4 * Copyright (C) 1991, 1992 Linus Torvalds
8 * Some corrections by tytso.
11 /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
14 /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
17 #include <linux/init.h>
18 #include <linux/export.h>
19 #include <linux/kernel.h>
20 #include <linux/slab.h>
22 #include <linux/namei.h>
23 #include <linux/pagemap.h>
24 #include <linux/fsnotify.h>
25 #include <linux/personality.h>
26 #include <linux/security.h>
27 #include <linux/ima.h>
28 #include <linux/syscalls.h>
29 #include <linux/mount.h>
30 #include <linux/audit.h>
31 #include <linux/capability.h>
32 #include <linux/file.h>
33 #include <linux/fcntl.h>
34 #include <linux/device_cgroup.h>
35 #include <linux/fs_struct.h>
36 #include <linux/posix_acl.h>
37 #include <linux/hash.h>
38 #include <asm/uaccess.h>
43 /* [Feb-1997 T. Schoebel-Theuer]
44 * Fundamental changes in the pathname lookup mechanisms (namei)
45 * were necessary because of omirr. The reason is that omirr needs
46 * to know the _real_ pathname, not the user-supplied one, in case
47 * of symlinks (and also when transname replacements occur).
49 * The new code replaces the old recursive symlink resolution with
50 * an iterative one (in case of non-nested symlink chains). It does
51 * this with calls to <fs>_follow_link().
52 * As a side effect, dir_namei(), _namei() and follow_link() are now
53 * replaced with a single function lookup_dentry() that can handle all
54 * the special cases of the former code.
56 * With the new dcache, the pathname is stored at each inode, at least as
57 * long as the refcount of the inode is positive. As a side effect, the
58 * size of the dcache depends on the inode cache and thus is dynamic.
60 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
61 * resolution to correspond with current state of the code.
63 * Note that the symlink resolution is not *completely* iterative.
64 * There is still a significant amount of tail- and mid- recursion in
65 * the algorithm. Also, note that <fs>_readlink() is not used in
66 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
67 * may return different results than <fs>_follow_link(). Many virtual
68 * filesystems (including /proc) exhibit this behavior.
71 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
72 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
73 * and the name already exists in form of a symlink, try to create the new
74 * name indicated by the symlink. The old code always complained that the
75 * name already exists, due to not following the symlink even if its target
76 * is nonexistent. The new semantics affects also mknod() and link() when
77 * the name is a symlink pointing to a non-existent name.
79 * I don't know which semantics is the right one, since I have no access
80 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
81 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
82 * "old" one. Personally, I think the new semantics is much more logical.
83 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
84 * file does succeed in both HP-UX and SunOs, but not in Solaris
85 * and in the old Linux semantics.
88 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
89 * semantics. See the comments in "open_namei" and "do_link" below.
91 * [10-Sep-98 Alan Modra] Another symlink change.
94 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
95 * inside the path - always follow.
96 * in the last component in creation/removal/renaming - never follow.
97 * if LOOKUP_FOLLOW passed - follow.
98 * if the pathname has trailing slashes - follow.
99 * otherwise - don't follow.
100 * (applied in that order).
102 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
103 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
104 * During the 2.4 we need to fix the userland stuff depending on it -
105 * hopefully we will be able to get rid of that wart in 2.5. So far only
106 * XEmacs seems to be relying on it...
109 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
110 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
111 * any extra contention...
114 /* In order to reduce some races, while at the same time doing additional
115 * checking and hopefully speeding things up, we copy filenames to the
116 * kernel data space before using them..
118 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
119 * PATH_MAX includes the nul terminator --RR.
121 void final_putname(struct filename *name)
123 if (name->separate) {
124 __putname(name->name);
131 #define EMBEDDED_NAME_MAX (PATH_MAX - sizeof(struct filename))
133 static struct filename *
134 getname_flags(const char __user *filename, int flags, int *empty)
136 struct filename *result, *err;
141 result = audit_reusename(filename);
145 result = __getname();
146 if (unlikely(!result))
147 return ERR_PTR(-ENOMEM);
150 * First, try to embed the struct filename inside the names_cache
153 kname = (char *)result + sizeof(*result);
154 result->name = kname;
155 result->separate = false;
156 max = EMBEDDED_NAME_MAX;
159 len = strncpy_from_user(kname, filename, max);
160 if (unlikely(len < 0)) {
166 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
167 * separate struct filename so we can dedicate the entire
168 * names_cache allocation for the pathname, and re-do the copy from
171 if (len == EMBEDDED_NAME_MAX && max == EMBEDDED_NAME_MAX) {
172 kname = (char *)result;
174 result = kzalloc(sizeof(*result), GFP_KERNEL);
176 err = ERR_PTR(-ENOMEM);
177 result = (struct filename *)kname;
180 result->name = kname;
181 result->separate = true;
186 /* The empty path is special. */
187 if (unlikely(!len)) {
190 err = ERR_PTR(-ENOENT);
191 if (!(flags & LOOKUP_EMPTY))
195 err = ERR_PTR(-ENAMETOOLONG);
196 if (unlikely(len >= PATH_MAX))
199 result->uptr = filename;
200 audit_getname(result);
204 final_putname(result);
209 getname(const char __user * filename)
211 return getname_flags(filename, 0, NULL);
213 EXPORT_SYMBOL(getname);
215 #ifdef CONFIG_AUDITSYSCALL
216 void putname(struct filename *name)
218 if (unlikely(!audit_dummy_context()))
219 return audit_putname(name);
224 static int check_acl(struct inode *inode, int mask)
226 #ifdef CONFIG_FS_POSIX_ACL
227 struct posix_acl *acl;
229 if (mask & MAY_NOT_BLOCK) {
230 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
233 /* no ->get_acl() calls in RCU mode... */
234 if (acl == ACL_NOT_CACHED)
236 return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
239 acl = get_cached_acl(inode, ACL_TYPE_ACCESS);
242 * A filesystem can force a ACL callback by just never filling the
243 * ACL cache. But normally you'd fill the cache either at inode
244 * instantiation time, or on the first ->get_acl call.
246 * If the filesystem doesn't have a get_acl() function at all, we'll
247 * just create the negative cache entry.
249 if (acl == ACL_NOT_CACHED) {
250 if (inode->i_op->get_acl) {
251 acl = inode->i_op->get_acl(inode, ACL_TYPE_ACCESS);
255 set_cached_acl(inode, ACL_TYPE_ACCESS, NULL);
261 int error = posix_acl_permission(inode, acl, mask);
262 posix_acl_release(acl);
271 * This does the basic permission checking
273 static int acl_permission_check(struct inode *inode, int mask)
275 unsigned int mode = inode->i_mode;
277 if (likely(uid_eq(current_fsuid(), inode->i_uid)))
280 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
281 int error = check_acl(inode, mask);
282 if (error != -EAGAIN)
286 if (in_group_p(inode->i_gid))
291 * If the DACs are ok we don't need any capability check.
293 if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
299 * generic_permission - check for access rights on a Posix-like filesystem
300 * @inode: inode to check access rights for
301 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
303 * Used to check for read/write/execute permissions on a file.
304 * We use "fsuid" for this, letting us set arbitrary permissions
305 * for filesystem access without changing the "normal" uids which
306 * are used for other things.
308 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
309 * request cannot be satisfied (eg. requires blocking or too much complexity).
310 * It would then be called again in ref-walk mode.
312 int generic_permission(struct inode *inode, int mask)
317 * Do the basic permission checks.
319 ret = acl_permission_check(inode, mask);
323 if (S_ISDIR(inode->i_mode)) {
324 /* DACs are overridable for directories */
325 if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
327 if (!(mask & MAY_WRITE))
328 if (capable_wrt_inode_uidgid(inode,
329 CAP_DAC_READ_SEARCH))
334 * Read/write DACs are always overridable.
335 * Executable DACs are overridable when there is
336 * at least one exec bit set.
338 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
339 if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
343 * Searching includes executable on directories, else just read.
345 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
346 if (mask == MAY_READ)
347 if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH))
354 * We _really_ want to just do "generic_permission()" without
355 * even looking at the inode->i_op values. So we keep a cache
356 * flag in inode->i_opflags, that says "this has not special
357 * permission function, use the fast case".
359 static inline int do_inode_permission(struct inode *inode, int mask)
361 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
362 if (likely(inode->i_op->permission))
363 return inode->i_op->permission(inode, mask);
365 /* This gets set once for the inode lifetime */
366 spin_lock(&inode->i_lock);
367 inode->i_opflags |= IOP_FASTPERM;
368 spin_unlock(&inode->i_lock);
370 return generic_permission(inode, mask);
374 * __inode_permission - Check for access rights to a given inode
375 * @inode: Inode to check permission on
376 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
378 * Check for read/write/execute permissions on an inode.
380 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
382 * This does not check for a read-only file system. You probably want
383 * inode_permission().
385 int __inode_permission(struct inode *inode, int mask)
389 if (unlikely(mask & MAY_WRITE)) {
391 * Nobody gets write access to an immutable file.
393 if (IS_IMMUTABLE(inode))
397 retval = do_inode_permission(inode, mask);
401 retval = devcgroup_inode_permission(inode, mask);
405 return security_inode_permission(inode, mask);
409 * sb_permission - Check superblock-level permissions
410 * @sb: Superblock of inode to check permission on
411 * @inode: Inode to check permission on
412 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
414 * Separate out file-system wide checks from inode-specific permission checks.
416 static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
418 if (unlikely(mask & MAY_WRITE)) {
419 umode_t mode = inode->i_mode;
421 /* Nobody gets write access to a read-only fs. */
422 if ((sb->s_flags & MS_RDONLY) &&
423 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
430 * inode_permission - Check for access rights to a given inode
431 * @inode: Inode to check permission on
432 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
434 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
435 * this, letting us set arbitrary permissions for filesystem access without
436 * changing the "normal" UIDs which are used for other things.
438 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
440 int inode_permission(struct inode *inode, int mask)
444 retval = sb_permission(inode->i_sb, inode, mask);
447 return __inode_permission(inode, mask);
451 * path_get - get a reference to a path
452 * @path: path to get the reference to
454 * Given a path increment the reference count to the dentry and the vfsmount.
456 void path_get(const struct path *path)
461 EXPORT_SYMBOL(path_get);
464 * path_put - put a reference to a path
465 * @path: path to put the reference to
467 * Given a path decrement the reference count to the dentry and the vfsmount.
469 void path_put(const struct path *path)
474 EXPORT_SYMBOL(path_put);
477 * Path walking has 2 modes, rcu-walk and ref-walk (see
478 * Documentation/filesystems/path-lookup.txt). In situations when we can't
479 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
480 * normal reference counts on dentries and vfsmounts to transition to rcu-walk
481 * mode. Refcounts are grabbed at the last known good point before rcu-walk
482 * got stuck, so ref-walk may continue from there. If this is not successful
483 * (eg. a seqcount has changed), then failure is returned and it's up to caller
484 * to restart the path walk from the beginning in ref-walk mode.
