Staging: rtl8192* needs semaphore.h
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / namei.c
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1 /*
2 * linux/fs/namei.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
7 /*
8 * Some corrections by tytso.
9 */
11 /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
12 * lookup logic.
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>
20 #include <linux/fs.h>
21 #include <linux/namei.h>
22 #include <linux/quotaops.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 <asm/uaccess.h>
38 #include "internal.h"
40 /* [Feb-1997 T. Schoebel-Theuer]
41 * Fundamental changes in the pathname lookup mechanisms (namei)
42 * were necessary because of omirr. The reason is that omirr needs
43 * to know the _real_ pathname, not the user-supplied one, in case
44 * of symlinks (and also when transname replacements occur).
46 * The new code replaces the old recursive symlink resolution with
47 * an iterative one (in case of non-nested symlink chains). It does
48 * this with calls to <fs>_follow_link().
49 * As a side effect, dir_namei(), _namei() and follow_link() are now
50 * replaced with a single function lookup_dentry() that can handle all
51 * the special cases of the former code.
53 * With the new dcache, the pathname is stored at each inode, at least as
54 * long as the refcount of the inode is positive. As a side effect, the
55 * size of the dcache depends on the inode cache and thus is dynamic.
57 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
58 * resolution to correspond with current state of the code.
60 * Note that the symlink resolution is not *completely* iterative.
61 * There is still a significant amount of tail- and mid- recursion in
62 * the algorithm. Also, note that <fs>_readlink() is not used in
63 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
64 * may return different results than <fs>_follow_link(). Many virtual
65 * filesystems (including /proc) exhibit this behavior.
68 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
69 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
70 * and the name already exists in form of a symlink, try to create the new
71 * name indicated by the symlink. The old code always complained that the
72 * name already exists, due to not following the symlink even if its target
73 * is nonexistent. The new semantics affects also mknod() and link() when
74 * the name is a symlink pointing to a non-existant name.
76 * I don't know which semantics is the right one, since I have no access
77 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
78 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
79 * "old" one. Personally, I think the new semantics is much more logical.
80 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
81 * file does succeed in both HP-UX and SunOs, but not in Solaris
82 * and in the old Linux semantics.
85 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
86 * semantics. See the comments in "open_namei" and "do_link" below.
88 * [10-Sep-98 Alan Modra] Another symlink change.
91 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
92 * inside the path - always follow.
93 * in the last component in creation/removal/renaming - never follow.
94 * if LOOKUP_FOLLOW passed - follow.
95 * if the pathname has trailing slashes - follow.
96 * otherwise - don't follow.
97 * (applied in that order).
99 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
100 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
101 * During the 2.4 we need to fix the userland stuff depending on it -
102 * hopefully we will be able to get rid of that wart in 2.5. So far only
103 * XEmacs seems to be relying on it...
106 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
107 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
108 * any extra contention...
111 /* In order to reduce some races, while at the same time doing additional
112 * checking and hopefully speeding things up, we copy filenames to the
113 * kernel data space before using them..
115 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
116 * PATH_MAX includes the nul terminator --RR.
118 static int do_getname(const char __user *filename, char *page)
120 int retval;
121 unsigned long len = PATH_MAX;
123 if (!segment_eq(get_fs(), KERNEL_DS)) {
124 if ((unsigned long) filename >= TASK_SIZE)
125 return -EFAULT;
126 if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
127 len = TASK_SIZE - (unsigned long) filename;
130 retval = strncpy_from_user(page, filename, len);
131 if (retval > 0) {
132 if (retval < len)
133 return 0;
134 return -ENAMETOOLONG;
135 } else if (!retval)
136 retval = -ENOENT;
137 return retval;
140 char * getname(const char __user * filename)
142 char *tmp, *result;
144 result = ERR_PTR(-ENOMEM);
145 tmp = __getname();
146 if (tmp) {
147 int retval = do_getname(filename, tmp);
149 result = tmp;
150 if (retval < 0) {
151 __putname(tmp);
152 result = ERR_PTR(retval);
155 audit_getname(result);
156 return result;
159 #ifdef CONFIG_AUDITSYSCALL
160 void putname(const char *name)
162 if (unlikely(!audit_dummy_context()))
163 audit_putname(name);
164 else
165 __putname(name);
167 EXPORT_SYMBOL(putname);
168 #endif
171 * This does basic POSIX ACL permission checking
173 static int acl_permission_check(struct inode *inode, int mask,
174 int (*check_acl)(struct inode *inode, int mask))
176 umode_t mode = inode->i_mode;
178 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
180 if (current_fsuid() == inode->i_uid)
181 mode >>= 6;
182 else {
183 if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
184 int error = check_acl(inode, mask);
185 if (error != -EAGAIN)
186 return error;
189 if (in_group_p(inode->i_gid))
190 mode >>= 3;
194 * If the DACs are ok we don't need any capability check.
196 if ((mask & ~mode) == 0)
197 return 0;
198 return -EACCES;
202 * generic_permission - check for access rights on a Posix-like filesystem
203 * @inode: inode to check access rights for
204 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
205 * @check_acl: optional callback to check for Posix ACLs
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 int generic_permission(struct inode *inode, int mask,
213 int (*check_acl)(struct inode *inode, int mask))
215 int ret;
218 * Do the basic POSIX ACL permission checks.
220 ret = acl_permission_check(inode, mask, check_acl);
221 if (ret != -EACCES)
222 return ret;
225 * Read/write DACs are always overridable.
226 * Executable DACs are overridable if at least one exec bit is set.
228 if (!(mask & MAY_EXEC) || execute_ok(inode))
229 if (capable(CAP_DAC_OVERRIDE))
230 return 0;
233 * Searching includes executable on directories, else just read.
235 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
236 if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
237 if (capable(CAP_DAC_READ_SEARCH))
238 return 0;
240 return -EACCES;
244 * inode_permission - check for access rights to a given inode
245 * @inode: inode to check permission on
246 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
248 * Used to check for read/write/execute permissions on an inode.
249 * We use "fsuid" for this, letting us set arbitrary permissions
250 * for filesystem access without changing the "normal" uids which
251 * are used for other things.
253 int inode_permission(struct inode *inode, int mask)
255 int retval;
257 if (mask & MAY_WRITE) {
258 umode_t mode = inode->i_mode;
261 * Nobody gets write access to a read-only fs.
263 if (IS_RDONLY(inode) &&
264 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
265 return -EROFS;
268 * Nobody gets write access to an immutable file.
270 if (IS_IMMUTABLE(inode))
271 return -EACCES;
274 if (inode->i_op->permission)
275 retval = inode->i_op->permission(inode, mask);
276 else
277 retval = generic_permission(inode, mask, inode->i_op->check_acl);
279 if (retval)
280 return retval;
282 retval = devcgroup_inode_permission(inode, mask);
283 if (retval)
284 return retval;
286 return security_inode_permission(inode,
287 mask & (MAY_READ|MAY_WRITE|MAY_EXEC|MAY_APPEND));
291 * file_permission - check for additional access rights to a given file
292 * @file: file to check access rights for
293 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
295 * Used to check for read/write/execute permissions on an already opened
296 * file.
298 * Note:
299 * Do not use this function in new code. All access checks should
300 * be done using inode_permission().
302 int file_permission(struct file *file, int mask)
304 return inode_permission(file->f_path.dentry->d_inode, mask);
308 * get_write_access() gets write permission for a file.
309 * put_write_access() releases this write permission.
310 * This is used for regular files.
311 * We cannot support write (and maybe mmap read-write shared) accesses and
312 * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
313 * can have the following values:
314 * 0: no writers, no VM_DENYWRITE mappings
315 * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
316 * > 0: (i_writecount) users are writing to the file.
318 * Normally we operate on that counter with atomic_{inc,dec} and it's safe
319 * except for the cases where we don't hold i_writecount yet. Then we need to
320 * use {get,deny}_write_access() - these functions check the sign and refuse
321 * to do the change if sign is wrong. Exclusion between them is provided by
322 * the inode->i_lock spinlock.
