inode;
1730 * Do we need to follow links? We _really_ want to be able
1731 * to do this check without having to look at inode->i_op,
1732 * so we keep a cache of "no, this doesn't need follow_link"
1733 * for the common case.
1735 static inline int should_follow_link(struct nameidata *nd, struct path *link,
1737 struct inode *inode, unsigned seq)
1739 if (likely(!d_is_symlink(link->dentry)))
1743 /* make sure that d_is_symlink above matches inode */
1744 if (nd->flags & LOOKUP_RCU) {
1745 if (read_seqcount_retry(&link->dentry->d_seq, seq))
1748 return pick_link(nd, link, inode, seq);
1751 enum {WALK_GET = 1, WALK_PUT = 2};
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_PUT)
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 if (flags & WALK_PUT)
1795 err = should_follow_link(nd, &path, flags & WALK_GET, inode, seq);
1798 path_to_nameidata(&path, nd);
1805 * We can do the critical dentry name comparison and hashing
1806 * operations one word at a time, but we are limited to:
1808 * - Architectures with fast unaligned word accesses. We could
1809 * do a "get_unaligned()" if this helps and is sufficiently
1812 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1813 * do not trap on the (extremely unlikely) case of a page
1814 * crossing operation.
1816 * - Furthermore, we need an efficient 64-bit compile for the
1817 * 64-bit case in order to generate the "number of bytes in
1818 * the final mask". Again, that could be replaced with a
1819 * efficient population count instruction or similar.
1821 #ifdef CONFIG_DCACHE_WORD_ACCESS
1823 #include <asm/word-at-a-time.h>
1827 /* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */
1829 #elif defined(CONFIG_64BIT)
1831 * Register pressure in the mixing function is an issue, particularly
1832 * on 32-bit x86, but almost any function requires one state value and
1833 * one temporary. Instead, use a function designed for two state values
1834 * and no temporaries.
1836 * This function cannot create a collision in only two iterations, so
1837 * we have two iterations to achieve avalanche. In those two iterations,
1838 * we have six layers of mixing, which is enough to spread one bit's
1839 * influence out to 2^6 = 64 state bits.
1841 * Rotate constants are scored by considering either 64 one-bit input
1842 * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the
1843 * probability of that delta causing a change to each of the 128 output
1844 * bits, using a sample of random initial states.
1846 * The Shannon entropy of the computed probabilities is then summed
1847 * to produce a score. Ideally, any input change has a 50% chance of
1848 * toggling any given output bit.
1850 * Mixing scores (in bits) for (12,45):
1851 * Input delta: 1-bit 2-bit
1852 * 1 round: 713.3 42542.6
1853 * 2 rounds: 2753.7 140389.8
1854 * 3 rounds: 5954.1 233458.2
1855 * 4 rounds: 7862.6 256672.2
1856 * Perfect: 8192 258048
1857 * (64*128) (64*63/2 * 128)
1859 #define HASH_MIX(x, y, a) \
1861 y ^= x, x = rol64(x,12),\
1862 x += y, y = rol64(y,45),\
1866 * Fold two longs into one 32-bit hash value. This must be fast, but
1867 * latency isn't quite as critical, as there is a fair bit of additional
1868 * work done before the hash value is used.
1870 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
1872 y ^= x * GOLDEN_RATIO_64;
1873 y *= GOLDEN_RATIO_64;
1877 #else /* 32-bit case */
1880 * Mixing scores (in bits) for (7,20):
1881 * Input delta: 1-bit 2-bit
1882 * 1 round: 330.3 9201.6
1883 * 2 rounds: 1246.4 25475.4
1884 * 3 rounds: 1907.1 31295.1
1885 * 4 rounds: 2042.3 31718.6
1886 * Perfect: 2048 31744
1887 * (32*64) (32*31/2 * 64)
1889 #define HASH_MIX(x, y, a) \
1891 y ^= x, x = rol32(x, 7),\
1892 x += y, y = rol32(y,20),\
1895 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
1897 /* Use arch-optimized multiply if one exists */
1898 return __hash_32(y ^ __hash_32(x));
1904 * Return the hash of a string of known length. This is carfully
1905 * designed to match hash_name(), which is the more critical function.
1906 * In particular, we must end by hashing a final word containing 0..7
1907 * payload bytes, to match the way that hash_name() iterates until it
1908 * finds the delimiter after the name.
1910 unsigned int full_name_hash(const char *name, unsigned int len)
1912 unsigned long a, x = 0, y = 0;
1917 a = load_unaligned_zeropad(name);
1918 if (len < sizeof(unsigned long))
1921 name += sizeof(unsigned long);
1922 len -= sizeof(unsigned long);
1924 x ^= a & bytemask_from_count(len);
1926 return fold_hash(x, y);
1928 EXPORT_SYMBOL(full_name_hash);
1930 /* Return the "hash_len" (hash and length) of a null-terminated string */
1931 u64 hashlen_string(const char *name)
1933 unsigned long a = 0, x = 0, y = 0, adata, mask, len;
1934 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
1936 len = -sizeof(unsigned long);
1939 len += sizeof(unsigned long);
1940 a = load_unaligned_zeropad(name+len);
1941 } while (!has_zero(a, &adata, &constants));
1943 adata = prep_zero_mask(a, adata, &constants);
1944 mask = create_zero_mask(adata);
1945 x ^= a & zero_bytemask(mask);
1947 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
1949 EXPORT_SYMBOL(hashlen_string);
1952 * Calculate the length and hash of the path component, and
1953 * return the "hash_len" as the result.
1955 static inline u64 hash_name(const char *name)
1957 unsigned long a = 0, b, x = 0, y = 0, adata, bdata, mask, len;
1958 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
1960 len = -sizeof(unsigned long);
1963 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 char *name, unsigned int len)
1981 unsigned long hash = init_name_hash();
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 char *name)
1991 unsigned long hash = init_name_hash();
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 char *name)
2010 unsigned long hash = init_name_hash();
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(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_GET | WALK_PUT);
2102 err = walk_component(nd, WALK_GET);
2108 const char *s = get_link(nd);
2117 nd->stack[nd->depth - 1].name = name;
2122 if (unlikely(!d_can_lookup(nd->path.dentry))) {
2123 if (nd->flags & LOOKUP_RCU) {
2124 if (unlazy_walk(nd, NULL, 0))
2132 static const char *path_init(struct nameidata *nd, unsigned flags)
2135 const char *s = nd->name->name;
2137 nd->last_type = LAST_ROOT; /* if there are only slashes... */
2138 nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT;
2140 if (flags & LOOKUP_ROOT) {
2141 struct dentry *root = nd->root.dentry;
2142 struct inode *inode = root->d_inode;
2144 if (!d_can_lookup(root))
2145 return ERR_PTR(-ENOTDIR);
2146 retval = inode_permission(inode, MAY_EXEC);
2148 return ERR_PTR(retval);
2150 nd->path = nd->root;
2152 if (flags & LOOKUP_RCU) {
2154 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
2155 nd->root_seq = nd->seq;
2156 nd->m_seq = read_seqbegin(&mount_lock);
2158 path_get(&nd->path);
2163 nd->root.mnt = NULL;
2164 nd->path.mnt = NULL;
2165 nd->path.dentry = NULL;
2167 nd->m_seq = read_seqbegin(&mount_lock);
2169 if (flags & LOOKUP_RCU)
2172 if (likely(!nd_jump_root(nd)))
2174 nd->root.mnt = NULL;
2176 return ERR_PTR(-ECHILD);
2177 } else if (nd->dfd == AT_FDCWD) {
2178 if (flags & LOOKUP_RCU) {
2179 struct fs_struct *fs = current->fs;
2185 seq = read_seqcount_begin(&fs->seq);
2187 nd->inode = nd->path.dentry->d_inode;
2188 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
2189 } while (read_seqcount_retry(&fs->seq, seq));
2191 get_fs_pwd(current->fs, &nd->path);
2192 nd->inode = nd->path.dentry->d_inode;
2196 /* Caller must check execute permissions on the starting path component */
2197 struct fd f = fdget_raw(nd->dfd);
2198 struct dentry *dentry;
2201 return ERR_PTR(-EBADF);
2203 dentry = f.file->f_path.dentry;
2206 if (!d_can_lookup(dentry)) {
2208 return ERR_PTR(-ENOTDIR);
2212 nd->path = f.file->f_path;
2213 if (flags & LOOKUP_RCU) {