487 static inline void lock_rcu_walk(void)
489 br_read_lock(&vfsmount_lock);
493 static inline void unlock_rcu_walk(void)
496 br_read_unlock(&vfsmount_lock);
500 * unlazy_walk - try to switch to ref-walk mode.
501 * @nd: nameidata pathwalk data
502 * @dentry: child of nd->path.dentry or NULL
503 * Returns: 0 on success, -ECHILD on failure
505 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
506 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
507 * @nd or NULL. Must be called from rcu-walk context.
509 static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
511 struct fs_struct *fs = current->fs;
512 struct dentry *parent = nd->path.dentry;
515 BUG_ON(!(nd->flags & LOOKUP_RCU));
516 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
518 spin_lock(&fs->lock);
519 if (nd->root.mnt != fs->root.mnt ||
520 nd->root.dentry != fs->root.dentry)
523 spin_lock(&parent->d_lock);
525 if (!__d_rcu_to_refcount(parent, nd->seq))
527 BUG_ON(nd->inode != parent->d_inode);
529 if (dentry->d_parent != parent)
531 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
532 if (!__d_rcu_to_refcount(dentry, nd->seq))
535 * If the sequence check on the child dentry passed, then
536 * the child has not been removed from its parent. This
537 * means the parent dentry must be valid and able to take
538 * a reference at this point.
540 BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
541 BUG_ON(!parent->d_count);
543 spin_unlock(&dentry->d_lock);
545 spin_unlock(&parent->d_lock);
548 spin_unlock(&fs->lock);
550 mntget(nd->path.mnt);
553 nd->flags &= ~LOOKUP_RCU;
557 spin_unlock(&dentry->d_lock);
559 spin_unlock(&parent->d_lock);
562 spin_unlock(&fs->lock);
566 static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
568 return dentry->d_op->d_revalidate(dentry, flags);
572 * complete_walk - successful completion of path walk
573 * @nd: pointer nameidata
575 * If we had been in RCU mode, drop out of it and legitimize nd->path.
576 * Revalidate the final result, unless we'd already done that during
577 * the path walk or the filesystem doesn't ask for it. Return 0 on
578 * success, -error on failure. In case of failure caller does not
579 * need to drop nd->path.
581 static int complete_walk(struct nameidata *nd)
583 struct dentry *dentry = nd->path.dentry;
586 if (nd->flags & LOOKUP_RCU) {
587 nd->flags &= ~LOOKUP_RCU;
588 if (!(nd->flags & LOOKUP_ROOT))
590 spin_lock(&dentry->d_lock);
591 if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) {
592 spin_unlock(&dentry->d_lock);
596 BUG_ON(nd->inode != dentry->d_inode);
597 spin_unlock(&dentry->d_lock);
598 mntget(nd->path.mnt);
602 if (likely(!(nd->flags & LOOKUP_JUMPED)))
605 if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
608 status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
619 static __always_inline void set_root(struct nameidata *nd)
622 get_fs_root(current->fs, &nd->root);
625 static int link_path_walk(const char *, struct nameidata *);
627 static __always_inline void set_root_rcu(struct nameidata *nd)
630 struct fs_struct *fs = current->fs;
634 seq = read_seqcount_begin(&fs->seq);
636 nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
637 } while (read_seqcount_retry(&fs->seq, seq));
641 static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
653 nd->flags |= LOOKUP_JUMPED;
655 nd->inode = nd->path.dentry->d_inode;
657 ret = link_path_walk(link, nd);
661 return PTR_ERR(link);
664 static void path_put_conditional(struct path *path, struct nameidata *nd)
667 if (path->mnt != nd->path.mnt)
671 static inline void path_to_nameidata(const struct path *path,
672 struct nameidata *nd)
674 if (!(nd->flags & LOOKUP_RCU)) {
675 dput(nd->path.dentry);
676 if (nd->path.mnt != path->mnt)
677 mntput(nd->path.mnt);
679 nd->path.mnt = path->mnt;
680 nd->path.dentry = path->dentry;
684 * Helper to directly jump to a known parsed path from ->follow_link,
685 * caller must have taken a reference to path beforehand.
687 void nd_jump_link(struct nameidata *nd, struct path *path)
692 nd->inode = nd->path.dentry->d_inode;
693 nd->flags |= LOOKUP_JUMPED;
696 static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
698 struct inode *inode = link->dentry->d_inode;
699 if (inode->i_op->put_link)
700 inode->i_op->put_link(link->dentry, nd, cookie);
704 int sysctl_protected_symlinks __read_mostly = 0;
705 int sysctl_protected_hardlinks __read_mostly = 0;
708 * may_follow_link - Check symlink following for unsafe situations
709 * @link: The path of the symlink
710 * @nd: nameidata pathwalk data
712 * In the case of the sysctl_protected_symlinks sysctl being enabled,
713 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
714 * in a sticky world-writable directory. This is to protect privileged
715 * processes from failing races against path names that may change out
716 * from under them by way of other users creating malicious symlinks.
717 * It will permit symlinks to be followed only when outside a sticky
718 * world-writable directory, or when the uid of the symlink and follower
719 * match, or when the directory owner matches the symlink's owner.
721 * Returns 0 if following the symlink is allowed, -ve on error.
723 static inline int may_follow_link(struct path *link, struct nameidata *nd)
725 const struct inode *inode;
726 const struct inode *parent;
728 if (!sysctl_protected_symlinks)
731 /* Allowed if owner and follower match. */
732 inode = link->dentry->d_inode;
733 if (uid_eq(current_cred()->fsuid, inode->i_uid))
736 /* Allowed if parent directory not sticky and world-writable. */
737 parent = nd->path.dentry->d_inode;
738 if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
741 /* Allowed if parent directory and link owner match. */
742 if (uid_eq(parent->i_uid, inode->i_uid))
745 audit_log_link_denied("follow_link", link);
746 path_put_conditional(link, nd);
752 * safe_hardlink_source - Check for safe hardlink conditions
753 * @inode: the source inode to hardlink from
755 * Return false if at least one of the following conditions:
756 * - inode is not a regular file
758 * - inode is setgid and group-exec
759 * - access failure for read and write
761 * Otherwise returns true.
763 static bool safe_hardlink_source(struct inode *inode)
765 umode_t mode = inode->i_mode;
767 /* Special files should not get pinned to the filesystem. */
771 /* Setuid files should not get pinned to the filesystem. */
775 /* Executable setgid files should not get pinned to the filesystem. */
776 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
779 /* Hardlinking to unreadable or unwritable sources is dangerous. */
780 if (inode_permission(inode, MAY_READ | MAY_WRITE))
787 * may_linkat - Check permissions for creating a hardlink
788 * @link: the source to hardlink from
790 * Block hardlink when all of:
791 * - sysctl_protected_hardlinks enabled
792 * - fsuid does not match inode
793 * - hardlink source is unsafe (see safe_hardlink_source() above)
796 * Returns 0 if successful, -ve on error.
798 static int may_linkat(struct path *link)
800 const struct cred *cred;
803 if (!sysctl_protected_hardlinks)
806 cred = current_cred();
807 inode = link->dentry->d_inode;
809 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
810 * otherwise, it must be a safe source.
812 if (uid_eq(cred->fsuid, inode->i_uid) || safe_hardlink_source(inode) ||
816 audit_log_link_denied("linkat", link);
820 static __always_inline int
821 follow_link(struct path *link, struct nameidata *nd, void **p)
823 struct dentry *dentry = link->dentry;
827 BUG_ON(nd->flags & LOOKUP_RCU);
829 if (link->mnt == nd->path.mnt)
833 if (unlikely(current->total_link_count >= 40))
834 goto out_put_nd_path;
837 current->total_link_count++;
840 nd_set_link(nd, NULL);
842 error = security_inode_follow_link(link->dentry, nd);
844 goto out_put_nd_path;
846 nd->last_type = LAST_BIND;
847 *p = dentry->d_inode->i_op->follow_link(dentry, nd);
850 goto out_put_nd_path;
855 error = __vfs_follow_link(nd, s);
857 put_link(nd, link, *p);
869 static int follow_up_rcu(struct path *path)
871 struct mount *mnt = real_mount(path->mnt);
872 struct mount *parent;
873 struct dentry *mountpoint;
875 parent = mnt->mnt_parent;
876 if (&parent->mnt == path->mnt)
878 mountpoint = mnt->mnt_mountpoint;
879 path->dentry = mountpoint;
880 path->mnt = &parent->mnt;
885 * follow_up - Find the mountpoint of path's vfsmount
887 * Given a path, find the mountpoint of its source file system.
888 * Replace @path with the path of the mountpoint in the parent mount.
891 * Return 1 if we went up a level and 0 if we were already at the
894 int follow_up(struct path *path)
896 struct mount *mnt = real_mount(path->mnt);
897 struct mount *parent;
898 struct dentry *mountpoint;
900 br_read_lock(&vfsmount_lock);
901 parent = mnt->mnt_parent;
903 br_read_unlock(&vfsmount_lock);
906 mntget(&parent->mnt);
907 mountpoint = dget(mnt->mnt_mountpoint);
908 br_read_unlock(&vfsmount_lock);
910 path->dentry = mountpoint;
912 path->mnt = &parent->mnt;
917 * Perform an automount
918 * - return -EISDIR to tell follow_managed() to stop and return the path we
921 static int follow_automount(struct path *path, unsigned flags,
924 struct vfsmount *mnt;
927 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
930 /* We don't want to mount if someone's just doing a stat -
931 * unless they're stat'ing a directory and appended a '/' to
934 * We do, however, want to mount if someone wants to open or
935 * create a file of any type under the mountpoint, wants to
936 * traverse through the mountpoint or wants to open the
937 * mounted directory. Also, autofs may mark negative dentries
938 * as being automount points. These will need the attentions
939 * of the daemon to instantiate them before they can be used.
941 if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
942 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
943 path->dentry->d_inode)
946 current->total_link_count++;
947 if (current->total_link_count >= 40)
950 mnt = path->dentry->d_op->d_automount(path);
953 * The filesystem is allowed to return -EISDIR here to indicate
954 * it doesn't want to automount. For instance, autofs would do
955 * this so that its userspace daemon can mount on this dentry.
957 * However, we can only permit this if it's a terminal point in
958 * the path being looked up; if it wasn't then the remainder of
959 * the path is inaccessible and we should say so.
961 if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT))
966 if (!mnt) /* mount collision */
970 /* lock_mount() may release path->mnt on error */
974 err = finish_automount(mnt, path);
978 /* Someone else made a mount here whilst we were busy */
983 path->dentry = dget(mnt->mnt_root);
992 * Handle a dentry that is managed in some way.
993 * - Flagged for transit management (autofs)
994 * - Flagged as mountpoint
995 * - Flagged as automount point
997 * This may only be called in refwalk mode.