325 int get_write_access(struct inode * inode)
327 spin_lock(&inode->i_lock);
328 if (atomic_read(&inode->i_writecount) < 0) {
329 spin_unlock(&inode->i_lock);
330 return -ETXTBSY;
332 atomic_inc(&inode->i_writecount);
333 spin_unlock(&inode->i_lock);
335 return 0;
338 int deny_write_access(struct file * file)
340 struct inode *inode = file->f_path.dentry->d_inode;
342 spin_lock(&inode->i_lock);
343 if (atomic_read(&inode->i_writecount) > 0) {
344 spin_unlock(&inode->i_lock);
345 return -ETXTBSY;
347 atomic_dec(&inode->i_writecount);
348 spin_unlock(&inode->i_lock);
350 return 0;
354 * path_get - get a reference to a path
355 * @path: path to get the reference to
357 * Given a path increment the reference count to the dentry and the vfsmount.
359 void path_get(struct path *path)
361 mntget(path->mnt);
362 dget(path->dentry);
364 EXPORT_SYMBOL(path_get);
367 * path_put - put a reference to a path
368 * @path: path to put the reference to
370 * Given a path decrement the reference count to the dentry and the vfsmount.
372 void path_put(struct path *path)
374 dput(path->dentry);
375 mntput(path->mnt);
377 EXPORT_SYMBOL(path_put);
380 * release_open_intent - free up open intent resources
381 * @nd: pointer to nameidata
383 void release_open_intent(struct nameidata *nd)
385 if (nd->intent.open.file->f_path.dentry == NULL)
386 put_filp(nd->intent.open.file);
387 else
388 fput(nd->intent.open.file);
391 static inline struct dentry *
392 do_revalidate(struct dentry *dentry, struct nameidata *nd)
394 int status = dentry->d_op->d_revalidate(dentry, nd);
395 if (unlikely(status <= 0)) {
397 * The dentry failed validation.
398 * If d_revalidate returned 0 attempt to invalidate
399 * the dentry otherwise d_revalidate is asking us
400 * to return a fail status.
402 if (!status) {
403 if (!d_invalidate(dentry)) {
404 dput(dentry);
405 dentry = NULL;
407 } else {
408 dput(dentry);
409 dentry = ERR_PTR(status);
412 return dentry;
416 * force_reval_path - force revalidation of a dentry
418 * In some situations the path walking code will trust dentries without
419 * revalidating them. This causes problems for filesystems that depend on
420 * d_revalidate to handle file opens (e.g. NFSv4). When FS_REVAL_DOT is set
421 * (which indicates that it's possible for the dentry to go stale), force
422 * a d_revalidate call before proceeding.
424 * Returns 0 if the revalidation was successful. If the revalidation fails,
425 * either return the error returned by d_revalidate or -ESTALE if the
426 * revalidation it just returned 0. If d_revalidate returns 0, we attempt to
427 * invalidate the dentry. It's up to the caller to handle putting references
428 * to the path if necessary.
430 static int
431 force_reval_path(struct path *path, struct nameidata *nd)
433 int status;
434 struct dentry *dentry = path->dentry;
437 * only check on filesystems where it's possible for the dentry to
438 * become stale. It's assumed that if this flag is set then the
439 * d_revalidate op will also be defined.
441 if (!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT))
442 return 0;
444 status = dentry->d_op->d_revalidate(dentry, nd);
445 if (status > 0)
446 return 0;
448 if (!status) {
449 d_invalidate(dentry);
450 status = -ESTALE;
452 return status;
456 * Short-cut version of permission(), for calling on directories
457 * during pathname resolution. Combines parts of permission()
458 * and generic_permission(), and tests ONLY for MAY_EXEC permission.
460 * If appropriate, check DAC only. If not appropriate, or
461 * short-cut DAC fails, then call ->permission() to do more
462 * complete permission check.
464 static int exec_permission(struct inode *inode)
466 int ret;
468 if (inode->i_op->permission) {
469 ret = inode->i_op->permission(inode, MAY_EXEC);
470 if (!ret)
471 goto ok;
472 return ret;
474 ret = acl_permission_check(inode, MAY_EXEC, inode->i_op->check_acl);
475 if (!ret)
476 goto ok;
478 if (capable(CAP_DAC_OVERRIDE) || capable(CAP_DAC_READ_SEARCH))
479 goto ok;
481 return ret;
483 return security_inode_permission(inode, MAY_EXEC);
486 static __always_inline void set_root(struct nameidata *nd)
488 if (!nd->root.mnt) {
489 struct fs_struct *fs = current->fs;
490 read_lock(&fs->lock);
491 nd->root = fs->root;
492 path_get(&nd->root);
493 read_unlock(&fs->lock);
497 static int link_path_walk(const char *, struct nameidata *);
499 static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
501 int res = 0;
502 char *name;
503 if (IS_ERR(link))
504 goto fail;
506 if (*link == '/') {
507 set_root(nd);
508 path_put(&nd->path);
509 nd->path = nd->root;
510 path_get(&nd->root);
513 res = link_path_walk(link, nd);
514 if (nd->depth || res || nd->last_type!=LAST_NORM)
515 return res;
517 * If it is an iterative symlinks resolution in open_namei() we
518 * have to copy the last component. And all that crap because of
519 * bloody create() on broken symlinks. Furrfu...
521 name = __getname();
522 if (unlikely(!name)) {
523 path_put(&nd->path);
524 return -ENOMEM;
526 strcpy(name, nd->last.name);
527 nd->last.name = name;
528 return 0;
529 fail:
530 path_put(&nd->path);
531 return PTR_ERR(link);
534 static void path_put_conditional(struct path *path, struct nameidata *nd)
536 dput(path->dentry);
537 if (path->mnt != nd->path.mnt)
538 mntput(path->mnt);
541 static inline void path_to_nameidata(struct path *path, struct nameidata *nd)
543 dput(nd->path.dentry);
544 if (nd->path.mnt != path->mnt)
545 mntput(nd->path.mnt);
546 nd->path.mnt = path->mnt;
547 nd->path.dentry = path->dentry;
550 static __always_inline int __do_follow_link(struct path *path, struct nameidata *nd)
552 int error;
553 void *cookie;
554 struct dentry *dentry = path->dentry;
556 touch_atime(path->mnt, dentry);
557 nd_set_link(nd, NULL);
559 if (path->mnt != nd->path.mnt) {
560 path_to_nameidata(path, nd);
561 dget(dentry);
563 mntget(path->mnt);
564 nd->last_type = LAST_BIND;
565 cookie = dentry->d_inode->i_op->follow_link(dentry, nd);
566 error = PTR_ERR(cookie);
567 if (!IS_ERR(cookie)) {
568 char *s = nd_get_link(nd);
569 error = 0;
570 if (s)
571 error = __vfs_follow_link(nd, s);
572 else if (nd->last_type == LAST_BIND) {
573 error = force_reval_path(&nd->path, nd);
574 if (error)
575 path_put(&nd->path);
577 if (dentry->d_inode->i_op->put_link)
578 dentry->d_inode->i_op->put_link(dentry, nd, cookie);
580 return error;
584 * This limits recursive symlink follows to 8, while
585 * limiting consecutive symlinks to 40.
587 * Without that kind of total limit, nasty chains of consecutive
588 * symlinks can cause almost arbitrarily long lookups.