2215 nd->inode = nd->path.dentry->d_inode;
2216 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
2218 path_get(&nd->path);
2219 nd->inode = nd->path.dentry->d_inode;
2226 static const char *trailing_symlink(struct nameidata *nd)
2229 int error = may_follow_link(nd);
2230 if (unlikely(error))
2231 return ERR_PTR(error);
2232 nd->flags |= LOOKUP_PARENT;
2233 nd->stack[0].name = NULL;
2238 static inline int lookup_last(struct nameidata *nd)
2240 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
2241 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2243 nd->flags &= ~LOOKUP_PARENT;
2244 return walk_component(nd,
2245 nd->flags & LOOKUP_FOLLOW
2247 ? WALK_PUT | WALK_GET
2252 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2253 static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path)
2255 const char *s = path_init(nd, flags);
2260 while (!(err = link_path_walk(s, nd))
2261 && ((err = lookup_last(nd)) > 0)) {
2262 s = trailing_symlink(nd);
2269 err = complete_walk(nd);
2271 if (!err && nd->flags & LOOKUP_DIRECTORY)
2272 if (!d_can_lookup(nd->path.dentry))
2276 nd->path.mnt = NULL;
2277 nd->path.dentry = NULL;
2283 static int filename_lookup(int dfd, struct filename *name, unsigned flags,
2284 struct path *path, struct path *root)
2287 struct nameidata nd;
2289 return PTR_ERR(name);
2290 if (unlikely(root)) {
2292 flags |= LOOKUP_ROOT;
2294 set_nameidata(&nd, dfd, name);
2295 retval = path_lookupat(&nd, flags | LOOKUP_RCU, path);
2296 if (unlikely(retval == -ECHILD))
2297 retval = path_lookupat(&nd, flags, path);
2298 if (unlikely(retval == -ESTALE))
2299 retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path);
2301 if (likely(!retval))
2302 audit_inode(name, path->dentry, flags & LOOKUP_PARENT);
2303 restore_nameidata();
2308 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2309 static int path_parentat(struct nameidata *nd, unsigned flags,
2310 struct path *parent)
2312 const char *s = path_init(nd, flags);
2316 err = link_path_walk(s, nd);
2318 err = complete_walk(nd);
2321 nd->path.mnt = NULL;
2322 nd->path.dentry = NULL;
2328 static struct filename *filename_parentat(int dfd, struct filename *name,
2329 unsigned int flags, struct path *parent,
2330 struct qstr *last, int *type)
2333 struct nameidata nd;
2337 set_nameidata(&nd, dfd, name);
2338 retval = path_parentat(&nd, flags | LOOKUP_RCU, parent);
2339 if (unlikely(retval == -ECHILD))
2340 retval = path_parentat(&nd, flags, parent);
2341 if (unlikely(retval == -ESTALE))
2342 retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent);
2343 if (likely(!retval)) {
2345 *type = nd.last_type;
2346 audit_inode(name, parent->dentry, LOOKUP_PARENT);
2349 name = ERR_PTR(retval);
2351 restore_nameidata();
2355 /* does lookup, returns the object with parent locked */
2356 struct dentry *kern_path_locked(const char *name, struct path *path)
2358 struct filename *filename;
2363 filename = filename_parentat(AT_FDCWD, getname_kernel(name), 0, path,
2365 if (IS_ERR(filename))
2366 return ERR_CAST(filename);
2367 if (unlikely(type != LAST_NORM)) {
2370 return ERR_PTR(-EINVAL);
2372 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
2373 d = __lookup_hash(&last, path->dentry, 0);
2375 inode_unlock(path->dentry->d_inode);
2382 int kern_path(const char *name, unsigned int flags, struct path *path)
2384 return filename_lookup(AT_FDCWD, getname_kernel(name),
2387 EXPORT_SYMBOL(kern_path);
2390 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2391 * @dentry: pointer to dentry of the base directory
2392 * @mnt: pointer to vfs mount of the base directory
2393 * @name: pointer to file name
2394 * @flags: lookup flags
2395 * @path: pointer to struct path to fill
2397 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
2398 const char *name, unsigned int flags,
2401 struct path root = {.mnt = mnt, .dentry = dentry};
2402 /* the first argument of filename_lookup() is ignored with root */
2403 return filename_lookup(AT_FDCWD, getname_kernel(name),
2404 flags , path, &root);
2406 EXPORT_SYMBOL(vfs_path_lookup);
2409 * lookup_hash - lookup single pathname component on already hashed name
2410 * @name: name and hash to lookup
2411 * @base: base directory to lookup from
2413 * The name must have been verified and hashed (see lookup_one_len()). Using
2414 * this after just full_name_hash() is unsafe.
2416 * This function also doesn't check for search permission on base directory.
2418 * Use lookup_one_len_unlocked() instead, unless you really know what you are
2421 * Do not hold i_mutex; this helper takes i_mutex if necessary.
2423 struct dentry *lookup_hash(const struct qstr *name, struct dentry *base)
2427 ret = lookup_dcache(name, base, 0);
2429 ret = lookup_slow(name, base, 0);
2433 EXPORT_SYMBOL(lookup_hash);
2436 * lookup_one_len - filesystem helper to lookup single pathname component
2437 * @name: pathname component to lookup
2438 * @base: base directory to lookup from
2439 * @len: maximum length @len should be interpreted to
2441 * Note that this routine is purely a helper for filesystem usage and should
2442 * not be called by generic code.
2444 * The caller must hold base->i_mutex.
2446 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
2452 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2456 this.hash = full_name_hash(name, len);
2458 return ERR_PTR(-EACCES);
2460 if (unlikely(name[0] == '.')) {
2461 if (len < 2 || (len == 2 && name[1] == '.'))
2462 return ERR_PTR(-EACCES);
2466 c = *(const unsigned char *)name++;
2467 if (c == '/' || c == '\0')
2468 return ERR_PTR(-EACCES);
2471 * See if the low-level filesystem might want
2472 * to use its own hash..
2474 if (base->d_flags & DCACHE_OP_HASH) {
2475 int err = base->d_op->d_hash(base, &this);
2477 return ERR_PTR(err);
2480 err = inode_permission(base->d_inode, MAY_EXEC);
2482 return ERR_PTR(err);
2484 return __lookup_hash(&this, base, 0);
2486 EXPORT_SYMBOL(lookup_one_len);
2489 * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
2490 * @name: pathname component to lookup
2491 * @base: base directory to lookup from
2492 * @len: maximum length @len should be interpreted to
2494 * Note that this routine is purely a helper for filesystem usage and should
2495 * not be called by generic code.
2497 * Unlike lookup_one_len, it should be called without the parent
2498 * i_mutex held, and will take the i_mutex itself if necessary.
2500 struct dentry *lookup_one_len_unlocked(const char *name,
2501 struct dentry *base, int len)
2509 this.hash = full_name_hash(name, len);
2511 return ERR_PTR(-EACCES);
2513 if (unlikely(name[0] == '.')) {
2514 if (len < 2 || (len == 2 && name[1] == '.'))
2515 return ERR_PTR(-EACCES);
2519 c = *(const unsigned char *)name++;
2520 if (c == '/' || c == '\0')
2521 return ERR_PTR(-EACCES);
2524 * See if the low-level filesystem might want
2525 * to use its own hash..
2527 if (base->d_flags & DCACHE_OP_HASH) {
2528 int err = base->d_op->d_hash(base, &this);
2530 return ERR_PTR(err);
2533 err = inode_permission(base->d_inode, MAY_EXEC);
2535 return ERR_PTR(err);
2537 return lookup_hash(&this, base);
2539 EXPORT_SYMBOL(lookup_one_len_unlocked);
2541 #ifdef CONFIG_UNIX98_PTYS
2542 int path_pts(struct path *path)
2544 /* Find something mounted on "pts" in the same directory as
2547 struct dentry *child, *parent;
2551 ret = path_parent_directory(path);
2555 parent = path->dentry;
2558 child = d_hash_and_lookup(parent, &this);
2562 path->dentry = child;
2569 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
2570 struct path *path, int *empty)
2572 return filename_lookup(dfd, getname_flags(name, flags, empty),
2575 EXPORT_SYMBOL(user_path_at_empty);
2578 * NB: most callers don't do anything directly with the reference to the
2579 * to struct filename, but the nd->last pointer points into the name string
2580 * allocated by getname. So we must hold the reference to it until all
2581 * path-walking is complete.