999 * Serialization is taken care of in namespace.c
1001 static int follow_managed(struct path *path, unsigned flags)
1003 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
1005 bool need_mntput = false;
1008 /* Given that we're not holding a lock here, we retain the value in a
1009 * local variable for each dentry as we look at it so that we don't see
1010 * the components of that value change under us */
1011 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1012 managed &= DCACHE_MANAGED_DENTRY,
1013 unlikely(managed != 0)) {
1014 /* Allow the filesystem to manage the transit without i_mutex
1016 if (managed & DCACHE_MANAGE_TRANSIT) {
1017 BUG_ON(!path->dentry->d_op);
1018 BUG_ON(!path->dentry->d_op->d_manage);
1019 ret = path->dentry->d_op->d_manage(path->dentry, false);
1024 /* Transit to a mounted filesystem. */
1025 if (managed & DCACHE_MOUNTED) {
1026 struct vfsmount *mounted = lookup_mnt(path);
1031 path->mnt = mounted;
1032 path->dentry = dget(mounted->mnt_root);
1037 /* Something is mounted on this dentry in another
1038 * namespace and/or whatever was mounted there in this
1039 * namespace got unmounted before we managed to get the
1043 /* Handle an automount point */
1044 if (managed & DCACHE_NEED_AUTOMOUNT) {
1045 ret = follow_automount(path, flags, &need_mntput);
1051 /* We didn't change the current path point */
1055 if (need_mntput && path->mnt == mnt)
1059 return ret < 0 ? ret : need_mntput;
1062 int follow_down_one(struct path *path)
1064 struct vfsmount *mounted;
1066 mounted = lookup_mnt(path);
1070 path->mnt = mounted;
1071 path->dentry = dget(mounted->mnt_root);
1077 static inline bool managed_dentry_might_block(struct dentry *dentry)
1079 return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
1080 dentry->d_op->d_manage(dentry, true) < 0);
1084 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1085 * we meet a managed dentry that would need blocking.
1087 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
1088 struct inode **inode)
1091 struct mount *mounted;
1093 * Don't forget we might have a non-mountpoint managed dentry
1094 * that wants to block transit.
1096 if (unlikely(managed_dentry_might_block(path->dentry)))
1099 if (!d_mountpoint(path->dentry))
1102 mounted = __lookup_mnt(path->mnt, path->dentry, 1);
1105 path->mnt = &mounted->mnt;
1106 path->dentry = mounted->mnt.mnt_root;
1107 nd->flags |= LOOKUP_JUMPED;
1108 nd->seq = read_seqcount_begin(&path->dentry->d_seq);
1110 * Update the inode too. We don't need to re-check the
1111 * dentry sequence number here after this d_inode read,
1112 * because a mount-point is always pinned.
1114 *inode = path->dentry->d_inode;
1119 static void follow_mount_rcu(struct nameidata *nd)
1121 while (d_mountpoint(nd->path.dentry)) {
1122 struct mount *mounted;
1123 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1);
1126 nd->path.mnt = &mounted->mnt;
1127 nd->path.dentry = mounted->mnt.mnt_root;
1128 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1132 static int follow_dotdot_rcu(struct nameidata *nd)
1137 if (nd->path.dentry == nd->root.dentry &&
1138 nd->path.mnt == nd->root.mnt) {
1141 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1142 struct dentry *old = nd->path.dentry;
1143 struct dentry *parent = old->d_parent;
1146 seq = read_seqcount_begin(&parent->d_seq);
1147 if (read_seqcount_retry(&old->d_seq, nd->seq))
1149 nd->path.dentry = parent;
1153 if (!follow_up_rcu(&nd->path))
1155 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1157 follow_mount_rcu(nd);
1158 nd->inode = nd->path.dentry->d_inode;
1162 nd->flags &= ~LOOKUP_RCU;
1163 if (!(nd->flags & LOOKUP_ROOT))
1164 nd->root.mnt = NULL;
1170 * Follow down to the covering mount currently visible to userspace. At each
1171 * point, the filesystem owning that dentry may be queried as to whether the
1172 * caller is permitted to proceed or not.
1174 int follow_down(struct path *path)
1179 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1180 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
1181 /* Allow the filesystem to manage the transit without i_mutex
1184 * We indicate to the filesystem if someone is trying to mount
1185 * something here. This gives autofs the chance to deny anyone
1186 * other than its daemon the right to mount on its
1189 * The filesystem may sleep at this point.
1191 if (managed & DCACHE_MANAGE_TRANSIT) {
1192 BUG_ON(!path->dentry->d_op);
1193 BUG_ON(!path->dentry->d_op->d_manage);
1194 ret = path->dentry->d_op->d_manage(
1195 path->dentry, false);
1197 return ret == -EISDIR ? 0 : ret;
1200 /* Transit to a mounted filesystem. */
1201 if (managed & DCACHE_MOUNTED) {
1202 struct vfsmount *mounted = lookup_mnt(path);
1207 path->mnt = mounted;
1208 path->dentry = dget(mounted->mnt_root);
1212 /* Don't handle automount points here */
1219 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1221 static void follow_mount(struct path *path)
1223 while (d_mountpoint(path->dentry)) {
1224 struct vfsmount *mounted = lookup_mnt(path);
1229 path->mnt = mounted;
1230 path->dentry = dget(mounted->mnt_root);
1234 static void follow_dotdot(struct nameidata *nd)
1239 struct dentry *old = nd->path.dentry;
1241 if (nd->path.dentry == nd->root.dentry &&
1242 nd->path.mnt == nd->root.mnt) {
1245 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1246 /* rare case of legitimate dget_parent()... */
1247 nd->path.dentry = dget_parent(nd->path.dentry);
1251 if (!follow_up(&nd->path))
1254 follow_mount(&nd->path);
1255 nd->inode = nd->path.dentry->d_inode;
1259 * This looks up the name in dcache, possibly revalidates the old dentry and
1260 * allocates a new one if not found or not valid. In the need_lookup argument
1261 * returns whether i_op->lookup is necessary.
1263 * dir->d_inode->i_mutex must be held
1265 static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir,
1266 unsigned int flags, bool *need_lookup)
1268 struct dentry *dentry;
1271 *need_lookup = false;
1272 dentry = d_lookup(dir, name);
1274 if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
1275 error = d_revalidate(dentry, flags);
1276 if (unlikely(error <= 0)) {
1279 return ERR_PTR(error);
1280 } else if (!d_invalidate(dentry)) {
1289 dentry = d_alloc(dir, name);
1290 if (unlikely(!dentry))
1291 return ERR_PTR(-ENOMEM);
1293 *need_lookup = true;
1299 * Call i_op->lookup on the dentry. The dentry must be negative but may be
1300 * hashed if it was pouplated with DCACHE_NEED_LOOKUP.
1302 * dir->d_inode->i_mutex must be held
1304 static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
1309 /* Don't create child dentry for a dead directory. */
1310 if (unlikely(IS_DEADDIR(dir))) {
1312 return ERR_PTR(-ENOENT);
1315 old = dir->i_op->lookup(dir, dentry, flags);
1316 if (unlikely(old)) {
1323 static struct dentry *__lookup_hash(struct qstr *name,
1324 struct dentry *base, unsigned int flags)
1327 struct dentry *dentry;
1329 dentry = lookup_dcache(name, base, flags, &need_lookup);
1333 return lookup_real(base->d_inode, dentry, flags);
1337 * It's more convoluted than I'd like it to be, but... it's still fairly
1338 * small and for now I'd prefer to have fast path as straight as possible.
1339 * It _is_ time-critical.
1341 static int lookup_fast(struct nameidata *nd,
1342 struct path *path, struct inode **inode)
1344 struct vfsmount *mnt = nd->path.mnt;
1345 struct dentry *dentry, *parent = nd->path.dentry;
1351 * Rename seqlock is not required here because in the off chance
1352 * of a false negative due to a concurrent rename, we're going to
1353 * do the non-racy lookup, below.
1355 if (nd->flags & LOOKUP_RCU) {
1357 dentry = __d_lookup_rcu(parent, &nd->last, &seq, nd->inode);
1362 * This sequence count validates that the inode matches
1363 * the dentry name information from lookup.
1365 *inode = dentry->d_inode;
1366 if (read_seqcount_retry(&dentry->d_seq, seq))
1370 * This sequence count validates that the parent had no
1371 * changes while we did the lookup of the dentry above.
1373 * The memory barrier in read_seqcount_begin of child is
1374 * enough, we can use __read_seqcount_retry here.
1376 if (__read_seqcount_retry(&parent->d_seq, nd->seq))
1380 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1381 status = d_revalidate(dentry, nd->flags);
1382 if (unlikely(status <= 0)) {
1383 if (status != -ECHILD)
1389 path->dentry = dentry;
1390 if (unlikely(!__follow_mount_rcu(nd, path, inode)))
1392 if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
1396 if (unlazy_walk(nd, dentry))
1399 dentry = __d_lookup(parent, &nd->last);
1402 if (unlikely(!dentry))
1405 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
1406 status = d_revalidate(dentry, nd->flags);
1407 if (unlikely(status <= 0)) {
1412 if (!d_invalidate(dentry)) {
1419 path->dentry = dentry;
1420 err = follow_managed(path, nd->flags);
1421 if (unlikely(err < 0)) {
1422 path_put_conditional(path, nd);
1426 nd->flags |= LOOKUP_JUMPED;
1427 *inode = path->dentry->d_inode;
1434 /* Fast lookup failed, do it the slow way */
1435 static int lookup_slow(struct nameidata *nd, struct path *path)
1437 struct dentry *dentry, *parent;
1440 parent = nd->path.dentry;
1441 BUG_ON(nd->inode != parent->d_inode);
1443 mutex_lock(&parent->d_inode->i_mutex);
1444 dentry = __lookup_hash(&nd->last, parent, nd->flags);
1445 mutex_unlock(&parent->d_inode->i_mutex);
1447 return PTR_ERR(dentry);
1448 path->mnt = nd->path.mnt;
1449 path->dentry = dentry;
1450 err = follow_managed(path, nd->flags);
1451 if (unlikely(err < 0)) {
1452 path_put_conditional(path, nd);
1456 nd->flags |= LOOKUP_JUMPED;
1460 static inline int may_lookup(struct nameidata *nd)
1462 if (nd->flags & LOOKUP_RCU) {
1463 int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1466 if (unlazy_walk(nd, NULL))
1469 return inode_permission(nd->inode, MAY_EXEC);
1472 static inline int handle_dots(struct nameidata *nd, int type)
1474 if (type == LAST_DOTDOT) {
1475 if (nd->flags & LOOKUP_RCU) {
1476 if (follow_dotdot_rcu(nd))
1484 static void terminate_walk(struct nameidata *nd)
1486 if (!(nd->flags & LOOKUP_RCU)) {
1487 path_put(&nd->path);
1489 nd->flags &= ~LOOKUP_RCU;
1490 if (!(nd->flags & LOOKUP_ROOT))
1491 nd->root.mnt = NULL;
1497 * Do we need to follow links? We _really_ want to be able
1498 * to do this check without having to look at inode->i_op,
1499 * so we keep a cache of "no, this doesn't need follow_link"
1500 * for the common case.