590 static inline int do_follow_link(struct path *path, struct nameidata *nd)
592 int err = -ELOOP;
593 if (current->link_count >= MAX_NESTED_LINKS)
594 goto loop;
595 if (current->total_link_count >= 40)
596 goto loop;
597 BUG_ON(nd->depth >= MAX_NESTED_LINKS);
598 cond_resched();
599 err = security_inode_follow_link(path->dentry, nd);
600 if (err)
601 goto loop;
602 current->link_count++;
603 current->total_link_count++;
604 nd->depth++;
605 err = __do_follow_link(path, nd);
606 path_put(path);
607 current->link_count--;
608 nd->depth--;
609 return err;
610 loop:
611 path_put_conditional(path, nd);
612 path_put(&nd->path);
613 return err;
616 int follow_up(struct path *path)
618 struct vfsmount *parent;
619 struct dentry *mountpoint;
620 spin_lock(&vfsmount_lock);
621 parent = path->mnt->mnt_parent;
622 if (parent == path->mnt) {
623 spin_unlock(&vfsmount_lock);
624 return 0;
626 mntget(parent);
627 mountpoint = dget(path->mnt->mnt_mountpoint);
628 spin_unlock(&vfsmount_lock);
629 dput(path->dentry);
630 path->dentry = mountpoint;
631 mntput(path->mnt);
632 path->mnt = parent;
633 return 1;
636 /* no need for dcache_lock, as serialization is taken care in
637 * namespace.c
639 static int __follow_mount(struct path *path)
641 int res = 0;
642 while (d_mountpoint(path->dentry)) {
643 struct vfsmount *mounted = lookup_mnt(path);
644 if (!mounted)
645 break;
646 dput(path->dentry);
647 if (res)
648 mntput(path->mnt);
649 path->mnt = mounted;
650 path->dentry = dget(mounted->mnt_root);
651 res = 1;
653 return res;
656 static void follow_mount(struct path *path)
658 while (d_mountpoint(path->dentry)) {
659 struct vfsmount *mounted = lookup_mnt(path);
660 if (!mounted)
661 break;
662 dput(path->dentry);
663 mntput(path->mnt);
664 path->mnt = mounted;
665 path->dentry = dget(mounted->mnt_root);
669 /* no need for dcache_lock, as serialization is taken care in
670 * namespace.c
672 int follow_down(struct path *path)
674 struct vfsmount *mounted;
676 mounted = lookup_mnt(path);
677 if (mounted) {
678 dput(path->dentry);
679 mntput(path->mnt);
680 path->mnt = mounted;
681 path->dentry = dget(mounted->mnt_root);
682 return 1;
684 return 0;
687 static __always_inline void follow_dotdot(struct nameidata *nd)
689 set_root(nd);
691 while(1) {
692 struct vfsmount *parent;
693 struct dentry *old = nd->path.dentry;
695 if (nd->path.dentry == nd->root.dentry &&
696 nd->path.mnt == nd->root.mnt) {
697 break;
699 spin_lock(&dcache_lock);
700 if (nd->path.dentry != nd->path.mnt->mnt_root) {
701 nd->path.dentry = dget(nd->path.dentry->d_parent);
702 spin_unlock(&dcache_lock);
703 dput(old);
704 break;
706 spin_unlock(&dcache_lock);
707 spin_lock(&vfsmount_lock);
708 parent = nd->path.mnt->mnt_parent;
709 if (parent == nd->path.mnt) {
710 spin_unlock(&vfsmount_lock);
711 break;
713 mntget(parent);
714 nd->path.dentry = dget(nd->path.mnt->mnt_mountpoint);
715 spin_unlock(&vfsmount_lock);
716 dput(old);
717 mntput(nd->path.mnt);
718 nd->path.mnt = parent;
720 follow_mount(&nd->path);
724 * It's more convoluted than I'd like it to be, but... it's still fairly
725 * small and for now I'd prefer to have fast path as straight as possible.
726 * It _is_ time-critical.
728 static int do_lookup(struct nameidata *nd, struct qstr *name,
729 struct path *path)
731 struct vfsmount *mnt = nd->path.mnt;
732 struct dentry *dentry, *parent;
733 struct inode *dir;
735 * See if the low-level filesystem might want
736 * to use its own hash..
738 if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
739 int err = nd->path.dentry->d_op->d_hash(nd->path.dentry, name);
740 if (err < 0)
741 return err;
744 dentry = __d_lookup(nd->path.dentry, name);
745 if (!dentry)
746 goto need_lookup;
747 if (dentry->d_op && dentry->d_op->d_revalidate)
748 goto need_revalidate;
749 done:
750 path->mnt = mnt;
751 path->dentry = dentry;
752 __follow_mount(path);
753 return 0;
755 need_lookup:
756 parent = nd->path.dentry;
757 dir = parent->d_inode;
759 mutex_lock(&dir->i_mutex);
761 * First re-do the cached lookup just in case it was created
762 * while we waited for the directory semaphore..
764 * FIXME! This could use version numbering or similar to
765 * avoid unnecessary cache lookups.
767 * The "dcache_lock" is purely to protect the RCU list walker
768 * from concurrent renames at this point (we mustn't get false
769 * negatives from the RCU list walk here, unlike the optimistic
770 * fast walk).
772 * so doing d_lookup() (with seqlock), instead of lockfree __d_lookup
774 dentry = d_lookup(parent, name);
775 if (!dentry) {
776 struct dentry *new;
778 /* Don't create child dentry for a dead directory. */
779 dentry = ERR_PTR(-ENOENT);
780 if (IS_DEADDIR(dir))
781 goto out_unlock;
783 new = d_alloc(parent, name);
784 dentry = ERR_PTR(-ENOMEM);
785 if (new) {
786 dentry = dir->i_op->lookup(dir, new, nd);
787 if (dentry)
788 dput(new);
789 else
790 dentry = new;
792 out_unlock:
793 mutex_unlock(&dir->i_mutex);
794 if (IS_ERR(dentry))
795 goto fail;
796 goto done;
800 * Uhhuh! Nasty case: the cache was re-populated while
801 * we waited on the semaphore. Need to revalidate.
803 mutex_unlock(&dir->i_mutex);
804 if (dentry->d_op && dentry->d_op->d_revalidate) {
805 dentry = do_revalidate(dentry, nd);
806 if (!dentry)
807 dentry = ERR_PTR(-ENOENT);
809 if (IS_ERR(dentry))
810 goto fail;
811 goto done;
813 need_revalidate:
814 dentry = do_revalidate(dentry, nd);
815 if (!dentry)
816 goto need_lookup;
817 if (IS_ERR(dentry))
818 goto fail;
819 goto done;
821 fail:
822 return PTR_ERR(dentry);
826 * This is a temporary kludge to deal with "automount" symlinks; proper
827 * solution is to trigger them on follow_mount(), so that do_lookup()
828 * would DTRT. To be killed before 2.6.34-final.
830 static inline int follow_on_final(struct inode *inode, unsigned lookup_flags)
832 return inode && unlikely(inode->i_op->follow_link) &&
833 ((lookup_flags & LOOKUP_FOLLOW) || S_ISDIR(inode->i_mode));
837 * Name resolution.
838 * This is the basic name resolution function, turning a pathname into
839 * the final dentry. We expect 'base' to be positive and a directory.
841 * Returns 0 and nd will have valid dentry and mnt on success.
842 * Returns error and drops reference to input namei data on failure.
844 static int link_path_walk(const char *name, struct nameidata *nd)
846 struct path next;
847 struct inode *inode;
848 int err;
849 unsigned int lookup_flags = nd->flags;
851 while (*name=='/')
852 name++;
853 if (!*name)
854 goto return_reval;
856 inode = nd->path.dentry->d_inode;
857 if (nd->depth)
858 lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);
860 /* At this point we know we have a real path component. */
861 for(;;) {
862 unsigned long hash;
863 struct qstr this;
864 unsigned int c;
866 nd->flags |= LOOKUP_CONTINUE;
867 err = exec_permission(inode);
868 if (err)
869 break;
871 this.name = name;
872 c = *(const unsigned char *)name;
874 hash = init_name_hash();
875 do {
876 name++;
877 hash = partial_name_hash(c, hash);
878 c = *(const unsigned char *)name;
879 } while (c && (c != '/'));
880 this.len = name - (const char *) this.name;
881 this.hash = end_name_hash(hash);
883 /* remove trailing slashes? */
884 if (!c)
885 goto last_component;
886 while (*++name == '/');
887 if (!*name)
888 goto last_with_slashes;
891 * "." and ".." are special - ".." especially so because it has
892 * to be able to know about the current root directory and
893 * parent relationships.
895 if (this.name[0] == '.') switch (this.len) {
896 default:
897 break;
898 case 2:
899 if (this.name[1] != '.')
900 break;
901 follow_dotdot(nd);
902 inode = nd->path.dentry->d_inode;
903 /* fallthrough */
904 case 1:
905 continue;
907 /* This does the actual lookups.. */
908 err = do_lookup(nd, &this, &next);
909 if (err)
910 break;
912 err = -ENOENT;
913 inode = next.dentry->d_inode;
914 if (!inode)
915 goto out_dput;
917 if (inode->i_op->follow_link) {
918 err = do_follow_link(&next, nd);
919 if (err)
920 goto return_err;
921 err = -ENOENT;
922 inode = nd->path.dentry->d_inode;
923 if (!inode)
924 break;
925 } else
926 path_to_nameidata(&next, nd);
927 err = -ENOTDIR;
928 if (!inode->i_op->lookup)
929 break;
930 continue;
931 /* here ends the main loop */
933 last_with_slashes:
934 lookup_flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
935 last_component:
936 /* Clear LOOKUP_CONTINUE iff it was previously unset */
937 nd->flags &= lookup_flags | ~LOOKUP_CONTINUE;
938 if (lookup_flags & LOOKUP_PARENT)
939 goto lookup_parent;
940 if (this.name[0] == '.') switch (this.len) {
941 default:
942 break;
943 case 2:
944 if (this.name[1] != '.')