2583 static inline struct filename *
2584 user_path_parent(int dfd, const char __user *path,
2585 struct path *parent,
2590 /* only LOOKUP_REVAL is allowed in extra flags */
2591 return filename_parentat(dfd, getname(path), flags & LOOKUP_REVAL,
2592 parent, last, type);
2596 * mountpoint_last - look up last component for umount
2597 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2598 * @path: pointer to container for result
2600 * This is a special lookup_last function just for umount. In this case, we
2601 * need to resolve the path without doing any revalidation.
2603 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2604 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2605 * in almost all cases, this lookup will be served out of the dcache. The only
2606 * cases where it won't are if nd->last refers to a symlink or the path is
2607 * bogus and it doesn't exist.
2610 * -error: if there was an error during lookup. This includes -ENOENT if the
2611 * lookup found a negative dentry. The nd->path reference will also be
2614 * 0: if we successfully resolved nd->path and found it to not to be a
2615 * symlink that needs to be followed. "path" will also be populated.
2616 * The nd->path reference will also be put.
2618 * 1: if we successfully resolved nd->last and found it to be a symlink
2619 * that needs to be followed. "path" will be populated with the path
2620 * to the link, and nd->path will *not* be put.
2623 mountpoint_last(struct nameidata *nd, struct path *path)
2626 struct dentry *dentry;
2627 struct dentry *dir = nd->path.dentry;
2629 /* If we're in rcuwalk, drop out of it to handle last component */
2630 if (nd->flags & LOOKUP_RCU) {
2631 if (unlazy_walk(nd, NULL, 0))
2635 nd->flags &= ~LOOKUP_PARENT;
2637 if (unlikely(nd->last_type != LAST_NORM)) {
2638 error = handle_dots(nd, nd->last_type);
2641 dentry = dget(nd->path.dentry);
2643 dentry = d_lookup(dir, &nd->last);
2646 * No cached dentry. Mounted dentries are pinned in the
2647 * cache, so that means that this dentry is probably
2648 * a symlink or the path doesn't actually point
2649 * to a mounted dentry.
2651 dentry = lookup_slow(&nd->last, dir,
2652 nd->flags | LOOKUP_NO_REVAL);
2654 return PTR_ERR(dentry);
2657 if (d_is_negative(dentry)) {
2663 path->dentry = dentry;
2664 path->mnt = nd->path.mnt;
2665 error = should_follow_link(nd, path, nd->flags & LOOKUP_FOLLOW,
2666 d_backing_inode(dentry), 0);
2667 if (unlikely(error))
2675 * path_mountpoint - look up a path to be umounted
2676 * @nd: lookup context
2677 * @flags: lookup flags
2678 * @path: pointer to container for result
2680 * Look up the given name, but don't attempt to revalidate the last component.
2681 * Returns 0 and "path" will be valid on success; Returns error otherwise.
2684 path_mountpoint(struct nameidata *nd, unsigned flags, struct path *path)
2686 const char *s = path_init(nd, flags);
2690 while (!(err = link_path_walk(s, nd)) &&
2691 (err = mountpoint_last(nd, path)) > 0) {
2692 s = trailing_symlink(nd);
2703 filename_mountpoint(int dfd, struct filename *name, struct path *path,
2706 struct nameidata nd;
2709 return PTR_ERR(name);
2710 set_nameidata(&nd, dfd, name);
2711 error = path_mountpoint(&nd, flags | LOOKUP_RCU, path);
2712 if (unlikely(error == -ECHILD))
2713 error = path_mountpoint(&nd, flags, path);
2714 if (unlikely(error == -ESTALE))
2715 error = path_mountpoint(&nd, flags | LOOKUP_REVAL, path);
2717 audit_inode(name, path->dentry, 0);
2718 restore_nameidata();
2724 * user_path_mountpoint_at - lookup a path from userland in order to umount it
2725 * @dfd: directory file descriptor
2726 * @name: pathname from userland
2727 * @flags: lookup flags
2728 * @path: pointer to container to hold result
2730 * A umount is a special case for path walking. We're not actually interested
2731 * in the inode in this situation, and ESTALE errors can be a problem. We
2732 * simply want track down the dentry and vfsmount attached at the mountpoint
2733 * and avoid revalidating the last component.
2735 * Returns 0 and populates "path" on success.
2738 user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags,
2741 return filename_mountpoint(dfd, getname(name), path, flags);
2745 kern_path_mountpoint(int dfd, const char *name, struct path *path,
2748 return filename_mountpoint(dfd, getname_kernel(name), path, flags);
2750 EXPORT_SYMBOL(kern_path_mountpoint);
2752 int __check_sticky(struct inode *dir, struct inode *inode)
2754 kuid_t fsuid = current_fsuid();
2756 if (uid_eq(inode->i_uid, fsuid))
2758 if (uid_eq(dir->i_uid, fsuid))
2760 return !capable_wrt_inode_uidgid(inode, CAP_FOWNER);
2762 EXPORT_SYMBOL(__check_sticky);
2765 * Check whether we can remove a link victim from directory dir, check
2766 * whether the type of victim is right.
2767 * 1. We can't do it if dir is read-only (done in permission())
2768 * 2. We should have write and exec permissions on dir
2769 * 3. We can't remove anything from append-only dir
2770 * 4. We can't do anything with immutable dir (done in permission())
2771 * 5. If the sticky bit on dir is set we should either
2772 * a. be owner of dir, or
2773 * b. be owner of victim, or
2774 * c. have CAP_FOWNER capability
2775 * 6. If the victim is append-only or immutable we can't do antyhing with
2776 * links pointing to it.
2777 * 7. If the victim has an unknown uid or gid we can't change the inode.
2778 * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2779 * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2780 * 10. We can't remove a root or mountpoint.
2781 * 11. We don't allow removal of NFS sillyrenamed files; it's handled by
2782 * nfs_async_unlink().
2784 static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
2786 struct inode *inode = d_backing_inode(victim);
2789 if (d_is_negative(victim))
2793 BUG_ON(victim->d_parent->d_inode != dir);
2794 audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
2796 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
2802 if (check_sticky(dir, inode) || IS_APPEND(inode) ||
2803 IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) || HAS_UNMAPPED_ID(inode))
2806 if (!d_is_dir(victim))
2808 if (IS_ROOT(victim))
2810 } else if (d_is_dir(victim))
2812 if (IS_DEADDIR(dir))
2814 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2819 /* Check whether we can create an object with dentry child in directory
2821 * 1. We can't do it if child already exists (open has special treatment for
2822 * this case, but since we are inlined it's OK)
2823 * 2. We can't do it if dir is read-only (done in permission())
2824 * 3. We can't do it if the fs can't represent the fsuid or fsgid.
2825 * 4. We should have write and exec permissions on dir
2826 * 5. We can't do it if dir is immutable (done in permission())
2828 static inline int may_create(struct inode *dir, struct dentry *child)
2830 struct user_namespace *s_user_ns;
2831 audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
2834 if (IS_DEADDIR(dir))
2836 s_user_ns = dir->i_sb->s_user_ns;
2837 if (!kuid_has_mapping(s_user_ns, current_fsuid()) ||
2838 !kgid_has_mapping(s_user_ns, current_fsgid()))
2840 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
2844 * p1 and p2 should be directories on the same fs.
2846 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2851 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2855 mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
2857 p = d_ancestor(p2, p1);
2859 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
2860 inode_lock_nested(p1->d_inode, I_MUTEX_CHILD);
2864 p = d_ancestor(p1, p2);
2866 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2867 inode_lock_nested(p2->d_inode, I_MUTEX_CHILD);
2871 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2872 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
2875 EXPORT_SYMBOL(lock_rename);
2877 void unlock_rename(struct dentry *p1, struct dentry *p2)
2879 inode_unlock(p1->d_inode);
2881 inode_unlock(p2->d_inode);
2882 mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
2885 EXPORT_SYMBOL(unlock_rename);
2887 int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2890 int error = may_create(dir, dentry);
2894 if (!dir->i_op->create)
2895 return -EACCES; /* shouldn't it be ENOSYS? */
2898 error = security_inode_create(dir, dentry, mode);
2901 error = dir->i_op->create(dir, dentry, mode, want_excl);
2903 fsnotify_create(dir, dentry);
2906 EXPORT_SYMBOL(vfs_create);
2908 bool may_open_dev(const struct path *path)
2910 return !(path->mnt->mnt_flags & MNT_NODEV) &&
2911 !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV);
2914 static int may_open(struct path *path, int acc_mode, int flag)
2916 struct dentry *dentry = path->dentry;
2917 struct inode *inode = dentry->d_inode;
2923 switch (inode->i_mode & S_IFMT) {
2927 if (acc_mode & MAY_WRITE)
2932 if (!may_open_dev(path))
2941 error = inode_permission(inode, MAY_OPEN | acc_mode);
2946 * An append-only file must be opened in append mode for writing.