1502 static inline int should_follow_link(struct inode *inode, int follow)
1504 if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1505 if (likely(inode->i_op->follow_link))
1508 /* This gets set once for the inode lifetime */
1509 spin_lock(&inode->i_lock);
1510 inode->i_opflags |= IOP_NOFOLLOW;
1511 spin_unlock(&inode->i_lock);
1516 static inline int walk_component(struct nameidata *nd, struct path *path,
1519 struct inode *inode;
1522 * "." and ".." are special - ".." especially so because it has
1523 * to be able to know about the current root directory and
1524 * parent relationships.
1526 if (unlikely(nd->last_type != LAST_NORM))
1527 return handle_dots(nd, nd->last_type);
1528 err = lookup_fast(nd, path, &inode);
1529 if (unlikely(err)) {
1533 err = lookup_slow(nd, path);
1537 inode = path->dentry->d_inode;
1543 if (should_follow_link(inode, follow)) {
1544 if (nd->flags & LOOKUP_RCU) {
1545 if (unlikely(nd->path.mnt != path->mnt ||
1546 unlazy_walk(nd, path->dentry))) {
1551 BUG_ON(inode != path->dentry->d_inode);
1554 path_to_nameidata(path, nd);
1559 path_to_nameidata(path, nd);
1566 * This limits recursive symlink follows to 8, while
1567 * limiting consecutive symlinks to 40.
1569 * Without that kind of total limit, nasty chains of consecutive
1570 * symlinks can cause almost arbitrarily long lookups.
1572 static inline int nested_symlink(struct path *path, struct nameidata *nd)
1576 if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
1577 path_put_conditional(path, nd);
1578 path_put(&nd->path);
1581 BUG_ON(nd->depth >= MAX_NESTED_LINKS);
1584 current->link_count++;
1587 struct path link = *path;
1590 res = follow_link(&link, nd, &cookie);
1593 res = walk_component(nd, path, LOOKUP_FOLLOW);
1594 put_link(nd, &link, cookie);
1597 current->link_count--;
1603 * We really don't want to look at inode->i_op->lookup
1604 * when we don't have to. So we keep a cache bit in
1605 * the inode ->i_opflags field that says "yes, we can
1606 * do lookup on this inode".
1608 static inline int can_lookup(struct inode *inode)
1610 if (likely(inode->i_opflags & IOP_LOOKUP))
1612 if (likely(!inode->i_op->lookup))
1615 /* We do this once for the lifetime of the inode */
1616 spin_lock(&inode->i_lock);
1617 inode->i_opflags |= IOP_LOOKUP;
1618 spin_unlock(&inode->i_lock);
1623 * We can do the critical dentry name comparison and hashing
1624 * operations one word at a time, but we are limited to:
1626 * - Architectures with fast unaligned word accesses. We could
1627 * do a "get_unaligned()" if this helps and is sufficiently
1630 * - Little-endian machines (so that we can generate the mask
1631 * of low bytes efficiently). Again, we *could* do a byte
1632 * swapping load on big-endian architectures if that is not
1633 * expensive enough to make the optimization worthless.
1635 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1636 * do not trap on the (extremely unlikely) case of a page
1637 * crossing operation.
1639 * - Furthermore, we need an efficient 64-bit compile for the
1640 * 64-bit case in order to generate the "number of bytes in
1641 * the final mask". Again, that could be replaced with a
1642 * efficient population count instruction or similar.
1644 #ifdef CONFIG_DCACHE_WORD_ACCESS
1646 #include <asm/word-at-a-time.h>
1650 static inline unsigned int fold_hash(unsigned long hash)
1652 return hash_64(hash, 32);
1655 #else /* 32-bit case */
1657 #define fold_hash(x) (x)
1661 unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1663 unsigned long a, mask;
1664 unsigned long hash = 0;
1667 a = load_unaligned_zeropad(name);
1668 if (len < sizeof(unsigned long))
1672 name += sizeof(unsigned long);
1673 len -= sizeof(unsigned long);
1677 mask = ~(~0ul << len*8);
1680 return fold_hash(hash);
1682 EXPORT_SYMBOL(full_name_hash);
1685 * Calculate the length and hash of the path component, and
1686 * return the length of the component;
1688 static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1690 unsigned long a, b, adata, bdata, mask, hash, len;
1691 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
1694 len = -sizeof(unsigned long);
1696 hash = (hash + a) * 9;
1697 len += sizeof(unsigned long);
1698 a = load_unaligned_zeropad(name+len);
1699 b = a ^ REPEAT_BYTE('/');
1700 } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
1702 adata = prep_zero_mask(a, adata, &constants);
1703 bdata = prep_zero_mask(b, bdata, &constants);
1705 mask = create_zero_mask(adata | bdata);
1707 hash += a & zero_bytemask(mask);
1708 *hashp = fold_hash(hash);
1710 return len + find_zero(mask);
1715 unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1717 unsigned long hash = init_name_hash();
1719 hash = partial_name_hash(*name++, hash);
1720 return end_name_hash(hash);
1722 EXPORT_SYMBOL(full_name_hash);
1725 * We know there's a real path component here of at least
1728 static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1730 unsigned long hash = init_name_hash();
1731 unsigned long len = 0, c;
1733 c = (unsigned char)*name;
1736 hash = partial_name_hash(c, hash);
1737 c = (unsigned char)name[len];
1738 } while (c && c != '/');
1739 *hashp = end_name_hash(hash);
1747 * This is the basic name resolution function, turning a pathname into
1748 * the final dentry. We expect 'base' to be positive and a directory.
1750 * Returns 0 and nd will have valid dentry and mnt on success.
1751 * Returns error and drops reference to input namei data on failure.
1753 static int link_path_walk(const char *name, struct nameidata *nd)
1763 /* At this point we know we have a real path component. */
1769 err = may_lookup(nd);
1773 len = hash_name(name, &this.hash);
1778 if (name[0] == '.') switch (len) {
1780 if (name[1] == '.') {
1782 nd->flags |= LOOKUP_JUMPED;
1788 if (likely(type == LAST_NORM)) {
1789 struct dentry *parent = nd->path.dentry;
1790 nd->flags &= ~LOOKUP_JUMPED;
1791 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
1792 err = parent->d_op->d_hash(parent, nd->inode,
1800 nd->last_type = type;
1805 * If it wasn't NUL, we know it was '/'. Skip that
1806 * slash, and continue until no more slashes.
1810 } while (unlikely(name[len] == '/'));
1816 err = walk_component(nd, &next, LOOKUP_FOLLOW);
1821 err = nested_symlink(&next, nd);
1825 if (!can_lookup(nd->inode)) {
1834 static int path_init(int dfd, const char *name, unsigned int flags,
1835 struct nameidata *nd, struct file **fp)
1839 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1840 nd->flags = flags | LOOKUP_JUMPED;
1842 if (flags & LOOKUP_ROOT) {
1843 struct inode *inode = nd->root.dentry->d_inode;
1845 if (!can_lookup(inode))
1847 retval = inode_permission(inode, MAY_EXEC);
1851 nd->path = nd->root;
1853 if (flags & LOOKUP_RCU) {
1855 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1857 path_get(&nd->path);
1862 nd->root.mnt = NULL;
1865 if (flags & LOOKUP_RCU) {
1870 path_get(&nd->root);
1872 nd->path = nd->root;
1873 } else if (dfd == AT_FDCWD) {
1874 if (flags & LOOKUP_RCU) {
1875 struct fs_struct *fs = current->fs;
1881 seq = read_seqcount_begin(&fs->seq);
1883 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1884 } while (read_seqcount_retry(&fs->seq, seq));
1886 get_fs_pwd(current->fs, &nd->path);
1889 /* Caller must check execute permissions on the starting path component */
1890 struct fd f = fdget_raw(dfd);
1891 struct dentry *dentry;
1896 dentry = f.file->f_path.dentry;
1899 if (!can_lookup(dentry->d_inode)) {
1905 nd->path = f.file->f_path;
1906 if (flags & LOOKUP_RCU) {
1909 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1912 path_get(&nd->path);
1917 nd->inode = nd->path.dentry->d_inode;
1921 static inline int lookup_last(struct nameidata *nd, struct path *path)
1923 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
1924 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
1926 nd->flags &= ~LOOKUP_PARENT;
1927 return walk_component(nd, path, nd->flags & LOOKUP_FOLLOW);
1930 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1931 static int path_lookupat(int dfd, const char *name,
1932 unsigned int flags, struct nameidata *nd)
1934 struct file *base = NULL;
1939 * Path walking is largely split up into 2 different synchronisation
1940 * schemes, rcu-walk and ref-walk (explained in
1941 * Documentation/filesystems/path-lookup.txt). These share much of the
1942 * path walk code, but some things particularly setup, cleanup, and
1943 * following mounts are sufficiently divergent that functions are
1944 * duplicated. Typically there is a function foo(), and its RCU
1945 * analogue, foo_rcu().
1947 * -ECHILD is the error number of choice (just to avoid clashes) that
1948 * is returned if some aspect of an rcu-walk fails. Such an error must
1949 * be handled by restarting a traditional ref-walk (which will always
1950 * be able to complete).
1952 err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base);
1957 current->total_link_count = 0;
1958 err = link_path_walk(name, nd);
1960 if (!err && !(flags & LOOKUP_PARENT)) {
1961 err = lookup_last(nd, &path);
1964 struct path link = path;
1965 err = may_follow_link(&link, nd);
1968 nd->flags |= LOOKUP_PARENT;
1969 err = follow_link(&link, nd, &cookie);
1972 err = lookup_last(nd, &path);
1973 put_link(nd, &link, cookie);
1978 err = complete_walk(nd);
1980 if (!err && nd->flags & LOOKUP_DIRECTORY) {
1981 if (!can_lookup(nd->inode)) {
1982 path_put(&nd->path);
1990 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
1991 path_put(&nd->root);
1992 nd->root.mnt = NULL;
1997 static int filename_lookup(int dfd, struct filename *name,
1998 unsigned int flags, struct nameidata *nd)
2000 int retval = path_lookupat(dfd, name->name, flags | LOOKUP_RCU, nd);
2001 if (unlikely(retval == -ECHILD))
2002 retval = path_lookupat(dfd, name->name, flags, nd);
2003 if (unlikely(retval == -ESTALE))
2004 retval = path_lookupat(dfd, name->name,
2005 flags | LOOKUP_REVAL, nd);
2007 if (likely(!retval))
2008 audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT);
2012 static int do_path_lookup(int dfd, const char *name,
2013 unsigned int flags, struct nameidata *nd)
2015 struct filename filename = { .name = name };
2017 return filename_lookup(dfd, &filename, flags, nd);
2020 /* does lookup, returns the object with parent locked */
2021 struct dentry *kern_path_locked(const char *name, struct path *path)
2023 struct nameidata nd;
2025 int err = do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, &nd);
2027 return ERR_PTR(err);
2028 if (nd.last_type != LAST_NORM) {
2030 return ERR_PTR(-EINVAL);
2032 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2033 d = __lookup_hash(&nd.last, nd.path.dentry, 0);
2035 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2043 int kern_path(const char *name, unsigned int flags, struct path *path)
2045 struct nameidata nd;
2046 int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
2053 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2054 * @dentry: pointer to dentry of the base directory
2055 * @mnt: pointer to vfs mount of the base directory
2056 * @name: pointer to file name
2057 * @flags: lookup flags
2058 * @path: pointer to struct path to fill
2060 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
2061 const char *name, unsigned int flags,
2064 struct nameidata nd;
2066 nd.root.dentry = dentry;
2068 BUG_ON(flags & LOOKUP_PARENT);
2069 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
2070 err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd);
2077 * Restricted form of lookup. Doesn't follow links, single-component only,
2078 * needs parent already locked. Doesn't follow mounts.
