4 * Copyright (C) 1991, 1992 Linus Torvalds
8 * Some corrections by tytso.
11 /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
14 /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
17 #include <linux/init.h>
18 #include <linux/export.h>
19 #include <linux/kernel.h>
20 #include <linux/slab.h>
22 #include <linux/namei.h>
23 #include <linux/pagemap.h>
24 #include <linux/fsnotify.h>
25 #include <linux/personality.h>
26 #include <linux/security.h>
27 #include <linux/ima.h>
28 #include <linux/syscalls.h>
29 #include <linux/mount.h>
30 #include <linux/audit.h>
31 #include <linux/capability.h>
32 #include <linux/file.h>
33 #include <linux/fcntl.h>
34 #include <linux/device_cgroup.h>
35 #include <linux/fs_struct.h>
36 #include <linux/posix_acl.h>
37 #include <asm/uaccess.h>
42 /* [Feb-1997 T. Schoebel-Theuer]
43 * Fundamental changes in the pathname lookup mechanisms (namei)
44 * were necessary because of omirr. The reason is that omirr needs
45 * to know the _real_ pathname, not the user-supplied one, in case
46 * of symlinks (and also when transname replacements occur).
48 * The new code replaces the old recursive symlink resolution with
49 * an iterative one (in case of non-nested symlink chains). It does
50 * this with calls to <fs>_follow_link().
51 * As a side effect, dir_namei(), _namei() and follow_link() are now
52 * replaced with a single function lookup_dentry() that can handle all
53 * the special cases of the former code.
55 * With the new dcache, the pathname is stored at each inode, at least as
56 * long as the refcount of the inode is positive. As a side effect, the
57 * size of the dcache depends on the inode cache and thus is dynamic.
59 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
60 * resolution to correspond with current state of the code.
62 * Note that the symlink resolution is not *completely* iterative.
63 * There is still a significant amount of tail- and mid- recursion in
64 * the algorithm. Also, note that <fs>_readlink() is not used in
65 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
66 * may return different results than <fs>_follow_link(). Many virtual
67 * filesystems (including /proc) exhibit this behavior.
70 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
71 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
72 * and the name already exists in form of a symlink, try to create the new
73 * name indicated by the symlink. The old code always complained that the
74 * name already exists, due to not following the symlink even if its target
75 * is nonexistent. The new semantics affects also mknod() and link() when
76 * the name is a symlink pointing to a non-existent name.
78 * I don't know which semantics is the right one, since I have no access
79 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
80 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
81 * "old" one. Personally, I think the new semantics is much more logical.
82 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
83 * file does succeed in both HP-UX and SunOs, but not in Solaris
84 * and in the old Linux semantics.
87 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
88 * semantics. See the comments in "open_namei" and "do_link" below.
90 * [10-Sep-98 Alan Modra] Another symlink change.
93 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
94 * inside the path - always follow.
95 * in the last component in creation/removal/renaming - never follow.
96 * if LOOKUP_FOLLOW passed - follow.
97 * if the pathname has trailing slashes - follow.
98 * otherwise - don't follow.
99 * (applied in that order).
101 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
102 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
103 * During the 2.4 we need to fix the userland stuff depending on it -
104 * hopefully we will be able to get rid of that wart in 2.5. So far only
105 * XEmacs seems to be relying on it...
108 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
109 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
110 * any extra contention...
113 /* In order to reduce some races, while at the same time doing additional
114 * checking and hopefully speeding things up, we copy filenames to the
115 * kernel data space before using them..
117 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
118 * PATH_MAX includes the nul terminator --RR.
120 void final_putname(struct filename *name)
122 if (name->separate) {
123 __putname(name->name);
130 #define EMBEDDED_NAME_MAX (PATH_MAX - sizeof(struct filename))
132 static struct filename *
133 getname_flags(const char __user *filename, int flags, int *empty)
135 struct filename *result, *err;
140 result = audit_reusename(filename);
144 result = __getname();
145 if (unlikely(!result))
146 return ERR_PTR(-ENOMEM);
149 * First, try to embed the struct filename inside the names_cache
152 kname = (char *)result + sizeof(*result);
153 result->name = kname;
154 result->separate = false;
155 max = EMBEDDED_NAME_MAX;
158 len = strncpy_from_user(kname, filename, max);
159 if (unlikely(len < 0)) {
165 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
166 * separate struct filename so we can dedicate the entire
167 * names_cache allocation for the pathname, and re-do the copy from
170 if (len == EMBEDDED_NAME_MAX && max == EMBEDDED_NAME_MAX) {
171 kname = (char *)result;
173 result = kzalloc(sizeof(*result), GFP_KERNEL);
175 err = ERR_PTR(-ENOMEM);
176 result = (struct filename *)kname;
179 result->name = kname;
180 result->separate = true;
185 /* The empty path is special. */
186 if (unlikely(!len)) {
189 err = ERR_PTR(-ENOENT);
190 if (!(flags & LOOKUP_EMPTY))
194 err = ERR_PTR(-ENAMETOOLONG);
195 if (unlikely(len >= PATH_MAX))
198 result->uptr = filename;
199 audit_getname(result);
203 final_putname(result);
208 getname(const char __user * filename)
210 return getname_flags(filename, 0, NULL);
212 EXPORT_SYMBOL(getname);
214 #ifdef CONFIG_AUDITSYSCALL
215 void putname(struct filename *name)
217 if (unlikely(!audit_dummy_context()))
218 return audit_putname(name);
223 static int check_acl(struct inode *inode, int mask)
225 #ifdef CONFIG_FS_POSIX_ACL
226 struct posix_acl *acl;
228 if (mask & MAY_NOT_BLOCK) {
229 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
232 /* no ->get_acl() calls in RCU mode... */
233 if (acl == ACL_NOT_CACHED)
235 return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
238 acl = get_cached_acl(inode, ACL_TYPE_ACCESS);
241 * A filesystem can force a ACL callback by just never filling the
242 * ACL cache. But normally you'd fill the cache either at inode
243 * instantiation time, or on the first ->get_acl call.
245 * If the filesystem doesn't have a get_acl() function at all, we'll
246 * just create the negative cache entry.
248 if (acl == ACL_NOT_CACHED) {
249 if (inode->i_op->get_acl) {
250 acl = inode->i_op->get_acl(inode, ACL_TYPE_ACCESS);
254 set_cached_acl(inode, ACL_TYPE_ACCESS, NULL);
260 int error = posix_acl_permission(inode, acl, mask);
261 posix_acl_release(acl);
270 * This does the basic permission checking
272 static int acl_permission_check(struct inode *inode, int mask)
274 unsigned int mode = inode->i_mode;
276 if (likely(uid_eq(current_fsuid(), inode->i_uid)))
279 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
280 int error = check_acl(inode, mask);
281 if (error != -EAGAIN)
285 if (in_group_p(inode->i_gid))
290 * If the DACs are ok we don't need any capability check.
292 if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
298 * generic_permission - check for access rights on a Posix-like filesystem
299 * @inode: inode to check access rights for
300 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
302 * Used to check for read/write/execute permissions on a file.
303 * We use "fsuid" for this, letting us set arbitrary permissions
304 * for filesystem access without changing the "normal" uids which
305 * are used for other things.
307 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
308 * request cannot be satisfied (eg. requires blocking or too much complexity).
309 * It would then be called again in ref-walk mode.
311 int generic_permission(struct inode *inode, int mask)
316 * Do the basic permission checks.
318 ret = acl_permission_check(inode, mask);
322 if (S_ISDIR(inode->i_mode)) {
323 /* DACs are overridable for directories */
324 if (inode_capable(inode, CAP_DAC_OVERRIDE))
326 if (!(mask & MAY_WRITE))
327 if (inode_capable(inode, CAP_DAC_READ_SEARCH))
332 * Read/write DACs are always overridable.
333 * Executable DACs are overridable when there is
334 * at least one exec bit set.
336 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
337 if (inode_capable(inode, CAP_DAC_OVERRIDE))
341 * Searching includes executable on directories, else just read.
343 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
344 if (mask == MAY_READ)
345 if (inode_capable(inode, CAP_DAC_READ_SEARCH))
352 * We _really_ want to just do "generic_permission()" without
353 * even looking at the inode->i_op values. So we keep a cache
354 * flag in inode->i_opflags, that says "this has not special
355 * permission function, use the fast case".
357 static inline int do_inode_permission(struct inode *inode, int mask)
359 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
360 if (likely(inode->i_op->permission))
361 return inode->i_op->permission(inode, mask);
363 /* This gets set once for the inode lifetime */
364 spin_lock(&inode->i_lock);
365 inode->i_opflags |= IOP_FASTPERM;
366 spin_unlock(&inode->i_lock);
368 return generic_permission(inode, mask);
372 * __inode_permission - Check for access rights to a given inode
373 * @inode: Inode to check permission on
374 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
376 * Check for read/write/execute permissions on an inode.
378 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
380 * This does not check for a read-only file system. You probably want
381 * inode_permission().
383 int __inode_permission(struct inode *inode, int mask)
387 if (unlikely(mask & MAY_WRITE)) {
389 * Nobody gets write access to an immutable file.
391 if (IS_IMMUTABLE(inode))
395 retval = do_inode_permission(inode, mask);
399 retval = devcgroup_inode_permission(inode, mask);
403 return security_inode_permission(inode, mask);
407 * sb_permission - Check superblock-level permissions
408 * @sb: Superblock of inode to check permission on
409 * @inode: Inode to check permission on
410 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
412 * Separate out file-system wide checks from inode-specific permission checks.
414 static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
416 if (unlikely(mask & MAY_WRITE)) {
417 umode_t mode = inode->i_mode;
419 /* Nobody gets write access to a read-only fs. */
420 if ((sb->s_flags & MS_RDONLY) &&
421 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
428 * inode_permission - Check for access rights to a given inode
429 * @inode: Inode to check permission on
430 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
432 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
433 * this, letting us set arbitrary permissions for filesystem access without
434 * changing the "normal" UIDs which are used for other things.
436 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
438 int inode_permission(struct inode *inode, int mask)
442 retval = sb_permission(inode->i_sb, inode, mask);
445 return __inode_permission(inode, mask);
449 * path_get - get a reference to a path
450 * @path: path to get the reference to
452 * Given a path increment the reference count to the dentry and the vfsmount.
454 void path_get(struct path *path)
459 EXPORT_SYMBOL(path_get);
462 * path_put - put a reference to a path
463 * @path: path to put the reference to
465 * Given a path decrement the reference count to the dentry and the vfsmount.
467 void path_put(struct path *path)
472 EXPORT_SYMBOL(path_put);
475 * Path walking has 2 modes, rcu-walk and ref-walk (see
476 * Documentation/filesystems/path-lookup.txt). In situations when we can't
477 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
478 * normal reference counts on dentries and vfsmounts to transition to rcu-walk
479 * mode. Refcounts are grabbed at the last known good point before rcu-walk
480 * got stuck, so ref-walk may continue from there. If this is not successful
481 * (eg. a seqcount has changed), then failure is returned and it's up to caller
482 * to restart the path walk from the beginning in ref-walk mode.
