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/module.h>
19 #include <linux/slab.h>
21 #include <linux/namei.h>
22 #include <linux/pagemap.h>
23 #include <linux/fsnotify.h>
24 #include <linux/personality.h>
25 #include <linux/security.h>
26 #include <linux/ima.h>
27 #include <linux/syscalls.h>
28 #include <linux/mount.h>
29 #include <linux/audit.h>
30 #include <linux/capability.h>
31 #include <linux/file.h>
32 #include <linux/fcntl.h>
33 #include <linux/device_cgroup.h>
34 #include <linux/fs_struct.h>
35 #include <asm/uaccess.h>
39 /* [Feb-1997 T. Schoebel-Theuer]
40 * Fundamental changes in the pathname lookup mechanisms (namei)
41 * were necessary because of omirr. The reason is that omirr needs
42 * to know the _real_ pathname, not the user-supplied one, in case
43 * of symlinks (and also when transname replacements occur).
45 * The new code replaces the old recursive symlink resolution with
46 * an iterative one (in case of non-nested symlink chains). It does
47 * this with calls to <fs>_follow_link().
48 * As a side effect, dir_namei(), _namei() and follow_link() are now
49 * replaced with a single function lookup_dentry() that can handle all
50 * the special cases of the former code.
52 * With the new dcache, the pathname is stored at each inode, at least as
53 * long as the refcount of the inode is positive. As a side effect, the
54 * size of the dcache depends on the inode cache and thus is dynamic.
56 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
57 * resolution to correspond with current state of the code.
59 * Note that the symlink resolution is not *completely* iterative.
60 * There is still a significant amount of tail- and mid- recursion in
61 * the algorithm. Also, note that <fs>_readlink() is not used in
62 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
63 * may return different results than <fs>_follow_link(). Many virtual
64 * filesystems (including /proc) exhibit this behavior.
67 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
68 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
69 * and the name already exists in form of a symlink, try to create the new
70 * name indicated by the symlink. The old code always complained that the
71 * name already exists, due to not following the symlink even if its target
72 * is nonexistent. The new semantics affects also mknod() and link() when
73 * the name is a symlink pointing to a non-existant name.
75 * I don't know which semantics is the right one, since I have no access
76 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
77 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
78 * "old" one. Personally, I think the new semantics is much more logical.
79 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
80 * file does succeed in both HP-UX and SunOs, but not in Solaris
81 * and in the old Linux semantics.
84 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
85 * semantics. See the comments in "open_namei" and "do_link" below.
87 * [10-Sep-98 Alan Modra] Another symlink change.
90 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
91 * inside the path - always follow.
92 * in the last component in creation/removal/renaming - never follow.
93 * if LOOKUP_FOLLOW passed - follow.
94 * if the pathname has trailing slashes - follow.
95 * otherwise - don't follow.
96 * (applied in that order).
98 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
99 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
100 * During the 2.4 we need to fix the userland stuff depending on it -
101 * hopefully we will be able to get rid of that wart in 2.5. So far only
102 * XEmacs seems to be relying on it...
105 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
106 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
107 * any extra contention...
110 /* In order to reduce some races, while at the same time doing additional
111 * checking and hopefully speeding things up, we copy filenames to the
112 * kernel data space before using them..
114 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
115 * PATH_MAX includes the nul terminator --RR.
117 static int do_getname(const char __user *filename, char *page)
120 unsigned long len = PATH_MAX;
122 if (!segment_eq(get_fs(), KERNEL_DS)) {
123 if ((unsigned long) filename >= TASK_SIZE)
125 if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
126 len = TASK_SIZE - (unsigned long) filename;
129 retval = strncpy_from_user(page, filename, len);
133 return -ENAMETOOLONG;
139 char * getname(const char __user * filename)
143 result = ERR_PTR(-ENOMEM);
146 int retval = do_getname(filename, tmp);
151 result = ERR_PTR(retval);
154 audit_getname(result);
158 #ifdef CONFIG_AUDITSYSCALL
159 void putname(const char *name)
161 if (unlikely(!audit_dummy_context()))
166 EXPORT_SYMBOL(putname);
170 * This does basic POSIX ACL permission checking
172 static int acl_permission_check(struct inode *inode, int mask, unsigned int flags,
173 int (*check_acl)(struct inode *inode, int mask, unsigned int flags))
175 umode_t mode = inode->i_mode;
177 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
179 if (current_fsuid() == inode->i_uid)
182 if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
183 int error = check_acl(inode, mask, flags);
184 if (error != -EAGAIN)
188 if (in_group_p(inode->i_gid))
193 * If the DACs are ok we don't need any capability check.
195 if ((mask & ~mode) == 0)
201 * generic_permission - check for access rights on a Posix-like filesystem
202 * @inode: inode to check access rights for
203 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
204 * @check_acl: optional callback to check for Posix ACLs
205 * @flags: IPERM_FLAG_ flags.
207 * Used to check for read/write/execute permissions on a file.
208 * We use "fsuid" for this, letting us set arbitrary permissions
209 * for filesystem access without changing the "normal" uids which
210 * are used for other things.
212 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
213 * request cannot be satisfied (eg. requires blocking or too much complexity).
214 * It would then be called again in ref-walk mode.
216 int generic_permission(struct inode *inode, int mask, unsigned int flags,
217 int (*check_acl)(struct inode *inode, int mask, unsigned int flags))
222 * Do the basic POSIX ACL permission checks.
224 ret = acl_permission_check(inode, mask, flags, check_acl);
229 * Read/write DACs are always overridable.
230 * Executable DACs are overridable if at least one exec bit is set.
232 if (!(mask & MAY_EXEC) || execute_ok(inode))
233 if (capable(CAP_DAC_OVERRIDE))
237 * Searching includes executable on directories, else just read.
239 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
240 if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
241 if (capable(CAP_DAC_READ_SEARCH))
248 * inode_permission - check for access rights to a given inode
249 * @inode: inode to check permission on
250 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
252 * Used to check for read/write/execute permissions on an inode.
253 * We use "fsuid" for this, letting us set arbitrary permissions
254 * for filesystem access without changing the "normal" uids which
255 * are used for other things.
257 int inode_permission(struct inode *inode, int mask)
261 if (mask & MAY_WRITE) {
262 umode_t mode = inode->i_mode;
265 * Nobody gets write access to a read-only fs.
267 if (IS_RDONLY(inode) &&
268 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
272 * Nobody gets write access to an immutable file.
274 if (IS_IMMUTABLE(inode))
278 if (inode->i_op->permission)
279 retval = inode->i_op->permission(inode, mask, 0);
281 retval = generic_permission(inode, mask, 0,
282 inode->i_op->check_acl);
287 retval = devcgroup_inode_permission(inode, mask);
291 return security_inode_permission(inode, mask);
295 * file_permission - check for additional access rights to a given file
296 * @file: file to check access rights for
297 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
299 * Used to check for read/write/execute permissions on an already opened
303 * Do not use this function in new code. All access checks should
304 * be done using inode_permission().
306 int file_permission(struct file *file, int mask)
308 return inode_permission(file->f_path.dentry->d_inode, mask);
312 * get_write_access() gets write permission for a file.
313 * put_write_access() releases this write permission.
314 * This is used for regular files.
315 * We cannot support write (and maybe mmap read-write shared) accesses and
316 * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
317 * can have the following values:
318 * 0: no writers, no VM_DENYWRITE mappings
319 * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
320 * > 0: (i_writecount) users are writing to the file.
322 * Normally we operate on that counter with atomic_{inc,dec} and it's safe
323 * except for the cases where we don't hold i_writecount yet. Then we need to
324 * use {get,deny}_write_access() - these functions check the sign and refuse
325 * to do the change if sign is wrong. Exclusion between them is provided by
326 * the inode->i_lock spinlock.
329 int get_write_access(struct inode * inode)
331 spin_lock(&inode->i_lock);
332 if (atomic_read(&inode->i_writecount) < 0) {
333 spin_unlock(&inode->i_lock);
336 atomic_inc(&inode->i_writecount);
337 spin_unlock(&inode->i_lock);
342 int deny_write_access(struct file * file)
344 struct inode *inode = file->f_path.dentry->d_inode;
346 spin_lock(&inode->i_lock);
347 if (atomic_read(&inode->i_writecount) > 0) {
348 spin_unlock(&inode->i_lock);
351 atomic_dec(&inode->i_writecount);
352 spin_unlock(&inode->i_lock);
356 EXPORT_SYMBOL(deny_write_access);
359 * path_get - get a reference to a path
360 * @path: path to get the reference to
362 * Given a path increment the reference count to the dentry and the vfsmount.
364 void path_get(struct path *path)
369 EXPORT_SYMBOL(path_get);
372 * path_put - put a reference to a path
373 * @path: path to put the reference to
375 * Given a path decrement the reference count to the dentry and the vfsmount.
377 void path_put(struct path *path)
382 EXPORT_SYMBOL(path_put);
385 * nameidata_drop_rcu - drop this nameidata out of rcu-walk
386 * @nd: nameidata pathwalk data to drop
387 * Returns: 0 on success, -ECHILD on failure
389 * Path walking has 2 modes, rcu-walk and ref-walk (see
390 * Documentation/filesystems/path-lookup.txt). __drop_rcu* functions attempt
391 * to drop out of rcu-walk mode and take normal reference counts on dentries
392 * and vfsmounts to transition to rcu-walk mode. __drop_rcu* functions take
393 * refcounts at the last known good point before rcu-walk got stuck, so
394 * ref-walk may continue from there. If this is not successful (eg. a seqcount
395 * has changed), then failure is returned and path walk restarts from the
396 * beginning in ref-walk mode.
398 * nameidata_drop_rcu attempts to drop the current nd->path and nd->root into
399 * ref-walk. Must be called from rcu-walk context.