2081 static struct dentry *lookup_hash(struct nameidata *nd)
2083 return __lookup_hash(&nd->last, nd->path.dentry, nd->flags);
2087 * lookup_one_len - filesystem helper to lookup single pathname component
2088 * @name: pathname component to lookup
2089 * @base: base directory to lookup from
2090 * @len: maximum length @len should be interpreted to
2092 * Note that this routine is purely a helper for filesystem usage and should
2093 * not be called by generic code. Also note that by using this function the
2094 * nameidata argument is passed to the filesystem methods and a filesystem
2095 * using this helper needs to be prepared for that.
2097 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
2103 WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
2107 this.hash = full_name_hash(name, len);
2109 return ERR_PTR(-EACCES);
2111 if (unlikely(name[0] == '.')) {
2112 if (len < 2 || (len == 2 && name[1] == '.'))
2113 return ERR_PTR(-EACCES);
2117 c = *(const unsigned char *)name++;
2118 if (c == '/' || c == '\0')
2119 return ERR_PTR(-EACCES);
2122 * See if the low-level filesystem might want
2123 * to use its own hash..
2125 if (base->d_flags & DCACHE_OP_HASH) {
2126 int err = base->d_op->d_hash(base, base->d_inode, &this);
2128 return ERR_PTR(err);
2131 err = inode_permission(base->d_inode, MAY_EXEC);
2133 return ERR_PTR(err);
2135 return __lookup_hash(&this, base, 0);
2138 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
2139 struct path *path, int *empty)
2141 struct nameidata nd;
2142 struct filename *tmp = getname_flags(name, flags, empty);
2143 int err = PTR_ERR(tmp);
2146 BUG_ON(flags & LOOKUP_PARENT);
2148 err = filename_lookup(dfd, tmp, flags, &nd);
2156 int user_path_at(int dfd, const char __user *name, unsigned flags,
2159 return user_path_at_empty(dfd, name, flags, path, NULL);
2163 * NB: most callers don't do anything directly with the reference to the
2164 * to struct filename, but the nd->last pointer points into the name string
2165 * allocated by getname. So we must hold the reference to it until all
2166 * path-walking is complete.
2168 static struct filename *
2169 user_path_parent(int dfd, const char __user *path, struct nameidata *nd,
2172 struct filename *s = getname(path);
2175 /* only LOOKUP_REVAL is allowed in extra flags */
2176 flags &= LOOKUP_REVAL;
2181 error = filename_lookup(dfd, s, flags | LOOKUP_PARENT, nd);
2184 return ERR_PTR(error);
2191 * It's inline, so penalty for filesystems that don't use sticky bit is
2194 static inline int check_sticky(struct inode *dir, struct inode *inode)
2196 kuid_t fsuid = current_fsuid();
2198 if (!(dir->i_mode & S_ISVTX))
2200 if (uid_eq(inode->i_uid, fsuid))
2202 if (uid_eq(dir->i_uid, fsuid))
2204 return !capable_wrt_inode_uidgid(inode, CAP_FOWNER);
2208 * Check whether we can remove a link victim from directory dir, check
2209 * whether the type of victim is right.
2210 * 1. We can't do it if dir is read-only (done in permission())
2211 * 2. We should have write and exec permissions on dir
2212 * 3. We can't remove anything from append-only dir
2213 * 4. We can't do anything with immutable dir (done in permission())
2214 * 5. If the sticky bit on dir is set we should either
2215 * a. be owner of dir, or
2216 * b. be owner of victim, or
2217 * c. have CAP_FOWNER capability
2218 * 6. If the victim is append-only or immutable we can't do antyhing with
2219 * links pointing to it.
2220 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2221 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2222 * 9. We can't remove a root or mountpoint.
2223 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2224 * nfs_async_unlink().
2226 static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
2230 if (!victim->d_inode)
2233 BUG_ON(victim->d_parent->d_inode != dir);
2234 audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
2236 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
2241 if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
2242 IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
2245 if (!S_ISDIR(victim->d_inode->i_mode))
2247 if (IS_ROOT(victim))
2249 } else if (S_ISDIR(victim->d_inode->i_mode))
2251 if (IS_DEADDIR(dir))
2253 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2258 /* Check whether we can create an object with dentry child in directory
2260 * 1. We can't do it if child already exists (open has special treatment for
2261 * this case, but since we are inlined it's OK)
2262 * 2. We can't do it if dir is read-only (done in permission())
2263 * 3. We should have write and exec permissions on dir
2264 * 4. We can't do it if dir is immutable (done in permission())
2266 static inline int may_create(struct inode *dir, struct dentry *child)
2268 audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
2271 if (IS_DEADDIR(dir))
2273 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
2277 * p1 and p2 should be directories on the same fs.
2279 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2284 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2288 mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2290 p = d_ancestor(p2, p1);
2292 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
2293 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
2297 p = d_ancestor(p1, p2);
2299 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2300 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2304 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2305 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2309 void unlock_rename(struct dentry *p1, struct dentry *p2)
2311 mutex_unlock(&p1->d_inode->i_mutex);
2313 mutex_unlock(&p2->d_inode->i_mutex);
2314 mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2318 int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2321 int error = may_create(dir, dentry);
2325 if (!dir->i_op->create)
2326 return -EACCES; /* shouldn't it be ENOSYS? */
2329 error = security_inode_create(dir, dentry, mode);
2332 error = dir->i_op->create(dir, dentry, mode, want_excl);
2334 fsnotify_create(dir, dentry);
2338 static int may_open(struct path *path, int acc_mode, int flag)
2340 struct dentry *dentry = path->dentry;
2341 struct inode *inode = dentry->d_inode;
2351 switch (inode->i_mode & S_IFMT) {
2355 if (acc_mode & MAY_WRITE)
2360 if (path->mnt->mnt_flags & MNT_NODEV)
2369 error = inode_permission(inode, acc_mode);
2374 * An append-only file must be opened in append mode for writing.
2376 if (IS_APPEND(inode)) {
2377 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
2383 /* O_NOATIME can only be set by the owner or superuser */
2384 if (flag & O_NOATIME && !inode_owner_or_capable(inode))
2390 static int handle_truncate(struct file *filp)
2392 struct path *path = &filp->f_path;
2393 struct inode *inode = path->dentry->d_inode;
2394 int error = get_write_access(inode);
2398 * Refuse to truncate files with mandatory locks held on them.
2400 error = locks_verify_locked(inode);
2402 error = security_path_truncate(path);
2404 error = do_truncate(path->dentry, 0,
2405 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
2408 put_write_access(inode);
2412 static inline int open_to_namei_flags(int flag)
2414 if ((flag & O_ACCMODE) == 3)
2419 static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode)
2421 int error = security_path_mknod(dir, dentry, mode, 0);
2425 error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
2429 return security_inode_create(dir->dentry->d_inode, dentry, mode);
2433 * Attempt to atomically look up, create and open a file from a negative
2436 * Returns 0 if successful. The file will have been created and attached to
2437 * @file by the filesystem calling finish_open().
2439 * Returns 1 if the file was looked up only or didn't need creating. The
2440 * caller will need to perform the open themselves. @path will have been
2441 * updated to point to the new dentry. This may be negative.
2443 * Returns an error code otherwise.
2445 static int atomic_open(struct nameidata *nd, struct dentry *dentry,
2446 struct path *path, struct file *file,
2447 const struct open_flags *op,
2448 bool got_write, bool need_lookup,
2451 struct inode *dir = nd->path.dentry->d_inode;
2452 unsigned open_flag = open_to_namei_flags(op->open_flag);
2456 int create_error = 0;
2457 struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
2459 BUG_ON(dentry->d_inode);
2461 /* Don't create child dentry for a dead directory. */
2462 if (unlikely(IS_DEADDIR(dir))) {
2468 if ((open_flag & O_CREAT) && !IS_POSIXACL(dir))
2469 mode &= ~current_umask();
2471 if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT)) {
2472 open_flag &= ~O_TRUNC;
2473 *opened |= FILE_CREATED;
2477 * Checking write permission is tricky, bacuse we don't know if we are
2478 * going to actually need it: O_CREAT opens should work as long as the
2479 * file exists. But checking existence breaks atomicity. The trick is
2480 * to check access and if not granted clear O_CREAT from the flags.
2482 * Another problem is returing the "right" error value (e.g. for an
2483 * O_EXCL open we want to return EEXIST not EROFS).
2485 if (((open_flag & (O_CREAT | O_TRUNC)) ||
2486 (open_flag & O_ACCMODE) != O_RDONLY) && unlikely(!got_write)) {
2487 if (!(open_flag & O_CREAT)) {
2489 * No O_CREATE -> atomicity not a requirement -> fall
2490 * back to lookup + open
2493 } else if (open_flag & (O_EXCL | O_TRUNC)) {
2494 /* Fall back and fail with the right error */
2495 create_error = -EROFS;
2498 /* No side effects, safe to clear O_CREAT */
2499 create_error = -EROFS;
2500 open_flag &= ~O_CREAT;
2504 if (open_flag & O_CREAT) {
2505 error = may_o_create(&nd->path, dentry, mode);
2507 create_error = error;
2508 if (open_flag & O_EXCL)
2510 open_flag &= ~O_CREAT;
2514 if (nd->flags & LOOKUP_DIRECTORY)
2515 open_flag |= O_DIRECTORY;
2517 file->f_path.dentry = DENTRY_NOT_SET;
2518 file->f_path.mnt = nd->path.mnt;
2519 error = dir->i_op->atomic_open(dir, dentry, file, open_flag, mode,
2522 if (create_error && error == -ENOENT)
2523 error = create_error;
2527 acc_mode = op->acc_mode;
2528 if (*opened & FILE_CREATED) {
2529 fsnotify_create(dir, dentry);
2530 acc_mode = MAY_OPEN;
2533 if (error) { /* returned 1, that is */
2534 if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
2538 if (file->f_path.dentry) {
2540 dentry = file->f_path.dentry;
2542 if (create_error && dentry->d_inode == NULL) {
2543 error = create_error;
2550 * We didn't have the inode before the open, so check open permission
2553 error = may_open(&file->f_path, acc_mode, open_flag);
2563 dentry = lookup_real(dir, dentry, nd->flags);
2565 return PTR_ERR(dentry);
2568 int open_flag = op->open_flag;
2570 error = create_error;
2571 if ((open_flag & O_EXCL)) {
2572 if (!dentry->d_inode)
2574 } else if (!dentry->d_inode) {
2576 } else if ((open_flag & O_TRUNC) &&
2577 S_ISREG(dentry->d_inode->i_mode)) {
2580 /* will fail later, go on to get the right error */
2584 path->dentry = dentry;
2585 path->mnt = nd->path.mnt;
2590 * Look up and maybe create and open the last component.