485 static inline void lock_rcu_walk(void)
487 br_read_lock(&vfsmount_lock);
491 static inline void unlock_rcu_walk(void)
494 br_read_unlock(&vfsmount_lock);
498 * unlazy_walk - try to switch to ref-walk mode.
499 * @nd: nameidata pathwalk data
500 * @dentry: child of nd->path.dentry or NULL
501 * Returns: 0 on success, -ECHILD on failure
503 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
504 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
505 * @nd or NULL. Must be called from rcu-walk context.
507 static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
509 struct fs_struct *fs = current->fs;
510 struct dentry *parent = nd->path.dentry;
513 BUG_ON(!(nd->flags & LOOKUP_RCU));
514 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
516 spin_lock(&fs->lock);
517 if (nd->root.mnt != fs->root.mnt ||
518 nd->root.dentry != fs->root.dentry)
521 spin_lock(&parent->d_lock);
523 if (!__d_rcu_to_refcount(parent, nd->seq))
525 BUG_ON(nd->inode != parent->d_inode);
527 if (dentry->d_parent != parent)
529 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
530 if (!__d_rcu_to_refcount(dentry, nd->seq))
533 * If the sequence check on the child dentry passed, then
534 * the child has not been removed from its parent. This
535 * means the parent dentry must be valid and able to take
536 * a reference at this point.
538 BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
539 BUG_ON(!parent->d_count);
541 spin_unlock(&dentry->d_lock);
543 spin_unlock(&parent->d_lock);
546 spin_unlock(&fs->lock);
548 mntget(nd->path.mnt);
551 nd->flags &= ~LOOKUP_RCU;
555 spin_unlock(&dentry->d_lock);
557 spin_unlock(&parent->d_lock);
560 spin_unlock(&fs->lock);
564 static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
566 return dentry->d_op->d_revalidate(dentry, flags);
570 * complete_walk - successful completion of path walk
571 * @nd: pointer nameidata
573 * If we had been in RCU mode, drop out of it and legitimize nd->path.
574 * Revalidate the final result, unless we'd already done that during
575 * the path walk or the filesystem doesn't ask for it. Return 0 on
576 * success, -error on failure. In case of failure caller does not
577 * need to drop nd->path.
579 static int complete_walk(struct nameidata *nd)
581 struct dentry *dentry = nd->path.dentry;
584 if (nd->flags & LOOKUP_RCU) {
585 nd->flags &= ~LOOKUP_RCU;
586 if (!(nd->flags & LOOKUP_ROOT))
588 spin_lock(&dentry->d_lock);
589 if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) {
590 spin_unlock(&dentry->d_lock);
594 BUG_ON(nd->inode != dentry->d_inode);
595 spin_unlock(&dentry->d_lock);
596 mntget(nd->path.mnt);
600 if (likely(!(nd->flags & LOOKUP_JUMPED)))
603 if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
606 if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
609 /* Note: we do not d_invalidate() */
610 status = d_revalidate(dentry, nd->flags);
621 static __always_inline void set_root(struct nameidata *nd)
624 get_fs_root(current->fs, &nd->root);
627 static int link_path_walk(const char *, struct nameidata *);
629 static __always_inline void set_root_rcu(struct nameidata *nd)
632 struct fs_struct *fs = current->fs;
636 seq = read_seqcount_begin(&fs->seq);
638 nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
639 } while (read_seqcount_retry(&fs->seq, seq));
643 static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
655 nd->flags |= LOOKUP_JUMPED;
657 nd->inode = nd->path.dentry->d_inode;
659 ret = link_path_walk(link, nd);
663 return PTR_ERR(link);
666 static void path_put_conditional(struct path *path, struct nameidata *nd)
669 if (path->mnt != nd->path.mnt)
673 static inline void path_to_nameidata(const struct path *path,
674 struct nameidata *nd)
676 if (!(nd->flags & LOOKUP_RCU)) {
677 dput(nd->path.dentry);
678 if (nd->path.mnt != path->mnt)
679 mntput(nd->path.mnt);
681 nd->path.mnt = path->mnt;
682 nd->path.dentry = path->dentry;
686 * Helper to directly jump to a known parsed path from ->follow_link,
687 * caller must have taken a reference to path beforehand.
689 void nd_jump_link(struct nameidata *nd, struct path *path)
694 nd->inode = nd->path.dentry->d_inode;
695 nd->flags |= LOOKUP_JUMPED;
697 BUG_ON(nd->inode->i_op->follow_link);
700 static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
702 struct inode *inode = link->dentry->d_inode;
703 if (inode->i_op->put_link)
704 inode->i_op->put_link(link->dentry, nd, cookie);
708 int sysctl_protected_symlinks __read_mostly = 0;
709 int sysctl_protected_hardlinks __read_mostly = 0;
712 * may_follow_link - Check symlink following for unsafe situations
713 * @link: The path of the symlink
714 * @nd: nameidata pathwalk data
716 * In the case of the sysctl_protected_symlinks sysctl being enabled,
717 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
718 * in a sticky world-writable directory. This is to protect privileged
719 * processes from failing races against path names that may change out
720 * from under them by way of other users creating malicious symlinks.
721 * It will permit symlinks to be followed only when outside a sticky
722 * world-writable directory, or when the uid of the symlink and follower
723 * match, or when the directory owner matches the symlink's owner.
725 * Returns 0 if following the symlink is allowed, -ve on error.
727 static inline int may_follow_link(struct path *link, struct nameidata *nd)
729 const struct inode *inode;
730 const struct inode *parent;
732 if (!sysctl_protected_symlinks)
735 /* Allowed if owner and follower match. */
736 inode = link->dentry->d_inode;
737 if (uid_eq(current_cred()->fsuid, inode->i_uid))
740 /* Allowed if parent directory not sticky and world-writable. */
741 parent = nd->path.dentry->d_inode;
742 if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
745 /* Allowed if parent directory and link owner match. */
746 if (uid_eq(parent->i_uid, inode->i_uid))
749 audit_log_link_denied("follow_link", link);
750 path_put_conditional(link, nd);
756 * safe_hardlink_source - Check for safe hardlink conditions
757 * @inode: the source inode to hardlink from
759 * Return false if at least one of the following conditions:
760 * - inode is not a regular file
762 * - inode is setgid and group-exec
763 * - access failure for read and write
765 * Otherwise returns true.
767 static bool safe_hardlink_source(struct inode *inode)
769 umode_t mode = inode->i_mode;
771 /* Special files should not get pinned to the filesystem. */
775 /* Setuid files should not get pinned to the filesystem. */
779 /* Executable setgid files should not get pinned to the filesystem. */
780 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
783 /* Hardlinking to unreadable or unwritable sources is dangerous. */
784 if (inode_permission(inode, MAY_READ | MAY_WRITE))
791 * may_linkat - Check permissions for creating a hardlink
792 * @link: the source to hardlink from
794 * Block hardlink when all of:
795 * - sysctl_protected_hardlinks enabled
796 * - fsuid does not match inode
797 * - hardlink source is unsafe (see safe_hardlink_source() above)
800 * Returns 0 if successful, -ve on error.
802 static int may_linkat(struct path *link)
804 const struct cred *cred;
807 if (!sysctl_protected_hardlinks)
810 cred = current_cred();
811 inode = link->dentry->d_inode;
813 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
814 * otherwise, it must be a safe source.
816 if (uid_eq(cred->fsuid, inode->i_uid) || safe_hardlink_source(inode) ||
820 audit_log_link_denied("linkat", link);
824 static __always_inline int
825 follow_link(struct path *link, struct nameidata *nd, void **p)
827 struct dentry *dentry = link->dentry;
831 BUG_ON(nd->flags & LOOKUP_RCU);
833 if (link->mnt == nd->path.mnt)
837 if (unlikely(current->total_link_count >= 40))
838 goto out_put_nd_path;
841 current->total_link_count++;
844 nd_set_link(nd, NULL);
846 error = security_inode_follow_link(link->dentry, nd);
848 goto out_put_nd_path;
850 nd->last_type = LAST_BIND;
851 *p = dentry->d_inode->i_op->follow_link(dentry, nd);
854 goto out_put_nd_path;
859 error = __vfs_follow_link(nd, s);
861 put_link(nd, link, *p);
873 static int follow_up_rcu(struct path *path)
875 struct mount *mnt = real_mount(path->mnt);
876 struct mount *parent;
877 struct dentry *mountpoint;
879 parent = mnt->mnt_parent;
880 if (&parent->mnt == path->mnt)
882 mountpoint = mnt->mnt_mountpoint;
883 path->dentry = mountpoint;
884 path->mnt = &parent->mnt;
889 * follow_up - Find the mountpoint of path's vfsmount
891 * Given a path, find the mountpoint of its source file system.
892 * Replace @path with the path of the mountpoint in the parent mount.
895 * Return 1 if we went up a level and 0 if we were already at the
898 int follow_up(struct path *path)
900 struct mount *mnt = real_mount(path->mnt);
901 struct mount *parent;
902 struct dentry *mountpoint;
904 br_read_lock(&vfsmount_lock);
905 parent = mnt->mnt_parent;
907 br_read_unlock(&vfsmount_lock);
910 mntget(&parent->mnt);
911 mountpoint = dget(mnt->mnt_mountpoint);
912 br_read_unlock(&vfsmount_lock);
914 path->dentry = mountpoint;
916 path->mnt = &parent->mnt;
921 * Perform an automount
922 * - return -EISDIR to tell follow_managed() to stop and return the path we
925 static int follow_automount(struct path *path, unsigned flags,
928 struct vfsmount *mnt;
931 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
934 /* We don't want to mount if someone's just doing a stat -
935 * unless they're stat'ing a directory and appended a '/' to
938 * We do, however, want to mount if someone wants to open or
939 * create a file of any type under the mountpoint, wants to
940 * traverse through the mountpoint or wants to open the
941 * mounted directory. Also, autofs may mark negative dentries
942 * as being automount points. These will need the attentions
943 * of the daemon to instantiate them before they can be used.
945 if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
946 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
947 path->dentry->d_inode)
950 current->total_link_count++;
951 if (current->total_link_count >= 40)
954 mnt = path->dentry->d_op->d_automount(path);
957 * The filesystem is allowed to return -EISDIR here to indicate
958 * it doesn't want to automount. For instance, autofs would do
959 * this so that its userspace daemon can mount on this dentry.
961 * However, we can only permit this if it's a terminal point in
962 * the path being looked up; if it wasn't then the remainder of
963 * the path is inaccessible and we should say so.
965 if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT))
970 if (!mnt) /* mount collision */
974 /* lock_mount() may release path->mnt on error */
978 err = finish_automount(mnt, path);
982 /* Someone else made a mount here whilst we were busy */
987 path->dentry = dget(mnt->mnt_root);
996 * Handle a dentry that is managed in some way.