2948 if (IS_APPEND(inode)) {
2949 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
2955 /* O_NOATIME can only be set by the owner or superuser */
2956 if (flag & O_NOATIME && !inode_owner_or_capable(inode))
2962 static int handle_truncate(struct file *filp)
2964 struct path *path = &filp->f_path;
2965 struct inode *inode = path->dentry->d_inode;
2966 int error = get_write_access(inode);
2970 * Refuse to truncate files with mandatory locks held on them.
2972 error = locks_verify_locked(filp);
2974 error = security_path_truncate(path);
2976 error = do_truncate(path->dentry, 0,
2977 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
2980 put_write_access(inode);
2984 static inline int open_to_namei_flags(int flag)
2986 if ((flag & O_ACCMODE) == 3)
2991 static int may_o_create(const struct path *dir, struct dentry *dentry, umode_t mode)
2993 int error = security_path_mknod(dir, dentry, mode, 0);
2997 error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
3001 return security_inode_create(dir->dentry->d_inode, dentry, mode);
3005 * Attempt to atomically look up, create and open a file from a negative
3008 * Returns 0 if successful. The file will have been created and attached to
3009 * @file by the filesystem calling finish_open().
3011 * Returns 1 if the file was looked up only or didn't need creating. The
3012 * caller will need to perform the open themselves. @path will have been
3013 * updated to point to the new dentry. This may be negative.
3015 * Returns an error code otherwise.
3017 static int atomic_open(struct nameidata *nd, struct dentry *dentry,
3018 struct path *path, struct file *file,
3019 const struct open_flags *op,
3020 int open_flag, umode_t mode,
3023 struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
3024 struct inode *dir = nd->path.dentry->d_inode;
3027 if (!(~open_flag & (O_EXCL | O_CREAT))) /* both O_EXCL and O_CREAT */
3028 open_flag &= ~O_TRUNC;
3030 if (nd->flags & LOOKUP_DIRECTORY)
3031 open_flag |= O_DIRECTORY;
3033 file->f_path.dentry = DENTRY_NOT_SET;
3034 file->f_path.mnt = nd->path.mnt;
3035 error = dir->i_op->atomic_open(dir, dentry, file,
3036 open_to_namei_flags(open_flag),
3038 d_lookup_done(dentry);
3041 * We didn't have the inode before the open, so check open
3044 int acc_mode = op->acc_mode;
3045 if (*opened & FILE_CREATED) {
3046 WARN_ON(!(open_flag & O_CREAT));
3047 fsnotify_create(dir, dentry);
3050 error = may_open(&file->f_path, acc_mode, open_flag);
3051 if (WARN_ON(error > 0))
3053 } else if (error > 0) {
3054 if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
3057 if (file->f_path.dentry) {
3059 dentry = file->f_path.dentry;
3061 if (*opened & FILE_CREATED)
3062 fsnotify_create(dir, dentry);
3063 path->dentry = dentry;
3064 path->mnt = nd->path.mnt;
3073 * Look up and maybe create and open the last component.
3075 * Must be called with i_mutex held on parent.
3077 * Returns 0 if the file was successfully atomically created (if necessary) and
3078 * opened. In this case the file will be returned attached to @file.
3080 * Returns 1 if the file was not completely opened at this time, though lookups
3081 * and creations will have been performed and the dentry returned in @path will
3082 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
3083 * specified then a negative dentry may be returned.
3085 * An error code is returned otherwise.
3087 * FILE_CREATE will be set in @*opened if the dentry was created and will be
3088 * cleared otherwise prior to returning.
3090 static int lookup_open(struct nameidata *nd, struct path *path,
3092 const struct open_flags *op,
3093 bool got_write, int *opened)
3095 struct dentry *dir = nd->path.dentry;
3096 struct inode *dir_inode = dir->d_inode;
3097 int open_flag = op->open_flag;
3098 struct dentry *dentry;
3099 int error, create_error = 0;
3100 umode_t mode = op->mode;
3101 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
3103 if (unlikely(IS_DEADDIR(dir_inode)))
3106 *opened &= ~FILE_CREATED;
3107 dentry = d_lookup(dir, &nd->last);
3110 dentry = d_alloc_parallel(dir, &nd->last, &wq);
3112 return PTR_ERR(dentry);
3114 if (d_in_lookup(dentry))
3117 if (!(dentry->d_flags & DCACHE_OP_REVALIDATE))
3120 error = d_revalidate(dentry, nd->flags);
3121 if (likely(error > 0))
3125 d_invalidate(dentry);
3129 if (dentry->d_inode) {
3130 /* Cached positive dentry: will open in f_op->open */
3135 * Checking write permission is tricky, bacuse we don't know if we are
3136 * going to actually need it: O_CREAT opens should work as long as the
3137 * file exists. But checking existence breaks atomicity. The trick is
3138 * to check access and if not granted clear O_CREAT from the flags.
3140 * Another problem is returing the "right" error value (e.g. for an
3141 * O_EXCL open we want to return EEXIST not EROFS).
3143 if (open_flag & O_CREAT) {
3144 if (!IS_POSIXACL(dir->d_inode))
3145 mode &= ~current_umask();
3146 if (unlikely(!got_write)) {
3147 create_error = -EROFS;
3148 open_flag &= ~O_CREAT;
3149 if (open_flag & (O_EXCL | O_TRUNC))
3151 /* No side effects, safe to clear O_CREAT */
3153 create_error = may_o_create(&nd->path, dentry, mode);
3155 open_flag &= ~O_CREAT;
3156 if (open_flag & O_EXCL)
3160 } else if ((open_flag & (O_TRUNC|O_WRONLY|O_RDWR)) &&
3161 unlikely(!got_write)) {
3163 * No O_CREATE -> atomicity not a requirement -> fall
3164 * back to lookup + open
3169 if (dir_inode->i_op->atomic_open) {
3170 error = atomic_open(nd, dentry, path, file, op, open_flag,
3172 if (unlikely(error == -ENOENT) && create_error)
3173 error = create_error;
3178 if (d_in_lookup(dentry)) {
3179 struct dentry *res = dir_inode->i_op->lookup(dir_inode, dentry,
3181 d_lookup_done(dentry);
3182 if (unlikely(res)) {
3184 error = PTR_ERR(res);
3192 /* Negative dentry, just create the file */
3193 if (!dentry->d_inode && (open_flag & O_CREAT)) {
3194 *opened |= FILE_CREATED;
3195 audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);
3196 if (!dir_inode->i_op->create) {
3200 error = dir_inode->i_op->create(dir_inode, dentry, mode,
3201 open_flag & O_EXCL);
3204 fsnotify_create(dir_inode, dentry);
3206 if (unlikely(create_error) && !dentry->d_inode) {
3207 error = create_error;
3211 path->dentry = dentry;
3212 path->mnt = nd->path.mnt;
3221 * Handle the last step of open()
3223 static int do_last(struct nameidata *nd,
3224 struct file *file, const struct open_flags *op,
3227 struct dentry *dir = nd->path.dentry;
3228 int open_flag = op->open_flag;
3229 bool will_truncate = (open_flag & O_TRUNC) != 0;
3230 bool got_write = false;
3231 int acc_mode = op->acc_mode;
3233 struct inode *inode;
3234 struct path save_parent = { .dentry = NULL, .mnt = NULL };
3236 bool retried = false;
3239 nd->flags &= ~LOOKUP_PARENT;
3240 nd->flags |= op->intent;
3242 if (nd->last_type != LAST_NORM) {
3243 error = handle_dots(nd, nd->last_type);
3244 if (unlikely(error))
3249 if (!(open_flag & O_CREAT)) {
3250 if (nd->last.name[nd->last.len])
3251 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
3252 /* we _can_ be in RCU mode here */
3253 error = lookup_fast(nd, &path, &inode, &seq);
3254 if (likely(error > 0))
3260 BUG_ON(nd->inode != dir->d_inode);
3261 BUG_ON(nd->flags & LOOKUP_RCU);
3263 /* create side of things */
3265 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
3266 * has been cleared when we got to the last component we are
3269 error = complete_walk(nd);
3273 audit_inode(nd->name, dir, LOOKUP_PARENT);
3274 /* trailing slashes? */
3275 if (unlikely(nd->last.name[nd->last.len]))
3280 if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
3281 error = mnt_want_write(nd->path.mnt);
3285 * do _not_ fail yet - we might not need that or fail with
3286 * a different error; let lookup_open() decide; we'll be
3287 * dropping this one anyway.
