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(const 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(const 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;
512 BUG_ON(!(nd->flags & LOOKUP_RCU));
515 * Get a reference to the parent first: we're
516 * going to make "path_put(nd->path)" valid in
517 * non-RCU context for "terminate_walk()".
519 * If this doesn't work, return immediately with
520 * RCU walking still active (and then we will do
521 * the RCU walk cleanup in terminate_walk()).
523 if (!lockref_get_not_dead(&parent->d_lockref))
527 * After the mntget(), we terminate_walk() will do
528 * the right thing for non-RCU mode, and all our
529 * subsequent exit cases should unlock_rcu_walk()
532 mntget(nd->path.mnt);
533 nd->flags &= ~LOOKUP_RCU;
536 * For a negative lookup, the lookup sequence point is the parents
537 * sequence point, and it only needs to revalidate the parent dentry.
539 * For a positive lookup, we need to move both the parent and the
540 * dentry from the RCU domain to be properly refcounted. And the
541 * sequence number in the dentry validates *both* dentry counters,
542 * since we checked the sequence number of the parent after we got
543 * the child sequence number. So we know the parent must still
544 * be valid if the child sequence number is still valid.
547 if (read_seqcount_retry(&parent->d_seq, nd->seq))
549 BUG_ON(nd->inode != parent->d_inode);
551 if (!lockref_get_not_dead(&dentry->d_lockref))
553 if (read_seqcount_retry(&dentry->d_seq, nd->seq))
558 * Sequence counts matched. Now make sure that the root is
559 * still valid and get it if required.
561 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
562 spin_lock(&fs->lock);
563 if (nd->root.mnt != fs->root.mnt || nd->root.dentry != fs->root.dentry)
564 goto unlock_and_drop_dentry;
566 spin_unlock(&fs->lock);
572 unlock_and_drop_dentry:
573 spin_unlock(&fs->lock);
581 if (!(nd->flags & LOOKUP_ROOT))
586 static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
588 return dentry->d_op->d_revalidate(dentry, flags);
592 * complete_walk - successful completion of path walk
593 * @nd: pointer nameidata
595 * If we had been in RCU mode, drop out of it and legitimize nd->path.
596 * Revalidate the final result, unless we'd already done that during
597 * the path walk or the filesystem doesn't ask for it. Return 0 on
598 * success, -error on failure. In case of failure caller does not
599 * need to drop nd->path.
601 static int complete_walk(struct nameidata *nd)
603 struct dentry *dentry = nd->path.dentry;
606 if (nd->flags & LOOKUP_RCU) {
607 nd->flags &= ~LOOKUP_RCU;
608 if (!(nd->flags & LOOKUP_ROOT))
611 if (unlikely(!lockref_get_not_dead(&dentry->d_lockref))) {
615 if (read_seqcount_retry(&dentry->d_seq, nd->seq)) {
620 mntget(nd->path.mnt);
624 if (likely(!(nd->flags & LOOKUP_JUMPED)))
627 if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
630 status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
641 static __always_inline void set_root(struct nameidata *nd)
644 get_fs_root(current->fs, &nd->root);
647 static int link_path_walk(const char *, struct nameidata *);
649 static __always_inline void set_root_rcu(struct nameidata *nd)
652 struct fs_struct *fs = current->fs;
656 seq = read_seqcount_begin(&fs->seq);
658 nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
659 } while (read_seqcount_retry(&fs->seq, seq));
663 static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
675 nd->flags |= LOOKUP_JUMPED;
677 nd->inode = nd->path.dentry->d_inode;
679 ret = link_path_walk(link, nd);
683 return PTR_ERR(link);
686 static void path_put_conditional(struct path *path, struct nameidata *nd)
689 if (path->mnt != nd->path.mnt)
693 static inline void path_to_nameidata(const struct path *path,
694 struct nameidata *nd)
696 if (!(nd->flags & LOOKUP_RCU)) {
697 dput(nd->path.dentry);
698 if (nd->path.mnt != path->mnt)
699 mntput(nd->path.mnt);
701 nd->path.mnt = path->mnt;
702 nd->path.dentry = path->dentry;
706 * Helper to directly jump to a known parsed path from ->follow_link,
707 * caller must have taken a reference to path beforehand.
709 void nd_jump_link(struct nameidata *nd, struct path *path)
714 nd->inode = nd->path.dentry->d_inode;
715 nd->flags |= LOOKUP_JUMPED;
718 static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
720 struct inode *inode = link->dentry->d_inode;
721 if (inode->i_op->put_link)
722 inode->i_op->put_link(link->dentry, nd, cookie);
726 int sysctl_protected_symlinks __read_mostly = 0;
727 int sysctl_protected_hardlinks __read_mostly = 0;
730 * may_follow_link - Check symlink following for unsafe situations
731 * @link: The path of the symlink
732 * @nd: nameidata pathwalk data
734 * In the case of the sysctl_protected_symlinks sysctl being enabled,
735 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
736 * in a sticky world-writable directory. This is to protect privileged
737 * processes from failing races against path names that may change out
738 * from under them by way of other users creating malicious symlinks.
739 * It will permit symlinks to be followed only when outside a sticky
740 * world-writable directory, or when the uid of the symlink and follower
741 * match, or when the directory owner matches the symlink's owner.
743 * Returns 0 if following the symlink is allowed, -ve on error.
745 static inline int may_follow_link(struct path *link, struct nameidata *nd)
747 const struct inode *inode;
748 const struct inode *parent;
750 if (!sysctl_protected_symlinks)
753 /* Allowed if owner and follower match. */
754 inode = link->dentry->d_inode;
755 if (uid_eq(current_cred()->fsuid, inode->i_uid))
758 /* Allowed if parent directory not sticky and world-writable. */
759 parent = nd->path.dentry->d_inode;
760 if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
763 /* Allowed if parent directory and link owner match. */
764 if (uid_eq(parent->i_uid, inode->i_uid))
767 audit_log_link_denied("follow_link", link);
768 path_put_conditional(link, nd);
774 * safe_hardlink_source - Check for safe hardlink conditions
775 * @inode: the source inode to hardlink from
777 * Return false if at least one of the following conditions:
778 * - inode is not a regular file
780 * - inode is setgid and group-exec
781 * - access failure for read and write
783 * Otherwise returns true.
785 static bool safe_hardlink_source(struct inode *inode)
787 umode_t mode = inode->i_mode;
789 /* Special files should not get pinned to the filesystem. */
793 /* Setuid files should not get pinned to the filesystem. */
797 /* Executable setgid files should not get pinned to the filesystem. */
798 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
801 /* Hardlinking to unreadable or unwritable sources is dangerous. */
802 if (inode_permission(inode, MAY_READ | MAY_WRITE))
809 * may_linkat - Check permissions for creating a hardlink
810 * @link: the source to hardlink from
812 * Block hardlink when all of:
813 * - sysctl_protected_hardlinks enabled
814 * - fsuid does not match inode
815 * - hardlink source is unsafe (see safe_hardlink_source() above)
818 * Returns 0 if successful, -ve on error.
820 static int may_linkat(struct path *link)
822 const struct cred *cred;
825 if (!sysctl_protected_hardlinks)
828 cred = current_cred();
829 inode = link->dentry->d_inode;
831 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
832 * otherwise, it must be a safe source.
834 if (uid_eq(cred->fsuid, inode->i_uid) || safe_hardlink_source(inode) ||
838 audit_log_link_denied("linkat", link);
842 static __always_inline int
843 follow_link(struct path *link, struct nameidata *nd, void **p)
845 struct dentry *dentry = link->dentry;
849 BUG_ON(nd->flags & LOOKUP_RCU);
851 if (link->mnt == nd->path.mnt)
855 if (unlikely(current->total_link_count >= 40))
856 goto out_put_nd_path;
859 current->total_link_count++;
862 nd_set_link(nd, NULL);
864 error = security_inode_follow_link(link->dentry, nd);
866 goto out_put_nd_path;
868 nd->last_type = LAST_BIND;
869 *p = dentry->d_inode->i_op->follow_link(dentry, nd);
872 goto out_put_nd_path;
877 error = __vfs_follow_link(nd, s);
879 put_link(nd, link, *p);
891 static int follow_up_rcu(struct path *path)
893 struct mount *mnt = real_mount(path->mnt);
894 struct mount *parent;
895 struct dentry *mountpoint;
897 parent = mnt->mnt_parent;
898 if (&parent->mnt == path->mnt)
900 mountpoint = mnt->mnt_mountpoint;
901 path->dentry = mountpoint;
902 path->mnt = &parent->mnt;
907 * follow_up - Find the mountpoint of path's vfsmount
909 * Given a path, find the mountpoint of its source file system.
910 * Replace @path with the path of the mountpoint in the parent mount.
913 * Return 1 if we went up a level and 0 if we were already at the
916 int follow_up(struct path *path)
918 struct mount *mnt = real_mount(path->mnt);
919 struct mount *parent;
920 struct dentry *mountpoint;
922 br_read_lock(&vfsmount_lock);
923 parent = mnt->mnt_parent;
925 br_read_unlock(&vfsmount_lock);
928 mntget(&parent->mnt);
929 mountpoint = dget(mnt->mnt_mountpoint);
930 br_read_unlock(&vfsmount_lock);
932 path->dentry = mountpoint;
934 path->mnt = &parent->mnt;
939 * Perform an automount
940 * - return -EISDIR to tell follow_managed() to stop and return the path we
943 static int follow_automount(struct path *path, unsigned flags,
946 struct vfsmount *mnt;
949 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
952 /* We don't want to mount if someone's just doing a stat -
953 * unless they're stat'ing a directory and appended a '/' to
956 * We do, however, want to mount if someone wants to open or
957 * create a file of any type under the mountpoint, wants to
958 * traverse through the mountpoint or wants to open the
959 * mounted directory. Also, autofs may mark negative dentries
960 * as being automount points. These will need the attentions
961 * of the daemon to instantiate them before they can be used.
963 if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
964 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
965 path->dentry->d_inode)
968 current->total_link_count++;
969 if (current->total_link_count >= 40)
972 mnt = path->dentry->d_op->d_automount(path);
975 * The filesystem is allowed to return -EISDIR here to indicate
976 * it doesn't want to automount. For instance, autofs would do
977 * this so that its userspace daemon can mount on this dentry.
979 * However, we can only permit this if it's a terminal point in
980 * the path being looked up; if it wasn't then the remainder of
981 * the path is inaccessible and we should say so.