945 break;
946 follow_dotdot(nd);
947 inode = nd->path.dentry->d_inode;
948 /* fallthrough */
949 case 1:
950 goto return_reval;
952 err = do_lookup(nd, &this, &next);
953 if (err)
954 break;
955 inode = next.dentry->d_inode;
956 if (follow_on_final(inode, lookup_flags)) {
957 err = do_follow_link(&next, nd);
958 if (err)
959 goto return_err;
960 inode = nd->path.dentry->d_inode;
961 } else
962 path_to_nameidata(&next, nd);
963 err = -ENOENT;
964 if (!inode)
965 break;
966 if (lookup_flags & LOOKUP_DIRECTORY) {
967 err = -ENOTDIR;
968 if (!inode->i_op->lookup)
969 break;
971 goto return_base;
972 lookup_parent:
973 nd->last = this;
974 nd->last_type = LAST_NORM;
975 if (this.name[0] != '.')
976 goto return_base;
977 if (this.len == 1)
978 nd->last_type = LAST_DOT;
979 else if (this.len == 2 && this.name[1] == '.')
980 nd->last_type = LAST_DOTDOT;
981 else
982 goto return_base;
983 return_reval:
985 * We bypassed the ordinary revalidation routines.
986 * We may need to check the cached dentry for staleness.
988 if (nd->path.dentry && nd->path.dentry->d_sb &&
989 (nd->path.dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)) {
990 err = -ESTALE;
991 /* Note: we do not d_invalidate() */
992 if (!nd->path.dentry->d_op->d_revalidate(
993 nd->path.dentry, nd))
994 break;
996 return_base:
997 return 0;
998 out_dput:
999 path_put_conditional(&next, nd);
1000 break;
1002 path_put(&nd->path);
1003 return_err:
1004 return err;
1007 static int path_walk(const char *name, struct nameidata *nd)
1009 struct path save = nd->path;
1010 int result;
1012 current->total_link_count = 0;
1014 /* make sure the stuff we saved doesn't go away */
1015 path_get(&save);
1017 result = link_path_walk(name, nd);
1018 if (result == -ESTALE) {
1019 /* nd->path had been dropped */
1020 current->total_link_count = 0;
1021 nd->path = save;
1022 path_get(&nd->path);
1023 nd->flags |= LOOKUP_REVAL;
1024 result = link_path_walk(name, nd);
1027 path_put(&save);
1029 return result;
1032 static int path_init(int dfd, const char *name, unsigned int flags, struct nameidata *nd)
1034 int retval = 0;
1035 int fput_needed;
1036 struct file *file;
1038 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1039 nd->flags = flags;
1040 nd->depth = 0;
1041 nd->root.mnt = NULL;
1043 if (*name=='/') {
1044 set_root(nd);
1045 nd->path = nd->root;
1046 path_get(&nd->root);
1047 } else if (dfd == AT_FDCWD) {
1048 struct fs_struct *fs = current->fs;
1049 read_lock(&fs->lock);
1050 nd->path = fs->pwd;
1051 path_get(&fs->pwd);
1052 read_unlock(&fs->lock);
1053 } else {
1054 struct dentry *dentry;
1056 file = fget_light(dfd, &fput_needed);
1057 retval = -EBADF;
1058 if (!file)
1059 goto out_fail;
1061 dentry = file->f_path.dentry;
1063 retval = -ENOTDIR;
1064 if (!S_ISDIR(dentry->d_inode->i_mode))
1065 goto fput_fail;
1067 retval = file_permission(file, MAY_EXEC);
1068 if (retval)
1069 goto fput_fail;
1071 nd->path = file->f_path;
1072 path_get(&file->f_path);
1074 fput_light(file, fput_needed);
1076 return 0;
1078 fput_fail:
1079 fput_light(file, fput_needed);
1080 out_fail:
1081 return retval;
1084 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1085 static int do_path_lookup(int dfd, const char *name,
1086 unsigned int flags, struct nameidata *nd)
1088 int retval = path_init(dfd, name, flags, nd);
1089 if (!retval)
1090 retval = path_walk(name, nd);
1091 if (unlikely(!retval && !audit_dummy_context() && nd->path.dentry &&
1092 nd->path.dentry->d_inode))
1093 audit_inode(name, nd->path.dentry);
1094 if (nd->root.mnt) {
1095 path_put(&nd->root);
1096 nd->root.mnt = NULL;
1098 return retval;
1101 int path_lookup(const char *name, unsigned int flags,
1102 struct nameidata *nd)
1104 return do_path_lookup(AT_FDCWD, name, flags, nd);
1107 int kern_path(const char *name, unsigned int flags, struct path *path)
1109 struct nameidata nd;
1110 int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
1111 if (!res)
1112 *path = nd.path;
1113 return res;
1117 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
1118 * @dentry: pointer to dentry of the base directory
1119 * @mnt: pointer to vfs mount of the base directory
1120 * @name: pointer to file name
1121 * @flags: lookup flags
1122 * @nd: pointer to nameidata
1124 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
1125 const char *name, unsigned int flags,
1126 struct nameidata *nd)
1128 int retval;
1130 /* same as do_path_lookup */
1131 nd->last_type = LAST_ROOT;
1132 nd->flags = flags;
1133 nd->depth = 0;
1135 nd->path.dentry = dentry;
1136 nd->path.mnt = mnt;
1137 path_get(&nd->path);
1138 nd->root = nd->path;
1139 path_get(&nd->root);
1141 retval = path_walk(name, nd);
1142 if (unlikely(!retval && !audit_dummy_context() && nd->path.dentry &&
1143 nd->path.dentry->d_inode))
1144 audit_inode(name, nd->path.dentry);
1146 path_put(&nd->root);
1147 nd->root.mnt = NULL;
1149 return retval;
1152 static struct dentry *__lookup_hash(struct qstr *name,
1153 struct dentry *base, struct nameidata *nd)
1155 struct dentry *dentry;
1156 struct inode *inode;
1157 int err;
1159 inode = base->d_inode;
1162 * See if the low-level filesystem might want
1163 * to use its own hash..
1165 if (base->d_op && base->d_op->d_hash) {
1166 err = base->d_op->d_hash(base, name);
1167 dentry = ERR_PTR(err);
1168 if (err < 0)
1169 goto out;
1172 dentry = __d_lookup(base, name);
1174 /* lockess __d_lookup may fail due to concurrent d_move()
1175 * in some unrelated directory, so try with d_lookup
1177 if (!dentry)
1178 dentry = d_lookup(base, name);
1180 if (dentry && dentry->d_op && dentry->d_op->d_revalidate)
1181 dentry = do_revalidate(dentry, nd);
1183 if (!dentry) {
1184 struct dentry *new;
1186 /* Don't create child dentry for a dead directory. */
1187 dentry = ERR_PTR(-ENOENT);
1188 if (IS_DEADDIR(inode))
1189 goto out;
1191 new = d_alloc(base, name);
1192 dentry = ERR_PTR(-ENOMEM);
1193 if (!new)
1194 goto out;
1195 dentry = inode->i_op->lookup(inode, new, nd);
1196 if (!dentry)
1197 dentry = new;
1198 else
1199 dput(new);
1201 out:
1202 return dentry;
1206 * Restricted form of lookup. Doesn't follow links, single-component only,
1207 * needs parent already locked. Doesn't follow mounts.
1208 * SMP-safe.
1210 static struct dentry *lookup_hash(struct nameidata *nd)
1212 int err;
1214 err = exec_permission(nd->path.dentry->d_inode);
1215 if (err)
1216 return ERR_PTR(err);
1217 return __lookup_hash(&nd->last, nd->path.dentry, nd);
1220 static int __lookup_one_len(const char *name, struct qstr *this,
1221 struct dentry *base, int len)
1223 unsigned long hash;
1224 unsigned int c;
1226 this->name = name;
1227 this->len = len;
1228 if (!len)
1229 return -EACCES;
1231 hash = init_name_hash();
1232 while (len--) {
1233 c = *(const unsigned char *)name++;
1234 if (c == '/' || c == '\0')
1235 return -EACCES;
1236 hash = partial_name_hash(c, hash);
1238 this->hash = end_name_hash(hash);
1239 return 0;
1243 * lookup_one_len - filesystem helper to lookup single pathname component
1244 * @name: pathname component to lookup
1245 * @base: base directory to lookup from
1246 * @len: maximum length @len should be interpreted to
1248 * Note that this routine is purely a helper for filesystem usage and should
1249 * not be called by generic code. Also note that by using this function the
1250 * nameidata argument is passed to the filesystem methods and a filesystem
1251 * using this helper needs to be prepared for that.