401 static int nameidata_drop_rcu(struct nameidata *nd)
403 struct fs_struct *fs = current->fs;
404 struct dentry *dentry = nd->path.dentry;
406 BUG_ON(!(nd->flags & LOOKUP_RCU));
408 spin_lock(&fs->lock);
409 if (nd->root.mnt != fs->root.mnt ||
410 nd->root.dentry != fs->root.dentry)
413 spin_lock(&dentry->d_lock);
414 if (!__d_rcu_to_refcount(dentry, nd->seq))
416 BUG_ON(nd->inode != dentry->d_inode);
417 spin_unlock(&dentry->d_lock);
420 spin_unlock(&fs->lock);
422 mntget(nd->path.mnt);
425 br_read_unlock(vfsmount_lock);
426 nd->flags &= ~LOOKUP_RCU;
429 spin_unlock(&dentry->d_lock);
432 spin_unlock(&fs->lock);
436 /* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
437 static inline int nameidata_drop_rcu_maybe(struct nameidata *nd)
439 if (nd->flags & LOOKUP_RCU)
440 return nameidata_drop_rcu(nd);
445 * nameidata_dentry_drop_rcu - drop nameidata and dentry out of rcu-walk
446 * @nd: nameidata pathwalk data to drop
447 * @dentry: dentry to drop
448 * Returns: 0 on success, -ECHILD on failure
450 * nameidata_dentry_drop_rcu attempts to drop the current nd->path and nd->root,
451 * and dentry into ref-walk. @dentry must be a path found by a do_lookup call on
452 * @nd. Must be called from rcu-walk context.
454 static int nameidata_dentry_drop_rcu(struct nameidata *nd, struct dentry *dentry)
456 struct fs_struct *fs = current->fs;
457 struct dentry *parent = nd->path.dentry;
459 BUG_ON(!(nd->flags & LOOKUP_RCU));
461 spin_lock(&fs->lock);
462 if (nd->root.mnt != fs->root.mnt ||
463 nd->root.dentry != fs->root.dentry)
466 spin_lock(&parent->d_lock);
467 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
468 if (!__d_rcu_to_refcount(dentry, nd->seq))
471 * If the sequence check on the child dentry passed, then the child has
472 * not been removed from its parent. This means the parent dentry must
473 * be valid and able to take a reference at this point.
475 BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
476 BUG_ON(!parent->d_count);
478 spin_unlock(&dentry->d_lock);
479 spin_unlock(&parent->d_lock);
482 spin_unlock(&fs->lock);
484 mntget(nd->path.mnt);
487 br_read_unlock(vfsmount_lock);
488 nd->flags &= ~LOOKUP_RCU;
491 spin_unlock(&dentry->d_lock);
492 spin_unlock(&parent->d_lock);
495 spin_unlock(&fs->lock);
499 /* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
500 static inline int nameidata_dentry_drop_rcu_maybe(struct nameidata *nd, struct dentry *dentry)
502 if (nd->flags & LOOKUP_RCU)
503 return nameidata_dentry_drop_rcu(nd, dentry);
508 * nameidata_drop_rcu_last - drop nameidata ending path walk out of rcu-walk
509 * @nd: nameidata pathwalk data to drop
510 * Returns: 0 on success, -ECHILD on failure
512 * nameidata_drop_rcu_last attempts to drop the current nd->path into ref-walk.
513 * nd->path should be the final element of the lookup, so nd->root is discarded.
514 * Must be called from rcu-walk context.
516 static int nameidata_drop_rcu_last(struct nameidata *nd)
518 struct dentry *dentry = nd->path.dentry;
520 BUG_ON(!(nd->flags & LOOKUP_RCU));
521 nd->flags &= ~LOOKUP_RCU;
523 spin_lock(&dentry->d_lock);
524 if (!__d_rcu_to_refcount(dentry, nd->seq))
526 BUG_ON(nd->inode != dentry->d_inode);
527 spin_unlock(&dentry->d_lock);
529 mntget(nd->path.mnt);
532 br_read_unlock(vfsmount_lock);
537 spin_unlock(&dentry->d_lock);
539 br_read_unlock(vfsmount_lock);
543 /* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
544 static inline int nameidata_drop_rcu_last_maybe(struct nameidata *nd)
546 if (likely(nd->flags & LOOKUP_RCU))
547 return nameidata_drop_rcu_last(nd);
552 * release_open_intent - free up open intent resources
553 * @nd: pointer to nameidata
555 void release_open_intent(struct nameidata *nd)
557 struct file *file = nd->intent.open.file;
559 if (file && !IS_ERR(file)) {
560 if (file->f_path.dentry == NULL)
567 static inline int d_revalidate(struct dentry *dentry, struct nameidata *nd)
569 return dentry->d_op->d_revalidate(dentry, nd);
572 static struct dentry *
573 do_revalidate(struct dentry *dentry, struct nameidata *nd)
575 int status = d_revalidate(dentry, nd);
576 if (unlikely(status <= 0)) {
578 * The dentry failed validation.
579 * If d_revalidate returned 0 attempt to invalidate
580 * the dentry otherwise d_revalidate is asking us
581 * to return a fail status.
585 dentry = ERR_PTR(status);
586 } else if (!d_invalidate(dentry)) {
594 static inline struct dentry *
595 do_revalidate_rcu(struct dentry *dentry, struct nameidata *nd)
597 int status = d_revalidate(dentry, nd);
598 if (likely(status > 0))
600 if (status == -ECHILD) {
601 if (nameidata_dentry_drop_rcu(nd, dentry))
602 return ERR_PTR(-ECHILD);
603 return do_revalidate(dentry, nd);
606 return ERR_PTR(status);
607 /* Don't d_invalidate in rcu-walk mode */
608 if (nameidata_dentry_drop_rcu(nd, dentry))
609 return ERR_PTR(-ECHILD);
610 if (!d_invalidate(dentry)) {
617 static inline int need_reval_dot(struct dentry *dentry)
619 if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
622 if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
629 * force_reval_path - force revalidation of a dentry
631 * In some situations the path walking code will trust dentries without
632 * revalidating them. This causes problems for filesystems that depend on
633 * d_revalidate to handle file opens (e.g. NFSv4). When FS_REVAL_DOT is set
634 * (which indicates that it's possible for the dentry to go stale), force
635 * a d_revalidate call before proceeding.
637 * Returns 0 if the revalidation was successful. If the revalidation fails,
638 * either return the error returned by d_revalidate or -ESTALE if the
639 * revalidation it just returned 0. If d_revalidate returns 0, we attempt to
640 * invalidate the dentry. It's up to the caller to handle putting references
641 * to the path if necessary.
644 force_reval_path(struct path *path, struct nameidata *nd)
647 struct dentry *dentry = path->dentry;
650 * only check on filesystems where it's possible for the dentry to
653 if (!need_reval_dot(dentry))
656 status = d_revalidate(dentry, nd);
661 d_invalidate(dentry);
668 * Short-cut version of permission(), for calling on directories
669 * during pathname resolution. Combines parts of permission()
670 * and generic_permission(), and tests ONLY for MAY_EXEC permission.
672 * If appropriate, check DAC only. If not appropriate, or
673 * short-cut DAC fails, then call ->permission() to do more
674 * complete permission check.
676 static inline int exec_permission(struct inode *inode, unsigned int flags)
680 if (inode->i_op->permission) {
681 ret = inode->i_op->permission(inode, MAY_EXEC, flags);
683 ret = acl_permission_check(inode, MAY_EXEC, flags,
684 inode->i_op->check_acl);
691 if (capable(CAP_DAC_OVERRIDE) || capable(CAP_DAC_READ_SEARCH))
696 return security_inode_exec_permission(inode, flags);
699 static __always_inline void set_root(struct nameidata *nd)
702 get_fs_root(current->fs, &nd->root);
705 static int link_path_walk(const char *, struct nameidata *);
707 static __always_inline void set_root_rcu(struct nameidata *nd)
710 struct fs_struct *fs = current->fs;
714 seq = read_seqcount_begin(&fs->seq);
716 nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
717 } while (read_seqcount_retry(&fs->seq, seq));
721 static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
734 nd->inode = nd->path.dentry->d_inode;
736 ret = link_path_walk(link, nd);
740 return PTR_ERR(link);
743 static void path_put_conditional(struct path *path, struct nameidata *nd)
746 if (path->mnt != nd->path.mnt)
750 static inline void path_to_nameidata(const struct path *path,
751 struct nameidata *nd)
753 if (!(nd->flags & LOOKUP_RCU)) {
754 dput(nd->path.dentry);
755 if (nd->path.mnt != path->mnt)
756 mntput(nd->path.mnt);
758 nd->path.mnt = path->mnt;
759 nd->path.dentry = path->dentry;
762 static __always_inline int
763 __do_follow_link(const struct path *link, struct nameidata *nd, void **p)
766 struct dentry *dentry = link->dentry;
768 BUG_ON(nd->flags & LOOKUP_RCU);
770 touch_atime(link->mnt, dentry);
771 nd_set_link(nd, NULL);
773 if (link->mnt == nd->path.mnt)
776 nd->last_type = LAST_BIND;
777 *p = dentry->d_inode->i_op->follow_link(dentry, nd);
780 char *s = nd_get_link(nd);
783 error = __vfs_follow_link(nd, s);
784 else if (nd->last_type == LAST_BIND) {
785 error = force_reval_path(&nd->path, nd);
794 * This limits recursive symlink follows to 8, while
795 * limiting consecutive symlinks to 40.
797 * Without that kind of total limit, nasty chains of consecutive
798 * symlinks can cause almost arbitrarily long lookups.