983 if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT))
988 if (!mnt) /* mount collision */
992 /* lock_mount() may release path->mnt on error */
996 err = finish_automount(mnt, path);
1000 /* Someone else made a mount here whilst we were busy */
1005 path->dentry = dget(mnt->mnt_root);
1014 * Handle a dentry that is managed in some way.
1015 * - Flagged for transit management (autofs)
1016 * - Flagged as mountpoint
1017 * - Flagged as automount point
1019 * This may only be called in refwalk mode.
1021 * Serialization is taken care of in namespace.c
1023 static int follow_managed(struct path *path, unsigned flags)
1025 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
1027 bool need_mntput = false;
1030 /* Given that we're not holding a lock here, we retain the value in a
1031 * local variable for each dentry as we look at it so that we don't see
1032 * the components of that value change under us */
1033 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1034 managed &= DCACHE_MANAGED_DENTRY,
1035 unlikely(managed != 0)) {
1036 /* Allow the filesystem to manage the transit without i_mutex
1038 if (managed & DCACHE_MANAGE_TRANSIT) {
1039 BUG_ON(!path->dentry->d_op);
1040 BUG_ON(!path->dentry->d_op->d_manage);
1041 ret = path->dentry->d_op->d_manage(path->dentry, false);
1046 /* Transit to a mounted filesystem. */
1047 if (managed & DCACHE_MOUNTED) {
1048 struct vfsmount *mounted = lookup_mnt(path);
1053 path->mnt = mounted;
1054 path->dentry = dget(mounted->mnt_root);
1059 /* Something is mounted on this dentry in another
1060 * namespace and/or whatever was mounted there in this
1061 * namespace got unmounted before we managed to get the
1065 /* Handle an automount point */
1066 if (managed & DCACHE_NEED_AUTOMOUNT) {
1067 ret = follow_automount(path, flags, &need_mntput);
1073 /* We didn't change the current path point */
1077 if (need_mntput && path->mnt == mnt)
1081 return ret < 0 ? ret : need_mntput;
1084 int follow_down_one(struct path *path)
1086 struct vfsmount *mounted;
1088 mounted = lookup_mnt(path);
1092 path->mnt = mounted;
1093 path->dentry = dget(mounted->mnt_root);
1099 static inline bool managed_dentry_might_block(struct dentry *dentry)
1101 return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
1102 dentry->d_op->d_manage(dentry, true) < 0);
1106 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1107 * we meet a managed dentry that would need blocking.
1109 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
1110 struct inode **inode)
1113 struct mount *mounted;
1115 * Don't forget we might have a non-mountpoint managed dentry
1116 * that wants to block transit.
1118 if (unlikely(managed_dentry_might_block(path->dentry)))
1121 if (!d_mountpoint(path->dentry))
1124 mounted = __lookup_mnt(path->mnt, path->dentry, 1);
1127 path->mnt = &mounted->mnt;
1128 path->dentry = mounted->mnt.mnt_root;
1129 nd->flags |= LOOKUP_JUMPED;
1130 nd->seq = read_seqcount_begin(&path->dentry->d_seq);
1132 * Update the inode too. We don't need to re-check the
1133 * dentry sequence number here after this d_inode read,
1134 * because a mount-point is always pinned.
1136 *inode = path->dentry->d_inode;
1141 static void follow_mount_rcu(struct nameidata *nd)
1143 while (d_mountpoint(nd->path.dentry)) {
1144 struct mount *mounted;
1145 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1);
1148 nd->path.mnt = &mounted->mnt;
1149 nd->path.dentry = mounted->mnt.mnt_root;
1150 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1154 static int follow_dotdot_rcu(struct nameidata *nd)
1159 if (nd->path.dentry == nd->root.dentry &&
1160 nd->path.mnt == nd->root.mnt) {
1163 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1164 struct dentry *old = nd->path.dentry;
1165 struct dentry *parent = old->d_parent;
1168 seq = read_seqcount_begin(&parent->d_seq);
1169 if (read_seqcount_retry(&old->d_seq, nd->seq))
1171 nd->path.dentry = parent;
1175 if (!follow_up_rcu(&nd->path))
1177 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1179 follow_mount_rcu(nd);
1180 nd->inode = nd->path.dentry->d_inode;
1184 nd->flags &= ~LOOKUP_RCU;
1185 if (!(nd->flags & LOOKUP_ROOT))
1186 nd->root.mnt = NULL;
1192 * Follow down to the covering mount currently visible to userspace. At each
1193 * point, the filesystem owning that dentry may be queried as to whether the
1194 * caller is permitted to proceed or not.
1196 int follow_down(struct path *path)
1201 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1202 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
1203 /* Allow the filesystem to manage the transit without i_mutex
1206 * We indicate to the filesystem if someone is trying to mount
1207 * something here. This gives autofs the chance to deny anyone
1208 * other than its daemon the right to mount on its
1211 * The filesystem may sleep at this point.
1213 if (managed & DCACHE_MANAGE_TRANSIT) {
1214 BUG_ON(!path->dentry->d_op);
1215 BUG_ON(!path->dentry->d_op->d_manage);
1216 ret = path->dentry->d_op->d_manage(
1217 path->dentry, false);
1219 return ret == -EISDIR ? 0 : ret;
1222 /* Transit to a mounted filesystem. */
1223 if (managed & DCACHE_MOUNTED) {
1224 struct vfsmount *mounted = lookup_mnt(path);
1229 path->mnt = mounted;
1230 path->dentry = dget(mounted->mnt_root);
1234 /* Don't handle automount points here */
1241 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1243 static void follow_mount(struct path *path)
1245 while (d_mountpoint(path->dentry)) {
1246 struct vfsmount *mounted = lookup_mnt(path);
1251 path->mnt = mounted;
1252 path->dentry = dget(mounted->mnt_root);
1256 static void follow_dotdot(struct nameidata *nd)
1261 struct dentry *old = nd->path.dentry;
1263 if (nd->path.dentry == nd->root.dentry &&
1264 nd->path.mnt == nd->root.mnt) {
1267 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1268 /* rare case of legitimate dget_parent()... */
1269 nd->path.dentry = dget_parent(nd->path.dentry);
1273 if (!follow_up(&nd->path))
1276 follow_mount(&nd->path);
1277 nd->inode = nd->path.dentry->d_inode;
1281 * This looks up the name in dcache, possibly revalidates the old dentry and
1282 * allocates a new one if not found or not valid. In the need_lookup argument
1283 * returns whether i_op->lookup is necessary.
1285 * dir->d_inode->i_mutex must be held
1287 static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir,
1288 unsigned int flags, bool *need_lookup)
1290 struct dentry *dentry;
1293 *need_lookup = false;
1294 dentry = d_lookup(dir, name);
1296 if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
1297 error = d_revalidate(dentry, flags);
1298 if (unlikely(error <= 0)) {
1301 return ERR_PTR(error);
1302 } else if (!d_invalidate(dentry)) {
1311 dentry = d_alloc(dir, name);
1312 if (unlikely(!dentry))
1313 return ERR_PTR(-ENOMEM);
1315 *need_lookup = true;
1321 * Call i_op->lookup on the dentry. The dentry must be negative but may be
1322 * hashed if it was pouplated with DCACHE_NEED_LOOKUP.
1324 * dir->d_inode->i_mutex must be held
1326 static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
1331 /* Don't create child dentry for a dead directory. */
1332 if (unlikely(IS_DEADDIR(dir))) {
1334 return ERR_PTR(-ENOENT);
1337 old = dir->i_op->lookup(dir, dentry, flags);
1338 if (unlikely(old)) {
1345 static struct dentry *__lookup_hash(struct qstr *name,
1346 struct dentry *base, unsigned int flags)
1349 struct dentry *dentry;
1351 dentry = lookup_dcache(name, base, flags, &need_lookup);
1355 return lookup_real(base->d_inode, dentry, flags);
1359 * It's more convoluted than I'd like it to be, but... it's still fairly
1360 * small and for now I'd prefer to have fast path as straight as possible.
1361 * It _is_ time-critical.
1363 static int lookup_fast(struct nameidata *nd,
1364 struct path *path, struct inode **inode)
1366 struct vfsmount *mnt = nd->path.mnt;
1367 struct dentry *dentry, *parent = nd->path.dentry;
1373 * Rename seqlock is not required here because in the off chance
1374 * of a false negative due to a concurrent rename, we're going to
1375 * do the non-racy lookup, below.
1377 if (nd->flags & LOOKUP_RCU) {
1379 dentry = __d_lookup_rcu(parent, &nd->last, &seq);
1384 * This sequence count validates that the inode matches
1385 * the dentry name information from lookup.
1387 *inode = dentry->d_inode;
1388 if (read_seqcount_retry(&dentry->d_seq, seq))
1392 * This sequence count validates that the parent had no
1393 * changes while we did the lookup of the dentry above.
1395 * The memory barrier in read_seqcount_begin of child is
1396 * enough, we can use __read_seqcount_retry here.
1398 if (__read_seqcount_retry(&parent->d_seq, nd->seq))
1402 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1403 status = d_revalidate(dentry, nd->flags);
1404 if (unlikely(status <= 0)) {
1405 if (status != -ECHILD)
1411 path->dentry = dentry;
1412 if (unlikely(!__follow_mount_rcu(nd, path, inode)))
1414 if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
1418 if (unlazy_walk(nd, dentry))
1421 dentry = __d_lookup(parent, &nd->last);
1424 if (unlikely(!dentry))
1427 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
1428 status = d_revalidate(dentry, nd->flags);
1429 if (unlikely(status <= 0)) {
1434 if (!d_invalidate(dentry)) {
1441 path->dentry = dentry;
1442 err = follow_managed(path, nd->flags);
1443 if (unlikely(err < 0)) {
1444 path_put_conditional(path, nd);
1448 nd->flags |= LOOKUP_JUMPED;
1449 *inode = path->dentry->d_inode;
1456 /* Fast lookup failed, do it the slow way */
1457 static int lookup_slow(struct nameidata *nd, struct path *path)
1459 struct dentry *dentry, *parent;
1462 parent = nd->path.dentry;
1463 BUG_ON(nd->inode != parent->d_inode);
1465 mutex_lock(&parent->d_inode->i_mutex);
1466 dentry = __lookup_hash(&nd->last, parent, nd->flags);
1467 mutex_unlock(&parent->d_inode->i_mutex);
1469 return PTR_ERR(dentry);
1470 path->mnt = nd->path.mnt;
1471 path->dentry = dentry;
1472 err = follow_managed(path, nd->flags);
1473 if (unlikely(err < 0)) {
1474 path_put_conditional(path, nd);
1478 nd->flags |= LOOKUP_JUMPED;
1482 static inline int may_lookup(struct nameidata *nd)
1484 if (nd->flags & LOOKUP_RCU) {
1485 int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1488 if (unlazy_walk(nd, NULL))
1491 return inode_permission(nd->inode, MAY_EXEC);
1494 static inline int handle_dots(struct nameidata *nd, int type)
1496 if (type == LAST_DOTDOT) {
1497 if (nd->flags & LOOKUP_RCU) {
1498 if (follow_dotdot_rcu(nd))
1506 static void terminate_walk(struct nameidata *nd)
1508 if (!(nd->flags & LOOKUP_RCU)) {
1509 path_put(&nd->path);
1511 nd->flags &= ~LOOKUP_RCU;
1512 if (!(nd->flags & LOOKUP_ROOT))
1513 nd->root.mnt = NULL;
1519 * Do we need to follow links? We _really_ want to be able
1520 * to do this check without having to look at inode->i_op,
1521 * so we keep a cache of "no, this doesn't need follow_link"
1522 * for the common case.