1253 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
1255 int err;
1256 struct qstr this;
1258 WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
1260 err = __lookup_one_len(name, &this, base, len);
1261 if (err)
1262 return ERR_PTR(err);
1264 err = exec_permission(base->d_inode);
1265 if (err)
1266 return ERR_PTR(err);
1267 return __lookup_hash(&this, base, NULL);
1270 int user_path_at(int dfd, const char __user *name, unsigned flags,
1271 struct path *path)
1273 struct nameidata nd;
1274 char *tmp = getname(name);
1275 int err = PTR_ERR(tmp);
1276 if (!IS_ERR(tmp)) {
1278 BUG_ON(flags & LOOKUP_PARENT);
1280 err = do_path_lookup(dfd, tmp, flags, &nd);
1281 putname(tmp);
1282 if (!err)
1283 *path = nd.path;
1285 return err;
1288 static int user_path_parent(int dfd, const char __user *path,
1289 struct nameidata *nd, char **name)
1291 char *s = getname(path);
1292 int error;
1294 if (IS_ERR(s))
1295 return PTR_ERR(s);
1297 error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd);
1298 if (error)
1299 putname(s);
1300 else
1301 *name = s;
1303 return error;
1307 * It's inline, so penalty for filesystems that don't use sticky bit is
1308 * minimal.
1310 static inline int check_sticky(struct inode *dir, struct inode *inode)
1312 uid_t fsuid = current_fsuid();
1314 if (!(dir->i_mode & S_ISVTX))
1315 return 0;
1316 if (inode->i_uid == fsuid)
1317 return 0;
1318 if (dir->i_uid == fsuid)
1319 return 0;
1320 return !capable(CAP_FOWNER);
1324 * Check whether we can remove a link victim from directory dir, check
1325 * whether the type of victim is right.
1326 * 1. We can't do it if dir is read-only (done in permission())
1327 * 2. We should have write and exec permissions on dir
1328 * 3. We can't remove anything from append-only dir
1329 * 4. We can't do anything with immutable dir (done in permission())
1330 * 5. If the sticky bit on dir is set we should either
1331 * a. be owner of dir, or
1332 * b. be owner of victim, or
1333 * c. have CAP_FOWNER capability
1334 * 6. If the victim is append-only or immutable we can't do antyhing with
1335 * links pointing to it.
1336 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
1337 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
1338 * 9. We can't remove a root or mountpoint.
1339 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
1340 * nfs_async_unlink().
1342 static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
1344 int error;
1346 if (!victim->d_inode)
1347 return -ENOENT;
1349 BUG_ON(victim->d_parent->d_inode != dir);
1350 audit_inode_child(victim->d_name.name, victim, dir);
1352 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
1353 if (error)
1354 return error;
1355 if (IS_APPEND(dir))
1356 return -EPERM;
1357 if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
1358 IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
1359 return -EPERM;
1360 if (isdir) {
1361 if (!S_ISDIR(victim->d_inode->i_mode))
1362 return -ENOTDIR;
1363 if (IS_ROOT(victim))
1364 return -EBUSY;
1365 } else if (S_ISDIR(victim->d_inode->i_mode))
1366 return -EISDIR;
1367 if (IS_DEADDIR(dir))
1368 return -ENOENT;
1369 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
1370 return -EBUSY;
1371 return 0;
1374 /* Check whether we can create an object with dentry child in directory
1375 * dir.
1376 * 1. We can't do it if child already exists (open has special treatment for
1377 * this case, but since we are inlined it's OK)
1378 * 2. We can't do it if dir is read-only (done in permission())
1379 * 3. We should have write and exec permissions on dir
1380 * 4. We can't do it if dir is immutable (done in permission())
1382 static inline int may_create(struct inode *dir, struct dentry *child)
1384 if (child->d_inode)
1385 return -EEXIST;
1386 if (IS_DEADDIR(dir))
1387 return -ENOENT;
1388 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
1392 * O_DIRECTORY translates into forcing a directory lookup.
1394 static inline int lookup_flags(unsigned int f)
1396 unsigned long retval = LOOKUP_FOLLOW;
1398 if (f & O_NOFOLLOW)
1399 retval &= ~LOOKUP_FOLLOW;
1401 if (f & O_DIRECTORY)
1402 retval |= LOOKUP_DIRECTORY;
1404 return retval;
1408 * p1 and p2 should be directories on the same fs.
1410 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
1412 struct dentry *p;
1414 if (p1 == p2) {
1415 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1416 return NULL;
1419 mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
1421 p = d_ancestor(p2, p1);
1422 if (p) {
1423 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
1424 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
1425 return p;
1428 p = d_ancestor(p1, p2);
1429 if (p) {
1430 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1431 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
1432 return p;
1435 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1436 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
1437 return NULL;
1440 void unlock_rename(struct dentry *p1, struct dentry *p2)
1442 mutex_unlock(&p1->d_inode->i_mutex);
1443 if (p1 != p2) {
1444 mutex_unlock(&p2->d_inode->i_mutex);
1445 mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
1449 int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
1450 struct nameidata *nd)
1452 int error = may_create(dir, dentry);
1454 if (error)
1455 return error;
1457 if (!dir->i_op->create)
1458 return -EACCES; /* shouldn't it be ENOSYS? */
1459 mode &= S_IALLUGO;
1460 mode |= S_IFREG;
1461 error = security_inode_create(dir, dentry, mode);
1462 if (error)
1463 return error;
1464 vfs_dq_init(dir);
1465 error = dir->i_op->create(dir, dentry, mode, nd);
1466 if (!error)
1467 fsnotify_create(dir, dentry);
1468 return error;
1471 int may_open(struct path *path, int acc_mode, int flag)
1473 struct dentry *dentry = path->dentry;
1474 struct inode *inode = dentry->d_inode;
1475 int error;
1477 if (!inode)
1478 return -ENOENT;
1480 switch (inode->i_mode & S_IFMT) {
1481 case S_IFLNK:
1482 return -ELOOP;
1483 case S_IFDIR:
1484 if (acc_mode & MAY_WRITE)
1485 return -EISDIR;
1486 break;
1487 case S_IFBLK:
1488 case S_IFCHR:
1489 if (path->mnt->mnt_flags & MNT_NODEV)
1490 return -EACCES;
1491 /*FALLTHRU*/
1492 case S_IFIFO:
1493 case S_IFSOCK:
1494 flag &= ~O_TRUNC;
1495 break;
1498 error = inode_permission(inode, acc_mode);
1499 if (error)
1500 return error;
1503 * An append-only file must be opened in append mode for writing.
1505 if (IS_APPEND(inode)) {
1506 if ((flag & FMODE_WRITE) && !(flag & O_APPEND))
1507 return -EPERM;
1508 if (flag & O_TRUNC)
1509 return -EPERM;
1512 /* O_NOATIME can only be set by the owner or superuser */
1513 if (flag & O_NOATIME && !is_owner_or_cap(inode))
1514 return -EPERM;
1517 * Ensure there are no outstanding leases on the file.
1519 return break_lease(inode, flag);
1522 static int handle_truncate(struct path *path)
1524 struct inode *inode = path->dentry->d_inode;
1525 int error = get_write_access(inode);
1526 if (error)
1527 return error;
1529 * Refuse to truncate files with mandatory locks held on them.
1531 error = locks_verify_locked(inode);
1532 if (!error)
1533 error = security_path_truncate(path, 0,
1534 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN);
1535 if (!error) {
1536 error = do_truncate(path->dentry, 0,
1537 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
1538 NULL);
1540 put_write_access(inode);
1541 return error;
1545 * Be careful about ever adding any more callers of this
1546 * function. Its flags must be in the namei format, not
1547 * what get passed to sys_open().