997 * - Flagged for transit management (autofs)
998 * - Flagged as mountpoint
999 * - Flagged as automount point
1001 * This may only be called in refwalk mode.
1003 * Serialization is taken care of in namespace.c
1005 static int follow_managed(struct path *path, unsigned flags)
1007 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
1009 bool need_mntput = false;
1012 /* Given that we're not holding a lock here, we retain the value in a
1013 * local variable for each dentry as we look at it so that we don't see
1014 * the components of that value change under us */
1015 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1016 managed &= DCACHE_MANAGED_DENTRY,
1017 unlikely(managed != 0)) {
1018 /* Allow the filesystem to manage the transit without i_mutex
1020 if (managed & DCACHE_MANAGE_TRANSIT) {
1021 BUG_ON(!path->dentry->d_op);
1022 BUG_ON(!path->dentry->d_op->d_manage);
1023 ret = path->dentry->d_op->d_manage(path->dentry, false);
1028 /* Transit to a mounted filesystem. */
1029 if (managed & DCACHE_MOUNTED) {
1030 struct vfsmount *mounted = lookup_mnt(path);
1035 path->mnt = mounted;
1036 path->dentry = dget(mounted->mnt_root);
1041 /* Something is mounted on this dentry in another
1042 * namespace and/or whatever was mounted there in this
1043 * namespace got unmounted before we managed to get the
1047 /* Handle an automount point */
1048 if (managed & DCACHE_NEED_AUTOMOUNT) {
1049 ret = follow_automount(path, flags, &need_mntput);
1055 /* We didn't change the current path point */
1059 if (need_mntput && path->mnt == mnt)
1063 return ret < 0 ? ret : need_mntput;
1066 int follow_down_one(struct path *path)
1068 struct vfsmount *mounted;
1070 mounted = lookup_mnt(path);
1074 path->mnt = mounted;
1075 path->dentry = dget(mounted->mnt_root);
1081 static inline bool managed_dentry_might_block(struct dentry *dentry)
1083 return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
1084 dentry->d_op->d_manage(dentry, true) < 0);
1088 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1089 * we meet a managed dentry that would need blocking.
1091 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
1092 struct inode **inode)
1095 struct mount *mounted;
1097 * Don't forget we might have a non-mountpoint managed dentry
1098 * that wants to block transit.
1100 if (unlikely(managed_dentry_might_block(path->dentry)))
1103 if (!d_mountpoint(path->dentry))
1106 mounted = __lookup_mnt(path->mnt, path->dentry, 1);
1109 path->mnt = &mounted->mnt;
1110 path->dentry = mounted->mnt.mnt_root;
1111 nd->flags |= LOOKUP_JUMPED;
1112 nd->seq = read_seqcount_begin(&path->dentry->d_seq);
1114 * Update the inode too. We don't need to re-check the
1115 * dentry sequence number here after this d_inode read,
1116 * because a mount-point is always pinned.
1118 *inode = path->dentry->d_inode;
1123 static void follow_mount_rcu(struct nameidata *nd)
1125 while (d_mountpoint(nd->path.dentry)) {
1126 struct mount *mounted;
1127 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1);
1130 nd->path.mnt = &mounted->mnt;
1131 nd->path.dentry = mounted->mnt.mnt_root;
1132 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1136 static int follow_dotdot_rcu(struct nameidata *nd)
1141 if (nd->path.dentry == nd->root.dentry &&
1142 nd->path.mnt == nd->root.mnt) {
1145 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1146 struct dentry *old = nd->path.dentry;
1147 struct dentry *parent = old->d_parent;
1150 seq = read_seqcount_begin(&parent->d_seq);
1151 if (read_seqcount_retry(&old->d_seq, nd->seq))
1153 nd->path.dentry = parent;
1157 if (!follow_up_rcu(&nd->path))
1159 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1161 follow_mount_rcu(nd);
1162 nd->inode = nd->path.dentry->d_inode;
1166 nd->flags &= ~LOOKUP_RCU;
1167 if (!(nd->flags & LOOKUP_ROOT))
1168 nd->root.mnt = NULL;
1174 * Follow down to the covering mount currently visible to userspace. At each
1175 * point, the filesystem owning that dentry may be queried as to whether the
1176 * caller is permitted to proceed or not.
1178 int follow_down(struct path *path)
1183 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1184 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
1185 /* Allow the filesystem to manage the transit without i_mutex
1188 * We indicate to the filesystem if someone is trying to mount
1189 * something here. This gives autofs the chance to deny anyone
1190 * other than its daemon the right to mount on its
1193 * The filesystem may sleep at this point.
1195 if (managed & DCACHE_MANAGE_TRANSIT) {
1196 BUG_ON(!path->dentry->d_op);
1197 BUG_ON(!path->dentry->d_op->d_manage);
1198 ret = path->dentry->d_op->d_manage(
1199 path->dentry, false);
1201 return ret == -EISDIR ? 0 : ret;
1204 /* Transit to a mounted filesystem. */
1205 if (managed & DCACHE_MOUNTED) {
1206 struct vfsmount *mounted = lookup_mnt(path);
1211 path->mnt = mounted;
1212 path->dentry = dget(mounted->mnt_root);
1216 /* Don't handle automount points here */
1223 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1225 static void follow_mount(struct path *path)
1227 while (d_mountpoint(path->dentry)) {
1228 struct vfsmount *mounted = lookup_mnt(path);
1233 path->mnt = mounted;
1234 path->dentry = dget(mounted->mnt_root);
1238 static void follow_dotdot(struct nameidata *nd)
1243 struct dentry *old = nd->path.dentry;
1245 if (nd->path.dentry == nd->root.dentry &&
1246 nd->path.mnt == nd->root.mnt) {
1249 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1250 /* rare case of legitimate dget_parent()... */
1251 nd->path.dentry = dget_parent(nd->path.dentry);
1255 if (!follow_up(&nd->path))
1258 follow_mount(&nd->path);
1259 nd->inode = nd->path.dentry->d_inode;
1263 * This looks up the name in dcache, possibly revalidates the old dentry and
1264 * allocates a new one if not found or not valid. In the need_lookup argument
1265 * returns whether i_op->lookup is necessary.
1267 * dir->d_inode->i_mutex must be held
1269 static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir,
1270 unsigned int flags, bool *need_lookup)
1272 struct dentry *dentry;
1275 *need_lookup = false;
1276 dentry = d_lookup(dir, name);
1278 if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
1279 error = d_revalidate(dentry, flags);
1280 if (unlikely(error <= 0)) {
1283 return ERR_PTR(error);
1284 } else if (!d_invalidate(dentry)) {
1293 dentry = d_alloc(dir, name);
1294 if (unlikely(!dentry))
1295 return ERR_PTR(-ENOMEM);
1297 *need_lookup = true;
1303 * Call i_op->lookup on the dentry. The dentry must be negative but may be
1304 * hashed if it was pouplated with DCACHE_NEED_LOOKUP.
1306 * dir->d_inode->i_mutex must be held
1308 static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
1313 /* Don't create child dentry for a dead directory. */
1314 if (unlikely(IS_DEADDIR(dir))) {
1316 return ERR_PTR(-ENOENT);
1319 old = dir->i_op->lookup(dir, dentry, flags);
1320 if (unlikely(old)) {
1327 static struct dentry *__lookup_hash(struct qstr *name,
1328 struct dentry *base, unsigned int flags)
1331 struct dentry *dentry;
1333 dentry = lookup_dcache(name, base, flags, &need_lookup);
1337 return lookup_real(base->d_inode, dentry, flags);
1341 * It's more convoluted than I'd like it to be, but... it's still fairly
1342 * small and for now I'd prefer to have fast path as straight as possible.
1343 * It _is_ time-critical.
1345 static int lookup_fast(struct nameidata *nd,
1346 struct path *path, struct inode **inode)
1348 struct vfsmount *mnt = nd->path.mnt;
1349 struct dentry *dentry, *parent = nd->path.dentry;
1355 * Rename seqlock is not required here because in the off chance
1356 * of a false negative due to a concurrent rename, we're going to
1357 * do the non-racy lookup, below.
1359 if (nd->flags & LOOKUP_RCU) {
1361 dentry = __d_lookup_rcu(parent, &nd->last, &seq, nd->inode);
1366 * This sequence count validates that the inode matches
1367 * the dentry name information from lookup.
1369 *inode = dentry->d_inode;
1370 if (read_seqcount_retry(&dentry->d_seq, seq))
1374 * This sequence count validates that the parent had no
1375 * changes while we did the lookup of the dentry above.
1377 * The memory barrier in read_seqcount_begin of child is
1378 * enough, we can use __read_seqcount_retry here.
1380 if (__read_seqcount_retry(&parent->d_seq, nd->seq))
1384 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1385 status = d_revalidate(dentry, nd->flags);
1386 if (unlikely(status <= 0)) {
1387 if (status != -ECHILD)
1393 path->dentry = dentry;
1394 if (unlikely(!__follow_mount_rcu(nd, path, inode)))
1396 if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
1400 if (unlazy_walk(nd, dentry))
1403 dentry = __d_lookup(parent, &nd->last);
1406 if (unlikely(!dentry))
1409 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
1410 status = d_revalidate(dentry, nd->flags);
1411 if (unlikely(status <= 0)) {
1416 if (!d_invalidate(dentry)) {
1423 path->dentry = dentry;
1424 err = follow_managed(path, nd->flags);
1425 if (unlikely(err < 0)) {
1426 path_put_conditional(path, nd);
1430 nd->flags |= LOOKUP_JUMPED;
1431 *inode = path->dentry->d_inode;
1438 /* Fast lookup failed, do it the slow way */
1439 static int lookup_slow(struct nameidata *nd, struct path *path)
1441 struct dentry *dentry, *parent;
1444 parent = nd->path.dentry;
1445 BUG_ON(nd->inode != parent->d_inode);
1447 mutex_lock(&parent->d_inode->i_mutex);
1448 dentry = __lookup_hash(&nd->last, parent, nd->flags);
1449 mutex_unlock(&parent->d_inode->i_mutex);
1451 return PTR_ERR(dentry);
1452 path->mnt = nd->path.mnt;
1453 path->dentry = dentry;
1454 err = follow_managed(path, nd->flags);
1455 if (unlikely(err < 0)) {
1456 path_put_conditional(path, nd);
1460 nd->flags |= LOOKUP_JUMPED;
1464 static inline int may_lookup(struct nameidata *nd)
1466 if (nd->flags & LOOKUP_RCU) {
1467 int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1470 if (unlazy_walk(nd, NULL))
1473 return inode_permission(nd->inode, MAY_EXEC);
1476 static inline int handle_dots(struct nameidata *nd, int type)
1478 if (type == LAST_DOTDOT) {
1479 if (nd->flags & LOOKUP_RCU) {
1480 if (follow_dotdot_rcu(nd))
1488 static void terminate_walk(struct nameidata *nd)
1490 if (!(nd->flags & LOOKUP_RCU)) {
1491 path_put(&nd->path);
1493 nd->flags &= ~LOOKUP_RCU;
1494 if (!(nd->flags & LOOKUP_ROOT))
1495 nd->root.mnt = NULL;
1501 * Do we need to follow links? We _really_ want to be able
1502 * to do this check without having to look at inode->i_op,
1503 * so we keep a cache of "no, this doesn't need follow_link"
1504 * for the common case.