3290 if (open_flag & O_CREAT)
3291 inode_lock(dir->d_inode);
3293 inode_lock_shared(dir->d_inode);
3294 error = lookup_open(nd, &path, file, op, got_write, opened);
3295 if (open_flag & O_CREAT)
3296 inode_unlock(dir->d_inode);
3298 inode_unlock_shared(dir->d_inode);
3304 if ((*opened & FILE_CREATED) ||
3305 !S_ISREG(file_inode(file)->i_mode))
3306 will_truncate = false;
3308 audit_inode(nd->name, file->f_path.dentry, 0);
3312 if (*opened & FILE_CREATED) {
3313 /* Don't check for write permission, don't truncate */
3314 open_flag &= ~O_TRUNC;
3315 will_truncate = false;
3317 path_to_nameidata(&path, nd);
3318 goto finish_open_created;
3322 * If atomic_open() acquired write access it is dropped now due to
3323 * possible mount and symlink following (this might be optimized away if
3327 mnt_drop_write(nd->path.mnt);
3331 if (unlikely(d_is_negative(path.dentry))) {
3332 path_to_nameidata(&path, nd);
3337 * create/update audit record if it already exists.
3339 audit_inode(nd->name, path.dentry, 0);
3341 if (unlikely((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))) {
3342 path_to_nameidata(&path, nd);
3346 error = follow_managed(&path, nd);
3347 if (unlikely(error < 0))
3350 seq = 0; /* out of RCU mode, so the value doesn't matter */
3351 inode = d_backing_inode(path.dentry);
3355 error = should_follow_link(nd, &path, nd->flags & LOOKUP_FOLLOW,
3357 if (unlikely(error))
3360 if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path.mnt) {
3361 path_to_nameidata(&path, nd);
3363 save_parent.dentry = nd->path.dentry;
3364 save_parent.mnt = mntget(path.mnt);
3365 nd->path.dentry = path.dentry;
3370 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3372 error = complete_walk(nd);
3374 path_put(&save_parent);
3377 audit_inode(nd->name, nd->path.dentry, 0);
3379 if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry))
3382 if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
3384 if (!d_is_reg(nd->path.dentry))
3385 will_truncate = false;
3387 if (will_truncate) {
3388 error = mnt_want_write(nd->path.mnt);
3393 finish_open_created:
3394 error = may_open(&nd->path, acc_mode, open_flag);
3397 BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
3398 error = vfs_open(&nd->path, file, current_cred());
3400 *opened |= FILE_OPENED;
3402 if (error == -EOPENSTALE)
3407 error = open_check_o_direct(file);
3409 error = ima_file_check(file, op->acc_mode, *opened);
3410 if (!error && will_truncate)
3411 error = handle_truncate(file);
3413 if (unlikely(error) && (*opened & FILE_OPENED))
3415 if (unlikely(error > 0)) {
3420 mnt_drop_write(nd->path.mnt);
3421 path_put(&save_parent);
3425 /* If no saved parent or already retried then can't retry */
3426 if (!save_parent.dentry || retried)
3429 BUG_ON(save_parent.dentry != dir);
3430 path_put(&nd->path);
3431 nd->path = save_parent;
3432 nd->inode = dir->d_inode;
3433 save_parent.mnt = NULL;
3434 save_parent.dentry = NULL;
3436 mnt_drop_write(nd->path.mnt);
3443 static int do_tmpfile(struct nameidata *nd, unsigned flags,
3444 const struct open_flags *op,
3445 struct file *file, int *opened)
3447 static const struct qstr name = QSTR_INIT("/", 1);
3448 struct dentry *child;
3451 int error = path_lookupat(nd, flags | LOOKUP_DIRECTORY, &path);
3452 if (unlikely(error))
3454 error = mnt_want_write(path.mnt);
3455 if (unlikely(error))
3457 dir = path.dentry->d_inode;
3458 /* we want directory to be writable */
3459 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
3462 if (!dir->i_op->tmpfile) {
3463 error = -EOPNOTSUPP;
3466 child = d_alloc(path.dentry, &name);
3467 if (unlikely(!child)) {
3472 path.dentry = child;
3473 error = dir->i_op->tmpfile(dir, child, op->mode);
3476 audit_inode(nd->name, child, 0);
3477 /* Don't check for other permissions, the inode was just created */
3478 error = may_open(&path, 0, op->open_flag);
3481 file->f_path.mnt = path.mnt;
3482 error = finish_open(file, child, NULL, opened);
3485 error = open_check_o_direct(file);
3488 } else if (!(op->open_flag & O_EXCL)) {
3489 struct inode *inode = file_inode(file);
3490 spin_lock(&inode->i_lock);
3491 inode->i_state |= I_LINKABLE;
3492 spin_unlock(&inode->i_lock);
3495 mnt_drop_write(path.mnt);
3501 static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file)
3504 int error = path_lookupat(nd, flags, &path);
3506 audit_inode(nd->name, path.dentry, 0);
3507 error = vfs_open(&path, file, current_cred());
3513 static struct file *path_openat(struct nameidata *nd,
3514 const struct open_flags *op, unsigned flags)
3521 file = get_empty_filp();
3525 file->f_flags = op->open_flag;
3527 if (unlikely(file->f_flags & __O_TMPFILE)) {
3528 error = do_tmpfile(nd, flags, op, file, &opened);
3532 if (unlikely(file->f_flags & O_PATH)) {
3533 error = do_o_path(nd, flags, file);
3535 opened |= FILE_OPENED;
3539 s = path_init(nd, flags);
3544 while (!(error = link_path_walk(s, nd)) &&
3545 (error = do_last(nd, file, op, &opened)) > 0) {
3546 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
3547 s = trailing_symlink(nd);
3555 if (!(opened & FILE_OPENED)) {
3559 if (unlikely(error)) {
3560 if (error == -EOPENSTALE) {
3561 if (flags & LOOKUP_RCU)
3566 file = ERR_PTR(error);
3571 struct file *do_filp_open(int dfd, struct filename *pathname,
3572 const struct open_flags *op)
3574 struct nameidata nd;
3575 int flags = op->lookup_flags;
3578 set_nameidata(&nd, dfd, pathname);
3579 filp = path_openat(&nd, op, flags | LOOKUP_RCU);
3580 if (unlikely(filp == ERR_PTR(-ECHILD)))
3581 filp = path_openat(&nd, op, flags);
3582 if (unlikely(filp == ERR_PTR(-ESTALE)))
3583 filp = path_openat(&nd, op, flags | LOOKUP_REVAL);
3584 restore_nameidata();
3588 struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
3589 const char *name, const struct open_flags *op)
3591 struct nameidata nd;
3593 struct filename *filename;
3594 int flags = op->lookup_flags | LOOKUP_ROOT;
3597 nd.root.dentry = dentry;
3599 if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN)
3600 return ERR_PTR(-ELOOP);
3602 filename = getname_kernel(name);
3603 if (IS_ERR(filename))
3604 return ERR_CAST(filename);
3606 set_nameidata(&nd, -1, filename);
3607 file = path_openat(&nd, op, flags | LOOKUP_RCU);
3608 if (unlikely(file == ERR_PTR(-ECHILD)))
3609 file = path_openat(&nd, op, flags);
3610 if (unlikely(file == ERR_PTR(-ESTALE)))
3611 file = path_openat(&nd, op, flags | LOOKUP_REVAL);
3612 restore_nameidata();
3617 static struct dentry *filename_create(int dfd, struct filename *name,
3618 struct path *path, unsigned int lookup_flags)
3620 struct dentry *dentry = ERR_PTR(-EEXIST);
3625 bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
3628 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3629 * other flags passed in are ignored!
3631 lookup_flags &= LOOKUP_REVAL;
3633 name = filename_parentat(dfd, name, lookup_flags, path, &last, &type);
3635 return ERR_CAST(name);
3638 * Yucky last component or no last component at all?
3639 * (foo/., foo/.., /////)
3641 if (unlikely(type != LAST_NORM))
3644 /* don't fail immediately if it's r/o, at least try to report other errors */
3645 err2 = mnt_want_write(path->mnt);
3647 * Do the final lookup.