1549 static int __open_namei_create(struct nameidata *nd, struct path *path,
1550 int flag, int mode)
1552 int error;
1553 struct dentry *dir = nd->path.dentry;
1555 if (!IS_POSIXACL(dir->d_inode))
1556 mode &= ~current_umask();
1557 error = security_path_mknod(&nd->path, path->dentry, mode, 0);
1558 if (error)
1559 goto out_unlock;
1560 error = vfs_create(dir->d_inode, path->dentry, mode, nd);
1561 out_unlock:
1562 mutex_unlock(&dir->d_inode->i_mutex);
1563 dput(nd->path.dentry);
1564 nd->path.dentry = path->dentry;
1565 if (error)
1566 return error;
1567 /* Don't check for write permission, don't truncate */
1568 return may_open(&nd->path, 0, flag & ~O_TRUNC);
1572 * Note that while the flag value (low two bits) for sys_open means:
1573 * 00 - read-only
1574 * 01 - write-only
1575 * 10 - read-write
1576 * 11 - special
1577 * it is changed into
1578 * 00 - no permissions needed
1579 * 01 - read-permission
1580 * 10 - write-permission
1581 * 11 - read-write
1582 * for the internal routines (ie open_namei()/follow_link() etc)
1583 * This is more logical, and also allows the 00 "no perm needed"
1584 * to be used for symlinks (where the permissions are checked
1585 * later).
1588 static inline int open_to_namei_flags(int flag)
1590 if ((flag+1) & O_ACCMODE)
1591 flag++;
1592 return flag;
1595 static int open_will_truncate(int flag, struct inode *inode)
1598 * We'll never write to the fs underlying
1599 * a device file.
1601 if (special_file(inode->i_mode))
1602 return 0;
1603 return (flag & O_TRUNC);
1607 * Note that the low bits of the passed in "open_flag"
1608 * are not the same as in the local variable "flag". See
1609 * open_to_namei_flags() for more details.
1611 struct file *do_filp_open(int dfd, const char *pathname,
1612 int open_flag, int mode, int acc_mode)
1614 struct file *filp;
1615 struct nameidata nd;
1616 int error;
1617 struct path path;
1618 struct dentry *dir;
1619 int count = 0;
1620 int will_truncate;
1621 int flag = open_to_namei_flags(open_flag);
1622 int force_reval = 0;
1625 * O_SYNC is implemented as __O_SYNC|O_DSYNC. As many places only
1626 * check for O_DSYNC if the need any syncing at all we enforce it's
1627 * always set instead of having to deal with possibly weird behaviour
1628 * for malicious applications setting only __O_SYNC.
1630 if (open_flag & __O_SYNC)
1631 open_flag |= O_DSYNC;
1633 if (!acc_mode)
1634 acc_mode = MAY_OPEN | ACC_MODE(open_flag);
1636 /* O_TRUNC implies we need access checks for write permissions */
1637 if (flag & O_TRUNC)
1638 acc_mode |= MAY_WRITE;
1640 /* Allow the LSM permission hook to distinguish append
1641 access from general write access. */
1642 if (flag & O_APPEND)
1643 acc_mode |= MAY_APPEND;
1646 * The simplest case - just a plain lookup.
1648 if (!(flag & O_CREAT)) {
1649 filp = get_empty_filp();
1651 if (filp == NULL)
1652 return ERR_PTR(-ENFILE);
1653 nd.intent.open.file = filp;
1654 filp->f_flags = open_flag;
1655 nd.intent.open.flags = flag;
1656 nd.intent.open.create_mode = 0;
1657 error = do_path_lookup(dfd, pathname,
1658 lookup_flags(flag)|LOOKUP_OPEN, &nd);
1659 if (IS_ERR(nd.intent.open.file)) {
1660 if (error == 0) {
1661 error = PTR_ERR(nd.intent.open.file);
1662 path_put(&nd.path);
1664 } else if (error)
1665 release_open_intent(&nd);
1666 if (error)
1667 return ERR_PTR(error);
1668 goto ok;
1672 * Create - we need to know the parent.
1674 reval:
1675 error = path_init(dfd, pathname, LOOKUP_PARENT, &nd);
1676 if (error)
1677 return ERR_PTR(error);
1678 if (force_reval)
1679 nd.flags |= LOOKUP_REVAL;
1680 error = path_walk(pathname, &nd);
1681 if (error) {
1682 if (nd.root.mnt)
1683 path_put(&nd.root);
1684 return ERR_PTR(error);
1686 if (unlikely(!audit_dummy_context()))
1687 audit_inode(pathname, nd.path.dentry);
1690 * We have the parent and last component. First of all, check
1691 * that we are not asked to creat(2) an obvious directory - that
1692 * will not do.
1694 error = -EISDIR;
1695 if (nd.last_type != LAST_NORM || nd.last.name[nd.last.len])
1696 goto exit_parent;
1698 error = -ENFILE;
1699 filp = get_empty_filp();
1700 if (filp == NULL)
1701 goto exit_parent;
1702 nd.intent.open.file = filp;
1703 filp->f_flags = open_flag;
1704 nd.intent.open.flags = flag;
1705 nd.intent.open.create_mode = mode;
1706 dir = nd.path.dentry;
1707 nd.flags &= ~LOOKUP_PARENT;
1708 nd.flags |= LOOKUP_CREATE | LOOKUP_OPEN;
1709 if (flag & O_EXCL)
1710 nd.flags |= LOOKUP_EXCL;
1711 mutex_lock(&dir->d_inode->i_mutex);
1712 path.dentry = lookup_hash(&nd);
1713 path.mnt = nd.path.mnt;
1715 do_last:
1716 error = PTR_ERR(path.dentry);
1717 if (IS_ERR(path.dentry)) {
1718 mutex_unlock(&dir->d_inode->i_mutex);
1719 goto exit;
1722 if (IS_ERR(nd.intent.open.file)) {
1723 error = PTR_ERR(nd.intent.open.file);
1724 goto exit_mutex_unlock;
1727 /* Negative dentry, just create the file */
1728 if (!path.dentry->d_inode) {
1730 * This write is needed to ensure that a
1731 * ro->rw transition does not occur between
1732 * the time when the file is created and when
1733 * a permanent write count is taken through
1734 * the 'struct file' in nameidata_to_filp().
1736 error = mnt_want_write(nd.path.mnt);
1737 if (error)
1738 goto exit_mutex_unlock;
1739 error = __open_namei_create(&nd, &path, flag, mode);
1740 if (error) {
1741 mnt_drop_write(nd.path.mnt);
1742 goto exit;
1744 filp = nameidata_to_filp(&nd);
1745 mnt_drop_write(nd.path.mnt);
1746 if (nd.root.mnt)
1747 path_put(&nd.root);
1748 if (!IS_ERR(filp)) {
1749 error = ima_file_check(filp, acc_mode);
1750 if (error) {
1751 fput(filp);
1752 filp = ERR_PTR(error);
1755 return filp;
1759 * It already exists.
1761 mutex_unlock(&dir->d_inode->i_mutex);
1762 audit_inode(pathname, path.dentry);
1764 error = -EEXIST;
1765 if (flag & O_EXCL)
1766 goto exit_dput;
1768 if (__follow_mount(&path)) {
1769 error = -ELOOP;
1770 if (flag & O_NOFOLLOW)
1771 goto exit_dput;
1774 error = -ENOENT;
1775 if (!path.dentry->d_inode)
1776 goto exit_dput;
1777 if (path.dentry->d_inode->i_op->follow_link)
1778 goto do_link;
1780 path_to_nameidata(&path, &nd);
1781 error = -EISDIR;
1782 if (S_ISDIR(path.dentry->d_inode->i_mode))
1783 goto exit;
1786 * Consider:
1787 * 1. may_open() truncates a file
1788 * 2. a rw->ro mount transition occurs
1789 * 3. nameidata_to_filp() fails due to
1790 * the ro mount.
1791 * That would be inconsistent, and should
1792 * be avoided. Taking this mnt write here
1793 * ensures that (2) can not occur.
1795 will_truncate = open_will_truncate(flag, nd.path.dentry->d_inode);
1796 if (will_truncate) {
1797 error = mnt_want_write(nd.path.mnt);
1798 if (error)
1799 goto exit;
1801 error = may_open(&nd.path, acc_mode, flag);
1802 if (error) {
1803 if (will_truncate)
1804 mnt_drop_write(nd.path.mnt);
1805 goto exit;
1807 filp = nameidata_to_filp(&nd);
1808 if (!IS_ERR(filp)) {
1809 error = ima_file_check(filp, acc_mode);
1810 if (error) {
1811 fput(filp);
1812 filp = ERR_PTR(error);
1815 if (!IS_ERR(filp)) {
1816 if (acc_mode & MAY_WRITE)
1817 vfs_dq_init(nd.path.dentry->d_inode);
1819 if (will_truncate) {
1820 error = handle_truncate(&nd.path);
1821 if (error) {
1822 fput(filp);
1823 filp = ERR_PTR(error);
1828 * It is now safe to drop the mnt write
1829 * because the filp has had a write taken
1830 * on its behalf.