2592 * Must be called with i_mutex held on parent.
2594 * Returns 0 if the file was successfully atomically created (if necessary) and
2595 * opened. In this case the file will be returned attached to @file.
2597 * Returns 1 if the file was not completely opened at this time, though lookups
2598 * and creations will have been performed and the dentry returned in @path will
2599 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
2600 * specified then a negative dentry may be returned.
2602 * An error code is returned otherwise.
2604 * FILE_CREATE will be set in @*opened if the dentry was created and will be
2605 * cleared otherwise prior to returning.
2607 static int lookup_open(struct nameidata *nd, struct path *path,
2609 const struct open_flags *op,
2610 bool got_write, int *opened)
2612 struct dentry *dir = nd->path.dentry;
2613 struct inode *dir_inode = dir->d_inode;
2614 struct dentry *dentry;
2618 *opened &= ~FILE_CREATED;
2619 dentry = lookup_dcache(&nd->last, dir, nd->flags, &need_lookup);
2621 return PTR_ERR(dentry);
2623 /* Cached positive dentry: will open in f_op->open */
2624 if (!need_lookup && dentry->d_inode)
2627 if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) {
2628 return atomic_open(nd, dentry, path, file, op, got_write,
2629 need_lookup, opened);
2633 BUG_ON(dentry->d_inode);
2635 dentry = lookup_real(dir_inode, dentry, nd->flags);
2637 return PTR_ERR(dentry);
2640 /* Negative dentry, just create the file */
2641 if (!dentry->d_inode && (op->open_flag & O_CREAT)) {
2642 umode_t mode = op->mode;
2643 if (!IS_POSIXACL(dir->d_inode))
2644 mode &= ~current_umask();
2646 * This write is needed to ensure that a
2647 * rw->ro transition does not occur between
2648 * the time when the file is created and when
2649 * a permanent write count is taken through
2650 * the 'struct file' in finish_open().
2656 *opened |= FILE_CREATED;
2657 error = security_path_mknod(&nd->path, dentry, mode, 0);
2660 error = vfs_create(dir->d_inode, dentry, mode,
2661 nd->flags & LOOKUP_EXCL);
2666 path->dentry = dentry;
2667 path->mnt = nd->path.mnt;
2676 * Handle the last step of open()
2678 static int do_last(struct nameidata *nd, struct path *path,
2679 struct file *file, const struct open_flags *op,
2680 int *opened, struct filename *name)
2682 struct dentry *dir = nd->path.dentry;
2683 int open_flag = op->open_flag;
2684 bool will_truncate = (open_flag & O_TRUNC) != 0;
2685 bool got_write = false;
2686 int acc_mode = op->acc_mode;
2687 struct inode *inode;
2688 bool symlink_ok = false;
2689 struct path save_parent = { .dentry = NULL, .mnt = NULL };
2690 bool retried = false;
2693 nd->flags &= ~LOOKUP_PARENT;
2694 nd->flags |= op->intent;
2696 switch (nd->last_type) {
2699 error = handle_dots(nd, nd->last_type);
2704 error = complete_walk(nd);
2707 audit_inode(name, nd->path.dentry, 0);
2708 if (open_flag & O_CREAT) {
2714 error = complete_walk(nd);
2717 audit_inode(name, dir, 0);
2721 if (!(open_flag & O_CREAT)) {
2722 if (nd->last.name[nd->last.len])
2723 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2724 if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
2726 /* we _can_ be in RCU mode here */
2727 error = lookup_fast(nd, path, &inode);
2734 BUG_ON(nd->inode != dir->d_inode);
2736 /* create side of things */
2738 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
2739 * has been cleared when we got to the last component we are
2742 error = complete_walk(nd);
2746 audit_inode(name, dir, LOOKUP_PARENT);
2748 /* trailing slashes? */
2749 if (nd->last.name[nd->last.len])
2754 if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
2755 error = mnt_want_write(nd->path.mnt);
2759 * do _not_ fail yet - we might not need that or fail with
2760 * a different error; let lookup_open() decide; we'll be
2761 * dropping this one anyway.
2764 mutex_lock(&dir->d_inode->i_mutex);
2765 error = lookup_open(nd, path, file, op, got_write, opened);
2766 mutex_unlock(&dir->d_inode->i_mutex);
2772 if ((*opened & FILE_CREATED) ||
2773 !S_ISREG(file_inode(file)->i_mode))
2774 will_truncate = false;
2776 audit_inode(name, file->f_path.dentry, 0);
2780 if (*opened & FILE_CREATED) {
2781 /* Don't check for write permission, don't truncate */
2782 open_flag &= ~O_TRUNC;
2783 will_truncate = false;
2784 acc_mode = MAY_OPEN;
2785 path_to_nameidata(path, nd);
2786 goto finish_open_created;
2790 * create/update audit record if it already exists.
2792 if (path->dentry->d_inode)
2793 audit_inode(name, path->dentry, 0);
2796 * If atomic_open() acquired write access it is dropped now due to
2797 * possible mount and symlink following (this might be optimized away if
2801 mnt_drop_write(nd->path.mnt);
2806 if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))
2809 error = follow_managed(path, nd->flags);
2814 nd->flags |= LOOKUP_JUMPED;
2816 BUG_ON(nd->flags & LOOKUP_RCU);
2817 inode = path->dentry->d_inode;
2819 /* we _can_ be in RCU mode here */
2822 path_to_nameidata(path, nd);
2826 if (should_follow_link(inode, !symlink_ok)) {
2827 if (nd->flags & LOOKUP_RCU) {
2828 if (unlikely(nd->path.mnt != path->mnt ||
2829 unlazy_walk(nd, path->dentry))) {
2834 BUG_ON(inode != path->dentry->d_inode);
2838 if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path->mnt) {
2839 path_to_nameidata(path, nd);
2841 save_parent.dentry = nd->path.dentry;
2842 save_parent.mnt = mntget(path->mnt);
2843 nd->path.dentry = path->dentry;
2847 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
2848 error = complete_walk(nd);
2850 path_put(&save_parent);
2854 if ((open_flag & O_CREAT) && S_ISDIR(nd->inode->i_mode))
2857 if ((nd->flags & LOOKUP_DIRECTORY) && !can_lookup(nd->inode))
2859 audit_inode(name, nd->path.dentry, 0);
2861 if (!S_ISREG(nd->inode->i_mode))
2862 will_truncate = false;
2864 if (will_truncate) {
2865 error = mnt_want_write(nd->path.mnt);
2870 finish_open_created:
2871 error = may_open(&nd->path, acc_mode, open_flag);
2874 file->f_path.mnt = nd->path.mnt;
2875 error = finish_open(file, nd->path.dentry, NULL, opened);
2877 if (error == -EOPENSTALE)
2882 error = open_check_o_direct(file);
2885 error = ima_file_check(file, op->acc_mode);
2889 if (will_truncate) {
2890 error = handle_truncate(file);
2896 mnt_drop_write(nd->path.mnt);
2897 path_put(&save_parent);
2902 path_put_conditional(path, nd);
2909 /* If no saved parent or already retried then can't retry */
2910 if (!save_parent.dentry || retried)
2913 BUG_ON(save_parent.dentry != dir);
2914 path_put(&nd->path);
2915 nd->path = save_parent;
2916 nd->inode = dir->d_inode;
2917 save_parent.mnt = NULL;
2918 save_parent.dentry = NULL;
2920 mnt_drop_write(nd->path.mnt);
2927 static struct file *path_openat(int dfd, struct filename *pathname,
2928 struct nameidata *nd, const struct open_flags *op, int flags)
2930 struct file *base = NULL;
2936 file = get_empty_filp();
2940 file->f_flags = op->open_flag;
2942 error = path_init(dfd, pathname->name, flags | LOOKUP_PARENT, nd, &base);
2943 if (unlikely(error))
2946 current->total_link_count = 0;
2947 error = link_path_walk(pathname->name, nd);
2948 if (unlikely(error))
2951 error = do_last(nd, &path, file, op, &opened, pathname);
2952 while (unlikely(error > 0)) { /* trailing symlink */
2953 struct path link = path;
2955 if (!(nd->flags & LOOKUP_FOLLOW)) {
2956 path_put_conditional(&path, nd);
2957 path_put(&nd->path);
2961 error = may_follow_link(&link, nd);
2962 if (unlikely(error))
2964 nd->flags |= LOOKUP_PARENT;
2965 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
2966 error = follow_link(&link, nd, &cookie);
2967 if (unlikely(error))
2969 error = do_last(nd, &path, file, op, &opened, pathname);
2970 put_link(nd, &link, cookie);
2973 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
2974 path_put(&nd->root);
2977 if (!(opened & FILE_OPENED)) {
2981 if (unlikely(error)) {
2982 if (error == -EOPENSTALE) {
2983 if (flags & LOOKUP_RCU)
2988 file = ERR_PTR(error);
2993 struct file *do_filp_open(int dfd, struct filename *pathname,
2994 const struct open_flags *op, int flags)
2996 struct nameidata nd;
2999 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
3000 if (unlikely(filp == ERR_PTR(-ECHILD)))
3001 filp = path_openat(dfd, pathname, &nd, op, flags);
3002 if (unlikely(filp == ERR_PTR(-ESTALE)))
3003 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
3007 struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
3008 const char *name, const struct open_flags *op, int flags)
3010 struct nameidata nd;
3012 struct filename filename = { .name = name };
3015 nd.root.dentry = dentry;
3017 flags |= LOOKUP_ROOT;
3019 if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
3020 return ERR_PTR(-ELOOP);
3022 file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_RCU);
3023 if (unlikely(file == ERR_PTR(-ECHILD)))
3024 file = path_openat(-1, &filename, &nd, op, flags);
3025 if (unlikely(file == ERR_PTR(-ESTALE)))
3026 file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_REVAL);
3030 struct dentry *kern_path_create(int dfd, const char *pathname,
3031 struct path *path, unsigned int lookup_flags)
3033 struct dentry *dentry = ERR_PTR(-EEXIST);
3034 struct nameidata nd;
3037 bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
3040 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3041 * other flags passed in are ignored!