3649 lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL;
3650 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
3651 dentry = __lookup_hash(&last, path->dentry, lookup_flags);
3656 if (d_is_positive(dentry))
3660 * Special case - lookup gave negative, but... we had foo/bar/
3661 * From the vfs_mknod() POV we just have a negative dentry -
3662 * all is fine. Let's be bastards - you had / on the end, you've
3663 * been asking for (non-existent) directory. -ENOENT for you.
3665 if (unlikely(!is_dir && last.name[last.len])) {
3669 if (unlikely(err2)) {
3677 dentry = ERR_PTR(error);
3679 inode_unlock(path->dentry->d_inode);
3681 mnt_drop_write(path->mnt);
3688 struct dentry *kern_path_create(int dfd, const char *pathname,
3689 struct path *path, unsigned int lookup_flags)
3691 return filename_create(dfd, getname_kernel(pathname),
3692 path, lookup_flags);
3694 EXPORT_SYMBOL(kern_path_create);
3696 void done_path_create(struct path *path, struct dentry *dentry)
3699 inode_unlock(path->dentry->d_inode);
3700 mnt_drop_write(path->mnt);
3703 EXPORT_SYMBOL(done_path_create);
3705 inline struct dentry *user_path_create(int dfd, const char __user *pathname,
3706 struct path *path, unsigned int lookup_flags)
3708 return filename_create(dfd, getname(pathname), path, lookup_flags);
3710 EXPORT_SYMBOL(user_path_create);
3712 int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
3714 int error = may_create(dir, dentry);
3719 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
3722 if (!dir->i_op->mknod)
3725 error = devcgroup_inode_mknod(mode, dev);
3729 error = security_inode_mknod(dir, dentry, mode, dev);
3733 error = dir->i_op->mknod(dir, dentry, mode, dev);
3735 fsnotify_create(dir, dentry);
3738 EXPORT_SYMBOL(vfs_mknod);
3740 static int may_mknod(umode_t mode)
3742 switch (mode & S_IFMT) {
3748 case 0: /* zero mode translates to S_IFREG */
3757 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
3760 struct dentry *dentry;
3763 unsigned int lookup_flags = 0;
3765 error = may_mknod(mode);
3769 dentry = user_path_create(dfd, filename, &path, lookup_flags);
3771 return PTR_ERR(dentry);
3773 if (!IS_POSIXACL(path.dentry->d_inode))
3774 mode &= ~current_umask();
3775 error = security_path_mknod(&path, dentry, mode, dev);
3778 switch (mode & S_IFMT) {
3779 case 0: case S_IFREG:
3780 error = vfs_create(path.dentry->d_inode,dentry,mode,true);
3782 ima_post_path_mknod(dentry);
3784 case S_IFCHR: case S_IFBLK:
3785 error = vfs_mknod(path.dentry->d_inode,dentry,mode,
3786 new_decode_dev(dev));
3788 case S_IFIFO: case S_IFSOCK:
3789 error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
3793 done_path_create(&path, dentry);
3794 if (retry_estale(error, lookup_flags)) {
3795 lookup_flags |= LOOKUP_REVAL;
3801 SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
3803 return sys_mknodat(AT_FDCWD, filename, mode, dev);
3806 int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
3808 int error = may_create(dir, dentry);
3809 unsigned max_links = dir->i_sb->s_max_links;
3814 if (!dir->i_op->mkdir)
3817 mode &= (S_IRWXUGO|S_ISVTX);
3818 error = security_inode_mkdir(dir, dentry, mode);
3822 if (max_links && dir->i_nlink >= max_links)
3825 error = dir->i_op->mkdir(dir, dentry, mode);
3827 fsnotify_mkdir(dir, dentry);
3830 EXPORT_SYMBOL(vfs_mkdir);
3832 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
3834 struct dentry *dentry;
3837 unsigned int lookup_flags = LOOKUP_DIRECTORY;
3840 dentry = user_path_create(dfd, pathname, &path, lookup_flags);
3842 return PTR_ERR(dentry);
3844 if (!IS_POSIXACL(path.dentry->d_inode))
3845 mode &= ~current_umask();
3846 error = security_path_mkdir(&path, dentry, mode);
3848 error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
3849 done_path_create(&path, dentry);
3850 if (retry_estale(error, lookup_flags)) {
3851 lookup_flags |= LOOKUP_REVAL;
3857 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
3859 return sys_mkdirat(AT_FDCWD, pathname, mode);
3862 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
3864 int error = may_delete(dir, dentry, 1);
3869 if (!dir->i_op->rmdir)
3873 inode_lock(dentry->d_inode);
3876 if (is_local_mountpoint(dentry))
3879 error = security_inode_rmdir(dir, dentry);
3883 shrink_dcache_parent(dentry);
3884 error = dir->i_op->rmdir(dir, dentry);
3888 dentry->d_inode->i_flags |= S_DEAD;
3890 detach_mounts(dentry);
3893 inode_unlock(dentry->d_inode);
3899 EXPORT_SYMBOL(vfs_rmdir);
3901 static long do_rmdir(int dfd, const char __user *pathname)
3904 struct filename *name;
3905 struct dentry *dentry;
3909 unsigned int lookup_flags = 0;
3911 name = user_path_parent(dfd, pathname,
3912 &path, &last, &type, lookup_flags);
3914 return PTR_ERR(name);
3928 error = mnt_want_write(path.mnt);
3932 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
3933 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
3934 error = PTR_ERR(dentry);
3937 if (!dentry->d_inode) {
3941 error = security_path_rmdir(&path, dentry);
3944 error = vfs_rmdir(path.dentry->d_inode, dentry);
3948 inode_unlock(path.dentry->d_inode);
3949 mnt_drop_write(path.mnt);
3953 if (retry_estale(error, lookup_flags)) {
3954 lookup_flags |= LOOKUP_REVAL;
3960 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
3962 return do_rmdir(AT_FDCWD, pathname);
3966 * vfs_unlink - unlink a filesystem object
3967 * @dir: parent directory
3969 * @delegated_inode: returns victim inode, if the inode is delegated.
3971 * The caller must hold dir->i_mutex.
3973 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
3974 * return a reference to the inode in delegated_inode. The caller
3975 * should then break the delegation on that inode and retry. Because
3976 * breaking a delegation may take a long time, the caller should drop
3977 * dir->i_mutex before doing so.
3979 * Alternatively, a caller may pass NULL for delegated_inode. This may
3980 * be appropriate for callers that expect the underlying filesystem not
3981 * to be NFS exported.
3983 int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode)
3985 struct inode *target = dentry->d_inode;
3986 int error = may_delete(dir, dentry, 0);
3991 if (!dir->i_op->unlink)
3995 if (is_local_mountpoint(dentry))
3998 error = security_inode_unlink(dir, dentry);
4000 error = try_break_deleg(target, delegated_inode);
4003 error = dir->i_op->unlink(dir, dentry);
4006 detach_mounts(dentry);
4011 inode_unlock(target);
4013 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
4014 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
4015 fsnotify_link_count(target);
4021 EXPORT_SYMBOL(vfs_unlink);
4024 * Make sure that the actual truncation of the file will occur outside its
4025 * directory's i_mutex. Truncate can take a long time if there is a lot of
4026 * writeout happening, and we don't want to prevent access to the directory
4027 * while waiting on the I/O.