800 static inline int do_follow_link(struct inode *inode, struct path *path, struct nameidata *nd)
805 /* We drop rcu-walk here */
806 if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry))
808 BUG_ON(inode != path->dentry->d_inode);
810 if (current->link_count >= MAX_NESTED_LINKS)
812 if (current->total_link_count >= 40)
814 BUG_ON(nd->depth >= MAX_NESTED_LINKS);
816 err = security_inode_follow_link(path->dentry, nd);
819 current->link_count++;
820 current->total_link_count++;
822 err = __do_follow_link(path, nd, &cookie);
823 if (!IS_ERR(cookie) && path->dentry->d_inode->i_op->put_link)
824 path->dentry->d_inode->i_op->put_link(path->dentry, nd, cookie);
826 current->link_count--;
830 path_put_conditional(path, nd);
835 static int follow_up_rcu(struct path *path)
837 struct vfsmount *parent;
838 struct dentry *mountpoint;
840 parent = path->mnt->mnt_parent;
841 if (parent == path->mnt)
843 mountpoint = path->mnt->mnt_mountpoint;
844 path->dentry = mountpoint;
849 int follow_up(struct path *path)
851 struct vfsmount *parent;
852 struct dentry *mountpoint;
854 br_read_lock(vfsmount_lock);
855 parent = path->mnt->mnt_parent;
856 if (parent == path->mnt) {
857 br_read_unlock(vfsmount_lock);
861 mountpoint = dget(path->mnt->mnt_mountpoint);
862 br_read_unlock(vfsmount_lock);
864 path->dentry = mountpoint;
871 * Perform an automount
872 * - return -EISDIR to tell follow_managed() to stop and return the path we
875 static int follow_automount(struct path *path, unsigned flags,
878 struct vfsmount *mnt;
881 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
884 /* We don't want to mount if someone supplied AT_NO_AUTOMOUNT
885 * and this is the terminal part of the path.
887 if ((flags & LOOKUP_NO_AUTOMOUNT) && !(flags & LOOKUP_CONTINUE))
888 return -EISDIR; /* we actually want to stop here */
890 /* We want to mount if someone is trying to open/create a file of any
891 * type under the mountpoint, wants to traverse through the mountpoint
892 * or wants to open the mounted directory.
894 * We don't want to mount if someone's just doing a stat and they've
895 * set AT_SYMLINK_NOFOLLOW - unless they're stat'ing a directory and
896 * appended a '/' to the name.
898 if (!(flags & LOOKUP_FOLLOW) &&
899 !(flags & (LOOKUP_CONTINUE | LOOKUP_DIRECTORY |
900 LOOKUP_OPEN | LOOKUP_CREATE)))
903 current->total_link_count++;
904 if (current->total_link_count >= 40)
907 mnt = path->dentry->d_op->d_automount(path);
910 * The filesystem is allowed to return -EISDIR here to indicate
911 * it doesn't want to automount. For instance, autofs would do
912 * this so that its userspace daemon can mount on this dentry.
914 * However, we can only permit this if it's a terminal point in
915 * the path being looked up; if it wasn't then the remainder of
916 * the path is inaccessible and we should say so.
918 if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_CONTINUE))
923 if (!mnt) /* mount collision */
926 err = finish_automount(mnt, path);
930 /* Someone else made a mount here whilst we were busy */
937 path->dentry = dget(mnt->mnt_root);
947 * Handle a dentry that is managed in some way.
948 * - Flagged for transit management (autofs)
949 * - Flagged as mountpoint
950 * - Flagged as automount point
952 * This may only be called in refwalk mode.
954 * Serialization is taken care of in namespace.c
956 static int follow_managed(struct path *path, unsigned flags)
959 bool need_mntput = false;
962 /* Given that we're not holding a lock here, we retain the value in a
963 * local variable for each dentry as we look at it so that we don't see
964 * the components of that value change under us */
965 while (managed = ACCESS_ONCE(path->dentry->d_flags),
966 managed &= DCACHE_MANAGED_DENTRY,
967 unlikely(managed != 0)) {
968 /* Allow the filesystem to manage the transit without i_mutex
970 if (managed & DCACHE_MANAGE_TRANSIT) {
971 BUG_ON(!path->dentry->d_op);
972 BUG_ON(!path->dentry->d_op->d_manage);
973 ret = path->dentry->d_op->d_manage(path->dentry,
976 return ret == -EISDIR ? 0 : ret;
979 /* Transit to a mounted filesystem. */
980 if (managed & DCACHE_MOUNTED) {
981 struct vfsmount *mounted = lookup_mnt(path);
987 path->dentry = dget(mounted->mnt_root);
992 /* Something is mounted on this dentry in another
993 * namespace and/or whatever was mounted there in this
994 * namespace got unmounted before we managed to get the
998 /* Handle an automount point */
999 if (managed & DCACHE_NEED_AUTOMOUNT) {
1000 ret = follow_automount(path, flags, &need_mntput);
1002 return ret == -EISDIR ? 0 : ret;
1006 /* We didn't change the current path point */
1012 int follow_down_one(struct path *path)
1014 struct vfsmount *mounted;
1016 mounted = lookup_mnt(path);
1020 path->mnt = mounted;
1021 path->dentry = dget(mounted->mnt_root);
1028 * Skip to top of mountpoint pile in rcuwalk mode. We abort the rcu-walk if we
1029 * meet a managed dentry and we're not walking to "..". True is returned to
1030 * continue, false to abort.
1032 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
1033 struct inode **inode, bool reverse_transit)
1035 while (d_mountpoint(path->dentry)) {
1036 struct vfsmount *mounted;
1037 if (unlikely(path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) &&
1039 path->dentry->d_op->d_manage(path->dentry, false, true) < 0)
1041 mounted = __lookup_mnt(path->mnt, path->dentry, 1);
1044 path->mnt = mounted;
1045 path->dentry = mounted->mnt_root;
1046 nd->seq = read_seqcount_begin(&path->dentry->d_seq);
1047 *inode = path->dentry->d_inode;
1050 if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
1051 return reverse_transit;
1055 static int follow_dotdot_rcu(struct nameidata *nd)
1057 struct inode *inode = nd->inode;
1062 if (nd->path.dentry == nd->root.dentry &&
1063 nd->path.mnt == nd->root.mnt) {
1066 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1067 struct dentry *old = nd->path.dentry;
1068 struct dentry *parent = old->d_parent;
1071 seq = read_seqcount_begin(&parent->d_seq);
1072 if (read_seqcount_retry(&old->d_seq, nd->seq))
1074 inode = parent->d_inode;
1075 nd->path.dentry = parent;
1079 if (!follow_up_rcu(&nd->path))
1081 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1082 inode = nd->path.dentry->d_inode;
1084 __follow_mount_rcu(nd, &nd->path, &inode, true);
1091 * Follow down to the covering mount currently visible to userspace. At each
1092 * point, the filesystem owning that dentry may be queried as to whether the
1093 * caller is permitted to proceed or not.
1095 * Care must be taken as namespace_sem may be held (indicated by mounting_here
1098 int follow_down(struct path *path, bool mounting_here)
1103 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1104 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
1105 /* Allow the filesystem to manage the transit without i_mutex
1108 * We indicate to the filesystem if someone is trying to mount
1109 * something here. This gives autofs the chance to deny anyone
1110 * other than its daemon the right to mount on its
1113 * The filesystem may sleep at this point.
1115 if (managed & DCACHE_MANAGE_TRANSIT) {
1116 BUG_ON(!path->dentry->d_op);
1117 BUG_ON(!path->dentry->d_op->d_manage);
1118 ret = path->dentry->d_op->d_manage(
1119 path->dentry, mounting_here, false);
1121 return ret == -EISDIR ? 0 : ret;
1124 /* Transit to a mounted filesystem. */
1125 if (managed & DCACHE_MOUNTED) {
1126 struct vfsmount *mounted = lookup_mnt(path);
1131 path->mnt = mounted;
1132 path->dentry = dget(mounted->mnt_root);
1136 /* Don't handle automount points here */
1143 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1145 static void follow_mount(struct path *path)
1147 while (d_mountpoint(path->dentry)) {
1148 struct vfsmount *mounted = lookup_mnt(path);
1153 path->mnt = mounted;
1154 path->dentry = dget(mounted->mnt_root);
1158 static void follow_dotdot(struct nameidata *nd)
1163 struct dentry *old = nd->path.dentry;
1165 if (nd->path.dentry == nd->root.dentry &&
1166 nd->path.mnt == nd->root.mnt) {
1169 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1170 /* rare case of legitimate dget_parent()... */
1171 nd->path.dentry = dget_parent(nd->path.dentry);
1175 if (!follow_up(&nd->path))
1178 follow_mount(&nd->path);
1179 nd->inode = nd->path.dentry->d_inode;
1183 * Allocate a dentry with name and parent, and perform a parent
1184 * directory ->lookup on it. Returns the new dentry, or ERR_PTR
1185 * on error. parent->d_inode->i_mutex must be held. d_lookup must
1186 * have verified that no child exists while under i_mutex.
1188 static struct dentry *d_alloc_and_lookup(struct dentry *parent,
1189 struct qstr *name, struct nameidata *nd)
1191 struct inode *inode = parent->d_inode;
1192 struct dentry *dentry;
1195 /* Don't create child dentry for a dead directory. */
1196 if (unlikely(IS_DEADDIR(inode)))
1197 return ERR_PTR(-ENOENT);
1199 dentry = d_alloc(parent, name);
1200 if (unlikely(!dentry))
1201 return ERR_PTR(-ENOMEM);
1203 old = inode->i_op->lookup(inode, dentry, nd);
1204 if (unlikely(old)) {
1212 * It's more convoluted than I'd like it to be, but... it's still fairly
1213 * small and for now I'd prefer to have fast path as straight as possible.
1214 * It _is_ time-critical.
1216 static int do_lookup(struct nameidata *nd, struct qstr *name,
1217 struct path *path, struct inode **inode)
1219 struct vfsmount *mnt = nd->path.mnt;
1220 struct dentry *dentry, *parent = nd->path.dentry;
1225 * See if the low-level filesystem might want
1226 * to use its own hash..
1228 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
1229 err = parent->d_op->d_hash(parent, nd->inode, name);
1235 * Rename seqlock is not required here because in the off chance
1236 * of a false negative due to a concurrent rename, we're going to
1237 * do the non-racy lookup, below.