1506 static inline int should_follow_link(struct inode *inode, int follow)
1508 if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1509 if (likely(inode->i_op->follow_link))
1512 /* This gets set once for the inode lifetime */
1513 spin_lock(&inode->i_lock);
1514 inode->i_opflags |= IOP_NOFOLLOW;
1515 spin_unlock(&inode->i_lock);
1520 static inline int walk_component(struct nameidata *nd, struct path *path,
1523 struct inode *inode;
1526 * "." and ".." are special - ".." especially so because it has
1527 * to be able to know about the current root directory and
1528 * parent relationships.
1530 if (unlikely(nd->last_type != LAST_NORM))
1531 return handle_dots(nd, nd->last_type);
1532 err = lookup_fast(nd, path, &inode);
1533 if (unlikely(err)) {
1537 err = lookup_slow(nd, path);
1541 inode = path->dentry->d_inode;
1547 if (should_follow_link(inode, follow)) {
1548 if (nd->flags & LOOKUP_RCU) {
1549 if (unlikely(unlazy_walk(nd, path->dentry))) {
1554 BUG_ON(inode != path->dentry->d_inode);
1557 path_to_nameidata(path, nd);
1562 path_to_nameidata(path, nd);
1569 * This limits recursive symlink follows to 8, while
1570 * limiting consecutive symlinks to 40.
1572 * Without that kind of total limit, nasty chains of consecutive
1573 * symlinks can cause almost arbitrarily long lookups.
1575 static inline int nested_symlink(struct path *path, struct nameidata *nd)
1579 if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
1580 path_put_conditional(path, nd);
1581 path_put(&nd->path);
1584 BUG_ON(nd->depth >= MAX_NESTED_LINKS);
1587 current->link_count++;
1590 struct path link = *path;
1593 res = follow_link(&link, nd, &cookie);
1596 res = walk_component(nd, path, LOOKUP_FOLLOW);
1597 put_link(nd, &link, cookie);
1600 current->link_count--;
1606 * We really don't want to look at inode->i_op->lookup
1607 * when we don't have to. So we keep a cache bit in
1608 * the inode ->i_opflags field that says "yes, we can
1609 * do lookup on this inode".
1611 static inline int can_lookup(struct inode *inode)
1613 if (likely(inode->i_opflags & IOP_LOOKUP))
1615 if (likely(!inode->i_op->lookup))
1618 /* We do this once for the lifetime of the inode */
1619 spin_lock(&inode->i_lock);
1620 inode->i_opflags |= IOP_LOOKUP;
1621 spin_unlock(&inode->i_lock);
1626 * We can do the critical dentry name comparison and hashing
1627 * operations one word at a time, but we are limited to:
1629 * - Architectures with fast unaligned word accesses. We could
1630 * do a "get_unaligned()" if this helps and is sufficiently
1633 * - Little-endian machines (so that we can generate the mask
1634 * of low bytes efficiently). Again, we *could* do a byte
1635 * swapping load on big-endian architectures if that is not
1636 * expensive enough to make the optimization worthless.
1638 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1639 * do not trap on the (extremely unlikely) case of a page
1640 * crossing operation.
1642 * - Furthermore, we need an efficient 64-bit compile for the
1643 * 64-bit case in order to generate the "number of bytes in
1644 * the final mask". Again, that could be replaced with a
1645 * efficient population count instruction or similar.
1647 #ifdef CONFIG_DCACHE_WORD_ACCESS
1649 #include <asm/word-at-a-time.h>
1653 static inline unsigned int fold_hash(unsigned long hash)
1655 hash += hash >> (8*sizeof(int));
1659 #else /* 32-bit case */
1661 #define fold_hash(x) (x)
1665 unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1667 unsigned long a, mask;
1668 unsigned long hash = 0;
1671 a = load_unaligned_zeropad(name);
1672 if (len < sizeof(unsigned long))
1676 name += sizeof(unsigned long);
1677 len -= sizeof(unsigned long);
1681 mask = ~(~0ul << len*8);
1684 return fold_hash(hash);
1686 EXPORT_SYMBOL(full_name_hash);
1689 * Calculate the length and hash of the path component, and
1690 * return the length of the component;
1692 static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1694 unsigned long a, b, adata, bdata, mask, hash, len;
1695 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
1698 len = -sizeof(unsigned long);
1700 hash = (hash + a) * 9;
1701 len += sizeof(unsigned long);
1702 a = load_unaligned_zeropad(name+len);
1703 b = a ^ REPEAT_BYTE('/');
1704 } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
1706 adata = prep_zero_mask(a, adata, &constants);
1707 bdata = prep_zero_mask(b, bdata, &constants);
1709 mask = create_zero_mask(adata | bdata);
1711 hash += a & zero_bytemask(mask);
1712 *hashp = fold_hash(hash);
1714 return len + find_zero(mask);
1719 unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1721 unsigned long hash = init_name_hash();
1723 hash = partial_name_hash(*name++, hash);
1724 return end_name_hash(hash);
1726 EXPORT_SYMBOL(full_name_hash);
1729 * We know there's a real path component here of at least
1732 static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1734 unsigned long hash = init_name_hash();
1735 unsigned long len = 0, c;
1737 c = (unsigned char)*name;
1740 hash = partial_name_hash(c, hash);
1741 c = (unsigned char)name[len];
1742 } while (c && c != '/');
1743 *hashp = end_name_hash(hash);
1751 * This is the basic name resolution function, turning a pathname into
1752 * the final dentry. We expect 'base' to be positive and a directory.
1754 * Returns 0 and nd will have valid dentry and mnt on success.
1755 * Returns error and drops reference to input namei data on failure.
1757 static int link_path_walk(const char *name, struct nameidata *nd)
1767 /* At this point we know we have a real path component. */
1773 err = may_lookup(nd);
1777 len = hash_name(name, &this.hash);
1782 if (name[0] == '.') switch (len) {
1784 if (name[1] == '.') {
1786 nd->flags |= LOOKUP_JUMPED;
1792 if (likely(type == LAST_NORM)) {
1793 struct dentry *parent = nd->path.dentry;
1794 nd->flags &= ~LOOKUP_JUMPED;
1795 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
1796 err = parent->d_op->d_hash(parent, nd->inode,
1804 nd->last_type = type;
1809 * If it wasn't NUL, we know it was '/'. Skip that
1810 * slash, and continue until no more slashes.
1814 } while (unlikely(name[len] == '/'));
1820 err = walk_component(nd, &next, LOOKUP_FOLLOW);
1825 err = nested_symlink(&next, nd);
1829 if (!can_lookup(nd->inode)) {
1838 static int path_init(int dfd, const char *name, unsigned int flags,
1839 struct nameidata *nd, struct file **fp)
1843 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1844 nd->flags = flags | LOOKUP_JUMPED;
1846 if (flags & LOOKUP_ROOT) {
1847 struct inode *inode = nd->root.dentry->d_inode;
1849 if (!can_lookup(inode))
1851 retval = inode_permission(inode, MAY_EXEC);
1855 nd->path = nd->root;
1857 if (flags & LOOKUP_RCU) {
1859 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1861 path_get(&nd->path);
1866 nd->root.mnt = NULL;
1869 if (flags & LOOKUP_RCU) {
1874 path_get(&nd->root);
1876 nd->path = nd->root;
1877 } else if (dfd == AT_FDCWD) {
1878 if (flags & LOOKUP_RCU) {
1879 struct fs_struct *fs = current->fs;
1885 seq = read_seqcount_begin(&fs->seq);
1887 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1888 } while (read_seqcount_retry(&fs->seq, seq));
1890 get_fs_pwd(current->fs, &nd->path);
1893 /* Caller must check execute permissions on the starting path component */
1894 struct fd f = fdget_raw(dfd);
1895 struct dentry *dentry;
1900 dentry = f.file->f_path.dentry;
1903 if (!can_lookup(dentry->d_inode)) {
1909 nd->path = f.file->f_path;
1910 if (flags & LOOKUP_RCU) {
1913 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1916 path_get(&nd->path);
1921 nd->inode = nd->path.dentry->d_inode;
1925 static inline int lookup_last(struct nameidata *nd, struct path *path)
1927 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
1928 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
1930 nd->flags &= ~LOOKUP_PARENT;
1931 return walk_component(nd, path, nd->flags & LOOKUP_FOLLOW);
1934 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1935 static int path_lookupat(int dfd, const char *name,
1936 unsigned int flags, struct nameidata *nd)
1938 struct file *base = NULL;
1943 * Path walking is largely split up into 2 different synchronisation
1944 * schemes, rcu-walk and ref-walk (explained in
1945 * Documentation/filesystems/path-lookup.txt). These share much of the
1946 * path walk code, but some things particularly setup, cleanup, and
1947 * following mounts are sufficiently divergent that functions are
1948 * duplicated. Typically there is a function foo(), and its RCU
1949 * analogue, foo_rcu().
1951 * -ECHILD is the error number of choice (just to avoid clashes) that
1952 * is returned if some aspect of an rcu-walk fails. Such an error must
1953 * be handled by restarting a traditional ref-walk (which will always
1954 * be able to complete).
1956 err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base);
1961 current->total_link_count = 0;
1962 err = link_path_walk(name, nd);
1964 if (!err && !(flags & LOOKUP_PARENT)) {
1965 err = lookup_last(nd, &path);
1968 struct path link = path;
1969 err = may_follow_link(&link, nd);
1972 nd->flags |= LOOKUP_PARENT;
1973 err = follow_link(&link, nd, &cookie);
1976 err = lookup_last(nd, &path);
1977 put_link(nd, &link, cookie);
1982 err = complete_walk(nd);
1984 if (!err && nd->flags & LOOKUP_DIRECTORY) {
1985 if (!nd->inode->i_op->lookup) {
1986 path_put(&nd->path);
1994 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
1995 path_put(&nd->root);
1996 nd->root.mnt = NULL;
2001 static int filename_lookup(int dfd, struct filename *name,
2002 unsigned int flags, struct nameidata *nd)
2004 int retval = path_lookupat(dfd, name->name, flags | LOOKUP_RCU, nd);
2005 if (unlikely(retval == -ECHILD))
2006 retval = path_lookupat(dfd, name->name, flags, nd);
2007 if (unlikely(retval == -ESTALE))
2008 retval = path_lookupat(dfd, name->name,
2009 flags | LOOKUP_REVAL, nd);
2011 if (likely(!retval))
2012 audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT);
2016 static int do_path_lookup(int dfd, const char *name,
2017 unsigned int flags, struct nameidata *nd)
2019 struct filename filename = { .name = name };
2021 return filename_lookup(dfd, &filename, flags, nd);
2024 /* does lookup, returns the object with parent locked */
2025 struct dentry *kern_path_locked(const char *name, struct path *path)
2027 struct nameidata nd;
2029 int err = do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, &nd);
2031 return ERR_PTR(err);
2032 if (nd.last_type != LAST_NORM) {
2034 return ERR_PTR(-EINVAL);
2036 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2037 d = __lookup_hash(&nd.last, nd.path.dentry, 0);
2039 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2047 int kern_path(const char *name, unsigned int flags, struct path *path)
2049 struct nameidata nd;
2050 int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
2057 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2058 * @dentry: pointer to dentry of the base directory
2059 * @mnt: pointer to vfs mount of the base directory
2060 * @name: pointer to file name
2061 * @flags: lookup flags
2062 * @path: pointer to struct path to fill
2064 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
2065 const char *name, unsigned int flags,
2068 struct nameidata nd;
2070 nd.root.dentry = dentry;
2072 BUG_ON(flags & LOOKUP_PARENT);
2073 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
2074 err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd);
2081 * Restricted form of lookup. Doesn't follow links, single-component only,
2082 * needs parent already locked. Doesn't follow mounts.