1524 static inline int should_follow_link(struct inode *inode, int follow)
1526 if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1527 if (likely(inode->i_op->follow_link))
1530 /* This gets set once for the inode lifetime */
1531 spin_lock(&inode->i_lock);
1532 inode->i_opflags |= IOP_NOFOLLOW;
1533 spin_unlock(&inode->i_lock);
1538 static inline int walk_component(struct nameidata *nd, struct path *path,
1541 struct inode *inode;
1544 * "." and ".." are special - ".." especially so because it has
1545 * to be able to know about the current root directory and
1546 * parent relationships.
1548 if (unlikely(nd->last_type != LAST_NORM))
1549 return handle_dots(nd, nd->last_type);
1550 err = lookup_fast(nd, path, &inode);
1551 if (unlikely(err)) {
1555 err = lookup_slow(nd, path);
1559 inode = path->dentry->d_inode;
1565 if (should_follow_link(inode, follow)) {
1566 if (nd->flags & LOOKUP_RCU) {
1567 if (unlikely(unlazy_walk(nd, path->dentry))) {
1572 BUG_ON(inode != path->dentry->d_inode);
1575 path_to_nameidata(path, nd);
1580 path_to_nameidata(path, nd);
1587 * This limits recursive symlink follows to 8, while
1588 * limiting consecutive symlinks to 40.
1590 * Without that kind of total limit, nasty chains of consecutive
1591 * symlinks can cause almost arbitrarily long lookups.
1593 static inline int nested_symlink(struct path *path, struct nameidata *nd)
1597 if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
1598 path_put_conditional(path, nd);
1599 path_put(&nd->path);
1602 BUG_ON(nd->depth >= MAX_NESTED_LINKS);
1605 current->link_count++;
1608 struct path link = *path;
1611 res = follow_link(&link, nd, &cookie);
1614 res = walk_component(nd, path, LOOKUP_FOLLOW);
1615 put_link(nd, &link, cookie);
1618 current->link_count--;
1624 * We really don't want to look at inode->i_op->lookup
1625 * when we don't have to. So we keep a cache bit in
1626 * the inode ->i_opflags field that says "yes, we can
1627 * do lookup on this inode".
1629 static inline int can_lookup(struct inode *inode)
1631 if (likely(inode->i_opflags & IOP_LOOKUP))
1633 if (likely(!inode->i_op->lookup))
1636 /* We do this once for the lifetime of the inode */
1637 spin_lock(&inode->i_lock);
1638 inode->i_opflags |= IOP_LOOKUP;
1639 spin_unlock(&inode->i_lock);
1644 * We can do the critical dentry name comparison and hashing
1645 * operations one word at a time, but we are limited to:
1647 * - Architectures with fast unaligned word accesses. We could
1648 * do a "get_unaligned()" if this helps and is sufficiently
1651 * - Little-endian machines (so that we can generate the mask
1652 * of low bytes efficiently). Again, we *could* do a byte
1653 * swapping load on big-endian architectures if that is not
1654 * expensive enough to make the optimization worthless.
1656 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1657 * do not trap on the (extremely unlikely) case of a page
1658 * crossing operation.
1660 * - Furthermore, we need an efficient 64-bit compile for the
1661 * 64-bit case in order to generate the "number of bytes in
1662 * the final mask". Again, that could be replaced with a
1663 * efficient population count instruction or similar.
1665 #ifdef CONFIG_DCACHE_WORD_ACCESS
1667 #include <asm/word-at-a-time.h>
1671 static inline unsigned int fold_hash(unsigned long hash)
1673 hash += hash >> (8*sizeof(int));
1677 #else /* 32-bit case */
1679 #define fold_hash(x) (x)
1683 unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1685 unsigned long a, mask;
1686 unsigned long hash = 0;
1689 a = load_unaligned_zeropad(name);
1690 if (len < sizeof(unsigned long))
1694 name += sizeof(unsigned long);
1695 len -= sizeof(unsigned long);
1699 mask = ~(~0ul << len*8);
1702 return fold_hash(hash);
1704 EXPORT_SYMBOL(full_name_hash);
1707 * Calculate the length and hash of the path component, and
1708 * return the length of the component;
1710 static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1712 unsigned long a, b, adata, bdata, mask, hash, len;
1713 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
1716 len = -sizeof(unsigned long);
1718 hash = (hash + a) * 9;
1719 len += sizeof(unsigned long);
1720 a = load_unaligned_zeropad(name+len);
1721 b = a ^ REPEAT_BYTE('/');
1722 } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
1724 adata = prep_zero_mask(a, adata, &constants);
1725 bdata = prep_zero_mask(b, bdata, &constants);
1727 mask = create_zero_mask(adata | bdata);
1729 hash += a & zero_bytemask(mask);
1730 *hashp = fold_hash(hash);
1732 return len + find_zero(mask);
1737 unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1739 unsigned long hash = init_name_hash();
1741 hash = partial_name_hash(*name++, hash);
1742 return end_name_hash(hash);
1744 EXPORT_SYMBOL(full_name_hash);
1747 * We know there's a real path component here of at least
1750 static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1752 unsigned long hash = init_name_hash();
1753 unsigned long len = 0, c;
1755 c = (unsigned char)*name;
1758 hash = partial_name_hash(c, hash);
1759 c = (unsigned char)name[len];
1760 } while (c && c != '/');
1761 *hashp = end_name_hash(hash);
1769 * This is the basic name resolution function, turning a pathname into
1770 * the final dentry. We expect 'base' to be positive and a directory.
1772 * Returns 0 and nd will have valid dentry and mnt on success.
1773 * Returns error and drops reference to input namei data on failure.
1775 static int link_path_walk(const char *name, struct nameidata *nd)
1785 /* At this point we know we have a real path component. */
1791 err = may_lookup(nd);
1795 len = hash_name(name, &this.hash);
1800 if (name[0] == '.') switch (len) {
1802 if (name[1] == '.') {
1804 nd->flags |= LOOKUP_JUMPED;
1810 if (likely(type == LAST_NORM)) {
1811 struct dentry *parent = nd->path.dentry;
1812 nd->flags &= ~LOOKUP_JUMPED;
1813 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
1814 err = parent->d_op->d_hash(parent, &this);
1821 nd->last_type = type;
1826 * If it wasn't NUL, we know it was '/'. Skip that
1827 * slash, and continue until no more slashes.
1831 } while (unlikely(name[len] == '/'));
1837 err = walk_component(nd, &next, LOOKUP_FOLLOW);
1842 err = nested_symlink(&next, nd);
1846 if (!can_lookup(nd->inode)) {
1855 static int path_init(int dfd, const char *name, unsigned int flags,
1856 struct nameidata *nd, struct file **fp)
1860 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1861 nd->flags = flags | LOOKUP_JUMPED;
1863 if (flags & LOOKUP_ROOT) {
1864 struct inode *inode = nd->root.dentry->d_inode;
1866 if (!can_lookup(inode))
1868 retval = inode_permission(inode, MAY_EXEC);
1872 nd->path = nd->root;
1874 if (flags & LOOKUP_RCU) {
1876 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1878 path_get(&nd->path);
1883 nd->root.mnt = NULL;
1886 if (flags & LOOKUP_RCU) {
1891 path_get(&nd->root);
1893 nd->path = nd->root;
1894 } else if (dfd == AT_FDCWD) {
1895 if (flags & LOOKUP_RCU) {
1896 struct fs_struct *fs = current->fs;
1902 seq = read_seqcount_begin(&fs->seq);
1904 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1905 } while (read_seqcount_retry(&fs->seq, seq));
1907 get_fs_pwd(current->fs, &nd->path);
1910 /* Caller must check execute permissions on the starting path component */
1911 struct fd f = fdget_raw(dfd);
1912 struct dentry *dentry;
1917 dentry = f.file->f_path.dentry;
1920 if (!can_lookup(dentry->d_inode)) {
1926 nd->path = f.file->f_path;
1927 if (flags & LOOKUP_RCU) {
1930 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1933 path_get(&nd->path);
1938 nd->inode = nd->path.dentry->d_inode;
1942 static inline int lookup_last(struct nameidata *nd, struct path *path)
1944 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
1945 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
1947 nd->flags &= ~LOOKUP_PARENT;
1948 return walk_component(nd, path, nd->flags & LOOKUP_FOLLOW);
1951 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1952 static int path_lookupat(int dfd, const char *name,
1953 unsigned int flags, struct nameidata *nd)
1955 struct file *base = NULL;
1960 * Path walking is largely split up into 2 different synchronisation
1961 * schemes, rcu-walk and ref-walk (explained in
1962 * Documentation/filesystems/path-lookup.txt). These share much of the
1963 * path walk code, but some things particularly setup, cleanup, and
1964 * following mounts are sufficiently divergent that functions are
1965 * duplicated. Typically there is a function foo(), and its RCU
1966 * analogue, foo_rcu().
1968 * -ECHILD is the error number of choice (just to avoid clashes) that
1969 * is returned if some aspect of an rcu-walk fails. Such an error must
1970 * be handled by restarting a traditional ref-walk (which will always
1971 * be able to complete).