1239 if (nd->flags & LOOKUP_RCU) {
1243 dentry = __d_lookup_rcu(parent, name, &seq, inode);
1245 if (nameidata_drop_rcu(nd))
1249 /* Memory barrier in read_seqcount_begin of child is enough */
1250 if (__read_seqcount_retry(&parent->d_seq, nd->seq))
1254 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1255 dentry = do_revalidate_rcu(dentry, nd);
1260 if (!(nd->flags & LOOKUP_RCU))
1264 path->dentry = dentry;
1265 if (likely(__follow_mount_rcu(nd, path, inode, false)))
1267 if (nameidata_drop_rcu(nd))
1271 dentry = __d_lookup(parent, name);
1275 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1276 dentry = do_revalidate(dentry, nd);
1284 path->dentry = dentry;
1285 err = follow_managed(path, nd->flags);
1286 if (unlikely(err < 0)) {
1287 path_put_conditional(path, nd);
1290 *inode = path->dentry->d_inode;
1294 dir = parent->d_inode;
1295 BUG_ON(nd->inode != dir);
1297 mutex_lock(&dir->i_mutex);
1299 * First re-do the cached lookup just in case it was created
1300 * while we waited for the directory semaphore, or the first
1301 * lookup failed due to an unrelated rename.
1303 * This could use version numbering or similar to avoid unnecessary
1304 * cache lookups, but then we'd have to do the first lookup in the
1305 * non-racy way. However in the common case here, everything should
1306 * be hot in cache, so would it be a big win?
1308 dentry = d_lookup(parent, name);
1309 if (likely(!dentry)) {
1310 dentry = d_alloc_and_lookup(parent, name, nd);
1311 mutex_unlock(&dir->i_mutex);
1317 * Uhhuh! Nasty case: the cache was re-populated while
1318 * we waited on the semaphore. Need to revalidate.
1320 mutex_unlock(&dir->i_mutex);
1324 return PTR_ERR(dentry);
1329 * This is the basic name resolution function, turning a pathname into
1330 * the final dentry. We expect 'base' to be positive and a directory.
1332 * Returns 0 and nd will have valid dentry and mnt on success.
1333 * Returns error and drops reference to input namei data on failure.
1335 static int link_path_walk(const char *name, struct nameidata *nd)
1339 unsigned int lookup_flags = nd->flags;
1347 lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);
1349 /* At this point we know we have a real path component. */
1351 struct inode *inode;
1356 nd->flags |= LOOKUP_CONTINUE;
1357 if (nd->flags & LOOKUP_RCU) {
1358 err = exec_permission(nd->inode, IPERM_FLAG_RCU);
1359 if (err == -ECHILD) {
1360 if (nameidata_drop_rcu(nd))
1366 err = exec_permission(nd->inode, 0);
1372 c = *(const unsigned char *)name;
1374 hash = init_name_hash();
1377 hash = partial_name_hash(c, hash);
1378 c = *(const unsigned char *)name;
1379 } while (c && (c != '/'));
1380 this.len = name - (const char *) this.name;
1381 this.hash = end_name_hash(hash);
1383 /* remove trailing slashes? */
1385 goto last_component;
1386 while (*++name == '/');
1388 goto last_with_slashes;
1391 * "." and ".." are special - ".." especially so because it has
1392 * to be able to know about the current root directory and
1393 * parent relationships.
1395 if (this.name[0] == '.') switch (this.len) {
1399 if (this.name[1] != '.')
1401 if (nd->flags & LOOKUP_RCU) {
1402 if (follow_dotdot_rcu(nd))
1410 /* This does the actual lookups.. */
1411 err = do_lookup(nd, &this, &next, &inode);
1418 if (inode->i_op->follow_link) {
1419 err = do_follow_link(inode, &next, nd);
1422 nd->inode = nd->path.dentry->d_inode;
1427 path_to_nameidata(&next, nd);
1431 if (!nd->inode->i_op->lookup)
1434 /* here ends the main loop */
1437 lookup_flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
1439 /* Clear LOOKUP_CONTINUE iff it was previously unset */
1440 nd->flags &= lookup_flags | ~LOOKUP_CONTINUE;
1441 if (lookup_flags & LOOKUP_PARENT)
1443 if (this.name[0] == '.') switch (this.len) {
1447 if (this.name[1] != '.')
1449 if (nd->flags & LOOKUP_RCU) {
1450 if (follow_dotdot_rcu(nd))
1458 err = do_lookup(nd, &this, &next, &inode);
1461 if (inode && unlikely(inode->i_op->follow_link) &&
1462 (lookup_flags & LOOKUP_FOLLOW)) {
1463 err = do_follow_link(inode, &next, nd);
1466 nd->inode = nd->path.dentry->d_inode;
1468 path_to_nameidata(&next, nd);
1474 if (lookup_flags & LOOKUP_DIRECTORY) {
1476 if (!nd->inode->i_op->lookup)
1482 nd->last_type = LAST_NORM;
1483 if (this.name[0] != '.')
1486 nd->last_type = LAST_DOT;
1487 else if (this.len == 2 && this.name[1] == '.')
1488 nd->last_type = LAST_DOTDOT;
1493 * We bypassed the ordinary revalidation routines.
1494 * We may need to check the cached dentry for staleness.
1496 if (need_reval_dot(nd->path.dentry)) {
1497 if (nameidata_drop_rcu_last_maybe(nd))
1499 /* Note: we do not d_invalidate() */
1500 err = d_revalidate(nd->path.dentry, nd);
1508 if (nameidata_drop_rcu_last_maybe(nd))
1512 if (!(nd->flags & LOOKUP_RCU))
1513 path_put_conditional(&next, nd);
1516 if (!(nd->flags & LOOKUP_RCU))
1517 path_put(&nd->path);
1522 static inline int path_walk_rcu(const char *name, struct nameidata *nd)
1524 current->total_link_count = 0;
1526 return link_path_walk(name, nd);
1529 static inline int path_walk_simple(const char *name, struct nameidata *nd)
1531 current->total_link_count = 0;
1533 return link_path_walk(name, nd);
1536 static int path_walk(const char *name, struct nameidata *nd)
1538 struct path save = nd->path;
1541 current->total_link_count = 0;
1543 /* make sure the stuff we saved doesn't go away */
1546 result = link_path_walk(name, nd);
1547 if (result == -ESTALE) {
1548 /* nd->path had been dropped */
1549 current->total_link_count = 0;
1551 nd->inode = save.dentry->d_inode;
1552 path_get(&nd->path);
1553 nd->flags |= LOOKUP_REVAL;
1554 result = link_path_walk(name, nd);
1562 static void path_finish_rcu(struct nameidata *nd)
1564 if (nd->flags & LOOKUP_RCU) {
1565 /* RCU dangling. Cancel it. */
1566 nd->flags &= ~LOOKUP_RCU;
1567 nd->root.mnt = NULL;
1569 br_read_unlock(vfsmount_lock);
1575 static int path_init_rcu(int dfd, const char *name, unsigned int flags, struct nameidata *nd)
1581 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1582 nd->flags = flags | LOOKUP_RCU;
1584 nd->root.mnt = NULL;
1588 struct fs_struct *fs = current->fs;
1591 br_read_lock(vfsmount_lock);
1595 seq = read_seqcount_begin(&fs->seq);
1596 nd->root = fs->root;
1597 nd->path = nd->root;
1598 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1599 } while (read_seqcount_retry(&fs->seq, seq));
1601 } else if (dfd == AT_FDCWD) {
1602 struct fs_struct *fs = current->fs;
1605 br_read_lock(vfsmount_lock);
1609 seq = read_seqcount_begin(&fs->seq);
1611 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1612 } while (read_seqcount_retry(&fs->seq, seq));
1615 struct dentry *dentry;
1617 file = fget_light(dfd, &fput_needed);
1622 dentry = file->f_path.dentry;
1625 if (!S_ISDIR(dentry->d_inode->i_mode))
1628 retval = file_permission(file, MAY_EXEC);
1632 nd->path = file->f_path;
1636 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1637 br_read_lock(vfsmount_lock);
1640 nd->inode = nd->path.dentry->d_inode;
1644 fput_light(file, fput_needed);
1649 static int path_init(int dfd, const char *name, unsigned int flags, struct nameidata *nd)
1655 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1658 nd->root.mnt = NULL;
1662 nd->path = nd->root;
1663 path_get(&nd->root);
1664 } else if (dfd == AT_FDCWD) {
1665 get_fs_pwd(current->fs, &nd->path);
1667 struct dentry *dentry;
1669 file = fget_light(dfd, &fput_needed);
1674 dentry = file->f_path.dentry;
1677 if (!S_ISDIR(dentry->d_inode->i_mode))
1680 retval = file_permission(file, MAY_EXEC);
1684 nd->path = file->f_path;
1685 path_get(&file->f_path);
1687 fput_light(file, fput_needed);
1689 nd->inode = nd->path.dentry->d_inode;
1693 fput_light(file, fput_needed);
1698 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1699 static int do_path_lookup(int dfd, const char *name,
1700 unsigned int flags, struct nameidata *nd)
1705 * Path walking is largely split up into 2 different synchronisation
1706 * schemes, rcu-walk and ref-walk (explained in
1707 * Documentation/filesystems/path-lookup.txt). These share much of the
1708 * path walk code, but some things particularly setup, cleanup, and
1709 * following mounts are sufficiently divergent that functions are
1710 * duplicated. Typically there is a function foo(), and its RCU
1711 * analogue, foo_rcu().
1713 * -ECHILD is the error number of choice (just to avoid clashes) that
1714 * is returned if some aspect of an rcu-walk fails. Such an error must
1715 * be handled by restarting a traditional ref-walk (which will always
1716 * be able to complete).