4029 static long do_unlinkat(int dfd, const char __user *pathname)
4032 struct filename *name;
4033 struct dentry *dentry;
4037 struct inode *inode = NULL;
4038 struct inode *delegated_inode = NULL;
4039 unsigned int lookup_flags = 0;
4041 name = user_path_parent(dfd, pathname,
4042 &path, &last, &type, lookup_flags);
4044 return PTR_ERR(name);
4047 if (type != LAST_NORM)
4050 error = mnt_want_write(path.mnt);
4054 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
4055 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
4056 error = PTR_ERR(dentry);
4057 if (!IS_ERR(dentry)) {
4058 /* Why not before? Because we want correct error value */
4059 if (last.name[last.len])
4061 inode = dentry->d_inode;
4062 if (d_is_negative(dentry))
4065 error = security_path_unlink(&path, dentry);
4068 error = vfs_unlink(path.dentry->d_inode, dentry, &delegated_inode);
4072 inode_unlock(path.dentry->d_inode);
4074 iput(inode); /* truncate the inode here */
4076 if (delegated_inode) {
4077 error = break_deleg_wait(&delegated_inode);
4081 mnt_drop_write(path.mnt);
4085 if (retry_estale(error, lookup_flags)) {
4086 lookup_flags |= LOOKUP_REVAL;
4093 if (d_is_negative(dentry))
4095 else if (d_is_dir(dentry))
4102 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
4104 if ((flag & ~AT_REMOVEDIR) != 0)
4107 if (flag & AT_REMOVEDIR)
4108 return do_rmdir(dfd, pathname);
4110 return do_unlinkat(dfd, pathname);
4113 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
4115 return do_unlinkat(AT_FDCWD, pathname);
4118 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
4120 int error = may_create(dir, dentry);
4125 if (!dir->i_op->symlink)
4128 error = security_inode_symlink(dir, dentry, oldname);
4132 error = dir->i_op->symlink(dir, dentry, oldname);
4134 fsnotify_create(dir, dentry);
4137 EXPORT_SYMBOL(vfs_symlink);
4139 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
4140 int, newdfd, const char __user *, newname)
4143 struct filename *from;
4144 struct dentry *dentry;
4146 unsigned int lookup_flags = 0;
4148 from = getname(oldname);
4150 return PTR_ERR(from);
4152 dentry = user_path_create(newdfd, newname, &path, lookup_flags);
4153 error = PTR_ERR(dentry);
4157 error = security_path_symlink(&path, dentry, from->name);
4159 error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
4160 done_path_create(&path, dentry);
4161 if (retry_estale(error, lookup_flags)) {
4162 lookup_flags |= LOOKUP_REVAL;
4170 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
4172 return sys_symlinkat(oldname, AT_FDCWD, newname);
4176 * vfs_link - create a new link
4177 * @old_dentry: object to be linked
4179 * @new_dentry: where to create the new link
4180 * @delegated_inode: returns inode needing a delegation break
4182 * The caller must hold dir->i_mutex
4184 * If vfs_link discovers a delegation on the to-be-linked file in need
4185 * of breaking, it will return -EWOULDBLOCK and return a reference to the
4186 * inode in delegated_inode. The caller should then break the delegation
4187 * and retry. Because breaking a delegation may take a long time, the
4188 * caller should drop the i_mutex before doing so.
4190 * Alternatively, a caller may pass NULL for delegated_inode. This may
4191 * be appropriate for callers that expect the underlying filesystem not
4192 * to be NFS exported.
4194 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode)
4196 struct inode *inode = old_dentry->d_inode;
4197 unsigned max_links = dir->i_sb->s_max_links;
4203 error = may_create(dir, new_dentry);
4207 if (dir->i_sb != inode->i_sb)
4211 * A link to an append-only or immutable file cannot be created.
4213 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
4216 * Updating the link count will likely cause i_uid and i_gid to
4217 * be writen back improperly if their true value is unknown to
4220 if (HAS_UNMAPPED_ID(inode))
4222 if (!dir->i_op->link)
4224 if (S_ISDIR(inode->i_mode))
4227 error = security_inode_link(old_dentry, dir, new_dentry);
4232 /* Make sure we don't allow creating hardlink to an unlinked file */
4233 if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
4235 else if (max_links && inode->i_nlink >= max_links)
4238 error = try_break_deleg(inode, delegated_inode);
4240 error = dir->i_op->link(old_dentry, dir, new_dentry);
4243 if (!error && (inode->i_state & I_LINKABLE)) {
4244 spin_lock(&inode->i_lock);
4245 inode->i_state &= ~I_LINKABLE;
4246 spin_unlock(&inode->i_lock);
4248 inode_unlock(inode);
4250 fsnotify_link(dir, inode, new_dentry);
4253 EXPORT_SYMBOL(vfs_link);
4256 * Hardlinks are often used in delicate situations. We avoid
4257 * security-related surprises by not following symlinks on the
4260 * We don't follow them on the oldname either to be compatible
4261 * with linux 2.0, and to avoid hard-linking to directories
4262 * and other special files. --ADM
4264 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
4265 int, newdfd, const char __user *, newname, int, flags)
4267 struct dentry *new_dentry;
4268 struct path old_path, new_path;
4269 struct inode *delegated_inode = NULL;
4273 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
4276 * To use null names we require CAP_DAC_READ_SEARCH
4277 * This ensures that not everyone will be able to create
4278 * handlink using the passed filedescriptor.
4280 if (flags & AT_EMPTY_PATH) {
4281 if (!capable(CAP_DAC_READ_SEARCH))
4286 if (flags & AT_SYMLINK_FOLLOW)
4287 how |= LOOKUP_FOLLOW;
4289 error = user_path_at(olddfd, oldname, how, &old_path);
4293 new_dentry = user_path_create(newdfd, newname, &new_path,
4294 (how & LOOKUP_REVAL));
4295 error = PTR_ERR(new_dentry);
4296 if (IS_ERR(new_dentry))
4300 if (old_path.mnt != new_path.mnt)
4302 error = may_linkat(&old_path);
4303 if (unlikely(error))
4305 error = security_path_link(old_path.dentry, &new_path, new_dentry);
4308 error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, &delegated_inode);
4310 done_path_create(&new_path, new_dentry);
4311 if (delegated_inode) {
4312 error = break_deleg_wait(&delegated_inode);
4314 path_put(&old_path);
4318 if (retry_estale(error, how)) {
4319 path_put(&old_path);
4320 how |= LOOKUP_REVAL;
4324 path_put(&old_path);
4329 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
4331 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
4335 * vfs_rename - rename a filesystem object
4336 * @old_dir: parent of source
4337 * @old_dentry: source
4338 * @new_dir: parent of destination
4339 * @new_dentry: destination
4340 * @delegated_inode: returns an inode needing a delegation break
4341 * @flags: rename flags
4343 * The caller must hold multiple mutexes--see lock_rename()).
4345 * If vfs_rename discovers a delegation in need of breaking at either
4346 * the source or destination, it will return -EWOULDBLOCK and return a
4347 * reference to the inode in delegated_inode. The caller should then
4348 * break the delegation and retry. Because breaking a delegation may
4349 * take a long time, the caller should drop all locks before doing
4352 * Alternatively, a caller may pass NULL for delegated_inode. This may
4353 * be appropriate for callers that expect the underlying filesystem not
4354 * to be NFS exported.
4356 * The worst of all namespace operations - renaming directory. "Perverted"
4357 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4359 * a) we can get into loop creation.
4360 * b) race potential - two innocent renames can create a loop together.
4361 * That's where 4.4 screws up. Current fix: serialization on
4362 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4364 * c) we have to lock _four_ objects - parents and victim (if it exists),
4365 * and source (if it is not a directory).
4366 * And that - after we got ->i_mutex on parents (until then we don't know
4367 * whether the target exists). Solution: try to be smart with locking
4368 * order for inodes. We rely on the fact that tree topology may change
4369 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4370 * move will be locked. Thus we can rank directories by the tree
4371 * (ancestors first) and rank all non-directories after them.
4372 * That works since everybody except rename does "lock parent, lookup,
4373 * lock child" and rename is under ->s_vfs_rename_mutex.
4374 * HOWEVER, it relies on the assumption that any object with ->lookup()
4375 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4376 * we'd better make sure that there's no link(2) for them.
4377 * d) conversion from fhandle to dentry may come in the wrong moment - when
4378 * we are removing the target. Solution: we will have to grab ->i_mutex
4379 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4380 * ->i_mutex on parents, which works but leads to some truly excessive
4383 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
4384 struct inode *new_dir, struct dentry *new_dentry,
4385 struct inode **delegated_inode, unsigned int flags)
4388 bool is_dir = d_is_dir(old_dentry);
4389 const unsigned char *old_name;
4390 struct inode *source = old_dentry->d_inode;
4391 struct inode *target = new_dentry->d_inode;
4392 bool new_is_dir = false;
4393 unsigned max_links = new_dir->i_sb->s_max_links;
4396 * Check source == target.
4397 * On overlayfs need to look at underlying inodes.
4399 if (vfs_select_inode(old_dentry, 0) == vfs_select_inode(new_dentry, 0))
4402 error = may_delete(old_dir, old_dentry, is_dir);
4407 error = may_create(new_dir, new_dentry);
4409 new_is_dir = d_is_dir(new_dentry);
4411 if (!(flags & RENAME_EXCHANGE))
4412 error = may_delete(new_dir, new_dentry, is_dir);
4414 error = may_delete(new_dir, new_dentry, new_is_dir);
4419 if (!old_dir->i_op->rename && !old_dir->i_op->rename2)
4422 if (flags && !old_dir->i_op->rename2)
4426 * If we are going to change the parent - check write permissions,
4427 * we'll need to flip '..'.