1973 err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base);
1978 current->total_link_count = 0;
1979 err = link_path_walk(name, nd);
1981 if (!err && !(flags & LOOKUP_PARENT)) {
1982 err = lookup_last(nd, &path);
1985 struct path link = path;
1986 err = may_follow_link(&link, nd);
1989 nd->flags |= LOOKUP_PARENT;
1990 err = follow_link(&link, nd, &cookie);
1993 err = lookup_last(nd, &path);
1994 put_link(nd, &link, cookie);
1999 err = complete_walk(nd);
2001 if (!err && nd->flags & LOOKUP_DIRECTORY) {
2002 if (!can_lookup(nd->inode)) {
2003 path_put(&nd->path);
2011 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
2012 path_put(&nd->root);
2013 nd->root.mnt = NULL;
2018 static int filename_lookup(int dfd, struct filename *name,
2019 unsigned int flags, struct nameidata *nd)
2021 int retval = path_lookupat(dfd, name->name, flags | LOOKUP_RCU, nd);
2022 if (unlikely(retval == -ECHILD))
2023 retval = path_lookupat(dfd, name->name, flags, nd);
2024 if (unlikely(retval == -ESTALE))
2025 retval = path_lookupat(dfd, name->name,
2026 flags | LOOKUP_REVAL, nd);
2028 if (likely(!retval))
2029 audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT);
2033 static int do_path_lookup(int dfd, const char *name,
2034 unsigned int flags, struct nameidata *nd)
2036 struct filename filename = { .name = name };
2038 return filename_lookup(dfd, &filename, flags, nd);
2041 /* does lookup, returns the object with parent locked */
2042 struct dentry *kern_path_locked(const char *name, struct path *path)
2044 struct nameidata nd;
2046 int err = do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, &nd);
2048 return ERR_PTR(err);
2049 if (nd.last_type != LAST_NORM) {
2051 return ERR_PTR(-EINVAL);
2053 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2054 d = __lookup_hash(&nd.last, nd.path.dentry, 0);
2056 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2064 int kern_path(const char *name, unsigned int flags, struct path *path)
2066 struct nameidata nd;
2067 int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
2074 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2075 * @dentry: pointer to dentry of the base directory
2076 * @mnt: pointer to vfs mount of the base directory
2077 * @name: pointer to file name
2078 * @flags: lookup flags
2079 * @path: pointer to struct path to fill
2081 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
2082 const char *name, unsigned int flags,
2085 struct nameidata nd;
2087 nd.root.dentry = dentry;
2089 BUG_ON(flags & LOOKUP_PARENT);
2090 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
2091 err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd);
2098 * Restricted form of lookup. Doesn't follow links, single-component only,
2099 * needs parent already locked. Doesn't follow mounts.
2102 static struct dentry *lookup_hash(struct nameidata *nd)
2104 return __lookup_hash(&nd->last, nd->path.dentry, nd->flags);
2108 * lookup_one_len - filesystem helper to lookup single pathname component
2109 * @name: pathname component to lookup
2110 * @base: base directory to lookup from
2111 * @len: maximum length @len should be interpreted to
2113 * Note that this routine is purely a helper for filesystem usage and should
2114 * not be called by generic code. Also note that by using this function the
2115 * nameidata argument is passed to the filesystem methods and a filesystem
2116 * using this helper needs to be prepared for that.
2118 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
2124 WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
2128 this.hash = full_name_hash(name, len);
2130 return ERR_PTR(-EACCES);
2132 if (unlikely(name[0] == '.')) {
2133 if (len < 2 || (len == 2 && name[1] == '.'))
2134 return ERR_PTR(-EACCES);
2138 c = *(const unsigned char *)name++;
2139 if (c == '/' || c == '\0')
2140 return ERR_PTR(-EACCES);
2143 * See if the low-level filesystem might want
2144 * to use its own hash..
2146 if (base->d_flags & DCACHE_OP_HASH) {
2147 int err = base->d_op->d_hash(base, &this);
2149 return ERR_PTR(err);
2152 err = inode_permission(base->d_inode, MAY_EXEC);
2154 return ERR_PTR(err);
2156 return __lookup_hash(&this, base, 0);
2159 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
2160 struct path *path, int *empty)
2162 struct nameidata nd;
2163 struct filename *tmp = getname_flags(name, flags, empty);
2164 int err = PTR_ERR(tmp);
2167 BUG_ON(flags & LOOKUP_PARENT);
2169 err = filename_lookup(dfd, tmp, flags, &nd);
2177 int user_path_at(int dfd, const char __user *name, unsigned flags,
2180 return user_path_at_empty(dfd, name, flags, path, NULL);
2184 * NB: most callers don't do anything directly with the reference to the
2185 * to struct filename, but the nd->last pointer points into the name string
2186 * allocated by getname. So we must hold the reference to it until all
2187 * path-walking is complete.
2189 static struct filename *
2190 user_path_parent(int dfd, const char __user *path, struct nameidata *nd,
2193 struct filename *s = getname(path);
2196 /* only LOOKUP_REVAL is allowed in extra flags */
2197 flags &= LOOKUP_REVAL;
2202 error = filename_lookup(dfd, s, flags | LOOKUP_PARENT, nd);
2205 return ERR_PTR(error);
2212 * umount_lookup_last - look up last component for umount
2213 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2214 * @path: pointer to container for result
2216 * This is a special lookup_last function just for umount. In this case, we
2217 * need to resolve the path without doing any revalidation.
2219 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2220 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2221 * in almost all cases, this lookup will be served out of the dcache. The only
2222 * cases where it won't are if nd->last refers to a symlink or the path is
2223 * bogus and it doesn't exist.
2226 * -error: if there was an error during lookup. This includes -ENOENT if the
2227 * lookup found a negative dentry. The nd->path reference will also be
2230 * 0: if we successfully resolved nd->path and found it to not to be a
2231 * symlink that needs to be followed. "path" will also be populated.
2232 * The nd->path reference will also be put.
2234 * 1: if we successfully resolved nd->last and found it to be a symlink
2235 * that needs to be followed. "path" will be populated with the path
2236 * to the link, and nd->path will *not* be put.
2239 umount_lookup_last(struct nameidata *nd, struct path *path)
2242 struct dentry *dentry;
2243 struct dentry *dir = nd->path.dentry;
2245 if (unlikely(nd->flags & LOOKUP_RCU)) {
2251 nd->flags &= ~LOOKUP_PARENT;
2253 if (unlikely(nd->last_type != LAST_NORM)) {
2254 error = handle_dots(nd, nd->last_type);
2256 dentry = dget(nd->path.dentry);
2260 mutex_lock(&dir->d_inode->i_mutex);
2261 dentry = d_lookup(dir, &nd->last);
2264 * No cached dentry. Mounted dentries are pinned in the cache,
2265 * so that means that this dentry is probably a symlink or the
2266 * path doesn't actually point to a mounted dentry.
2268 dentry = d_alloc(dir, &nd->last);
2272 dentry = lookup_real(dir->d_inode, dentry, nd->flags);
2274 error = PTR_ERR(dentry);
2277 mutex_unlock(&dir->d_inode->i_mutex);
2281 if (!dentry->d_inode) {
2285 path->dentry = dentry;
2286 path->mnt = mntget(nd->path.mnt);
2287 if (should_follow_link(dentry->d_inode,
2288 nd->flags & LOOKUP_FOLLOW))
2298 * path_umountat - look up a path to be umounted
2299 * @dfd: directory file descriptor to start walk from
2300 * @name: full pathname to walk
2301 * @flags: lookup flags
2302 * @nd: pathwalk nameidata
2304 * Look up the given name, but don't attempt to revalidate the last component.
2305 * Returns 0 and "path" will be valid on success; Retuns error otherwise.
2308 path_umountat(int dfd, const char *name, struct path *path, unsigned int flags)
2310 struct file *base = NULL;
2311 struct nameidata nd;
2314 err = path_init(dfd, name, flags | LOOKUP_PARENT, &nd, &base);
2318 current->total_link_count = 0;
2319 err = link_path_walk(name, &nd);
2323 /* If we're in rcuwalk, drop out of it to handle last component */
2324 if (nd.flags & LOOKUP_RCU) {
2325 err = unlazy_walk(&nd, NULL);
2327 terminate_walk(&nd);
2332 err = umount_lookup_last(&nd, path);
2335 struct path link = *path;
2336 err = may_follow_link(&link, &nd);
2339 nd.flags |= LOOKUP_PARENT;
2340 err = follow_link(&link, &nd, &cookie);
2343 err = umount_lookup_last(&nd, path);
2344 put_link(&nd, &link, cookie);
2350 if (nd.root.mnt && !(nd.flags & LOOKUP_ROOT))
2357 * user_path_umountat - lookup a path from userland in order to umount it
2358 * @dfd: directory file descriptor
2359 * @name: pathname from userland
2360 * @flags: lookup flags
2361 * @path: pointer to container to hold result
2363 * A umount is a special case for path walking. We're not actually interested
2364 * in the inode in this situation, and ESTALE errors can be a problem. We
2365 * simply want track down the dentry and vfsmount attached at the mountpoint
2366 * and avoid revalidating the last component.
2368 * Returns 0 and populates "path" on success.
2371 user_path_umountat(int dfd, const char __user *name, unsigned int flags,
2374 struct filename *s = getname(name);
2380 error = path_umountat(dfd, s->name, path, flags | LOOKUP_RCU);
2381 if (unlikely(error == -ECHILD))
2382 error = path_umountat(dfd, s->name, path, flags);
2383 if (unlikely(error == -ESTALE))
2384 error = path_umountat(dfd, s->name, path, flags | LOOKUP_REVAL);
2387 audit_inode(s, path->dentry, 0);
2394 * It's inline, so penalty for filesystems that don't use sticky bit is
2397 static inline int check_sticky(struct inode *dir, struct inode *inode)
2399 kuid_t fsuid = current_fsuid();
2401 if (!(dir->i_mode & S_ISVTX))
2403 if (uid_eq(inode->i_uid, fsuid))
2405 if (uid_eq(dir->i_uid, fsuid))
2407 return !inode_capable(inode, CAP_FOWNER);
2411 * Check whether we can remove a link victim from directory dir, check
2412 * whether the type of victim is right.