3043 lookup_flags &= LOOKUP_REVAL;
3045 error = do_path_lookup(dfd, pathname, LOOKUP_PARENT|lookup_flags, &nd);
3047 return ERR_PTR(error);
3050 * Yucky last component or no last component at all?
3051 * (foo/., foo/.., /////)
3053 if (nd.last_type != LAST_NORM)
3055 nd.flags &= ~LOOKUP_PARENT;
3056 nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL;
3058 /* don't fail immediately if it's r/o, at least try to report other errors */
3059 err2 = mnt_want_write(nd.path.mnt);
3061 * Do the final lookup.
3063 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
3064 dentry = lookup_hash(&nd);
3069 if (dentry->d_inode)
3072 * Special case - lookup gave negative, but... we had foo/bar/
3073 * From the vfs_mknod() POV we just have a negative dentry -
3074 * all is fine. Let's be bastards - you had / on the end, you've
3075 * been asking for (non-existent) directory. -ENOENT for you.
3077 if (unlikely(!is_dir && nd.last.name[nd.last.len])) {
3081 if (unlikely(err2)) {
3089 dentry = ERR_PTR(error);
3091 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3093 mnt_drop_write(nd.path.mnt);
3098 EXPORT_SYMBOL(kern_path_create);
3100 void done_path_create(struct path *path, struct dentry *dentry)
3103 mutex_unlock(&path->dentry->d_inode->i_mutex);
3104 mnt_drop_write(path->mnt);
3107 EXPORT_SYMBOL(done_path_create);
3109 struct dentry *user_path_create(int dfd, const char __user *pathname,
3110 struct path *path, unsigned int lookup_flags)
3112 struct filename *tmp = getname(pathname);
3115 return ERR_CAST(tmp);
3116 res = kern_path_create(dfd, tmp->name, path, lookup_flags);
3120 EXPORT_SYMBOL(user_path_create);
3122 int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
3124 int error = may_create(dir, dentry);
3129 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
3132 if (!dir->i_op->mknod)
3135 error = devcgroup_inode_mknod(mode, dev);
3139 error = security_inode_mknod(dir, dentry, mode, dev);
3143 error = dir->i_op->mknod(dir, dentry, mode, dev);
3145 fsnotify_create(dir, dentry);
3149 static int may_mknod(umode_t mode)
3151 switch (mode & S_IFMT) {
3157 case 0: /* zero mode translates to S_IFREG */
3166 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
3169 struct dentry *dentry;
3172 unsigned int lookup_flags = 0;
3174 error = may_mknod(mode);
3178 dentry = user_path_create(dfd, filename, &path, lookup_flags);
3180 return PTR_ERR(dentry);
3182 if (!IS_POSIXACL(path.dentry->d_inode))
3183 mode &= ~current_umask();
3184 error = security_path_mknod(&path, dentry, mode, dev);
3187 switch (mode & S_IFMT) {
3188 case 0: case S_IFREG:
3189 error = vfs_create(path.dentry->d_inode,dentry,mode,true);
3191 case S_IFCHR: case S_IFBLK:
3192 error = vfs_mknod(path.dentry->d_inode,dentry,mode,
3193 new_decode_dev(dev));
3195 case S_IFIFO: case S_IFSOCK:
3196 error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
3200 done_path_create(&path, dentry);
3201 if (retry_estale(error, lookup_flags)) {
3202 lookup_flags |= LOOKUP_REVAL;
3208 SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
3210 return sys_mknodat(AT_FDCWD, filename, mode, dev);
3213 int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
3215 int error = may_create(dir, dentry);
3216 unsigned max_links = dir->i_sb->s_max_links;
3221 if (!dir->i_op->mkdir)
3224 mode &= (S_IRWXUGO|S_ISVTX);
3225 error = security_inode_mkdir(dir, dentry, mode);
3229 if (max_links && dir->i_nlink >= max_links)
3232 error = dir->i_op->mkdir(dir, dentry, mode);
3234 fsnotify_mkdir(dir, dentry);
3238 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
3240 struct dentry *dentry;
3243 unsigned int lookup_flags = LOOKUP_DIRECTORY;
3246 dentry = user_path_create(dfd, pathname, &path, lookup_flags);
3248 return PTR_ERR(dentry);
3250 if (!IS_POSIXACL(path.dentry->d_inode))
3251 mode &= ~current_umask();
3252 error = security_path_mkdir(&path, dentry, mode);
3254 error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
3255 done_path_create(&path, dentry);
3256 if (retry_estale(error, lookup_flags)) {
3257 lookup_flags |= LOOKUP_REVAL;
3263 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
3265 return sys_mkdirat(AT_FDCWD, pathname, mode);
3269 * The dentry_unhash() helper will try to drop the dentry early: we
3270 * should have a usage count of 1 if we're the only user of this
3271 * dentry, and if that is true (possibly after pruning the dcache),
3272 * then we drop the dentry now.
3274 * A low-level filesystem can, if it choses, legally
3277 * if (!d_unhashed(dentry))
3280 * if it cannot handle the case of removing a directory
3281 * that is still in use by something else..
3283 void dentry_unhash(struct dentry *dentry)
3285 shrink_dcache_parent(dentry);
3286 spin_lock(&dentry->d_lock);
3287 if (dentry->d_count == 1)
3289 spin_unlock(&dentry->d_lock);
3292 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
3294 int error = may_delete(dir, dentry, 1);
3299 if (!dir->i_op->rmdir)
3303 mutex_lock(&dentry->d_inode->i_mutex);
3306 if (d_mountpoint(dentry))
3309 error = security_inode_rmdir(dir, dentry);
3313 shrink_dcache_parent(dentry);
3314 error = dir->i_op->rmdir(dir, dentry);
3318 dentry->d_inode->i_flags |= S_DEAD;
3322 mutex_unlock(&dentry->d_inode->i_mutex);
3329 static long do_rmdir(int dfd, const char __user *pathname)
3332 struct filename *name;
3333 struct dentry *dentry;
3334 struct nameidata nd;
3335 unsigned int lookup_flags = 0;
3337 name = user_path_parent(dfd, pathname, &nd, lookup_flags);
3339 return PTR_ERR(name);
3341 switch(nd.last_type) {
3353 nd.flags &= ~LOOKUP_PARENT;
3354 error = mnt_want_write(nd.path.mnt);
3358 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
3359 dentry = lookup_hash(&nd);
3360 error = PTR_ERR(dentry);
3363 if (!dentry->d_inode) {
3367 error = security_path_rmdir(&nd.path, dentry);
3370 error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
3374 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3375 mnt_drop_write(nd.path.mnt);
3379 if (retry_estale(error, lookup_flags)) {
3380 lookup_flags |= LOOKUP_REVAL;
3386 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
3388 return do_rmdir(AT_FDCWD, pathname);
3391 int vfs_unlink(struct inode *dir, struct dentry *dentry)
3393 int error = may_delete(dir, dentry, 0);
3398 if (!dir->i_op->unlink)
3401 mutex_lock(&dentry->d_inode->i_mutex);
3402 if (d_mountpoint(dentry))
3405 error = security_inode_unlink(dir, dentry);
3407 error = dir->i_op->unlink(dir, dentry);
3412 mutex_unlock(&dentry->d_inode->i_mutex);
3414 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3415 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
3416 fsnotify_link_count(dentry->d_inode);
3424 * Make sure that the actual truncation of the file will occur outside its
3425 * directory's i_mutex. Truncate can take a long time if there is a lot of
3426 * writeout happening, and we don't want to prevent access to the directory
3427 * while waiting on the I/O.
3429 static long do_unlinkat(int dfd, const char __user *pathname)
3432 struct filename *name;
3433 struct dentry *dentry;
3434 struct nameidata nd;
3435 struct inode *inode = NULL;
3436 unsigned int lookup_flags = 0;
3438 name = user_path_parent(dfd, pathname, &nd, lookup_flags);
3440 return PTR_ERR(name);
3443 if (nd.last_type != LAST_NORM)
3446 nd.flags &= ~LOOKUP_PARENT;
3447 error = mnt_want_write(nd.path.mnt);
3451 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
3452 dentry = lookup_hash(&nd);
3453 error = PTR_ERR(dentry);
3454 if (!IS_ERR(dentry)) {
3455 /* Why not before? Because we want correct error value */
3456 if (nd.last.name[nd.last.len])
3458 inode = dentry->d_inode;
3462 error = security_path_unlink(&nd.path, dentry);
3465 error = vfs_unlink(nd.path.dentry->d_inode, dentry);
3469 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3471 iput(inode); /* truncate the inode here */
3472 mnt_drop_write(nd.path.mnt);
3476 if (retry_estale(error, lookup_flags)) {
3477 lookup_flags |= LOOKUP_REVAL;
3484 error = !dentry->d_inode ? -ENOENT :
3485 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
3489 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
3491 if ((flag & ~AT_REMOVEDIR) != 0)
3494 if (flag & AT_REMOVEDIR)
3495 return do_rmdir(dfd, pathname);
3497 return do_unlinkat(dfd, pathname);
3500 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
3502 return do_unlinkat(AT_FDCWD, pathname);
3505 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
3507 int error = may_create(dir, dentry);
3512 if (!dir->i_op->symlink)
3515 error = security_inode_symlink(dir, dentry, oldname);
3519 error = dir->i_op->symlink(dir, dentry, oldname);
3521 fsnotify_create(dir, dentry);
3525 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
3526 int, newdfd, const char __user *, newname)
3529 struct filename *from;
3530 struct dentry *dentry;
3532 unsigned int lookup_flags = 0;
3534 from = getname(oldname);
3536 return PTR_ERR(from);
3538 dentry = user_path_create(newdfd, newname, &path, lookup_flags);
3539 error = PTR_ERR(dentry);
3543 error = security_path_symlink(&path, dentry, from->name);
3545 error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
3546 done_path_create(&path, dentry);
3547 if (retry_estale(error, lookup_flags)) {
3548 lookup_flags |= LOOKUP_REVAL;
3556 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
3558 return sys_symlinkat(oldname, AT_FDCWD, newname);
3561 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
3563 struct inode *inode = old_dentry->d_inode;
3564 unsigned max_links = dir->i_sb->s_max_links;
3570 error = may_create(dir, new_dentry);
3574 if (dir->i_sb != inode->i_sb)
3578 * A link to an append-only or immutable file cannot be created.