1832 if (will_truncate)
1833 mnt_drop_write(nd.path.mnt);
1834 if (nd.root.mnt)
1835 path_put(&nd.root);
1836 return filp;
1838 exit_mutex_unlock:
1839 mutex_unlock(&dir->d_inode->i_mutex);
1840 exit_dput:
1841 path_put_conditional(&path, &nd);
1842 exit:
1843 if (!IS_ERR(nd.intent.open.file))
1844 release_open_intent(&nd);
1845 exit_parent:
1846 if (nd.root.mnt)
1847 path_put(&nd.root);
1848 path_put(&nd.path);
1849 return ERR_PTR(error);
1851 do_link:
1852 error = -ELOOP;
1853 if (flag & O_NOFOLLOW)
1854 goto exit_dput;
1856 * This is subtle. Instead of calling do_follow_link() we do the
1857 * thing by hands. The reason is that this way we have zero link_count
1858 * and path_walk() (called from ->follow_link) honoring LOOKUP_PARENT.
1859 * After that we have the parent and last component, i.e.
1860 * we are in the same situation as after the first path_walk().
1861 * Well, almost - if the last component is normal we get its copy
1862 * stored in nd->last.name and we will have to putname() it when we
1863 * are done. Procfs-like symlinks just set LAST_BIND.
1865 nd.flags |= LOOKUP_PARENT;
1866 error = security_inode_follow_link(path.dentry, &nd);
1867 if (error)
1868 goto exit_dput;
1869 error = __do_follow_link(&path, &nd);
1870 path_put(&path);
1871 if (error) {
1872 /* Does someone understand code flow here? Or it is only
1873 * me so stupid? Anathema to whoever designed this non-sense
1874 * with "intent.open".
1876 release_open_intent(&nd);
1877 if (nd.root.mnt)
1878 path_put(&nd.root);
1879 if (error == -ESTALE && !force_reval) {
1880 force_reval = 1;
1881 goto reval;
1883 return ERR_PTR(error);
1885 nd.flags &= ~LOOKUP_PARENT;
1886 if (nd.last_type == LAST_BIND)
1887 goto ok;
1888 error = -EISDIR;
1889 if (nd.last_type != LAST_NORM)
1890 goto exit;
1891 if (nd.last.name[nd.last.len]) {
1892 __putname(nd.last.name);
1893 goto exit;
1895 error = -ELOOP;
1896 if (count++==32) {
1897 __putname(nd.last.name);
1898 goto exit;
1900 dir = nd.path.dentry;
1901 mutex_lock(&dir->d_inode->i_mutex);
1902 path.dentry = lookup_hash(&nd);
1903 path.mnt = nd.path.mnt;
1904 __putname(nd.last.name);
1905 goto do_last;
1909 * filp_open - open file and return file pointer
1911 * @filename: path to open
1912 * @flags: open flags as per the open(2) second argument
1913 * @mode: mode for the new file if O_CREAT is set, else ignored
1915 * This is the helper to open a file from kernelspace if you really
1916 * have to. But in generally you should not do this, so please move
1917 * along, nothing to see here..
1919 struct file *filp_open(const char *filename, int flags, int mode)
1921 return do_filp_open(AT_FDCWD, filename, flags, mode, 0);
1923 EXPORT_SYMBOL(filp_open);
1926 * lookup_create - lookup a dentry, creating it if it doesn't exist
1927 * @nd: nameidata info
1928 * @is_dir: directory flag
1930 * Simple function to lookup and return a dentry and create it
1931 * if it doesn't exist. Is SMP-safe.
1933 * Returns with nd->path.dentry->d_inode->i_mutex locked.
1935 struct dentry *lookup_create(struct nameidata *nd, int is_dir)
1937 struct dentry *dentry = ERR_PTR(-EEXIST);
1939 mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
1941 * Yucky last component or no last component at all?
1942 * (foo/., foo/.., /////)
1944 if (nd->last_type != LAST_NORM)
1945 goto fail;
1946 nd->flags &= ~LOOKUP_PARENT;
1947 nd->flags |= LOOKUP_CREATE | LOOKUP_EXCL;
1948 nd->intent.open.flags = O_EXCL;
1951 * Do the final lookup.
1953 dentry = lookup_hash(nd);
1954 if (IS_ERR(dentry))
1955 goto fail;
1957 if (dentry->d_inode)
1958 goto eexist;
1960 * Special case - lookup gave negative, but... we had foo/bar/
1961 * From the vfs_mknod() POV we just have a negative dentry -
1962 * all is fine. Let's be bastards - you had / on the end, you've
1963 * been asking for (non-existent) directory. -ENOENT for you.
1965 if (unlikely(!is_dir && nd->last.name[nd->last.len])) {
1966 dput(dentry);
1967 dentry = ERR_PTR(-ENOENT);
1969 return dentry;
1970 eexist:
1971 dput(dentry);
1972 dentry = ERR_PTR(-EEXIST);
1973 fail:
1974 return dentry;
1976 EXPORT_SYMBOL_GPL(lookup_create);
1978 int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1980 int error = may_create(dir, dentry);
1982 if (error)
1983 return error;
1985 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
1986 return -EPERM;
1988 if (!dir->i_op->mknod)
1989 return -EPERM;
1991 error = devcgroup_inode_mknod(mode, dev);
1992 if (error)
1993 return error;
1995 error = security_inode_mknod(dir, dentry, mode, dev);
1996 if (error)
1997 return error;
1999 vfs_dq_init(dir);
2000 error = dir->i_op->mknod(dir, dentry, mode, dev);
2001 if (!error)
2002 fsnotify_create(dir, dentry);
2003 return error;
2006 static int may_mknod(mode_t mode)
2008 switch (mode & S_IFMT) {
2009 case S_IFREG:
2010 case S_IFCHR:
2011 case S_IFBLK:
2012 case S_IFIFO:
2013 case S_IFSOCK:
2014 case 0: /* zero mode translates to S_IFREG */
2015 return 0;
2016 case S_IFDIR:
2017 return -EPERM;
2018 default:
2019 return -EINVAL;
2023 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, int, mode,
2024 unsigned, dev)
2026 int error;
2027 char *tmp;
2028 struct dentry *dentry;
2029 struct nameidata nd;
2031 if (S_ISDIR(mode))
2032 return -EPERM;
2034 error = user_path_parent(dfd, filename, &nd, &tmp);
2035 if (error)
2036 return error;
2038 dentry = lookup_create(&nd, 0);
2039 if (IS_ERR(dentry)) {
2040 error = PTR_ERR(dentry);
2041 goto out_unlock;
2043 if (!IS_POSIXACL(nd.path.dentry->d_inode))
2044 mode &= ~current_umask();
2045 error = may_mknod(mode);
2046 if (error)
2047 goto out_dput;
2048 error = mnt_want_write(nd.path.mnt);
2049 if (error)
2050 goto out_dput;
2051 error = security_path_mknod(&nd.path, dentry, mode, dev);
2052 if (error)
2053 goto out_drop_write;
2054 switch (mode & S_IFMT) {
2055 case 0: case S_IFREG:
2056 error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd);
2057 break;
2058 case S_IFCHR: case S_IFBLK:
2059 error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,
2060 new_decode_dev(dev));
2061 break;
2062 case S_IFIFO: case S_IFSOCK:
2063 error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);
2064 break;
2066 out_drop_write:
2067 mnt_drop_write(nd.path.mnt);
2068 out_dput:
2069 dput(dentry);
2070 out_unlock:
2071 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2072 path_put(&nd.path);
2073 putname(tmp);
2075 return error;
2078 SYSCALL_DEFINE3(mknod, const char __user *, filename, int, mode, unsigned, dev)
2080 return sys_mknodat(AT_FDCWD, filename, mode, dev);
2083 int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
2085 int error = may_create(dir, dentry);
2087 if (error)
2088 return error;
2090 if (!dir->i_op->mkdir)
2091 return -EPERM;
2093 mode &= (S_IRWXUGO|S_ISVTX);
2094 error = security_inode_mkdir(dir, dentry, mode);
2095 if (error)
2096 return error;
2098 vfs_dq_init(dir);
2099 error = dir->i_op->mkdir(dir, dentry, mode);
2100 if (!error)
2101 fsnotify_mkdir(dir, dentry);
2102 return error;
2105 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, int, mode)
2107 int error = 0;
2108 char * tmp;
2109 struct dentry *dentry;
2110 struct nameidata nd;
2112 error = user_path_parent(dfd, pathname, &nd, &tmp);
2113 if (error)
2114 goto out_err;
2116 dentry = lookup_create(&nd, 1);
2117 error = PTR_ERR(dentry);
2118 if (IS_ERR(dentry))
2119 goto out_unlock;
2121 if (!IS_POSIXACL(nd.path.dentry->d_inode))
2122 mode &= ~current_umask();
2123 error = mnt_want_write(nd.path.mnt);
2124 if (error)
2125 goto out_dput;
2126 error = security_path_mkdir(&nd.path, dentry, mode);
2127 if (error)
2128 goto out_drop_write;
2129 error = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
2130 out_drop_write:
2131 mnt_drop_write(nd.path.mnt);
2132 out_dput:
2133 dput(dentry);
2134 out_unlock:
2135 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2136 path_put(&nd.path);
2137 putname(tmp);
2138 out_err:
2139 return error;
2142 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, int, mode)
2144 return sys_mkdirat(AT_FDCWD, pathname, mode);
2148 * We try to drop the dentry early: we should have
2149 * a usage count of 2 if we're the only user of this
2150 * dentry, and if that is true (possibly after pruning
2151 * the dcache), then we drop the dentry now.