2413 * 1. We can't do it if dir is read-only (done in permission())
2414 * 2. We should have write and exec permissions on dir
2415 * 3. We can't remove anything from append-only dir
2416 * 4. We can't do anything with immutable dir (done in permission())
2417 * 5. If the sticky bit on dir is set we should either
2418 * a. be owner of dir, or
2419 * b. be owner of victim, or
2420 * c. have CAP_FOWNER capability
2421 * 6. If the victim is append-only or immutable we can't do antyhing with
2422 * links pointing to it.
2423 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2424 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2425 * 9. We can't remove a root or mountpoint.
2426 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2427 * nfs_async_unlink().
2429 static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
2433 if (!victim->d_inode)
2436 BUG_ON(victim->d_parent->d_inode != dir);
2437 audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
2439 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
2444 if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
2445 IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
2448 if (!S_ISDIR(victim->d_inode->i_mode))
2450 if (IS_ROOT(victim))
2452 } else if (S_ISDIR(victim->d_inode->i_mode))
2454 if (IS_DEADDIR(dir))
2456 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2461 /* Check whether we can create an object with dentry child in directory
2463 * 1. We can't do it if child already exists (open has special treatment for
2464 * this case, but since we are inlined it's OK)
2465 * 2. We can't do it if dir is read-only (done in permission())
2466 * 3. We should have write and exec permissions on dir
2467 * 4. We can't do it if dir is immutable (done in permission())
2469 static inline int may_create(struct inode *dir, struct dentry *child)
2473 if (IS_DEADDIR(dir))
2475 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
2479 * p1 and p2 should be directories on the same fs.
2481 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2486 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2490 mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2492 p = d_ancestor(p2, p1);
2494 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
2495 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
2499 p = d_ancestor(p1, p2);
2501 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2502 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2506 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2507 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2511 void unlock_rename(struct dentry *p1, struct dentry *p2)
2513 mutex_unlock(&p1->d_inode->i_mutex);
2515 mutex_unlock(&p2->d_inode->i_mutex);
2516 mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2520 int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2523 int error = may_create(dir, dentry);
2527 if (!dir->i_op->create)
2528 return -EACCES; /* shouldn't it be ENOSYS? */
2531 error = security_inode_create(dir, dentry, mode);
2534 error = dir->i_op->create(dir, dentry, mode, want_excl);
2536 fsnotify_create(dir, dentry);
2540 static int may_open(struct path *path, int acc_mode, int flag)
2542 struct dentry *dentry = path->dentry;
2543 struct inode *inode = dentry->d_inode;
2553 switch (inode->i_mode & S_IFMT) {
2557 if (acc_mode & MAY_WRITE)
2562 if (path->mnt->mnt_flags & MNT_NODEV)
2571 error = inode_permission(inode, acc_mode);
2576 * An append-only file must be opened in append mode for writing.
2578 if (IS_APPEND(inode)) {
2579 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
2585 /* O_NOATIME can only be set by the owner or superuser */
2586 if (flag & O_NOATIME && !inode_owner_or_capable(inode))
2592 static int handle_truncate(struct file *filp)
2594 struct path *path = &filp->f_path;
2595 struct inode *inode = path->dentry->d_inode;
2596 int error = get_write_access(inode);
2600 * Refuse to truncate files with mandatory locks held on them.
2602 error = locks_verify_locked(inode);
2604 error = security_path_truncate(path);
2606 error = do_truncate(path->dentry, 0,
2607 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
2610 put_write_access(inode);
2614 static inline int open_to_namei_flags(int flag)
2616 if ((flag & O_ACCMODE) == 3)
2621 static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode)
2623 int error = security_path_mknod(dir, dentry, mode, 0);
2627 error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
2631 return security_inode_create(dir->dentry->d_inode, dentry, mode);
2635 * Attempt to atomically look up, create and open a file from a negative
2638 * Returns 0 if successful. The file will have been created and attached to
2639 * @file by the filesystem calling finish_open().
2641 * Returns 1 if the file was looked up only or didn't need creating. The
2642 * caller will need to perform the open themselves. @path will have been
2643 * updated to point to the new dentry. This may be negative.
2645 * Returns an error code otherwise.
2647 static int atomic_open(struct nameidata *nd, struct dentry *dentry,
2648 struct path *path, struct file *file,
2649 const struct open_flags *op,
2650 bool got_write, bool need_lookup,
2653 struct inode *dir = nd->path.dentry->d_inode;
2654 unsigned open_flag = open_to_namei_flags(op->open_flag);
2658 int create_error = 0;
2659 struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
2661 BUG_ON(dentry->d_inode);
2663 /* Don't create child dentry for a dead directory. */
2664 if (unlikely(IS_DEADDIR(dir))) {
2670 if ((open_flag & O_CREAT) && !IS_POSIXACL(dir))
2671 mode &= ~current_umask();
2673 if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT)) {
2674 open_flag &= ~O_TRUNC;
2675 *opened |= FILE_CREATED;
2679 * Checking write permission is tricky, bacuse we don't know if we are
2680 * going to actually need it: O_CREAT opens should work as long as the
2681 * file exists. But checking existence breaks atomicity. The trick is
2682 * to check access and if not granted clear O_CREAT from the flags.
2684 * Another problem is returing the "right" error value (e.g. for an
2685 * O_EXCL open we want to return EEXIST not EROFS).
2687 if (((open_flag & (O_CREAT | O_TRUNC)) ||
2688 (open_flag & O_ACCMODE) != O_RDONLY) && unlikely(!got_write)) {
2689 if (!(open_flag & O_CREAT)) {
2691 * No O_CREATE -> atomicity not a requirement -> fall
2692 * back to lookup + open
2695 } else if (open_flag & (O_EXCL | O_TRUNC)) {
2696 /* Fall back and fail with the right error */
2697 create_error = -EROFS;
2700 /* No side effects, safe to clear O_CREAT */
2701 create_error = -EROFS;
2702 open_flag &= ~O_CREAT;
2706 if (open_flag & O_CREAT) {
2707 error = may_o_create(&nd->path, dentry, mode);
2709 create_error = error;
2710 if (open_flag & O_EXCL)
2712 open_flag &= ~O_CREAT;
2716 if (nd->flags & LOOKUP_DIRECTORY)
2717 open_flag |= O_DIRECTORY;
2719 file->f_path.dentry = DENTRY_NOT_SET;
2720 file->f_path.mnt = nd->path.mnt;
2721 error = dir->i_op->atomic_open(dir, dentry, file, open_flag, mode,
2724 if (create_error && error == -ENOENT)
2725 error = create_error;
2729 acc_mode = op->acc_mode;
2730 if (*opened & FILE_CREATED) {
2731 fsnotify_create(dir, dentry);
2732 acc_mode = MAY_OPEN;
2735 if (error) { /* returned 1, that is */
2736 if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
2740 if (file->f_path.dentry) {
2742 dentry = file->f_path.dentry;
2744 if (create_error && dentry->d_inode == NULL) {
2745 error = create_error;
2752 * We didn't have the inode before the open, so check open permission
2755 error = may_open(&file->f_path, acc_mode, open_flag);
2765 dentry = lookup_real(dir, dentry, nd->flags);
2767 return PTR_ERR(dentry);
2770 int open_flag = op->open_flag;
2772 error = create_error;
2773 if ((open_flag & O_EXCL)) {
2774 if (!dentry->d_inode)
2776 } else if (!dentry->d_inode) {
2778 } else if ((open_flag & O_TRUNC) &&
2779 S_ISREG(dentry->d_inode->i_mode)) {
2782 /* will fail later, go on to get the right error */
2786 path->dentry = dentry;
2787 path->mnt = nd->path.mnt;
2792 * Look up and maybe create and open the last component.
2794 * Must be called with i_mutex held on parent.
2796 * Returns 0 if the file was successfully atomically created (if necessary) and
2797 * opened. In this case the file will be returned attached to @file.
2799 * Returns 1 if the file was not completely opened at this time, though lookups
2800 * and creations will have been performed and the dentry returned in @path will
2801 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
2802 * specified then a negative dentry may be returned.
2804 * An error code is returned otherwise.
2806 * FILE_CREATE will be set in @*opened if the dentry was created and will be
2807 * cleared otherwise prior to returning.
2809 static int lookup_open(struct nameidata *nd, struct path *path,
2811 const struct open_flags *op,
2812 bool got_write, int *opened)
2814 struct dentry *dir = nd->path.dentry;
2815 struct inode *dir_inode = dir->d_inode;
2816 struct dentry *dentry;
2820 *opened &= ~FILE_CREATED;
2821 dentry = lookup_dcache(&nd->last, dir, nd->flags, &need_lookup);
2823 return PTR_ERR(dentry);
2825 /* Cached positive dentry: will open in f_op->open */
2826 if (!need_lookup && dentry->d_inode)
2829 if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) {
2830 return atomic_open(nd, dentry, path, file, op, got_write,
2831 need_lookup, opened);
2835 BUG_ON(dentry->d_inode);
2837 dentry = lookup_real(dir_inode, dentry, nd->flags);
2839 return PTR_ERR(dentry);
2842 /* Negative dentry, just create the file */
2843 if (!dentry->d_inode && (op->open_flag & O_CREAT)) {
2844 umode_t mode = op->mode;
2845 if (!IS_POSIXACL(dir->d_inode))
2846 mode &= ~current_umask();
2848 * This write is needed to ensure that a
2849 * rw->ro transition does not occur between
2850 * the time when the file is created and when
2851 * a permanent write count is taken through
2852 * the 'struct file' in finish_open().