2085 static struct dentry *lookup_hash(struct nameidata *nd)
2087 return __lookup_hash(&nd->last, nd->path.dentry, nd->flags);
2091 * lookup_one_len - filesystem helper to lookup single pathname component
2092 * @name: pathname component to lookup
2093 * @base: base directory to lookup from
2094 * @len: maximum length @len should be interpreted to
2096 * Note that this routine is purely a helper for filesystem usage and should
2097 * not be called by generic code. Also note that by using this function the
2098 * nameidata argument is passed to the filesystem methods and a filesystem
2099 * using this helper needs to be prepared for that.
2101 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
2107 WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
2111 this.hash = full_name_hash(name, len);
2113 return ERR_PTR(-EACCES);
2115 if (unlikely(name[0] == '.')) {
2116 if (len < 2 || (len == 2 && name[1] == '.'))
2117 return ERR_PTR(-EACCES);
2121 c = *(const unsigned char *)name++;
2122 if (c == '/' || c == '\0')
2123 return ERR_PTR(-EACCES);
2126 * See if the low-level filesystem might want
2127 * to use its own hash..
2129 if (base->d_flags & DCACHE_OP_HASH) {
2130 int err = base->d_op->d_hash(base, base->d_inode, &this);
2132 return ERR_PTR(err);
2135 err = inode_permission(base->d_inode, MAY_EXEC);
2137 return ERR_PTR(err);
2139 return __lookup_hash(&this, base, 0);
2142 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
2143 struct path *path, int *empty)
2145 struct nameidata nd;
2146 struct filename *tmp = getname_flags(name, flags, empty);
2147 int err = PTR_ERR(tmp);
2150 BUG_ON(flags & LOOKUP_PARENT);
2152 err = filename_lookup(dfd, tmp, flags, &nd);
2160 int user_path_at(int dfd, const char __user *name, unsigned flags,
2163 return user_path_at_empty(dfd, name, flags, path, NULL);
2167 * NB: most callers don't do anything directly with the reference to the
2168 * to struct filename, but the nd->last pointer points into the name string
2169 * allocated by getname. So we must hold the reference to it until all
2170 * path-walking is complete.
2172 static struct filename *
2173 user_path_parent(int dfd, const char __user *path, struct nameidata *nd,
2176 struct filename *s = getname(path);
2179 /* only LOOKUP_REVAL is allowed in extra flags */
2180 flags &= LOOKUP_REVAL;
2185 error = filename_lookup(dfd, s, flags | LOOKUP_PARENT, nd);
2188 return ERR_PTR(error);
2195 * It's inline, so penalty for filesystems that don't use sticky bit is
2198 static inline int check_sticky(struct inode *dir, struct inode *inode)
2200 kuid_t fsuid = current_fsuid();
2202 if (!(dir->i_mode & S_ISVTX))
2204 if (uid_eq(inode->i_uid, fsuid))
2206 if (uid_eq(dir->i_uid, fsuid))
2208 return !inode_capable(inode, CAP_FOWNER);
2212 * Check whether we can remove a link victim from directory dir, check
2213 * whether the type of victim is right.
2214 * 1. We can't do it if dir is read-only (done in permission())
2215 * 2. We should have write and exec permissions on dir
2216 * 3. We can't remove anything from append-only dir
2217 * 4. We can't do anything with immutable dir (done in permission())
2218 * 5. If the sticky bit on dir is set we should either
2219 * a. be owner of dir, or
2220 * b. be owner of victim, or
2221 * c. have CAP_FOWNER capability
2222 * 6. If the victim is append-only or immutable we can't do antyhing with
2223 * links pointing to it.
2224 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2225 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2226 * 9. We can't remove a root or mountpoint.
2227 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2228 * nfs_async_unlink().
2230 static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
2234 if (!victim->d_inode)
2237 BUG_ON(victim->d_parent->d_inode != dir);
2238 audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
2240 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
2245 if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
2246 IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
2249 if (!S_ISDIR(victim->d_inode->i_mode))
2251 if (IS_ROOT(victim))
2253 } else if (S_ISDIR(victim->d_inode->i_mode))
2255 if (IS_DEADDIR(dir))
2257 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2262 /* Check whether we can create an object with dentry child in directory
2264 * 1. We can't do it if child already exists (open has special treatment for
2265 * this case, but since we are inlined it's OK)
2266 * 2. We can't do it if dir is read-only (done in permission())
2267 * 3. We should have write and exec permissions on dir
2268 * 4. We can't do it if dir is immutable (done in permission())
2270 static inline int may_create(struct inode *dir, struct dentry *child)
2274 if (IS_DEADDIR(dir))
2276 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
2280 * p1 and p2 should be directories on the same fs.
2282 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2287 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2291 mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2293 p = d_ancestor(p2, p1);
2295 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
2296 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
2300 p = d_ancestor(p1, p2);
2302 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2303 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2307 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2308 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2312 void unlock_rename(struct dentry *p1, struct dentry *p2)
2314 mutex_unlock(&p1->d_inode->i_mutex);
2316 mutex_unlock(&p2->d_inode->i_mutex);
2317 mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2321 int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2324 int error = may_create(dir, dentry);
2328 if (!dir->i_op->create)
2329 return -EACCES; /* shouldn't it be ENOSYS? */
2332 error = security_inode_create(dir, dentry, mode);
2335 error = dir->i_op->create(dir, dentry, mode, want_excl);
2337 fsnotify_create(dir, dentry);
2341 static int may_open(struct path *path, int acc_mode, int flag)
2343 struct dentry *dentry = path->dentry;
2344 struct inode *inode = dentry->d_inode;
2354 switch (inode->i_mode & S_IFMT) {
2358 if (acc_mode & MAY_WRITE)
2363 if (path->mnt->mnt_flags & MNT_NODEV)
2372 error = inode_permission(inode, acc_mode);
2377 * An append-only file must be opened in append mode for writing.
2379 if (IS_APPEND(inode)) {
2380 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
2386 /* O_NOATIME can only be set by the owner or superuser */
2387 if (flag & O_NOATIME && !inode_owner_or_capable(inode))
2393 static int handle_truncate(struct file *filp)
2395 struct path *path = &filp->f_path;
2396 struct inode *inode = path->dentry->d_inode;
2397 int error = get_write_access(inode);
2401 * Refuse to truncate files with mandatory locks held on them.
2403 error = locks_verify_locked(inode);
2405 error = security_path_truncate(path);
2407 error = do_truncate(path->dentry, 0,
2408 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
2411 put_write_access(inode);
2415 static inline int open_to_namei_flags(int flag)
2417 if ((flag & O_ACCMODE) == 3)
2422 static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode)
2424 int error = security_path_mknod(dir, dentry, mode, 0);
2428 error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
2432 return security_inode_create(dir->dentry->d_inode, dentry, mode);
2436 * Attempt to atomically look up, create and open a file from a negative
2439 * Returns 0 if successful. The file will have been created and attached to
2440 * @file by the filesystem calling finish_open().
2442 * Returns 1 if the file was looked up only or didn't need creating. The
2443 * caller will need to perform the open themselves. @path will have been
2444 * updated to point to the new dentry. This may be negative.
2446 * Returns an error code otherwise.
2448 static int atomic_open(struct nameidata *nd, struct dentry *dentry,
2449 struct path *path, struct file *file,
2450 const struct open_flags *op,
2451 bool got_write, bool need_lookup,
2454 struct inode *dir = nd->path.dentry->d_inode;
2455 unsigned open_flag = open_to_namei_flags(op->open_flag);
2459 int create_error = 0;
2460 struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
2462 BUG_ON(dentry->d_inode);
2464 /* Don't create child dentry for a dead directory. */
2465 if (unlikely(IS_DEADDIR(dir))) {
2471 if ((open_flag & O_CREAT) && !IS_POSIXACL(dir))
2472 mode &= ~current_umask();
2474 if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT)) {
2475 open_flag &= ~O_TRUNC;
2476 *opened |= FILE_CREATED;
2480 * Checking write permission is tricky, bacuse we don't know if we are
2481 * going to actually need it: O_CREAT opens should work as long as the
2482 * file exists. But checking existence breaks atomicity. The trick is
2483 * to check access and if not granted clear O_CREAT from the flags.
2485 * Another problem is returing the "right" error value (e.g. for an
2486 * O_EXCL open we want to return EEXIST not EROFS).
2488 if (((open_flag & (O_CREAT | O_TRUNC)) ||
2489 (open_flag & O_ACCMODE) != O_RDONLY) && unlikely(!got_write)) {
2490 if (!(open_flag & O_CREAT)) {
2492 * No O_CREATE -> atomicity not a requirement -> fall
2493 * back to lookup + open
2496 } else if (open_flag & (O_EXCL | O_TRUNC)) {
2497 /* Fall back and fail with the right error */
2498 create_error = -EROFS;
2501 /* No side effects, safe to clear O_CREAT */
2502 create_error = -EROFS;
2503 open_flag &= ~O_CREAT;
2507 if (open_flag & O_CREAT) {
2508 error = may_o_create(&nd->path, dentry, mode);
2510 create_error = error;
2511 if (open_flag & O_EXCL)
2513 open_flag &= ~O_CREAT;
2517 if (nd->flags & LOOKUP_DIRECTORY)
2518 open_flag |= O_DIRECTORY;
2520 file->f_path.dentry = DENTRY_NOT_SET;
2521 file->f_path.mnt = nd->path.mnt;
2522 error = dir->i_op->atomic_open(dir, dentry, file, open_flag, mode,
2525 if (create_error && error == -ENOENT)
2526 error = create_error;
2530 acc_mode = op->acc_mode;
2531 if (*opened & FILE_CREATED) {
2532 fsnotify_create(dir, dentry);
2533 acc_mode = MAY_OPEN;
2536 if (error) { /* returned 1, that is */
2537 if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
2541 if (file->f_path.dentry) {
2543 dentry = file->f_path.dentry;
2545 if (create_error && dentry->d_inode == NULL) {
2546 error = create_error;
2553 * We didn't have the inode before the open, so check open permission
2556 error = may_open(&file->f_path, acc_mode, open_flag);
2566 dentry = lookup_real(dir, dentry, nd->flags);
2568 return PTR_ERR(dentry);
2571 int open_flag = op->open_flag;
2573 error = create_error;
2574 if ((open_flag & O_EXCL)) {
2575 if (!dentry->d_inode)
2577 } else if (!dentry->d_inode) {
2579 } else if ((open_flag & O_TRUNC) &&
2580 S_ISREG(dentry->d_inode->i_mode)) {
2583 /* will fail later, go on to get the right error */
2587 path->dentry = dentry;
2588 path->mnt = nd->path.mnt;
2593 * Look up and maybe create and open the last component.