1718 retval = path_init_rcu(dfd, name, flags, nd);
1719 if (unlikely(retval))
1721 retval = path_walk_rcu(name, nd);
1722 path_finish_rcu(nd);
1724 path_put(&nd->root);
1725 nd->root.mnt = NULL;
1728 if (unlikely(retval == -ECHILD || retval == -ESTALE)) {
1729 /* slower, locked walk */
1730 if (retval == -ESTALE)
1731 flags |= LOOKUP_REVAL;
1732 retval = path_init(dfd, name, flags, nd);
1733 if (unlikely(retval))
1735 retval = path_walk(name, nd);
1737 path_put(&nd->root);
1738 nd->root.mnt = NULL;
1742 if (likely(!retval)) {
1743 if (unlikely(!audit_dummy_context())) {
1744 if (nd->path.dentry && nd->inode)
1745 audit_inode(name, nd->path.dentry);
1752 int path_lookup(const char *name, unsigned int flags,
1753 struct nameidata *nd)
1755 return do_path_lookup(AT_FDCWD, name, flags, nd);
1758 int kern_path(const char *name, unsigned int flags, struct path *path)
1760 struct nameidata nd;
1761 int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
1768 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
1769 * @dentry: pointer to dentry of the base directory
1770 * @mnt: pointer to vfs mount of the base directory
1771 * @name: pointer to file name
1772 * @flags: lookup flags
1773 * @nd: pointer to nameidata
1775 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
1776 const char *name, unsigned int flags,
1777 struct nameidata *nd)
1781 /* same as do_path_lookup */
1782 nd->last_type = LAST_ROOT;
1786 nd->path.dentry = dentry;
1788 path_get(&nd->path);
1789 nd->root = nd->path;
1790 path_get(&nd->root);
1791 nd->inode = nd->path.dentry->d_inode;
1793 retval = path_walk(name, nd);
1794 if (unlikely(!retval && !audit_dummy_context() && nd->path.dentry &&
1796 audit_inode(name, nd->path.dentry);
1798 path_put(&nd->root);
1799 nd->root.mnt = NULL;
1804 static struct dentry *__lookup_hash(struct qstr *name,
1805 struct dentry *base, struct nameidata *nd)
1807 struct inode *inode = base->d_inode;
1808 struct dentry *dentry;
1811 err = exec_permission(inode, 0);
1813 return ERR_PTR(err);
1816 * See if the low-level filesystem might want
1817 * to use its own hash..
1819 if (base->d_flags & DCACHE_OP_HASH) {
1820 err = base->d_op->d_hash(base, inode, name);
1821 dentry = ERR_PTR(err);
1827 * Don't bother with __d_lookup: callers are for creat as
1828 * well as unlink, so a lot of the time it would cost
1831 dentry = d_lookup(base, name);
1833 if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE))
1834 dentry = do_revalidate(dentry, nd);
1837 dentry = d_alloc_and_lookup(base, name, nd);
1843 * Restricted form of lookup. Doesn't follow links, single-component only,
1844 * needs parent already locked. Doesn't follow mounts.
1847 struct dentry *lookup_hash(struct nameidata *nd)
1849 return __lookup_hash(&nd->last, nd->path.dentry, nd);
1851 EXPORT_SYMBOL(lookup_hash);
1853 int __lookup_one_len(const char *name, struct qstr *this,
1854 struct dentry *base, int len)
1864 hash = init_name_hash();
1866 c = *(const unsigned char *)name++;
1867 if (c == '/' || c == '\0')
1869 hash = partial_name_hash(c, hash);
1871 this->hash = end_name_hash(hash);
1874 EXPORT_SYMBOL(__lookup_one_len);
1877 * lookup_one_len - filesystem helper to lookup single pathname component
1878 * @name: pathname component to lookup
1879 * @base: base directory to lookup from
1880 * @len: maximum length @len should be interpreted to
1882 * Note that this routine is purely a helper for filesystem usage and should
1883 * not be called by generic code. Also note that by using this function the
1884 * nameidata argument is passed to the filesystem methods and a filesystem
1885 * using this helper needs to be prepared for that.
1887 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
1892 WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
1894 err = __lookup_one_len(name, &this, base, len);
1896 return ERR_PTR(err);
1898 return __lookup_hash(&this, base, NULL);
1901 int user_path_at(int dfd, const char __user *name, unsigned flags,
1904 struct nameidata nd;
1905 char *tmp = getname(name);
1906 int err = PTR_ERR(tmp);
1909 BUG_ON(flags & LOOKUP_PARENT);
1911 err = do_path_lookup(dfd, tmp, flags, &nd);
1919 static int user_path_parent(int dfd, const char __user *path,
1920 struct nameidata *nd, char **name)
1922 char *s = getname(path);
1928 error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd);
1938 * It's inline, so penalty for filesystems that don't use sticky bit is
1941 static inline int check_sticky(struct inode *dir, struct inode *inode)
1943 uid_t fsuid = current_fsuid();
1945 if (!(dir->i_mode & S_ISVTX))
1947 if (inode->i_uid == fsuid)
1949 if (dir->i_uid == fsuid)
1951 return !capable(CAP_FOWNER);
1955 * Check whether we can remove a link victim from directory dir, check
1956 * whether the type of victim is right.
1957 * 1. We can't do it if dir is read-only (done in permission())
1958 * 2. We should have write and exec permissions on dir
1959 * 3. We can't remove anything from append-only dir
1960 * 4. We can't do anything with immutable dir (done in permission())
1961 * 5. If the sticky bit on dir is set we should either
1962 * a. be owner of dir, or
1963 * b. be owner of victim, or
1964 * c. have CAP_FOWNER capability
1965 * 6. If the victim is append-only or immutable we can't do antyhing with
1966 * links pointing to it.
1967 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
1968 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
1969 * 9. We can't remove a root or mountpoint.
1970 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
1971 * nfs_async_unlink().
1973 static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
1977 if (!victim->d_inode)
1980 BUG_ON(victim->d_parent->d_inode != dir);
1981 audit_inode_child(victim, dir);
1983 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
1988 if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
1989 IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
1992 if (!S_ISDIR(victim->d_inode->i_mode))
1994 if (IS_ROOT(victim))
1996 } else if (S_ISDIR(victim->d_inode->i_mode))
1998 if (IS_DEADDIR(dir))
2000 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2005 /* Check whether we can create an object with dentry child in directory
2007 * 1. We can't do it if child already exists (open has special treatment for
2008 * this case, but since we are inlined it's OK)
2009 * 2. We can't do it if dir is read-only (done in permission())
2010 * 3. We should have write and exec permissions on dir
2011 * 4. We can't do it if dir is immutable (done in permission())
2013 static inline int may_create(struct inode *dir, struct dentry *child)
2017 if (IS_DEADDIR(dir))
2019 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
2023 * p1 and p2 should be directories on the same fs.
2025 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2030 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2034 mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2036 p = d_ancestor(p2, p1);
2038 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
2039 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
2043 p = d_ancestor(p1, p2);
2045 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2046 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2050 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2051 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2055 void unlock_rename(struct dentry *p1, struct dentry *p2)
2057 mutex_unlock(&p1->d_inode->i_mutex);
2059 mutex_unlock(&p2->d_inode->i_mutex);
2060 mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2064 int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
2065 struct nameidata *nd)
2067 int error = may_create(dir, dentry);
2072 if (!dir->i_op->create)
2073 return -EACCES; /* shouldn't it be ENOSYS? */
2076 error = security_inode_create(dir, dentry, mode);
2079 error = dir->i_op->create(dir, dentry, mode, nd);
2081 fsnotify_create(dir, dentry);
2085 int may_open(struct path *path, int acc_mode, int flag)
2087 struct dentry *dentry = path->dentry;
2088 struct inode *inode = dentry->d_inode;
2094 switch (inode->i_mode & S_IFMT) {
2098 if (acc_mode & MAY_WRITE)
2103 if (path->mnt->mnt_flags & MNT_NODEV)
2112 error = inode_permission(inode, acc_mode);
2117 * An append-only file must be opened in append mode for writing.
2119 if (IS_APPEND(inode)) {
2120 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
2126 /* O_NOATIME can only be set by the owner or superuser */
2127 if (flag & O_NOATIME && !is_owner_or_cap(inode))
2131 * Ensure there are no outstanding leases on the file.
2133 return break_lease(inode, flag);
2136 static int handle_truncate(struct file *filp)
2138 struct path *path = &filp->f_path;
2139 struct inode *inode = path->dentry->d_inode;
2140 int error = get_write_access(inode);
2144 * Refuse to truncate files with mandatory locks held on them.
2146 error = locks_verify_locked(inode);
2148 error = security_path_truncate(path);
2150 error = do_truncate(path->dentry, 0,
2151 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
2154 put_write_access(inode);
2159 * Be careful about ever adding any more callers of this
2160 * function. Its flags must be in the namei format, not
2161 * what get passed to sys_open().