2858 *opened |= FILE_CREATED;
2859 error = security_path_mknod(&nd->path, dentry, mode, 0);
2862 error = vfs_create(dir->d_inode, dentry, mode,
2863 nd->flags & LOOKUP_EXCL);
2868 path->dentry = dentry;
2869 path->mnt = nd->path.mnt;
2878 * Handle the last step of open()
2880 static int do_last(struct nameidata *nd, struct path *path,
2881 struct file *file, const struct open_flags *op,
2882 int *opened, struct filename *name)
2884 struct dentry *dir = nd->path.dentry;
2885 int open_flag = op->open_flag;
2886 bool will_truncate = (open_flag & O_TRUNC) != 0;
2887 bool got_write = false;
2888 int acc_mode = op->acc_mode;
2889 struct inode *inode;
2890 bool symlink_ok = false;
2891 struct path save_parent = { .dentry = NULL, .mnt = NULL };
2892 bool retried = false;
2895 nd->flags &= ~LOOKUP_PARENT;
2896 nd->flags |= op->intent;
2898 if (nd->last_type != LAST_NORM) {
2899 error = handle_dots(nd, nd->last_type);
2905 if (!(open_flag & O_CREAT)) {
2906 if (nd->last.name[nd->last.len])
2907 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2908 if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
2910 /* we _can_ be in RCU mode here */
2911 error = lookup_fast(nd, path, &inode);
2918 BUG_ON(nd->inode != dir->d_inode);
2920 /* create side of things */
2922 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
2923 * has been cleared when we got to the last component we are
2926 error = complete_walk(nd);
2930 audit_inode(name, dir, LOOKUP_PARENT);
2932 /* trailing slashes? */
2933 if (nd->last.name[nd->last.len])
2938 if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
2939 error = mnt_want_write(nd->path.mnt);
2943 * do _not_ fail yet - we might not need that or fail with
2944 * a different error; let lookup_open() decide; we'll be
2945 * dropping this one anyway.
2948 mutex_lock(&dir->d_inode->i_mutex);
2949 error = lookup_open(nd, path, file, op, got_write, opened);
2950 mutex_unlock(&dir->d_inode->i_mutex);
2956 if ((*opened & FILE_CREATED) ||
2957 !S_ISREG(file_inode(file)->i_mode))
2958 will_truncate = false;
2960 audit_inode(name, file->f_path.dentry, 0);
2964 if (*opened & FILE_CREATED) {
2965 /* Don't check for write permission, don't truncate */
2966 open_flag &= ~O_TRUNC;
2967 will_truncate = false;
2968 acc_mode = MAY_OPEN;
2969 path_to_nameidata(path, nd);
2970 goto finish_open_created;
2974 * create/update audit record if it already exists.
2976 if (path->dentry->d_inode)
2977 audit_inode(name, path->dentry, 0);
2980 * If atomic_open() acquired write access it is dropped now due to
2981 * possible mount and symlink following (this might be optimized away if
2985 mnt_drop_write(nd->path.mnt);
2990 if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))
2993 error = follow_managed(path, nd->flags);
2998 nd->flags |= LOOKUP_JUMPED;
3000 BUG_ON(nd->flags & LOOKUP_RCU);
3001 inode = path->dentry->d_inode;
3003 /* we _can_ be in RCU mode here */
3006 path_to_nameidata(path, nd);
3010 if (should_follow_link(inode, !symlink_ok)) {
3011 if (nd->flags & LOOKUP_RCU) {
3012 if (unlikely(unlazy_walk(nd, path->dentry))) {
3017 BUG_ON(inode != path->dentry->d_inode);
3021 if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path->mnt) {
3022 path_to_nameidata(path, nd);
3024 save_parent.dentry = nd->path.dentry;
3025 save_parent.mnt = mntget(path->mnt);
3026 nd->path.dentry = path->dentry;
3030 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3032 error = complete_walk(nd);
3034 path_put(&save_parent);
3037 audit_inode(name, nd->path.dentry, 0);
3039 if ((open_flag & O_CREAT) && S_ISDIR(nd->inode->i_mode))
3042 if ((nd->flags & LOOKUP_DIRECTORY) && !can_lookup(nd->inode))
3044 if (!S_ISREG(nd->inode->i_mode))
3045 will_truncate = false;
3047 if (will_truncate) {
3048 error = mnt_want_write(nd->path.mnt);
3053 finish_open_created:
3054 error = may_open(&nd->path, acc_mode, open_flag);
3057 file->f_path.mnt = nd->path.mnt;
3058 error = finish_open(file, nd->path.dentry, NULL, opened);
3060 if (error == -EOPENSTALE)
3065 error = open_check_o_direct(file);
3068 error = ima_file_check(file, op->acc_mode);
3072 if (will_truncate) {
3073 error = handle_truncate(file);
3079 mnt_drop_write(nd->path.mnt);
3080 path_put(&save_parent);
3085 path_put_conditional(path, nd);
3092 /* If no saved parent or already retried then can't retry */
3093 if (!save_parent.dentry || retried)
3096 BUG_ON(save_parent.dentry != dir);
3097 path_put(&nd->path);
3098 nd->path = save_parent;
3099 nd->inode = dir->d_inode;
3100 save_parent.mnt = NULL;
3101 save_parent.dentry = NULL;
3103 mnt_drop_write(nd->path.mnt);
3110 static int do_tmpfile(int dfd, struct filename *pathname,
3111 struct nameidata *nd, int flags,
3112 const struct open_flags *op,
3113 struct file *file, int *opened)
3115 static const struct qstr name = QSTR_INIT("/", 1);
3116 struct dentry *dentry, *child;
3118 int error = path_lookupat(dfd, pathname->name,
3119 flags | LOOKUP_DIRECTORY, nd);
3120 if (unlikely(error))
3122 error = mnt_want_write(nd->path.mnt);
3123 if (unlikely(error))
3125 /* we want directory to be writable */
3126 error = inode_permission(nd->inode, MAY_WRITE | MAY_EXEC);
3129 dentry = nd->path.dentry;
3130 dir = dentry->d_inode;
3131 if (!dir->i_op->tmpfile) {
3132 error = -EOPNOTSUPP;
3135 child = d_alloc(dentry, &name);
3136 if (unlikely(!child)) {
3140 nd->flags &= ~LOOKUP_DIRECTORY;
3141 nd->flags |= op->intent;
3142 dput(nd->path.dentry);
3143 nd->path.dentry = child;
3144 error = dir->i_op->tmpfile(dir, nd->path.dentry, op->mode);
3147 audit_inode(pathname, nd->path.dentry, 0);
3148 error = may_open(&nd->path, op->acc_mode, op->open_flag);
3151 file->f_path.mnt = nd->path.mnt;
3152 error = finish_open(file, nd->path.dentry, NULL, opened);
3155 error = open_check_o_direct(file);
3158 } else if (!(op->open_flag & O_EXCL)) {
3159 struct inode *inode = file_inode(file);
3160 spin_lock(&inode->i_lock);
3161 inode->i_state |= I_LINKABLE;
3162 spin_unlock(&inode->i_lock);
3165 mnt_drop_write(nd->path.mnt);
3167 path_put(&nd->path);
3171 static struct file *path_openat(int dfd, struct filename *pathname,
3172 struct nameidata *nd, const struct open_flags *op, int flags)
3174 struct file *base = NULL;
3180 file = get_empty_filp();
3184 file->f_flags = op->open_flag;
3186 if (unlikely(file->f_flags & __O_TMPFILE)) {
3187 error = do_tmpfile(dfd, pathname, nd, flags, op, file, &opened);
3191 error = path_init(dfd, pathname->name, flags | LOOKUP_PARENT, nd, &base);
3192 if (unlikely(error))
3195 current->total_link_count = 0;
3196 error = link_path_walk(pathname->name, nd);
3197 if (unlikely(error))
3200 error = do_last(nd, &path, file, op, &opened, pathname);
3201 while (unlikely(error > 0)) { /* trailing symlink */
3202 struct path link = path;
3204 if (!(nd->flags & LOOKUP_FOLLOW)) {
3205 path_put_conditional(&path, nd);
3206 path_put(&nd->path);
3210 error = may_follow_link(&link, nd);
3211 if (unlikely(error))
3213 nd->flags |= LOOKUP_PARENT;
3214 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
3215 error = follow_link(&link, nd, &cookie);
3216 if (unlikely(error))
3218 error = do_last(nd, &path, file, op, &opened, pathname);
3219 put_link(nd, &link, cookie);
3222 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
3223 path_put(&nd->root);
3226 if (!(opened & FILE_OPENED)) {
3230 if (unlikely(error)) {
3231 if (error == -EOPENSTALE) {
3232 if (flags & LOOKUP_RCU)
3237 file = ERR_PTR(error);
3242 struct file *do_filp_open(int dfd, struct filename *pathname,
3243 const struct open_flags *op)
3245 struct nameidata nd;
3246 int flags = op->lookup_flags;
3249 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
3250 if (unlikely(filp == ERR_PTR(-ECHILD)))
3251 filp = path_openat(dfd, pathname, &nd, op, flags);
3252 if (unlikely(filp == ERR_PTR(-ESTALE)))
3253 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
3257 struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
3258 const char *name, const struct open_flags *op)
3260 struct nameidata nd;
3262 struct filename filename = { .name = name };
3263 int flags = op->lookup_flags | LOOKUP_ROOT;
3266 nd.root.dentry = dentry;
3268 if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
3269 return ERR_PTR(-ELOOP);
3271 file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_RCU);
3272 if (unlikely(file == ERR_PTR(-ECHILD)))
3273 file = path_openat(-1, &filename, &nd, op, flags);
3274 if (unlikely(file == ERR_PTR(-ESTALE)))
3275 file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_REVAL);
3279 struct dentry *kern_path_create(int dfd, const char *pathname,
3280 struct path *path, unsigned int lookup_flags)
3282 struct dentry *dentry = ERR_PTR(-EEXIST);
3283 struct nameidata nd;
3286 bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
3289 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3290 * other flags passed in are ignored!
3292 lookup_flags &= LOOKUP_REVAL;
3294 error = do_path_lookup(dfd, pathname, LOOKUP_PARENT|lookup_flags, &nd);
3296 return ERR_PTR(error);
3299 * Yucky last component or no last component at all?
3300 * (foo/., foo/.., /////)
3302 if (nd.last_type != LAST_NORM)
3304 nd.flags &= ~LOOKUP_PARENT;
3305 nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL;
3307 /* don't fail immediately if it's r/o, at least try to report other errors */
3308 err2 = mnt_want_write(nd.path.mnt);
3310 * Do the final lookup.
3312 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
3313 dentry = lookup_hash(&nd);
3318 if (dentry->d_inode)
3321 * Special case - lookup gave negative, but... we had foo/bar/
3322 * From the vfs_mknod() POV we just have a negative dentry -
3323 * all is fine. Let's be bastards - you had / on the end, you've
3324 * been asking for (non-existent) directory. -ENOENT for you.