2595 * Must be called with i_mutex held on parent.
2597 * Returns 0 if the file was successfully atomically created (if necessary) and
2598 * opened. In this case the file will be returned attached to @file.
2600 * Returns 1 if the file was not completely opened at this time, though lookups
2601 * and creations will have been performed and the dentry returned in @path will
2602 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
2603 * specified then a negative dentry may be returned.
2605 * An error code is returned otherwise.
2607 * FILE_CREATE will be set in @*opened if the dentry was created and will be
2608 * cleared otherwise prior to returning.
2610 static int lookup_open(struct nameidata *nd, struct path *path,
2612 const struct open_flags *op,
2613 bool got_write, int *opened)
2615 struct dentry *dir = nd->path.dentry;
2616 struct inode *dir_inode = dir->d_inode;
2617 struct dentry *dentry;
2621 *opened &= ~FILE_CREATED;
2622 dentry = lookup_dcache(&nd->last, dir, nd->flags, &need_lookup);
2624 return PTR_ERR(dentry);
2626 /* Cached positive dentry: will open in f_op->open */
2627 if (!need_lookup && dentry->d_inode)
2630 if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) {
2631 return atomic_open(nd, dentry, path, file, op, got_write,
2632 need_lookup, opened);
2636 BUG_ON(dentry->d_inode);
2638 dentry = lookup_real(dir_inode, dentry, nd->flags);
2640 return PTR_ERR(dentry);
2643 /* Negative dentry, just create the file */
2644 if (!dentry->d_inode && (op->open_flag & O_CREAT)) {
2645 umode_t mode = op->mode;
2646 if (!IS_POSIXACL(dir->d_inode))
2647 mode &= ~current_umask();
2649 * This write is needed to ensure that a
2650 * rw->ro transition does not occur between
2651 * the time when the file is created and when
2652 * a permanent write count is taken through
2653 * the 'struct file' in finish_open().
2659 *opened |= FILE_CREATED;
2660 error = security_path_mknod(&nd->path, dentry, mode, 0);
2663 error = vfs_create(dir->d_inode, dentry, mode,
2664 nd->flags & LOOKUP_EXCL);
2669 path->dentry = dentry;
2670 path->mnt = nd->path.mnt;
2679 * Handle the last step of open()
2681 static int do_last(struct nameidata *nd, struct path *path,
2682 struct file *file, const struct open_flags *op,
2683 int *opened, struct filename *name)
2685 struct dentry *dir = nd->path.dentry;
2686 int open_flag = op->open_flag;
2687 bool will_truncate = (open_flag & O_TRUNC) != 0;
2688 bool got_write = false;
2689 int acc_mode = op->acc_mode;
2690 struct inode *inode;
2691 bool symlink_ok = false;
2692 struct path save_parent = { .dentry = NULL, .mnt = NULL };
2693 bool retried = false;
2696 nd->flags &= ~LOOKUP_PARENT;
2697 nd->flags |= op->intent;
2699 switch (nd->last_type) {
2702 error = handle_dots(nd, nd->last_type);
2707 error = complete_walk(nd);
2710 audit_inode(name, nd->path.dentry, 0);
2711 if (open_flag & O_CREAT) {
2717 error = complete_walk(nd);
2720 audit_inode(name, dir, 0);
2724 if (!(open_flag & O_CREAT)) {
2725 if (nd->last.name[nd->last.len])
2726 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2727 if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
2729 /* we _can_ be in RCU mode here */
2730 error = lookup_fast(nd, path, &inode);
2737 BUG_ON(nd->inode != dir->d_inode);
2739 /* create side of things */
2741 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
2742 * has been cleared when we got to the last component we are
2745 error = complete_walk(nd);
2749 audit_inode(name, dir, 0);
2751 /* trailing slashes? */
2752 if (nd->last.name[nd->last.len])
2757 if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
2758 error = mnt_want_write(nd->path.mnt);
2762 * do _not_ fail yet - we might not need that or fail with
2763 * a different error; let lookup_open() decide; we'll be
2764 * dropping this one anyway.
2767 mutex_lock(&dir->d_inode->i_mutex);
2768 error = lookup_open(nd, path, file, op, got_write, opened);
2769 mutex_unlock(&dir->d_inode->i_mutex);
2775 if ((*opened & FILE_CREATED) ||
2776 !S_ISREG(file_inode(file)->i_mode))
2777 will_truncate = false;
2779 audit_inode(name, file->f_path.dentry, 0);
2783 if (*opened & FILE_CREATED) {
2784 /* Don't check for write permission, don't truncate */
2785 open_flag &= ~O_TRUNC;
2786 will_truncate = false;
2787 acc_mode = MAY_OPEN;
2788 path_to_nameidata(path, nd);
2789 goto finish_open_created;
2793 * create/update audit record if it already exists.
2795 if (path->dentry->d_inode)
2796 audit_inode(name, path->dentry, 0);
2799 * If atomic_open() acquired write access it is dropped now due to
2800 * possible mount and symlink following (this might be optimized away if
2804 mnt_drop_write(nd->path.mnt);
2809 if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))
2812 error = follow_managed(path, nd->flags);
2817 nd->flags |= LOOKUP_JUMPED;
2819 BUG_ON(nd->flags & LOOKUP_RCU);
2820 inode = path->dentry->d_inode;
2822 /* we _can_ be in RCU mode here */
2825 path_to_nameidata(path, nd);
2829 if (should_follow_link(inode, !symlink_ok)) {
2830 if (nd->flags & LOOKUP_RCU) {
2831 if (unlikely(unlazy_walk(nd, path->dentry))) {
2836 BUG_ON(inode != path->dentry->d_inode);
2840 if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path->mnt) {
2841 path_to_nameidata(path, nd);
2843 save_parent.dentry = nd->path.dentry;
2844 save_parent.mnt = mntget(path->mnt);
2845 nd->path.dentry = path->dentry;
2849 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
2850 error = complete_walk(nd);
2852 path_put(&save_parent);
2856 if ((open_flag & O_CREAT) && S_ISDIR(nd->inode->i_mode))
2859 if ((nd->flags & LOOKUP_DIRECTORY) && !nd->inode->i_op->lookup)
2861 audit_inode(name, nd->path.dentry, 0);
2863 if (!S_ISREG(nd->inode->i_mode))
2864 will_truncate = false;
2866 if (will_truncate) {
2867 error = mnt_want_write(nd->path.mnt);
2872 finish_open_created:
2873 error = may_open(&nd->path, acc_mode, open_flag);
2876 file->f_path.mnt = nd->path.mnt;
2877 error = finish_open(file, nd->path.dentry, NULL, opened);
2879 if (error == -EOPENSTALE)
2884 error = open_check_o_direct(file);
2887 error = ima_file_check(file, op->acc_mode);
2891 if (will_truncate) {
2892 error = handle_truncate(file);
2898 mnt_drop_write(nd->path.mnt);
2899 path_put(&save_parent);
2904 path_put_conditional(path, nd);
2911 /* If no saved parent or already retried then can't retry */
2912 if (!save_parent.dentry || retried)
2915 BUG_ON(save_parent.dentry != dir);
2916 path_put(&nd->path);
2917 nd->path = save_parent;
2918 nd->inode = dir->d_inode;
2919 save_parent.mnt = NULL;
2920 save_parent.dentry = NULL;
2922 mnt_drop_write(nd->path.mnt);
2929 static struct file *path_openat(int dfd, struct filename *pathname,
2930 struct nameidata *nd, const struct open_flags *op, int flags)
2932 struct file *base = NULL;
2938 file = get_empty_filp();
2942 file->f_flags = op->open_flag;
2944 error = path_init(dfd, pathname->name, flags | LOOKUP_PARENT, nd, &base);
2945 if (unlikely(error))
2948 current->total_link_count = 0;
2949 error = link_path_walk(pathname->name, nd);
2950 if (unlikely(error))
2953 error = do_last(nd, &path, file, op, &opened, pathname);
2954 while (unlikely(error > 0)) { /* trailing symlink */
2955 struct path link = path;
2957 if (!(nd->flags & LOOKUP_FOLLOW)) {
2958 path_put_conditional(&path, nd);
2959 path_put(&nd->path);
2963 error = may_follow_link(&link, nd);
2964 if (unlikely(error))
2966 nd->flags |= LOOKUP_PARENT;
2967 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
2968 error = follow_link(&link, nd, &cookie);
2969 if (unlikely(error))
2971 error = do_last(nd, &path, file, op, &opened, pathname);
2972 put_link(nd, &link, cookie);
2975 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
2976 path_put(&nd->root);
2979 if (!(opened & FILE_OPENED)) {
2983 if (unlikely(error)) {
2984 if (error == -EOPENSTALE) {
2985 if (flags & LOOKUP_RCU)
2990 file = ERR_PTR(error);
2995 struct file *do_filp_open(int dfd, struct filename *pathname,
2996 const struct open_flags *op, int flags)
2998 struct nameidata nd;
3001 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
3002 if (unlikely(filp == ERR_PTR(-ECHILD)))
3003 filp = path_openat(dfd, pathname, &nd, op, flags);
3004 if (unlikely(filp == ERR_PTR(-ESTALE)))
3005 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
3009 struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
3010 const char *name, const struct open_flags *op, int flags)
3012 struct nameidata nd;
3014 struct filename filename = { .name = name };
3017 nd.root.dentry = dentry;
3019 flags |= LOOKUP_ROOT;
3021 if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
3022 return ERR_PTR(-ELOOP);
3024 file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_RCU);
3025 if (unlikely(file == ERR_PTR(-ECHILD)))
3026 file = path_openat(-1, &filename, &nd, op, flags);
3027 if (unlikely(file == ERR_PTR(-ESTALE)))
3028 file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_REVAL);
3032 struct dentry *kern_path_create(int dfd, const char *pathname,
3033 struct path *path, unsigned int lookup_flags)
3035 struct dentry *dentry = ERR_PTR(-EEXIST);
3036 struct nameidata nd;
3039 bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
3042 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3043 * other flags passed in are ignored!