3580 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
3582 if (!dir->i_op->link)
3584 if (S_ISDIR(inode->i_mode))
3587 error = security_inode_link(old_dentry, dir, new_dentry);
3591 mutex_lock(&inode->i_mutex);
3592 /* Make sure we don't allow creating hardlink to an unlinked file */
3593 if (inode->i_nlink == 0)
3595 else if (max_links && inode->i_nlink >= max_links)
3598 error = dir->i_op->link(old_dentry, dir, new_dentry);
3599 mutex_unlock(&inode->i_mutex);
3601 fsnotify_link(dir, inode, new_dentry);
3606 * Hardlinks are often used in delicate situations. We avoid
3607 * security-related surprises by not following symlinks on the
3610 * We don't follow them on the oldname either to be compatible
3611 * with linux 2.0, and to avoid hard-linking to directories
3612 * and other special files. --ADM
3614 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
3615 int, newdfd, const char __user *, newname, int, flags)
3617 struct dentry *new_dentry;
3618 struct path old_path, new_path;
3622 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
3625 * To use null names we require CAP_DAC_READ_SEARCH
3626 * This ensures that not everyone will be able to create
3627 * handlink using the passed filedescriptor.
3629 if (flags & AT_EMPTY_PATH) {
3630 if (!capable(CAP_DAC_READ_SEARCH))
3635 if (flags & AT_SYMLINK_FOLLOW)
3636 how |= LOOKUP_FOLLOW;
3638 error = user_path_at(olddfd, oldname, how, &old_path);
3642 new_dentry = user_path_create(newdfd, newname, &new_path,
3643 (how & LOOKUP_REVAL));
3644 error = PTR_ERR(new_dentry);
3645 if (IS_ERR(new_dentry))
3649 if (old_path.mnt != new_path.mnt)
3651 error = may_linkat(&old_path);
3652 if (unlikely(error))
3654 error = security_path_link(old_path.dentry, &new_path, new_dentry);
3657 error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry);
3659 done_path_create(&new_path, new_dentry);
3660 if (retry_estale(error, how)) {
3661 path_put(&old_path);
3662 how |= LOOKUP_REVAL;
3666 path_put(&old_path);
3671 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
3673 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
3677 * The worst of all namespace operations - renaming directory. "Perverted"
3678 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3680 * a) we can get into loop creation. Check is done in is_subdir().
3681 * b) race potential - two innocent renames can create a loop together.
3682 * That's where 4.4 screws up. Current fix: serialization on
3683 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
3685 * c) we have to lock _three_ objects - parents and victim (if it exists).
3686 * And that - after we got ->i_mutex on parents (until then we don't know
3687 * whether the target exists). Solution: try to be smart with locking
3688 * order for inodes. We rely on the fact that tree topology may change
3689 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
3690 * move will be locked. Thus we can rank directories by the tree
3691 * (ancestors first) and rank all non-directories after them.
3692 * That works since everybody except rename does "lock parent, lookup,
3693 * lock child" and rename is under ->s_vfs_rename_mutex.
3694 * HOWEVER, it relies on the assumption that any object with ->lookup()
3695 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3696 * we'd better make sure that there's no link(2) for them.
3697 * d) conversion from fhandle to dentry may come in the wrong moment - when
3698 * we are removing the target. Solution: we will have to grab ->i_mutex
3699 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
3700 * ->i_mutex on parents, which works but leads to some truly excessive
3703 static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
3704 struct inode *new_dir, struct dentry *new_dentry)
3707 struct inode *target = new_dentry->d_inode;
3708 unsigned max_links = new_dir->i_sb->s_max_links;
3711 * If we are going to change the parent - check write permissions,
3712 * we'll need to flip '..'.
3714 if (new_dir != old_dir) {
3715 error = inode_permission(old_dentry->d_inode, MAY_WRITE);
3720 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3726 mutex_lock(&target->i_mutex);
3729 if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
3733 if (max_links && !target && new_dir != old_dir &&
3734 new_dir->i_nlink >= max_links)
3738 shrink_dcache_parent(new_dentry);
3739 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3744 target->i_flags |= S_DEAD;
3745 dont_mount(new_dentry);
3749 mutex_unlock(&target->i_mutex);
3752 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3753 d_move(old_dentry,new_dentry);
3757 static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
3758 struct inode *new_dir, struct dentry *new_dentry)
3760 struct inode *target = new_dentry->d_inode;
3763 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3769 mutex_lock(&target->i_mutex);
3772 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
3775 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3780 dont_mount(new_dentry);
3781 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3782 d_move(old_dentry, new_dentry);
3785 mutex_unlock(&target->i_mutex);
3790 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
3791 struct inode *new_dir, struct dentry *new_dentry)
3794 int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
3795 const unsigned char *old_name;
3797 if (old_dentry->d_inode == new_dentry->d_inode)
3800 error = may_delete(old_dir, old_dentry, is_dir);
3804 if (!new_dentry->d_inode)
3805 error = may_create(new_dir, new_dentry);
3807 error = may_delete(new_dir, new_dentry, is_dir);
3811 if (!old_dir->i_op->rename)
3814 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
3817 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
3819 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
3821 fsnotify_move(old_dir, new_dir, old_name, is_dir,
3822 new_dentry->d_inode, old_dentry);
3823 fsnotify_oldname_free(old_name);
3828 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
3829 int, newdfd, const char __user *, newname)
3831 struct dentry *old_dir, *new_dir;
3832 struct dentry *old_dentry, *new_dentry;
3833 struct dentry *trap;
3834 struct nameidata oldnd, newnd;
3835 struct filename *from;
3836 struct filename *to;
3837 unsigned int lookup_flags = 0;
3838 bool should_retry = false;
3841 from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags);
3843 error = PTR_ERR(from);
3847 to = user_path_parent(newdfd, newname, &newnd, lookup_flags);
3849 error = PTR_ERR(to);
3854 if (oldnd.path.mnt != newnd.path.mnt)
3857 old_dir = oldnd.path.dentry;
3859 if (oldnd.last_type != LAST_NORM)
3862 new_dir = newnd.path.dentry;
3863 if (newnd.last_type != LAST_NORM)
3866 error = mnt_want_write(oldnd.path.mnt);
3870 oldnd.flags &= ~LOOKUP_PARENT;
3871 newnd.flags &= ~LOOKUP_PARENT;
3872 newnd.flags |= LOOKUP_RENAME_TARGET;
3874 trap = lock_rename(new_dir, old_dir);
3876 old_dentry = lookup_hash(&oldnd);
3877 error = PTR_ERR(old_dentry);
3878 if (IS_ERR(old_dentry))
3880 /* source must exist */
3882 if (!old_dentry->d_inode)
3884 /* unless the source is a directory trailing slashes give -ENOTDIR */
3885 if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
3887 if (oldnd.last.name[oldnd.last.len])
3889 if (newnd.last.name[newnd.last.len])
3892 /* source should not be ancestor of target */
3894 if (old_dentry == trap)
3896 new_dentry = lookup_hash(&newnd);
3897 error = PTR_ERR(new_dentry);
3898 if (IS_ERR(new_dentry))
3900 /* target should not be an ancestor of source */
3902 if (new_dentry == trap)
3905 error = security_path_rename(&oldnd.path, old_dentry,
3906 &newnd.path, new_dentry);
3909 error = vfs_rename(old_dir->d_inode, old_dentry,
3910 new_dir->d_inode, new_dentry);
3916 unlock_rename(new_dir, old_dir);
3917 mnt_drop_write(oldnd.path.mnt);
3919 if (retry_estale(error, lookup_flags))
3920 should_retry = true;
3921 path_put(&newnd.path);
3924 path_put(&oldnd.path);
3927 should_retry = false;
3928 lookup_flags |= LOOKUP_REVAL;
3935 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
3937 return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
3940 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
3944 len = PTR_ERR(link);
3949 if (len > (unsigned) buflen)
3951 if (copy_to_user(buffer, link, len))
3958 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
3959 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
3960 * using) it for any given inode is up to filesystem.
3962 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3964 struct nameidata nd;
3969 cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
3971 return PTR_ERR(cookie);
3973 res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
3974 if (dentry->d_inode->i_op->put_link)
3975 dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
3979 int vfs_follow_link(struct nameidata *nd, const char *link)
3981 return __vfs_follow_link(nd, link);
3984 /* get the link contents into pagecache */
3985 static char *page_getlink(struct dentry * dentry, struct page **ppage)
3989 struct address_space *mapping = dentry->d_inode->i_mapping;
3990 page = read_mapping_page(mapping, 0, NULL);
3995 nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
3999 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4001 struct page *page = NULL;
4002 char *s = page_getlink(dentry, &page);
4003 int res = vfs_readlink(dentry,buffer,buflen,s);
4006 page_cache_release(page);
4011 void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
4013 struct page *page = NULL;
4014 nd_set_link(nd, page_getlink(dentry, &page));
4018 void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
4020 struct page *page = cookie;
4024 page_cache_release(page);
4029 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4031 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
4033 struct address_space *mapping = inode->i_mapping;
4038 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
4040 flags |= AOP_FLAG_NOFS;
4043 err = pagecache_write_begin(NULL, mapping, 0, len-1,
4044 flags, &page, &fsdata);
4048 kaddr = kmap_atomic(page);
4049 memcpy(kaddr, symname, len-1);
4050 kunmap_atomic(kaddr);
4052 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
4059 mark_inode_dirty(inode);
4065 int page_symlink(struct inode *inode, const char *symname, int len)
4067 return __page_symlink(inode, symname, len,
4068 !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
4071 const struct inode_operations page_symlink_inode_operations = {
4072 .readlink = generic_readlink,
4073 .follow_link = page_follow_link_light,
4074 .put_link = page_put_link,
4077 EXPORT_SYMBOL(user_path_at);
4078 EXPORT_SYMBOL(follow_down_one);
4079 EXPORT_SYMBOL(follow_down);
4080 EXPORT_SYMBOL(follow_up);
4081 EXPORT_SYMBOL(get_write_access); /* nfsd */
4082 EXPORT_SYMBOL(lock_rename);
4083 EXPORT_SYMBOL(lookup_one_len);
4084 EXPORT_SYMBOL(page_follow_link_light);
4085 EXPORT_SYMBOL(page_put_link);
4086 EXPORT_SYMBOL(page_readlink);
4087 EXPORT_SYMBOL(__page_symlink);
4088 EXPORT_SYMBOL(page_symlink);
4089 EXPORT_SYMBOL(page_symlink_inode_operations);
4090 EXPORT_SYMBOL(kern_path);
4091 EXPORT_SYMBOL(vfs_path_lookup);
4092 EXPORT_SYMBOL(inode_permission);
4093 EXPORT_SYMBOL(unlock_rename);
4094 EXPORT_SYMBOL(vfs_create);
4095 EXPORT_SYMBOL(vfs_follow_link);
4096 EXPORT_SYMBOL(vfs_link);
4097 EXPORT_SYMBOL(vfs_mkdir);
4098 EXPORT_SYMBOL(vfs_mknod);
4099 EXPORT_SYMBOL(generic_permission);
4100 EXPORT_SYMBOL(vfs_readlink);
4101 EXPORT_SYMBOL(vfs_rename);
4102 EXPORT_SYMBOL(vfs_rmdir);
4103 EXPORT_SYMBOL(vfs_symlink);
4104 EXPORT_SYMBOL(vfs_unlink);
4105 EXPORT_SYMBOL(dentry_unhash);
4106 EXPORT_SYMBOL(generic_readlink);