3326 if (unlikely(!is_dir && nd.last.name[nd.last.len])) {
3330 if (unlikely(err2)) {
3338 dentry = ERR_PTR(error);
3340 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3342 mnt_drop_write(nd.path.mnt);
3347 EXPORT_SYMBOL(kern_path_create);
3349 void done_path_create(struct path *path, struct dentry *dentry)
3352 mutex_unlock(&path->dentry->d_inode->i_mutex);
3353 mnt_drop_write(path->mnt);
3356 EXPORT_SYMBOL(done_path_create);
3358 struct dentry *user_path_create(int dfd, const char __user *pathname,
3359 struct path *path, unsigned int lookup_flags)
3361 struct filename *tmp = getname(pathname);
3364 return ERR_CAST(tmp);
3365 res = kern_path_create(dfd, tmp->name, path, lookup_flags);
3369 EXPORT_SYMBOL(user_path_create);
3371 int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
3373 int error = may_create(dir, dentry);
3378 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
3381 if (!dir->i_op->mknod)
3384 error = devcgroup_inode_mknod(mode, dev);
3388 error = security_inode_mknod(dir, dentry, mode, dev);
3392 error = dir->i_op->mknod(dir, dentry, mode, dev);
3394 fsnotify_create(dir, dentry);
3398 static int may_mknod(umode_t mode)
3400 switch (mode & S_IFMT) {
3406 case 0: /* zero mode translates to S_IFREG */
3415 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
3418 struct dentry *dentry;
3421 unsigned int lookup_flags = 0;
3423 error = may_mknod(mode);
3427 dentry = user_path_create(dfd, filename, &path, lookup_flags);
3429 return PTR_ERR(dentry);
3431 if (!IS_POSIXACL(path.dentry->d_inode))
3432 mode &= ~current_umask();
3433 error = security_path_mknod(&path, dentry, mode, dev);
3436 switch (mode & S_IFMT) {
3437 case 0: case S_IFREG:
3438 error = vfs_create(path.dentry->d_inode,dentry,mode,true);
3440 case S_IFCHR: case S_IFBLK:
3441 error = vfs_mknod(path.dentry->d_inode,dentry,mode,
3442 new_decode_dev(dev));
3444 case S_IFIFO: case S_IFSOCK:
3445 error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
3449 done_path_create(&path, dentry);
3450 if (retry_estale(error, lookup_flags)) {
3451 lookup_flags |= LOOKUP_REVAL;
3457 SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
3459 return sys_mknodat(AT_FDCWD, filename, mode, dev);
3462 int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
3464 int error = may_create(dir, dentry);
3465 unsigned max_links = dir->i_sb->s_max_links;
3470 if (!dir->i_op->mkdir)
3473 mode &= (S_IRWXUGO|S_ISVTX);
3474 error = security_inode_mkdir(dir, dentry, mode);
3478 if (max_links && dir->i_nlink >= max_links)
3481 error = dir->i_op->mkdir(dir, dentry, mode);
3483 fsnotify_mkdir(dir, dentry);
3487 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
3489 struct dentry *dentry;
3492 unsigned int lookup_flags = LOOKUP_DIRECTORY;
3495 dentry = user_path_create(dfd, pathname, &path, lookup_flags);
3497 return PTR_ERR(dentry);
3499 if (!IS_POSIXACL(path.dentry->d_inode))
3500 mode &= ~current_umask();
3501 error = security_path_mkdir(&path, dentry, mode);
3503 error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
3504 done_path_create(&path, dentry);
3505 if (retry_estale(error, lookup_flags)) {
3506 lookup_flags |= LOOKUP_REVAL;
3512 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
3514 return sys_mkdirat(AT_FDCWD, pathname, mode);
3518 * The dentry_unhash() helper will try to drop the dentry early: we
3519 * should have a usage count of 1 if we're the only user of this
3520 * dentry, and if that is true (possibly after pruning the dcache),
3521 * then we drop the dentry now.
3523 * A low-level filesystem can, if it choses, legally
3526 * if (!d_unhashed(dentry))
3529 * if it cannot handle the case of removing a directory
3530 * that is still in use by something else..
3532 void dentry_unhash(struct dentry *dentry)
3534 shrink_dcache_parent(dentry);
3535 spin_lock(&dentry->d_lock);
3536 if (dentry->d_lockref.count == 1)
3538 spin_unlock(&dentry->d_lock);
3541 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
3543 int error = may_delete(dir, dentry, 1);
3548 if (!dir->i_op->rmdir)
3552 mutex_lock(&dentry->d_inode->i_mutex);
3555 if (d_mountpoint(dentry))
3558 error = security_inode_rmdir(dir, dentry);
3562 shrink_dcache_parent(dentry);
3563 error = dir->i_op->rmdir(dir, dentry);
3567 dentry->d_inode->i_flags |= S_DEAD;
3571 mutex_unlock(&dentry->d_inode->i_mutex);
3578 static long do_rmdir(int dfd, const char __user *pathname)
3581 struct filename *name;
3582 struct dentry *dentry;
3583 struct nameidata nd;
3584 unsigned int lookup_flags = 0;
3586 name = user_path_parent(dfd, pathname, &nd, lookup_flags);
3588 return PTR_ERR(name);
3590 switch(nd.last_type) {
3602 nd.flags &= ~LOOKUP_PARENT;
3603 error = mnt_want_write(nd.path.mnt);
3607 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
3608 dentry = lookup_hash(&nd);
3609 error = PTR_ERR(dentry);
3612 if (!dentry->d_inode) {
3616 error = security_path_rmdir(&nd.path, dentry);
3619 error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
3623 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3624 mnt_drop_write(nd.path.mnt);
3628 if (retry_estale(error, lookup_flags)) {
3629 lookup_flags |= LOOKUP_REVAL;
3635 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
3637 return do_rmdir(AT_FDCWD, pathname);
3640 int vfs_unlink(struct inode *dir, struct dentry *dentry)
3642 int error = may_delete(dir, dentry, 0);
3647 if (!dir->i_op->unlink)
3650 mutex_lock(&dentry->d_inode->i_mutex);
3651 if (d_mountpoint(dentry))
3654 error = security_inode_unlink(dir, dentry);
3656 error = dir->i_op->unlink(dir, dentry);
3661 mutex_unlock(&dentry->d_inode->i_mutex);
3663 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3664 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
3665 fsnotify_link_count(dentry->d_inode);
3673 * Make sure that the actual truncation of the file will occur outside its
3674 * directory's i_mutex. Truncate can take a long time if there is a lot of
3675 * writeout happening, and we don't want to prevent access to the directory
3676 * while waiting on the I/O.
3678 static long do_unlinkat(int dfd, const char __user *pathname)
3681 struct filename *name;
3682 struct dentry *dentry;
3683 struct nameidata nd;
3684 struct inode *inode = NULL;
3685 unsigned int lookup_flags = 0;
3687 name = user_path_parent(dfd, pathname, &nd, lookup_flags);
3689 return PTR_ERR(name);
3692 if (nd.last_type != LAST_NORM)
3695 nd.flags &= ~LOOKUP_PARENT;
3696 error = mnt_want_write(nd.path.mnt);
3700 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
3701 dentry = lookup_hash(&nd);
3702 error = PTR_ERR(dentry);
3703 if (!IS_ERR(dentry)) {
3704 /* Why not before? Because we want correct error value */
3705 if (nd.last.name[nd.last.len])
3707 inode = dentry->d_inode;
3711 error = security_path_unlink(&nd.path, dentry);
3714 error = vfs_unlink(nd.path.dentry->d_inode, dentry);
3718 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3720 iput(inode); /* truncate the inode here */
3721 mnt_drop_write(nd.path.mnt);
3725 if (retry_estale(error, lookup_flags)) {
3726 lookup_flags |= LOOKUP_REVAL;
3733 error = !dentry->d_inode ? -ENOENT :
3734 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
3738 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
3740 if ((flag & ~AT_REMOVEDIR) != 0)
3743 if (flag & AT_REMOVEDIR)
3744 return do_rmdir(dfd, pathname);
3746 return do_unlinkat(dfd, pathname);
3749 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
3751 return do_unlinkat(AT_FDCWD, pathname);
3754 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
3756 int error = may_create(dir, dentry);
3761 if (!dir->i_op->symlink)
3764 error = security_inode_symlink(dir, dentry, oldname);
3768 error = dir->i_op->symlink(dir, dentry, oldname);
3770 fsnotify_create(dir, dentry);
3774 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
3775 int, newdfd, const char __user *, newname)
3778 struct filename *from;
3779 struct dentry *dentry;
3781 unsigned int lookup_flags = 0;
3783 from = getname(oldname);
3785 return PTR_ERR(from);
3787 dentry = user_path_create(newdfd, newname, &path, lookup_flags);
3788 error = PTR_ERR(dentry);
3792 error = security_path_symlink(&path, dentry, from->name);
3794 error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
3795 done_path_create(&path, dentry);
3796 if (retry_estale(error, lookup_flags)) {
3797 lookup_flags |= LOOKUP_REVAL;
3805 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
3807 return sys_symlinkat(oldname, AT_FDCWD, newname);
3810 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
3812 struct inode *inode = old_dentry->d_inode;
3813 unsigned max_links = dir->i_sb->s_max_links;
3819 error = may_create(dir, new_dentry);
3823 if (dir->i_sb != inode->i_sb)
3827 * A link to an append-only or immutable file cannot be created.
3829 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
3831 if (!dir->i_op->link)
3833 if (S_ISDIR(inode->i_mode))
3836 error = security_inode_link(old_dentry, dir, new_dentry);
3840 mutex_lock(&inode->i_mutex);
3841 /* Make sure we don't allow creating hardlink to an unlinked file */
3842 if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
3844 else if (max_links && inode->i_nlink >= max_links)
3847 error = dir->i_op->link(old_dentry, dir, new_dentry);
3849 if (!error && (inode->i_state & I_LINKABLE)) {
3850 spin_lock(&inode->i_lock);
3851 inode->i_state &= ~I_LINKABLE;
3852 spin_unlock(&inode->i_lock);
3854 mutex_unlock(&inode->i_mutex);
3856 fsnotify_link(dir, inode, new_dentry);
3861 * Hardlinks are often used in delicate situations. We avoid
3862 * security-related surprises by not following symlinks on the
3865 * We don't follow them on the oldname either to be compatible
3866 * with linux 2.0, and to avoid hard-linking to directories
3867 * and other special files. --ADM
3869 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
3870 int, newdfd, const char __user *, newname, int, flags)
3872 struct dentry *new_dentry;
3873 struct path old_path, new_path;
3877 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
3880 * To use null names we require CAP_DAC_READ_SEARCH
3881 * This ensures that not everyone will be able to create
3882 * handlink using the passed filedescriptor.