3045 lookup_flags &= LOOKUP_REVAL;
3047 error = do_path_lookup(dfd, pathname, LOOKUP_PARENT|lookup_flags, &nd);
3049 return ERR_PTR(error);
3052 * Yucky last component or no last component at all?
3053 * (foo/., foo/.., /////)
3055 if (nd.last_type != LAST_NORM)
3057 nd.flags &= ~LOOKUP_PARENT;
3058 nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL;
3060 /* don't fail immediately if it's r/o, at least try to report other errors */
3061 err2 = mnt_want_write(nd.path.mnt);
3063 * Do the final lookup.
3065 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
3066 dentry = lookup_hash(&nd);
3071 if (dentry->d_inode)
3074 * Special case - lookup gave negative, but... we had foo/bar/
3075 * From the vfs_mknod() POV we just have a negative dentry -
3076 * all is fine. Let's be bastards - you had / on the end, you've
3077 * been asking for (non-existent) directory. -ENOENT for you.
3079 if (unlikely(!is_dir && nd.last.name[nd.last.len])) {
3083 if (unlikely(err2)) {
3091 dentry = ERR_PTR(error);
3093 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3095 mnt_drop_write(nd.path.mnt);
3100 EXPORT_SYMBOL(kern_path_create);
3102 void done_path_create(struct path *path, struct dentry *dentry)
3105 mutex_unlock(&path->dentry->d_inode->i_mutex);
3106 mnt_drop_write(path->mnt);
3109 EXPORT_SYMBOL(done_path_create);
3111 struct dentry *user_path_create(int dfd, const char __user *pathname,
3112 struct path *path, unsigned int lookup_flags)
3114 struct filename *tmp = getname(pathname);
3117 return ERR_CAST(tmp);
3118 res = kern_path_create(dfd, tmp->name, path, lookup_flags);
3122 EXPORT_SYMBOL(user_path_create);
3124 int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
3126 int error = may_create(dir, dentry);
3131 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
3134 if (!dir->i_op->mknod)
3137 error = devcgroup_inode_mknod(mode, dev);
3141 error = security_inode_mknod(dir, dentry, mode, dev);
3145 error = dir->i_op->mknod(dir, dentry, mode, dev);
3147 fsnotify_create(dir, dentry);
3151 static int may_mknod(umode_t mode)
3153 switch (mode & S_IFMT) {
3159 case 0: /* zero mode translates to S_IFREG */
3168 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
3171 struct dentry *dentry;
3174 unsigned int lookup_flags = 0;
3176 error = may_mknod(mode);
3180 dentry = user_path_create(dfd, filename, &path, lookup_flags);
3182 return PTR_ERR(dentry);
3184 if (!IS_POSIXACL(path.dentry->d_inode))
3185 mode &= ~current_umask();
3186 error = security_path_mknod(&path, dentry, mode, dev);
3189 switch (mode & S_IFMT) {
3190 case 0: case S_IFREG:
3191 error = vfs_create(path.dentry->d_inode,dentry,mode,true);
3193 case S_IFCHR: case S_IFBLK:
3194 error = vfs_mknod(path.dentry->d_inode,dentry,mode,
3195 new_decode_dev(dev));
3197 case S_IFIFO: case S_IFSOCK:
3198 error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
3202 done_path_create(&path, dentry);
3203 if (retry_estale(error, lookup_flags)) {
3204 lookup_flags |= LOOKUP_REVAL;
3210 SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
3212 return sys_mknodat(AT_FDCWD, filename, mode, dev);
3215 int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
3217 int error = may_create(dir, dentry);
3218 unsigned max_links = dir->i_sb->s_max_links;
3223 if (!dir->i_op->mkdir)
3226 mode &= (S_IRWXUGO|S_ISVTX);
3227 error = security_inode_mkdir(dir, dentry, mode);
3231 if (max_links && dir->i_nlink >= max_links)
3234 error = dir->i_op->mkdir(dir, dentry, mode);
3236 fsnotify_mkdir(dir, dentry);
3240 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
3242 struct dentry *dentry;
3245 unsigned int lookup_flags = LOOKUP_DIRECTORY;
3248 dentry = user_path_create(dfd, pathname, &path, lookup_flags);
3250 return PTR_ERR(dentry);
3252 if (!IS_POSIXACL(path.dentry->d_inode))
3253 mode &= ~current_umask();
3254 error = security_path_mkdir(&path, dentry, mode);
3256 error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
3257 done_path_create(&path, dentry);
3258 if (retry_estale(error, lookup_flags)) {
3259 lookup_flags |= LOOKUP_REVAL;
3265 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
3267 return sys_mkdirat(AT_FDCWD, pathname, mode);
3271 * The dentry_unhash() helper will try to drop the dentry early: we
3272 * should have a usage count of 1 if we're the only user of this
3273 * dentry, and if that is true (possibly after pruning the dcache),
3274 * then we drop the dentry now.
3276 * A low-level filesystem can, if it choses, legally
3279 * if (!d_unhashed(dentry))
3282 * if it cannot handle the case of removing a directory
3283 * that is still in use by something else..
3285 void dentry_unhash(struct dentry *dentry)
3287 shrink_dcache_parent(dentry);
3288 spin_lock(&dentry->d_lock);
3289 if (dentry->d_count == 1)
3291 spin_unlock(&dentry->d_lock);
3294 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
3296 int error = may_delete(dir, dentry, 1);
3301 if (!dir->i_op->rmdir)
3305 mutex_lock(&dentry->d_inode->i_mutex);
3308 if (d_mountpoint(dentry))
3311 error = security_inode_rmdir(dir, dentry);
3315 shrink_dcache_parent(dentry);
3316 error = dir->i_op->rmdir(dir, dentry);
3320 dentry->d_inode->i_flags |= S_DEAD;
3324 mutex_unlock(&dentry->d_inode->i_mutex);
3331 static long do_rmdir(int dfd, const char __user *pathname)
3334 struct filename *name;
3335 struct dentry *dentry;
3336 struct nameidata nd;
3337 unsigned int lookup_flags = 0;
3339 name = user_path_parent(dfd, pathname, &nd, lookup_flags);
3341 return PTR_ERR(name);
3343 switch(nd.last_type) {
3355 nd.flags &= ~LOOKUP_PARENT;
3356 error = mnt_want_write(nd.path.mnt);
3360 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
3361 dentry = lookup_hash(&nd);
3362 error = PTR_ERR(dentry);
3365 if (!dentry->d_inode) {
3369 error = security_path_rmdir(&nd.path, dentry);
3372 error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
3376 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3377 mnt_drop_write(nd.path.mnt);
3381 if (retry_estale(error, lookup_flags)) {
3382 lookup_flags |= LOOKUP_REVAL;
3388 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
3390 return do_rmdir(AT_FDCWD, pathname);
3393 int vfs_unlink(struct inode *dir, struct dentry *dentry)
3395 int error = may_delete(dir, dentry, 0);
3400 if (!dir->i_op->unlink)
3403 mutex_lock(&dentry->d_inode->i_mutex);
3404 if (d_mountpoint(dentry))
3407 error = security_inode_unlink(dir, dentry);
3409 error = dir->i_op->unlink(dir, dentry);
3414 mutex_unlock(&dentry->d_inode->i_mutex);
3416 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3417 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
3418 fsnotify_link_count(dentry->d_inode);
3426 * Make sure that the actual truncation of the file will occur outside its
3427 * directory's i_mutex. Truncate can take a long time if there is a lot of
3428 * writeout happening, and we don't want to prevent access to the directory
3429 * while waiting on the I/O.
3431 static long do_unlinkat(int dfd, const char __user *pathname)
3434 struct filename *name;
3435 struct dentry *dentry;
3436 struct nameidata nd;
3437 struct inode *inode = NULL;
3438 unsigned int lookup_flags = 0;
3440 name = user_path_parent(dfd, pathname, &nd, lookup_flags);
3442 return PTR_ERR(name);
3445 if (nd.last_type != LAST_NORM)
3448 nd.flags &= ~LOOKUP_PARENT;
3449 error = mnt_want_write(nd.path.mnt);
3453 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
3454 dentry = lookup_hash(&nd);
3455 error = PTR_ERR(dentry);
3456 if (!IS_ERR(dentry)) {
3457 /* Why not before? Because we want correct error value */
3458 if (nd.last.name[nd.last.len])
3460 inode = dentry->d_inode;
3464 error = security_path_unlink(&nd.path, dentry);
3467 error = vfs_unlink(nd.path.dentry->d_inode, dentry);
3471 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3473 iput(inode); /* truncate the inode here */
3474 mnt_drop_write(nd.path.mnt);
3478 if (retry_estale(error, lookup_flags)) {
3479 lookup_flags |= LOOKUP_REVAL;
3486 error = !dentry->d_inode ? -ENOENT :
3487 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
3491 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
3493 if ((flag & ~AT_REMOVEDIR) != 0)
3496 if (flag & AT_REMOVEDIR)
3497 return do_rmdir(dfd, pathname);
3499 return do_unlinkat(dfd, pathname);
3502 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
3504 return do_unlinkat(AT_FDCWD, pathname);
3507 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
3509 int error = may_create(dir, dentry);
3514 if (!dir->i_op->symlink)
3517 error = security_inode_symlink(dir, dentry, oldname);
3521 error = dir->i_op->symlink(dir, dentry, oldname);
3523 fsnotify_create(dir, dentry);
3527 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
3528 int, newdfd, const char __user *, newname)
3531 struct filename *from;
3532 struct dentry *dentry;
3534 unsigned int lookup_flags = 0;
3536 from = getname(oldname);
3538 return PTR_ERR(from);
3540 dentry = user_path_create(newdfd, newname, &path, lookup_flags);
3541 error = PTR_ERR(dentry);
3545 error = security_path_symlink(&path, dentry, from->name);
3547 error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
3548 done_path_create(&path, dentry);
3549 if (retry_estale(error, lookup_flags)) {
3550 lookup_flags |= LOOKUP_REVAL;
3558 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
3560 return sys_symlinkat(oldname, AT_FDCWD, newname);
3563 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
3565 struct inode *inode = old_dentry->d_inode;
3566 unsigned max_links = dir->i_sb->s_max_links;
3572 error = may_create(dir, new_dentry);
3576 if (dir->i_sb != inode->i_sb)
3580 * A link to an append-only or immutable file cannot be created.