4429 if (new_dir != old_dir) {
4431 error = inode_permission(source, MAY_WRITE);
4435 if ((flags & RENAME_EXCHANGE) && new_is_dir) {
4436 error = inode_permission(target, MAY_WRITE);
4442 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
4447 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
4449 if (!is_dir || (flags & RENAME_EXCHANGE))
4450 lock_two_nondirectories(source, target);
4455 if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry))
4458 if (max_links && new_dir != old_dir) {
4460 if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
4462 if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
4463 old_dir->i_nlink >= max_links)
4466 if (is_dir && !(flags & RENAME_EXCHANGE) && target)
4467 shrink_dcache_parent(new_dentry);
4469 error = try_break_deleg(source, delegated_inode);
4473 if (target && !new_is_dir) {
4474 error = try_break_deleg(target, delegated_inode);
4478 if (!old_dir->i_op->rename2) {
4479 error = old_dir->i_op->rename(old_dir, old_dentry,
4480 new_dir, new_dentry);
4482 WARN_ON(old_dir->i_op->rename != NULL);
4483 error = old_dir->i_op->rename2(old_dir, old_dentry,
4484 new_dir, new_dentry, flags);
4489 if (!(flags & RENAME_EXCHANGE) && target) {
4491 target->i_flags |= S_DEAD;
4492 dont_mount(new_dentry);
4493 detach_mounts(new_dentry);
4495 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
4496 if (!(flags & RENAME_EXCHANGE))
4497 d_move(old_dentry, new_dentry);
4499 d_exchange(old_dentry, new_dentry);
4502 if (!is_dir || (flags & RENAME_EXCHANGE))
4503 unlock_two_nondirectories(source, target);
4505 inode_unlock(target);
4508 fsnotify_move(old_dir, new_dir, old_name, is_dir,
4509 !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
4510 if (flags & RENAME_EXCHANGE) {
4511 fsnotify_move(new_dir, old_dir, old_dentry->d_name.name,
4512 new_is_dir, NULL, new_dentry);
4515 fsnotify_oldname_free(old_name);
4519 EXPORT_SYMBOL(vfs_rename);
4521 SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
4522 int, newdfd, const char __user *, newname, unsigned int, flags)
4524 struct dentry *old_dentry, *new_dentry;
4525 struct dentry *trap;
4526 struct path old_path, new_path;
4527 struct qstr old_last, new_last;
4528 int old_type, new_type;
4529 struct inode *delegated_inode = NULL;
4530 struct filename *from;
4531 struct filename *to;
4532 unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET;
4533 bool should_retry = false;
4536 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
4539 if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
4540 (flags & RENAME_EXCHANGE))
4543 if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD))
4546 if (flags & RENAME_EXCHANGE)
4550 from = user_path_parent(olddfd, oldname,
4551 &old_path, &old_last, &old_type, lookup_flags);
4553 error = PTR_ERR(from);
4557 to = user_path_parent(newdfd, newname,
4558 &new_path, &new_last, &new_type, lookup_flags);
4560 error = PTR_ERR(to);
4565 if (old_path.mnt != new_path.mnt)
4569 if (old_type != LAST_NORM)
4572 if (flags & RENAME_NOREPLACE)
4574 if (new_type != LAST_NORM)
4577 error = mnt_want_write(old_path.mnt);
4582 trap = lock_rename(new_path.dentry, old_path.dentry);
4584 old_dentry = __lookup_hash(&old_last, old_path.dentry, lookup_flags);
4585 error = PTR_ERR(old_dentry);
4586 if (IS_ERR(old_dentry))
4588 /* source must exist */
4590 if (d_is_negative(old_dentry))
4592 new_dentry = __lookup_hash(&new_last, new_path.dentry, lookup_flags | target_flags);
4593 error = PTR_ERR(new_dentry);
4594 if (IS_ERR(new_dentry))
4597 if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
4599 if (flags & RENAME_EXCHANGE) {
4601 if (d_is_negative(new_dentry))
4604 if (!d_is_dir(new_dentry)) {
4606 if (new_last.name[new_last.len])
4610 /* unless the source is a directory trailing slashes give -ENOTDIR */
4611 if (!d_is_dir(old_dentry)) {
4613 if (old_last.name[old_last.len])
4615 if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len])
4618 /* source should not be ancestor of target */
4620 if (old_dentry == trap)
4622 /* target should not be an ancestor of source */
4623 if (!(flags & RENAME_EXCHANGE))
4625 if (new_dentry == trap)
4628 error = security_path_rename(&old_path, old_dentry,
4629 &new_path, new_dentry, flags);
4632 error = vfs_rename(old_path.dentry->d_inode, old_dentry,
4633 new_path.dentry->d_inode, new_dentry,
4634 &delegated_inode, flags);
4640 unlock_rename(new_path.dentry, old_path.dentry);
4641 if (delegated_inode) {
4642 error = break_deleg_wait(&delegated_inode);
4646 mnt_drop_write(old_path.mnt);
4648 if (retry_estale(error, lookup_flags))
4649 should_retry = true;
4650 path_put(&new_path);
4653 path_put(&old_path);
4656 should_retry = false;
4657 lookup_flags |= LOOKUP_REVAL;
4664 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
4665 int, newdfd, const char __user *, newname)
4667 return sys_renameat2(olddfd, oldname, newdfd, newname, 0);
4670 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
4672 return sys_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
4675 int vfs_whiteout(struct inode *dir, struct dentry *dentry)
4677 int error = may_create(dir, dentry);
4681 if (!dir->i_op->mknod)
4684 return dir->i_op->mknod(dir, dentry,
4685 S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
4687 EXPORT_SYMBOL(vfs_whiteout);
4689 int readlink_copy(char __user *buffer, int buflen, const char *link)
4691 int len = PTR_ERR(link);
4696 if (len > (unsigned) buflen)
4698 if (copy_to_user(buffer, link, len))
4705 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
4706 * have ->get_link() not calling nd_jump_link(). Using (or not using) it
4707 * for any given inode is up to filesystem.
4709 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4711 DEFINE_DELAYED_CALL(done);
4712 struct inode *inode = d_inode(dentry);
4713 const char *link = inode->i_link;
4717 link = inode->i_op->get_link(dentry, inode, &done);
4719 return PTR_ERR(link);
4721 res = readlink_copy(buffer, buflen, link);
4722 do_delayed_call(&done);
4725 EXPORT_SYMBOL(generic_readlink);
4727 /* get the link contents into pagecache */
4728 const char *page_get_link(struct dentry *dentry, struct inode *inode,
4729 struct delayed_call *callback)
4733 struct address_space *mapping = inode->i_mapping;
4736 page = find_get_page(mapping, 0);
4738 return ERR_PTR(-ECHILD);
4739 if (!PageUptodate(page)) {
4741 return ERR_PTR(-ECHILD);
4744 page = read_mapping_page(mapping, 0, NULL);
4748 set_delayed_call(callback, page_put_link, page);
4749 BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
4750 kaddr = page_address(page);
4751 nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1);
4755 EXPORT_SYMBOL(page_get_link);
4757 void page_put_link(void *arg)
4761 EXPORT_SYMBOL(page_put_link);
4763 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4765 DEFINE_DELAYED_CALL(done);
4766 int res = readlink_copy(buffer, buflen,
4767 page_get_link(dentry, d_inode(dentry),
4769 do_delayed_call(&done);
4772 EXPORT_SYMBOL(page_readlink);
4775 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4777 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
4779 struct address_space *mapping = inode->i_mapping;
4783 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
4785 flags |= AOP_FLAG_NOFS;
4788 err = pagecache_write_begin(NULL, mapping, 0, len-1,
4789 flags, &page, &fsdata);
4793 memcpy(page_address(page), symname, len-1);
4795 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
4802 mark_inode_dirty(inode);
4807 EXPORT_SYMBOL(__page_symlink);
4809 int page_symlink(struct inode *inode, const char *symname, int len)
4811 return __page_symlink(inode, symname, len,
4812 !mapping_gfp_constraint(inode->i_mapping, __GFP_FS));
4814 EXPORT_SYMBOL(page_symlink);
4816 const struct inode_operations page_symlink_inode_operations = {
4817 .readlink = generic_readlink,
4818 .get_link = page_get_link,
4820 EXPORT_SYMBOL(page_symlink_inode_operations);