2163 static int __open_namei_create(struct nameidata *nd, struct path *path,
2164 int open_flag, int mode)
2167 struct dentry *dir = nd->path.dentry;
2169 if (!IS_POSIXACL(dir->d_inode))
2170 mode &= ~current_umask();
2171 error = security_path_mknod(&nd->path, path->dentry, mode, 0);
2174 error = vfs_create(dir->d_inode, path->dentry, mode, nd);
2176 mutex_unlock(&dir->d_inode->i_mutex);
2177 dput(nd->path.dentry);
2178 nd->path.dentry = path->dentry;
2182 /* Don't check for write permission, don't truncate */
2183 return may_open(&nd->path, 0, open_flag & ~O_TRUNC);
2187 * Note that while the flag value (low two bits) for sys_open means:
2192 * it is changed into
2193 * 00 - no permissions needed
2194 * 01 - read-permission
2195 * 10 - write-permission
2197 * for the internal routines (ie open_namei()/follow_link() etc)
2198 * This is more logical, and also allows the 00 "no perm needed"
2199 * to be used for symlinks (where the permissions are checked
2203 static inline int open_to_namei_flags(int flag)
2205 if ((flag+1) & O_ACCMODE)
2210 static int open_will_truncate(int flag, struct inode *inode)
2213 * We'll never write to the fs underlying
2216 if (special_file(inode->i_mode))
2218 return (flag & O_TRUNC);
2221 static struct file *finish_open(struct nameidata *nd,
2222 int open_flag, int acc_mode)
2228 will_truncate = open_will_truncate(open_flag, nd->path.dentry->d_inode);
2229 if (will_truncate) {
2230 error = mnt_want_write(nd->path.mnt);
2234 error = may_open(&nd->path, acc_mode, open_flag);
2237 mnt_drop_write(nd->path.mnt);
2240 filp = nameidata_to_filp(nd);
2241 if (!IS_ERR(filp)) {
2242 error = ima_file_check(filp, acc_mode);
2245 filp = ERR_PTR(error);
2248 if (!IS_ERR(filp)) {
2249 if (will_truncate) {
2250 error = handle_truncate(filp);
2253 filp = ERR_PTR(error);
2258 * It is now safe to drop the mnt write
2259 * because the filp has had a write taken
2263 mnt_drop_write(nd->path.mnt);
2264 path_put(&nd->path);
2268 path_put(&nd->path);
2269 return ERR_PTR(error);
2273 * Handle O_CREAT case for do_filp_open
2275 static struct file *do_last(struct nameidata *nd, struct path *path,
2276 int open_flag, int acc_mode,
2277 int mode, const char *pathname)
2279 struct dentry *dir = nd->path.dentry;
2281 int error = -EISDIR;
2283 switch (nd->last_type) {
2286 dir = nd->path.dentry;
2288 if (need_reval_dot(dir)) {
2289 int status = d_revalidate(nd->path.dentry, nd);
2301 audit_inode(pathname, dir);
2305 /* trailing slashes? */
2306 if (nd->last.name[nd->last.len])
2309 mutex_lock(&dir->d_inode->i_mutex);
2311 path->dentry = lookup_hash(nd);
2312 path->mnt = nd->path.mnt;
2314 error = PTR_ERR(path->dentry);
2315 if (IS_ERR(path->dentry)) {
2316 mutex_unlock(&dir->d_inode->i_mutex);
2320 if (IS_ERR(nd->intent.open.file)) {
2321 error = PTR_ERR(nd->intent.open.file);
2322 goto exit_mutex_unlock;
2325 /* Negative dentry, just create the file */
2326 if (!path->dentry->d_inode) {
2328 * This write is needed to ensure that a
2329 * ro->rw transition does not occur between
2330 * the time when the file is created and when
2331 * a permanent write count is taken through
2332 * the 'struct file' in nameidata_to_filp().
2334 error = mnt_want_write(nd->path.mnt);
2336 goto exit_mutex_unlock;
2337 error = __open_namei_create(nd, path, open_flag, mode);
2339 mnt_drop_write(nd->path.mnt);
2342 filp = nameidata_to_filp(nd);
2343 mnt_drop_write(nd->path.mnt);
2344 path_put(&nd->path);
2345 if (!IS_ERR(filp)) {
2346 error = ima_file_check(filp, acc_mode);
2349 filp = ERR_PTR(error);
2356 * It already exists.
2358 mutex_unlock(&dir->d_inode->i_mutex);
2359 audit_inode(pathname, path->dentry);
2362 if (open_flag & O_EXCL)
2365 error = follow_managed(path, nd->flags);
2370 if (!path->dentry->d_inode)
2373 if (path->dentry->d_inode->i_op->follow_link)
2376 path_to_nameidata(path, nd);
2377 nd->inode = path->dentry->d_inode;
2379 if (S_ISDIR(nd->inode->i_mode))
2382 filp = finish_open(nd, open_flag, acc_mode);
2386 mutex_unlock(&dir->d_inode->i_mutex);
2388 path_put_conditional(path, nd);
2390 path_put(&nd->path);
2391 return ERR_PTR(error);
2395 * Note that the low bits of the passed in "open_flag"
2396 * are not the same as in the local variable "flag". See
2397 * open_to_namei_flags() for more details.
2399 struct file *do_filp_open(int dfd, const char *pathname,
2400 int open_flag, int mode, int acc_mode)
2403 struct nameidata nd;
2407 int flag = open_to_namei_flags(open_flag);
2410 if (!(open_flag & O_CREAT))
2413 /* Must never be set by userspace */
2414 open_flag &= ~FMODE_NONOTIFY;
2417 * O_SYNC is implemented as __O_SYNC|O_DSYNC. As many places only
2418 * check for O_DSYNC if the need any syncing at all we enforce it's
2419 * always set instead of having to deal with possibly weird behaviour
2420 * for malicious applications setting only __O_SYNC.
2422 if (open_flag & __O_SYNC)
2423 open_flag |= O_DSYNC;
2426 acc_mode = MAY_OPEN | ACC_MODE(open_flag);
2428 /* O_TRUNC implies we need access checks for write permissions */
2429 if (open_flag & O_TRUNC)
2430 acc_mode |= MAY_WRITE;
2432 /* Allow the LSM permission hook to distinguish append
2433 access from general write access. */
2434 if (open_flag & O_APPEND)
2435 acc_mode |= MAY_APPEND;
2437 flags = LOOKUP_OPEN;
2438 if (open_flag & O_CREAT) {
2439 flags |= LOOKUP_CREATE;
2440 if (open_flag & O_EXCL)
2441 flags |= LOOKUP_EXCL;
2443 if (open_flag & O_DIRECTORY)
2444 flags |= LOOKUP_DIRECTORY;
2445 if (!(open_flag & O_NOFOLLOW))
2446 flags |= LOOKUP_FOLLOW;
2448 filp = get_empty_filp();
2450 return ERR_PTR(-ENFILE);
2452 filp->f_flags = open_flag;
2453 nd.intent.open.file = filp;
2454 nd.intent.open.flags = flag;
2455 nd.intent.open.create_mode = mode;
2457 if (open_flag & O_CREAT)
2460 /* !O_CREAT, simple open */
2461 error = do_path_lookup(dfd, pathname, flags, &nd);
2462 if (unlikely(error))
2465 if (!(nd.flags & LOOKUP_FOLLOW)) {
2466 if (nd.inode->i_op->follow_link)
2470 if (nd.flags & LOOKUP_DIRECTORY) {
2471 if (!nd.inode->i_op->lookup)
2474 audit_inode(pathname, nd.path.dentry);
2475 filp = finish_open(&nd, open_flag, acc_mode);
2477 release_open_intent(&nd);
2483 filp = ERR_PTR(error);
2487 /* OK, have to create the file. Find the parent. */
2488 error = path_init_rcu(dfd, pathname,
2489 LOOKUP_PARENT | (flags & LOOKUP_REVAL), &nd);
2492 error = path_walk_rcu(pathname, &nd);
2493 path_finish_rcu(&nd);
2494 if (unlikely(error == -ECHILD || error == -ESTALE)) {
2495 /* slower, locked walk */
2496 if (error == -ESTALE) {
2498 flags |= LOOKUP_REVAL;
2500 error = path_init(dfd, pathname,
2501 LOOKUP_PARENT | (flags & LOOKUP_REVAL), &nd);
2505 error = path_walk_simple(pathname, &nd);
2507 if (unlikely(error))
2509 if (unlikely(!audit_dummy_context()))
2510 audit_inode(pathname, nd.path.dentry);
2513 * We have the parent and last component.
2516 filp = do_last(&nd, &path, open_flag, acc_mode, mode, pathname);
2517 while (unlikely(!filp)) { /* trailing symlink */
2518 struct path link = path;
2519 struct inode *linki = link.dentry->d_inode;
2522 if (!(nd.flags & LOOKUP_FOLLOW))
2527 * This is subtle. Instead of calling do_follow_link() we do
2528 * the thing by hands. The reason is that this way we have zero
2529 * link_count and path_walk() (called from ->follow_link)
2530 * honoring LOOKUP_PARENT. After that we have the parent and
2531 * last component, i.e. we are in the same situation as after
2532 * the first path_walk(). Well, almost - if the last component
2533 * is normal we get its copy stored in nd->last.name and we will
2534 * have to putname() it when we are done. Procfs-like symlinks
2535 * just set LAST_BIND.
2537 nd.flags |= LOOKUP_PARENT;
2538 error = security_inode_follow_link(link.dentry, &nd);
2541 error = __do_follow_link(&link, &nd, &cookie);
2542 if (unlikely(error)) {
2543 if (!IS_ERR(cookie) && linki->i_op->put_link)
2544 linki->i_op->put_link(link.dentry, &nd, cookie);
2545 /* nd.path had been dropped */
2549 nd.flags &= ~LOOKUP_PARENT;
2550 filp = do_last(&nd, &path, open_flag, acc_mode, mode, pathname);
2551 if (linki->i_op->put_link)
2552 linki->i_op->put_link(link.dentry, &nd, cookie);
2558 if (filp == ERR_PTR(-ESTALE) && !(flags & LOOKUP_REVAL))
2560 release_open_intent(&nd);
2564 path_put_conditional(&path, &nd);
2568 filp = ERR_PTR(error);
2573 * filp_open - open file and return file pointer
2575 * @filename: path to open
2576 * @flags: open flags as per the open(2) second argument
2577 * @mode: mode for the new file if O_CREAT is set, else ignored
2579 * This is the helper to open a file from kernelspace if you really
2580 * have to. But in generally you should not do this, so please move
2581 * along, nothing to see here..
2583 struct file *filp_open(const char *filename, int flags, int mode)
2585 return do_filp_open(AT_FDCWD, filename, flags, mode, 0);
2587 EXPORT_SYMBOL(filp_open);
2590 * lookup_create - lookup a dentry, creating it if it doesn't exist
2591 * @nd: nameidata info
2592 * @is_dir: directory flag
2594 * Simple function to lookup and return a dentry and create it
2595 * if it doesn't exist. Is SMP-safe.
2597 * Returns with nd->path.dentry->d_inode->i_mutex locked.
2599 struct dentry *lookup_create(struct nameidata *nd, int is_dir)
2601 struct dentry *dentry = ERR_PTR(-EEXIST);
2603 mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2605 * Yucky last component or no last component at all?