3582 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
3584 if (!dir->i_op->link)
3586 if (S_ISDIR(inode->i_mode))
3589 error = security_inode_link(old_dentry, dir, new_dentry);
3593 mutex_lock(&inode->i_mutex);
3594 /* Make sure we don't allow creating hardlink to an unlinked file */
3595 if (inode->i_nlink == 0)
3597 else if (max_links && inode->i_nlink >= max_links)
3600 error = dir->i_op->link(old_dentry, dir, new_dentry);
3601 mutex_unlock(&inode->i_mutex);
3603 fsnotify_link(dir, inode, new_dentry);
3608 * Hardlinks are often used in delicate situations. We avoid
3609 * security-related surprises by not following symlinks on the
3612 * We don't follow them on the oldname either to be compatible
3613 * with linux 2.0, and to avoid hard-linking to directories
3614 * and other special files. --ADM
3616 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
3617 int, newdfd, const char __user *, newname, int, flags)
3619 struct dentry *new_dentry;
3620 struct path old_path, new_path;
3624 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
3627 * To use null names we require CAP_DAC_READ_SEARCH
3628 * This ensures that not everyone will be able to create
3629 * handlink using the passed filedescriptor.
3631 if (flags & AT_EMPTY_PATH) {
3632 if (!capable(CAP_DAC_READ_SEARCH))
3637 if (flags & AT_SYMLINK_FOLLOW)
3638 how |= LOOKUP_FOLLOW;
3640 error = user_path_at(olddfd, oldname, how, &old_path);
3644 new_dentry = user_path_create(newdfd, newname, &new_path,
3645 (how & LOOKUP_REVAL));
3646 error = PTR_ERR(new_dentry);
3647 if (IS_ERR(new_dentry))
3651 if (old_path.mnt != new_path.mnt)
3653 error = may_linkat(&old_path);
3654 if (unlikely(error))
3656 error = security_path_link(old_path.dentry, &new_path, new_dentry);
3659 error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry);
3661 done_path_create(&new_path, new_dentry);
3662 if (retry_estale(error, how)) {
3663 how |= LOOKUP_REVAL;
3667 path_put(&old_path);
3672 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
3674 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
3678 * The worst of all namespace operations - renaming directory. "Perverted"
3679 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3681 * a) we can get into loop creation. Check is done in is_subdir().
3682 * b) race potential - two innocent renames can create a loop together.
3683 * That's where 4.4 screws up. Current fix: serialization on
3684 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
3686 * c) we have to lock _three_ objects - parents and victim (if it exists).
3687 * And that - after we got ->i_mutex on parents (until then we don't know
3688 * whether the target exists). Solution: try to be smart with locking
3689 * order for inodes. We rely on the fact that tree topology may change
3690 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
3691 * move will be locked. Thus we can rank directories by the tree
3692 * (ancestors first) and rank all non-directories after them.
3693 * That works since everybody except rename does "lock parent, lookup,
3694 * lock child" and rename is under ->s_vfs_rename_mutex.
3695 * HOWEVER, it relies on the assumption that any object with ->lookup()
3696 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3697 * we'd better make sure that there's no link(2) for them.
3698 * d) conversion from fhandle to dentry may come in the wrong moment - when
3699 * we are removing the target. Solution: we will have to grab ->i_mutex
3700 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
3701 * ->i_mutex on parents, which works but leads to some truly excessive
3704 static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
3705 struct inode *new_dir, struct dentry *new_dentry)
3708 struct inode *target = new_dentry->d_inode;
3709 unsigned max_links = new_dir->i_sb->s_max_links;
3712 * If we are going to change the parent - check write permissions,
3713 * we'll need to flip '..'.
3715 if (new_dir != old_dir) {
3716 error = inode_permission(old_dentry->d_inode, MAY_WRITE);
3721 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3727 mutex_lock(&target->i_mutex);
3730 if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
3734 if (max_links && !target && new_dir != old_dir &&
3735 new_dir->i_nlink >= max_links)
3739 shrink_dcache_parent(new_dentry);
3740 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3745 target->i_flags |= S_DEAD;
3746 dont_mount(new_dentry);
3750 mutex_unlock(&target->i_mutex);
3753 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3754 d_move(old_dentry,new_dentry);
3758 static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
3759 struct inode *new_dir, struct dentry *new_dentry)
3761 struct inode *target = new_dentry->d_inode;
3764 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3770 mutex_lock(&target->i_mutex);
3773 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
3776 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3781 dont_mount(new_dentry);
3782 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3783 d_move(old_dentry, new_dentry);
3786 mutex_unlock(&target->i_mutex);
3791 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
3792 struct inode *new_dir, struct dentry *new_dentry)
3795 int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
3796 const unsigned char *old_name;
3798 if (old_dentry->d_inode == new_dentry->d_inode)
3801 error = may_delete(old_dir, old_dentry, is_dir);
3805 if (!new_dentry->d_inode)
3806 error = may_create(new_dir, new_dentry);
3808 error = may_delete(new_dir, new_dentry, is_dir);
3812 if (!old_dir->i_op->rename)
3815 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
3818 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
3820 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
3822 fsnotify_move(old_dir, new_dir, old_name, is_dir,
3823 new_dentry->d_inode, old_dentry);
3824 fsnotify_oldname_free(old_name);
3829 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
3830 int, newdfd, const char __user *, newname)
3832 struct dentry *old_dir, *new_dir;
3833 struct dentry *old_dentry, *new_dentry;
3834 struct dentry *trap;
3835 struct nameidata oldnd, newnd;
3836 struct filename *from;
3837 struct filename *to;
3838 unsigned int lookup_flags = 0;
3839 bool should_retry = false;
3842 from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags);
3844 error = PTR_ERR(from);
3848 to = user_path_parent(newdfd, newname, &newnd, lookup_flags);
3850 error = PTR_ERR(to);
3855 if (oldnd.path.mnt != newnd.path.mnt)
3858 old_dir = oldnd.path.dentry;
3860 if (oldnd.last_type != LAST_NORM)
3863 new_dir = newnd.path.dentry;
3864 if (newnd.last_type != LAST_NORM)
3867 error = mnt_want_write(oldnd.path.mnt);
3871 oldnd.flags &= ~LOOKUP_PARENT;
3872 newnd.flags &= ~LOOKUP_PARENT;
3873 newnd.flags |= LOOKUP_RENAME_TARGET;
3875 trap = lock_rename(new_dir, old_dir);
3877 old_dentry = lookup_hash(&oldnd);
3878 error = PTR_ERR(old_dentry);
3879 if (IS_ERR(old_dentry))
3881 /* source must exist */
3883 if (!old_dentry->d_inode)
3885 /* unless the source is a directory trailing slashes give -ENOTDIR */
3886 if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
3888 if (oldnd.last.name[oldnd.last.len])
3890 if (newnd.last.name[newnd.last.len])
3893 /* source should not be ancestor of target */
3895 if (old_dentry == trap)
3897 new_dentry = lookup_hash(&newnd);
3898 error = PTR_ERR(new_dentry);
3899 if (IS_ERR(new_dentry))
3901 /* target should not be an ancestor of source */
3903 if (new_dentry == trap)
3906 error = security_path_rename(&oldnd.path, old_dentry,
3907 &newnd.path, new_dentry);
3910 error = vfs_rename(old_dir->d_inode, old_dentry,
3911 new_dir->d_inode, new_dentry);
3917 unlock_rename(new_dir, old_dir);
3918 mnt_drop_write(oldnd.path.mnt);
3920 if (retry_estale(error, lookup_flags))
3921 should_retry = true;
3922 path_put(&newnd.path);
3925 path_put(&oldnd.path);
3928 should_retry = false;
3929 lookup_flags |= LOOKUP_REVAL;
3936 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
3938 return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
3941 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
3945 len = PTR_ERR(link);
3950 if (len > (unsigned) buflen)
3952 if (copy_to_user(buffer, link, len))
3959 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
3960 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
3961 * using) it for any given inode is up to filesystem.
3963 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3965 struct nameidata nd;
3970 cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
3972 return PTR_ERR(cookie);
3974 res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
3975 if (dentry->d_inode->i_op->put_link)
3976 dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
3980 int vfs_follow_link(struct nameidata *nd, const char *link)
3982 return __vfs_follow_link(nd, link);
3985 /* get the link contents into pagecache */
3986 static char *page_getlink(struct dentry * dentry, struct page **ppage)
3990 struct address_space *mapping = dentry->d_inode->i_mapping;
3991 page = read_mapping_page(mapping, 0, NULL);
3996 nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
4000 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4002 struct page *page = NULL;
4003 char *s = page_getlink(dentry, &page);
4004 int res = vfs_readlink(dentry,buffer,buflen,s);
4007 page_cache_release(page);
4012 void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
4014 struct page *page = NULL;
4015 nd_set_link(nd, page_getlink(dentry, &page));
4019 void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
4021 struct page *page = cookie;
4025 page_cache_release(page);
4030 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4032 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
4034 struct address_space *mapping = inode->i_mapping;
4039 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
4041 flags |= AOP_FLAG_NOFS;
4044 err = pagecache_write_begin(NULL, mapping, 0, len-1,
4045 flags, &page, &fsdata);
4049 kaddr = kmap_atomic(page);
4050 memcpy(kaddr, symname, len-1);
4051 kunmap_atomic(kaddr);
4053 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
4060 mark_inode_dirty(inode);
4066 int page_symlink(struct inode *inode, const char *symname, int len)
4068 return __page_symlink(inode, symname, len,
4069 !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
4072 const struct inode_operations page_symlink_inode_operations = {
4073 .readlink = generic_readlink,
4074 .follow_link = page_follow_link_light,
4075 .put_link = page_put_link,
4078 EXPORT_SYMBOL(user_path_at);
4079 EXPORT_SYMBOL(follow_down_one);
4080 EXPORT_SYMBOL(follow_down);
4081 EXPORT_SYMBOL(follow_up);
4082 EXPORT_SYMBOL(get_write_access); /* nfsd */
4083 EXPORT_SYMBOL(lock_rename);
4084 EXPORT_SYMBOL(lookup_one_len);
4085 EXPORT_SYMBOL(page_follow_link_light);
4086 EXPORT_SYMBOL(page_put_link);
4087 EXPORT_SYMBOL(page_readlink);
4088 EXPORT_SYMBOL(__page_symlink);
4089 EXPORT_SYMBOL(page_symlink);
4090 EXPORT_SYMBOL(page_symlink_inode_operations);
4091 EXPORT_SYMBOL(kern_path);
4092 EXPORT_SYMBOL(vfs_path_lookup);
4093 EXPORT_SYMBOL(inode_permission);
4094 EXPORT_SYMBOL(unlock_rename);
4095 EXPORT_SYMBOL(vfs_create);
4096 EXPORT_SYMBOL(vfs_follow_link);
4097 EXPORT_SYMBOL(vfs_link);
4098 EXPORT_SYMBOL(vfs_mkdir);
4099 EXPORT_SYMBOL(vfs_mknod);
4100 EXPORT_SYMBOL(generic_permission);
4101 EXPORT_SYMBOL(vfs_readlink);
4102 EXPORT_SYMBOL(vfs_rename);
4103 EXPORT_SYMBOL(vfs_rmdir);
4104 EXPORT_SYMBOL(vfs_symlink);
4105 EXPORT_SYMBOL(vfs_unlink);
4106 EXPORT_SYMBOL(dentry_unhash);
4107 EXPORT_SYMBOL(generic_readlink);