3884 if (flags & AT_EMPTY_PATH) {
3885 if (!capable(CAP_DAC_READ_SEARCH))
3890 if (flags & AT_SYMLINK_FOLLOW)
3891 how |= LOOKUP_FOLLOW;
3893 error = user_path_at(olddfd, oldname, how, &old_path);
3897 new_dentry = user_path_create(newdfd, newname, &new_path,
3898 (how & LOOKUP_REVAL));
3899 error = PTR_ERR(new_dentry);
3900 if (IS_ERR(new_dentry))
3904 if (old_path.mnt != new_path.mnt)
3906 error = may_linkat(&old_path);
3907 if (unlikely(error))
3909 error = security_path_link(old_path.dentry, &new_path, new_dentry);
3912 error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry);
3914 done_path_create(&new_path, new_dentry);
3915 if (retry_estale(error, how)) {
3916 how |= LOOKUP_REVAL;
3920 path_put(&old_path);
3925 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
3927 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
3931 * The worst of all namespace operations - renaming directory. "Perverted"
3932 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3934 * a) we can get into loop creation. Check is done in is_subdir().
3935 * b) race potential - two innocent renames can create a loop together.
3936 * That's where 4.4 screws up. Current fix: serialization on
3937 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
3939 * c) we have to lock _three_ objects - parents and victim (if it exists).
3940 * And that - after we got ->i_mutex on parents (until then we don't know
3941 * whether the target exists). Solution: try to be smart with locking
3942 * order for inodes. We rely on the fact that tree topology may change
3943 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
3944 * move will be locked. Thus we can rank directories by the tree
3945 * (ancestors first) and rank all non-directories after them.
3946 * That works since everybody except rename does "lock parent, lookup,
3947 * lock child" and rename is under ->s_vfs_rename_mutex.
3948 * HOWEVER, it relies on the assumption that any object with ->lookup()
3949 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3950 * we'd better make sure that there's no link(2) for them.
3951 * d) conversion from fhandle to dentry may come in the wrong moment - when
3952 * we are removing the target. Solution: we will have to grab ->i_mutex
3953 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
3954 * ->i_mutex on parents, which works but leads to some truly excessive
3957 static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
3958 struct inode *new_dir, struct dentry *new_dentry)
3961 struct inode *target = new_dentry->d_inode;
3962 unsigned max_links = new_dir->i_sb->s_max_links;
3965 * If we are going to change the parent - check write permissions,
3966 * we'll need to flip '..'.
3968 if (new_dir != old_dir) {
3969 error = inode_permission(old_dentry->d_inode, MAY_WRITE);
3974 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3980 mutex_lock(&target->i_mutex);
3983 if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
3987 if (max_links && !target && new_dir != old_dir &&
3988 new_dir->i_nlink >= max_links)
3992 shrink_dcache_parent(new_dentry);
3993 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3998 target->i_flags |= S_DEAD;
3999 dont_mount(new_dentry);
4003 mutex_unlock(&target->i_mutex);
4006 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
4007 d_move(old_dentry,new_dentry);
4011 static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
4012 struct inode *new_dir, struct dentry *new_dentry)
4014 struct inode *target = new_dentry->d_inode;
4017 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
4023 mutex_lock(&target->i_mutex);
4026 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
4029 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
4034 dont_mount(new_dentry);
4035 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
4036 d_move(old_dentry, new_dentry);
4039 mutex_unlock(&target->i_mutex);
4044 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
4045 struct inode *new_dir, struct dentry *new_dentry)
4048 int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
4049 const unsigned char *old_name;
4051 if (old_dentry->d_inode == new_dentry->d_inode)
4054 error = may_delete(old_dir, old_dentry, is_dir);
4058 if (!new_dentry->d_inode)
4059 error = may_create(new_dir, new_dentry);
4061 error = may_delete(new_dir, new_dentry, is_dir);
4065 if (!old_dir->i_op->rename)
4068 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
4071 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
4073 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
4075 fsnotify_move(old_dir, new_dir, old_name, is_dir,
4076 new_dentry->d_inode, old_dentry);
4077 fsnotify_oldname_free(old_name);
4082 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
4083 int, newdfd, const char __user *, newname)
4085 struct dentry *old_dir, *new_dir;
4086 struct dentry *old_dentry, *new_dentry;
4087 struct dentry *trap;
4088 struct nameidata oldnd, newnd;
4089 struct filename *from;
4090 struct filename *to;
4091 unsigned int lookup_flags = 0;
4092 bool should_retry = false;
4095 from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags);
4097 error = PTR_ERR(from);
4101 to = user_path_parent(newdfd, newname, &newnd, lookup_flags);
4103 error = PTR_ERR(to);
4108 if (oldnd.path.mnt != newnd.path.mnt)
4111 old_dir = oldnd.path.dentry;
4113 if (oldnd.last_type != LAST_NORM)
4116 new_dir = newnd.path.dentry;
4117 if (newnd.last_type != LAST_NORM)
4120 error = mnt_want_write(oldnd.path.mnt);
4124 oldnd.flags &= ~LOOKUP_PARENT;
4125 newnd.flags &= ~LOOKUP_PARENT;
4126 newnd.flags |= LOOKUP_RENAME_TARGET;
4128 trap = lock_rename(new_dir, old_dir);
4130 old_dentry = lookup_hash(&oldnd);
4131 error = PTR_ERR(old_dentry);
4132 if (IS_ERR(old_dentry))
4134 /* source must exist */
4136 if (!old_dentry->d_inode)
4138 /* unless the source is a directory trailing slashes give -ENOTDIR */
4139 if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
4141 if (oldnd.last.name[oldnd.last.len])
4143 if (newnd.last.name[newnd.last.len])
4146 /* source should not be ancestor of target */
4148 if (old_dentry == trap)
4150 new_dentry = lookup_hash(&newnd);
4151 error = PTR_ERR(new_dentry);
4152 if (IS_ERR(new_dentry))
4154 /* target should not be an ancestor of source */
4156 if (new_dentry == trap)
4159 error = security_path_rename(&oldnd.path, old_dentry,
4160 &newnd.path, new_dentry);
4163 error = vfs_rename(old_dir->d_inode, old_dentry,
4164 new_dir->d_inode, new_dentry);
4170 unlock_rename(new_dir, old_dir);
4171 mnt_drop_write(oldnd.path.mnt);
4173 if (retry_estale(error, lookup_flags))
4174 should_retry = true;
4175 path_put(&newnd.path);
4178 path_put(&oldnd.path);
4181 should_retry = false;
4182 lookup_flags |= LOOKUP_REVAL;
4189 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
4191 return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
4194 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
4198 len = PTR_ERR(link);
4203 if (len > (unsigned) buflen)
4205 if (copy_to_user(buffer, link, len))
4212 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
4213 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
4214 * using) it for any given inode is up to filesystem.
4216 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4218 struct nameidata nd;
4223 cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
4225 return PTR_ERR(cookie);
4227 res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
4228 if (dentry->d_inode->i_op->put_link)
4229 dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
4233 int vfs_follow_link(struct nameidata *nd, const char *link)
4235 return __vfs_follow_link(nd, link);
4238 /* get the link contents into pagecache */
4239 static char *page_getlink(struct dentry * dentry, struct page **ppage)
4243 struct address_space *mapping = dentry->d_inode->i_mapping;
4244 page = read_mapping_page(mapping, 0, NULL);
4249 nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
4253 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4255 struct page *page = NULL;
4256 char *s = page_getlink(dentry, &page);
4257 int res = vfs_readlink(dentry,buffer,buflen,s);
4260 page_cache_release(page);
4265 void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
4267 struct page *page = NULL;
4268 nd_set_link(nd, page_getlink(dentry, &page));
4272 void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
4274 struct page *page = cookie;
4278 page_cache_release(page);
4283 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4285 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
4287 struct address_space *mapping = inode->i_mapping;
4292 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
4294 flags |= AOP_FLAG_NOFS;
4297 err = pagecache_write_begin(NULL, mapping, 0, len-1,
4298 flags, &page, &fsdata);
4302 kaddr = kmap_atomic(page);
4303 memcpy(kaddr, symname, len-1);
4304 kunmap_atomic(kaddr);
4306 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
4313 mark_inode_dirty(inode);
4319 int page_symlink(struct inode *inode, const char *symname, int len)
4321 return __page_symlink(inode, symname, len,
4322 !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
4325 const struct inode_operations page_symlink_inode_operations = {
4326 .readlink = generic_readlink,
4327 .follow_link = page_follow_link_light,
4328 .put_link = page_put_link,
4331 EXPORT_SYMBOL(user_path_at);
4332 EXPORT_SYMBOL(follow_down_one);
4333 EXPORT_SYMBOL(follow_down);
4334 EXPORT_SYMBOL(follow_up);
4335 EXPORT_SYMBOL(get_write_access); /* nfsd */
4336 EXPORT_SYMBOL(lock_rename);
4337 EXPORT_SYMBOL(lookup_one_len);
4338 EXPORT_SYMBOL(page_follow_link_light);
4339 EXPORT_SYMBOL(page_put_link);
4340 EXPORT_SYMBOL(page_readlink);
4341 EXPORT_SYMBOL(__page_symlink);
4342 EXPORT_SYMBOL(page_symlink);
4343 EXPORT_SYMBOL(page_symlink_inode_operations);
4344 EXPORT_SYMBOL(kern_path);
4345 EXPORT_SYMBOL(vfs_path_lookup);
4346 EXPORT_SYMBOL(inode_permission);
4347 EXPORT_SYMBOL(unlock_rename);
4348 EXPORT_SYMBOL(vfs_create);
4349 EXPORT_SYMBOL(vfs_follow_link);
4350 EXPORT_SYMBOL(vfs_link);
4351 EXPORT_SYMBOL(vfs_mkdir);
4352 EXPORT_SYMBOL(vfs_mknod);
4353 EXPORT_SYMBOL(generic_permission);
4354 EXPORT_SYMBOL(vfs_readlink);
4355 EXPORT_SYMBOL(vfs_rename);
4356 EXPORT_SYMBOL(vfs_rmdir);
4357 EXPORT_SYMBOL(vfs_symlink);
4358 EXPORT_SYMBOL(vfs_unlink);
4359 EXPORT_SYMBOL(dentry_unhash);
4360 EXPORT_SYMBOL(generic_readlink);