2606 * (foo/., foo/.., /////)
2608 if (nd->last_type != LAST_NORM)
2610 nd->flags &= ~LOOKUP_PARENT;
2611 nd->flags |= LOOKUP_CREATE | LOOKUP_EXCL;
2612 nd->intent.open.flags = O_EXCL;
2615 * Do the final lookup.
2617 dentry = lookup_hash(nd);
2621 if (dentry->d_inode)
2624 * Special case - lookup gave negative, but... we had foo/bar/
2625 * From the vfs_mknod() POV we just have a negative dentry -
2626 * all is fine. Let's be bastards - you had / on the end, you've
2627 * been asking for (non-existent) directory. -ENOENT for you.
2629 if (unlikely(!is_dir && nd->last.name[nd->last.len])) {
2631 dentry = ERR_PTR(-ENOENT);
2636 dentry = ERR_PTR(-EEXIST);
2640 EXPORT_SYMBOL_GPL(lookup_create);
2642 int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
2644 int error = may_create(dir, dentry);
2649 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
2652 if (!dir->i_op->mknod)
2655 error = devcgroup_inode_mknod(mode, dev);
2659 error = security_inode_mknod(dir, dentry, mode, dev);
2663 error = dir->i_op->mknod(dir, dentry, mode, dev);
2665 fsnotify_create(dir, dentry);
2669 static int may_mknod(mode_t mode)
2671 switch (mode & S_IFMT) {
2677 case 0: /* zero mode translates to S_IFREG */
2686 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, int, mode,
2691 struct dentry *dentry;
2692 struct nameidata nd;
2697 error = user_path_parent(dfd, filename, &nd, &tmp);
2701 dentry = lookup_create(&nd, 0);
2702 if (IS_ERR(dentry)) {
2703 error = PTR_ERR(dentry);
2706 if (!IS_POSIXACL(nd.path.dentry->d_inode))
2707 mode &= ~current_umask();
2708 error = may_mknod(mode);
2711 error = mnt_want_write(nd.path.mnt);
2714 error = security_path_mknod(&nd.path, dentry, mode, dev);
2716 goto out_drop_write;
2717 switch (mode & S_IFMT) {
2718 case 0: case S_IFREG:
2719 error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd);
2721 case S_IFCHR: case S_IFBLK:
2722 error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,
2723 new_decode_dev(dev));
2725 case S_IFIFO: case S_IFSOCK:
2726 error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);
2730 mnt_drop_write(nd.path.mnt);
2734 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2741 SYSCALL_DEFINE3(mknod, const char __user *, filename, int, mode, unsigned, dev)
2743 return sys_mknodat(AT_FDCWD, filename, mode, dev);
2746 int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
2748 int error = may_create(dir, dentry);
2753 if (!dir->i_op->mkdir)
2756 mode &= (S_IRWXUGO|S_ISVTX);
2757 error = security_inode_mkdir(dir, dentry, mode);
2761 error = dir->i_op->mkdir(dir, dentry, mode);
2763 fsnotify_mkdir(dir, dentry);
2767 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, int, mode)
2771 struct dentry *dentry;
2772 struct nameidata nd;
2774 error = user_path_parent(dfd, pathname, &nd, &tmp);
2778 dentry = lookup_create(&nd, 1);
2779 error = PTR_ERR(dentry);
2783 if (!IS_POSIXACL(nd.path.dentry->d_inode))
2784 mode &= ~current_umask();
2785 error = mnt_want_write(nd.path.mnt);
2788 error = security_path_mkdir(&nd.path, dentry, mode);
2790 goto out_drop_write;
2791 error = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
2793 mnt_drop_write(nd.path.mnt);
2797 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2804 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, int, mode)
2806 return sys_mkdirat(AT_FDCWD, pathname, mode);
2810 * We try to drop the dentry early: we should have
2811 * a usage count of 2 if we're the only user of this
2812 * dentry, and if that is true (possibly after pruning
2813 * the dcache), then we drop the dentry now.
2815 * A low-level filesystem can, if it choses, legally
2818 * if (!d_unhashed(dentry))
2821 * if it cannot handle the case of removing a directory
2822 * that is still in use by something else..
2824 void dentry_unhash(struct dentry *dentry)
2827 shrink_dcache_parent(dentry);
2828 spin_lock(&dentry->d_lock);
2829 if (dentry->d_count == 2)
2831 spin_unlock(&dentry->d_lock);
2834 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
2836 int error = may_delete(dir, dentry, 1);
2841 if (!dir->i_op->rmdir)
2844 mutex_lock(&dentry->d_inode->i_mutex);
2845 dentry_unhash(dentry);
2846 if (d_mountpoint(dentry))
2849 error = security_inode_rmdir(dir, dentry);
2851 error = dir->i_op->rmdir(dir, dentry);
2853 dentry->d_inode->i_flags |= S_DEAD;
2858 mutex_unlock(&dentry->d_inode->i_mutex);
2867 static long do_rmdir(int dfd, const char __user *pathname)
2871 struct dentry *dentry;
2872 struct nameidata nd;
2874 error = user_path_parent(dfd, pathname, &nd, &name);
2878 switch(nd.last_type) {
2890 nd.flags &= ~LOOKUP_PARENT;
2892 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2893 dentry = lookup_hash(&nd);
2894 error = PTR_ERR(dentry);
2897 error = mnt_want_write(nd.path.mnt);
2900 error = security_path_rmdir(&nd.path, dentry);
2903 error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
2905 mnt_drop_write(nd.path.mnt);
2909 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2916 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
2918 return do_rmdir(AT_FDCWD, pathname);
2921 int vfs_unlink(struct inode *dir, struct dentry *dentry)
2923 int error = may_delete(dir, dentry, 0);
2928 if (!dir->i_op->unlink)
2931 mutex_lock(&dentry->d_inode->i_mutex);
2932 if (d_mountpoint(dentry))
2935 error = security_inode_unlink(dir, dentry);
2937 error = dir->i_op->unlink(dir, dentry);
2942 mutex_unlock(&dentry->d_inode->i_mutex);
2944 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
2945 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
2946 fsnotify_link_count(dentry->d_inode);
2954 * Make sure that the actual truncation of the file will occur outside its
2955 * directory's i_mutex. Truncate can take a long time if there is a lot of
2956 * writeout happening, and we don't want to prevent access to the directory
2957 * while waiting on the I/O.
2959 static long do_unlinkat(int dfd, const char __user *pathname)
2963 struct dentry *dentry;
2964 struct nameidata nd;
2965 struct inode *inode = NULL;
2967 error = user_path_parent(dfd, pathname, &nd, &name);
2972 if (nd.last_type != LAST_NORM)
2975 nd.flags &= ~LOOKUP_PARENT;
2977 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2978 dentry = lookup_hash(&nd);
2979 error = PTR_ERR(dentry);
2980 if (!IS_ERR(dentry)) {
2981 /* Why not before? Because we want correct error value */
2982 if (nd.last.name[nd.last.len])
2984 inode = dentry->d_inode;
2987 error = mnt_want_write(nd.path.mnt);
2990 error = security_path_unlink(&nd.path, dentry);
2993 error = vfs_unlink(nd.path.dentry->d_inode, dentry);
2995 mnt_drop_write(nd.path.mnt);
2999 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3001 iput(inode); /* truncate the inode here */
3008 error = !dentry->d_inode ? -ENOENT :
3009 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
3013 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
3015 if ((flag & ~AT_REMOVEDIR) != 0)
3018 if (flag & AT_REMOVEDIR)
3019 return do_rmdir(dfd, pathname);
3021 return do_unlinkat(dfd, pathname);
3024 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
3026 return do_unlinkat(AT_FDCWD, pathname);
3029 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
3031 int error = may_create(dir, dentry);
3036 if (!dir->i_op->symlink)
3039 error = security_inode_symlink(dir, dentry, oldname);
3043 error = dir->i_op->symlink(dir, dentry, oldname);
3045 fsnotify_create(dir, dentry);
3049 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
3050 int, newdfd, const char __user *, newname)
3055 struct dentry *dentry;
3056 struct nameidata nd;
3058 from = getname(oldname);
3060 return PTR_ERR(from);
3062 error = user_path_parent(newdfd, newname, &nd, &to);
3066 dentry = lookup_create(&nd, 0);
3067 error = PTR_ERR(dentry);
3071 error = mnt_want_write(nd.path.mnt);
3074 error = security_path_symlink(&nd.path, dentry, from);
3076 goto out_drop_write;
3077 error = vfs_symlink(nd.path.dentry->d_inode, dentry, from);
3079 mnt_drop_write(nd.path.mnt);
3083 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3091 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
3093 return sys_symlinkat(oldname, AT_FDCWD, newname);
3096 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
3098 struct inode *inode = old_dentry->d_inode;
3104 error = may_create(dir, new_dentry);
3108 if (dir->i_sb != inode->i_sb)
3112 * A link to an append-only or immutable file cannot be created.
3114 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
3116 if (!dir->i_op->link)
3118 if (S_ISDIR(inode->i_mode))
3121 error = security_inode_link(old_dentry, dir, new_dentry);
3125 mutex_lock(&inode->i_mutex);
3126 error = dir->i_op->link(old_dentry, dir, new_dentry);
3127 mutex_unlock(&inode->i_mutex);
3129 fsnotify_link(dir, inode, new_dentry);
3134 * Hardlinks are often used in delicate situations. We avoid
3135 * security-related surprises by not following symlinks on the
3138 * We don't follow them on the oldname either to be compatible
3139 * with linux 2.0, and to avoid hard-linking to directories
3140 * and other special files. --ADM
3142 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
3143 int, newdfd, const char __user *, newname, int, flags)
3145 struct dentry *new_dentry;
3146 struct nameidata nd;
3147 struct path old_path;
3151 if ((flags & ~AT_SYMLINK_FOLLOW) != 0)
3154 error = user_path_at(olddfd, oldname,
3155 flags & AT_SYMLINK_FOLLOW ? LOOKUP_FOLLOW : 0,
3160 error = user_path_parent(newdfd, newname, &nd, &to);
3164 if (old_path.mnt != nd.path.mnt)
3166 new_dentry = lookup_create(&nd, 0);
3167 error = PTR_ERR(new_dentry);
3168 if (IS_ERR(new_dentry))
3170 error = mnt_want_write(nd.path.mnt);
3173 error = security_path_link(old_path.dentry, &nd.path, new_dentry);
3175 goto out_drop_write;
3176 error = vfs_link(old_path.dentry, nd.path.dentry->d_inode, new_dentry);
3178 mnt_drop_write(nd.path.mnt);
3182 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3187 path_put(&old_path);
3192 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
3194 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
3198 * The worst of all namespace operations - renaming directory. "Perverted"
3199 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3201 * a) we can get into loop creation. Check is done in is_subdir().
3202 * b) race potential - two innocent renames can create a loop together.
3203 * That's where 4.4 screws up. Current fix: serialization on
3204 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
3206 * c) we have to lock _three_ objects - parents and victim (if it exists).
3207 * And that - after we got ->i_mutex on parents (until then we don't know
3208 * whether the target exists). Solution: try to be smart with locking
3209 * order for inodes. We rely on the fact that tree topology may change
3210 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
3211 * move will be locked. Thus we can rank directories by the tree
3212 * (ancestors first) and rank all non-directories after them.
3213 * That works since everybody except rename does "lock parent, lookup,
3214 * lock child" and rename is under ->s_vfs_rename_mutex.
3215 * HOWEVER, it relies on the assumption that any object with ->lookup()
3216 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3217 * we'd better make sure that there's no link(2) for them.
3218 * d) some filesystems don't support opened-but-unlinked directories,
3219 * either because of layout or because they are not ready to deal with
3220 * all cases correctly. The latter will be fixed (taking this sort of
3221 * stuff into VFS), but the former is not going away. Solution: the same
3222 * trick as in rmdir().
3223 * e) conversion from fhandle to dentry may come in the wrong moment - when
3224 * we are removing the target. Solution: we will have to grab ->i_mutex
3225 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
3226 * ->i_mutex on parents, which works but leads to some truly excessive
3229 static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
3230 struct inode *new_dir, struct dentry *new_dentry)
3233 struct inode *target;
3236 * If we are going to change the parent - check write permissions,
3237 * we'll need to flip '..'.
3239 if (new_dir != old_dir) {
3240 error = inode_permission(old_dentry->d_inode, MAY_WRITE);
3245 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3249 target = new_dentry->d_inode;
3251 mutex_lock(&target->i_mutex);
3252 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
3256 dentry_unhash(new_dentry);
3257 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3261 target->i_flags |= S_DEAD;
3262 dont_mount(new_dentry);
3264 mutex_unlock(&target->i_mutex);
3265 if (d_unhashed(new_dentry))
3266 d_rehash(new_dentry);
3270 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3271 d_move(old_dentry,new_dentry);
3275 static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
3276 struct inode *new_dir, struct dentry *new_dentry)
3278 struct inode *target;
3281 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3286 target = new_dentry->d_inode;
3288 mutex_lock(&target->i_mutex);
3289 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
3292 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3295 dont_mount(new_dentry);
3296 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3297 d_move(old_dentry, new_dentry);
3300 mutex_unlock(&target->i_mutex);
3305 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
3306 struct inode *new_dir, struct dentry *new_dentry)
3309 int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
3310 const unsigned char *old_name;
3312 if (old_dentry->d_inode == new_dentry->d_inode)
3315 error = may_delete(old_dir, old_dentry, is_dir);
3319 if (!new_dentry->d_inode)
3320 error = may_create(new_dir, new_dentry);
3322 error = may_delete(new_dir, new_dentry, is_dir);
3326 if (!old_dir->i_op->rename)
3329 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
3332 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
3334 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
3336 fsnotify_move(old_dir, new_dir, old_name, is_dir,
3337 new_dentry->d_inode, old_dentry);
3338 fsnotify_oldname_free(old_name);
3343 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
3344 int, newdfd, const char __user *, newname)
3346 struct dentry *old_dir, *new_dir;
3347 struct dentry *old_dentry, *new_dentry;
3348 struct dentry *trap;
3349 struct nameidata oldnd, newnd;
3354 error = user_path_parent(olddfd, oldname, &oldnd, &from);
3358 error = user_path_parent(newdfd, newname, &newnd, &to);
3363 if (oldnd.path.mnt != newnd.path.mnt)
3366 old_dir = oldnd.path.dentry;
3368 if (oldnd.last_type != LAST_NORM)
3371 new_dir = newnd.path.dentry;
3372 if (newnd.last_type != LAST_NORM)
3375 oldnd.flags &= ~LOOKUP_PARENT;
3376 newnd.flags &= ~LOOKUP_PARENT;
3377 newnd.flags |= LOOKUP_RENAME_TARGET;
3379 trap = lock_rename(new_dir, old_dir);
3381 old_dentry = lookup_hash(&oldnd);
3382 error = PTR_ERR(old_dentry);
3383 if (IS_ERR(old_dentry))
3385 /* source must exist */
3387 if (!old_dentry->d_inode)
3389 /* unless the source is a directory trailing slashes give -ENOTDIR */
3390 if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
3392 if (oldnd.last.name[oldnd.last.len])
3394 if (newnd.last.name[newnd.last.len])
3397 /* source should not be ancestor of target */
3399 if (old_dentry == trap)
3401 new_dentry = lookup_hash(&newnd);
3402 error = PTR_ERR(new_dentry);
3403 if (IS_ERR(new_dentry))
3405 /* target should not be an ancestor of source */
3407 if (new_dentry == trap)
3410 error = mnt_want_write(oldnd.path.mnt);
3413 error = security_path_rename(&oldnd.path, old_dentry,
3414 &newnd.path, new_dentry);
3417 error = vfs_rename(old_dir->d_inode, old_dentry,
3418 new_dir->d_inode, new_dentry);
3420 mnt_drop_write(oldnd.path.mnt);
3426 unlock_rename(new_dir, old_dir);
3428 path_put(&newnd.path);
3431 path_put(&oldnd.path);
3437 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
3439 return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
3442 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
3446 len = PTR_ERR(link);
3451 if (len > (unsigned) buflen)
3453 if (copy_to_user(buffer, link, len))
3460 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
3461 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
3462 * using) it for any given inode is up to filesystem.
3464 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3466 struct nameidata nd;
3471 cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
3473 return PTR_ERR(cookie);
3475 res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
3476 if (dentry->d_inode->i_op->put_link)
3477 dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
3481 int vfs_follow_link(struct nameidata *nd, const char *link)
3483 return __vfs_follow_link(nd, link);
3486 /* get the link contents into pagecache */
3487 static char *page_getlink(struct dentry * dentry, struct page **ppage)
3491 struct address_space *mapping = dentry->d_inode->i_mapping;
3492 page = read_mapping_page(mapping, 0, NULL);
3497 nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
3501 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3503 struct page *page = NULL;
3504 char *s = page_getlink(dentry, &page);
3505 int res = vfs_readlink(dentry,buffer,buflen,s);
3508 page_cache_release(page);
3513 void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
3515 struct page *page = NULL;
3516 nd_set_link(nd, page_getlink(dentry, &page));
3520 void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
3522 struct page *page = cookie;
3526 page_cache_release(page);
3531 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
3533 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
3535 struct address_space *mapping = inode->i_mapping;
3540 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
3542 flags |= AOP_FLAG_NOFS;
3545 err = pagecache_write_begin(NULL, mapping, 0, len-1,
3546 flags, &page, &fsdata);
3550 kaddr = kmap_atomic(page, KM_USER0);
3551 memcpy(kaddr, symname, len-1);
3552 kunmap_atomic(kaddr, KM_USER0);
3554 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
3561 mark_inode_dirty(inode);
3567 int page_symlink(struct inode *inode, const char *symname, int len)
3569 return __page_symlink(inode, symname, len,
3570 !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
3573 const struct inode_operations page_symlink_inode_operations = {
3574 .readlink = generic_readlink,
3575 .follow_link = page_follow_link_light,
3576 .put_link = page_put_link,
3579 EXPORT_SYMBOL(user_path_at);
3580 EXPORT_SYMBOL(follow_down_one);
3581 EXPORT_SYMBOL(follow_down);
3582 EXPORT_SYMBOL(follow_up);
3583 EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
3584 EXPORT_SYMBOL(getname);
3585 EXPORT_SYMBOL(lock_rename);
3586 EXPORT_SYMBOL(lookup_one_len);
3587 EXPORT_SYMBOL(page_follow_link_light);
3588 EXPORT_SYMBOL(page_put_link);
3589 EXPORT_SYMBOL(page_readlink);
3590 EXPORT_SYMBOL(__page_symlink);
3591 EXPORT_SYMBOL(page_symlink);
3592 EXPORT_SYMBOL(page_symlink_inode_operations);
3593 EXPORT_SYMBOL(path_lookup);
3594 EXPORT_SYMBOL(kern_path);
3595 EXPORT_SYMBOL(vfs_path_lookup);
3596 EXPORT_SYMBOL(inode_permission);
3597 EXPORT_SYMBOL(file_permission);
3598 EXPORT_SYMBOL(unlock_rename);
3599 EXPORT_SYMBOL(vfs_create);
3600 EXPORT_SYMBOL(vfs_follow_link);
3601 EXPORT_SYMBOL(vfs_link);
3602 EXPORT_SYMBOL(vfs_mkdir);
3603 EXPORT_SYMBOL(vfs_mknod);
3604 EXPORT_SYMBOL(generic_permission);
3605 EXPORT_SYMBOL(vfs_readlink);
3606 EXPORT_SYMBOL(vfs_rename);
3607 EXPORT_SYMBOL(vfs_rmdir);
3608 EXPORT_SYMBOL(vfs_symlink);
3609 EXPORT_SYMBOL(vfs_unlink);
3610 EXPORT_SYMBOL(dentry_unhash);
3611 EXPORT_SYMBOL(generic_readlink);