2153 * A low-level filesystem can, if it choses, legally
2154 * do a
2156 * if (!d_unhashed(dentry))
2157 * return -EBUSY;
2159 * if it cannot handle the case of removing a directory
2160 * that is still in use by something else..
2162 void dentry_unhash(struct dentry *dentry)
2164 dget(dentry);
2165 shrink_dcache_parent(dentry);
2166 spin_lock(&dcache_lock);
2167 spin_lock(&dentry->d_lock);
2168 if (atomic_read(&dentry->d_count) == 2)
2169 __d_drop(dentry);
2170 spin_unlock(&dentry->d_lock);
2171 spin_unlock(&dcache_lock);
2174 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
2176 int error = may_delete(dir, dentry, 1);
2178 if (error)
2179 return error;
2181 if (!dir->i_op->rmdir)
2182 return -EPERM;
2184 vfs_dq_init(dir);
2186 mutex_lock(&dentry->d_inode->i_mutex);
2187 dentry_unhash(dentry);
2188 if (d_mountpoint(dentry))
2189 error = -EBUSY;
2190 else {
2191 error = security_inode_rmdir(dir, dentry);
2192 if (!error) {
2193 error = dir->i_op->rmdir(dir, dentry);
2194 if (!error)
2195 dentry->d_inode->i_flags |= S_DEAD;
2198 mutex_unlock(&dentry->d_inode->i_mutex);
2199 if (!error) {
2200 d_delete(dentry);
2202 dput(dentry);
2204 return error;
2207 static long do_rmdir(int dfd, const char __user *pathname)
2209 int error = 0;
2210 char * name;
2211 struct dentry *dentry;
2212 struct nameidata nd;
2214 error = user_path_parent(dfd, pathname, &nd, &name);
2215 if (error)
2216 return error;
2218 switch(nd.last_type) {
2219 case LAST_DOTDOT:
2220 error = -ENOTEMPTY;
2221 goto exit1;
2222 case LAST_DOT:
2223 error = -EINVAL;
2224 goto exit1;
2225 case LAST_ROOT:
2226 error = -EBUSY;
2227 goto exit1;
2230 nd.flags &= ~LOOKUP_PARENT;
2232 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2233 dentry = lookup_hash(&nd);
2234 error = PTR_ERR(dentry);
2235 if (IS_ERR(dentry))
2236 goto exit2;
2237 error = mnt_want_write(nd.path.mnt);
2238 if (error)
2239 goto exit3;
2240 error = security_path_rmdir(&nd.path, dentry);
2241 if (error)
2242 goto exit4;
2243 error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
2244 exit4:
2245 mnt_drop_write(nd.path.mnt);
2246 exit3:
2247 dput(dentry);
2248 exit2:
2249 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2250 exit1:
2251 path_put(&nd.path);
2252 putname(name);
2253 return error;
2256 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
2258 return do_rmdir(AT_FDCWD, pathname);
2261 int vfs_unlink(struct inode *dir, struct dentry *dentry)
2263 int error = may_delete(dir, dentry, 0);
2265 if (error)
2266 return error;
2268 if (!dir->i_op->unlink)
2269 return -EPERM;
2271 vfs_dq_init(dir);
2273 mutex_lock(&dentry->d_inode->i_mutex);
2274 if (d_mountpoint(dentry))
2275 error = -EBUSY;
2276 else {
2277 error = security_inode_unlink(dir, dentry);
2278 if (!error)
2279 error = dir->i_op->unlink(dir, dentry);
2281 mutex_unlock(&dentry->d_inode->i_mutex);
2283 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
2284 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
2285 fsnotify_link_count(dentry->d_inode);
2286 d_delete(dentry);
2289 return error;
2293 * Make sure that the actual truncation of the file will occur outside its
2294 * directory's i_mutex. Truncate can take a long time if there is a lot of
2295 * writeout happening, and we don't want to prevent access to the directory
2296 * while waiting on the I/O.
2298 static long do_unlinkat(int dfd, const char __user *pathname)
2300 int error;
2301 char *name;
2302 struct dentry *dentry;
2303 struct nameidata nd;
2304 struct inode *inode = NULL;
2306 error = user_path_parent(dfd, pathname, &nd, &name);
2307 if (error)
2308 return error;
2310 error = -EISDIR;
2311 if (nd.last_type != LAST_NORM)
2312 goto exit1;
2314 nd.flags &= ~LOOKUP_PARENT;
2316 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2317 dentry = lookup_hash(&nd);
2318 error = PTR_ERR(dentry);
2319 if (!IS_ERR(dentry)) {
2320 /* Why not before? Because we want correct error value */
2321 if (nd.last.name[nd.last.len])
2322 goto slashes;
2323 inode = dentry->d_inode;
2324 if (inode)
2325 atomic_inc(&inode->i_count);
2326 error = mnt_want_write(nd.path.mnt);
2327 if (error)
2328 goto exit2;
2329 error = security_path_unlink(&nd.path, dentry);
2330 if (error)
2331 goto exit3;
2332 error = vfs_unlink(nd.path.dentry->d_inode, dentry);
2333 exit3:
2334 mnt_drop_write(nd.path.mnt);
2335 exit2:
2336 dput(dentry);
2338 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2339 if (inode)
2340 iput(inode); /* truncate the inode here */
2341 exit1:
2342 path_put(&nd.path);
2343 putname(name);
2344 return error;
2346 slashes:
2347 error = !dentry->d_inode ? -ENOENT :
2348 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
2349 goto exit2;
2352 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
2354 if ((flag & ~AT_REMOVEDIR) != 0)
2355 return -EINVAL;
2357 if (flag & AT_REMOVEDIR)
2358 return do_rmdir(dfd, pathname);
2360 return do_unlinkat(dfd, pathname);
2363 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
2365 return do_unlinkat(AT_FDCWD, pathname);
2368 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
2370 int error = may_create(dir, dentry);
2372 if (error)
2373 return error;
2375 if (!dir->i_op->symlink)
2376 return -EPERM;
2378 error = security_inode_symlink(dir, dentry, oldname);
2379 if (error)
2380 return error;
2382 vfs_dq_init(dir);
2383 error = dir->i_op->symlink(dir, dentry, oldname);
2384 if (!error)
2385 fsnotify_create(dir, dentry);
2386 return error;
2389 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
2390 int, newdfd, const char __user *, newname)
2392 int error;
2393 char *from;
2394 char *to;
2395 struct dentry *dentry;
2396 struct nameidata nd;
2398 from = getname(oldname);
2399 if (IS_ERR(from))
2400 return PTR_ERR(from);
2402 error = user_path_parent(newdfd, newname, &nd, &to);
2403 if (error)
2404 goto out_putname;
2406 dentry = lookup_create(&nd, 0);
2407 error = PTR_ERR(dentry);
2408 if (IS_ERR(dentry))
2409 goto out_unlock;
2411 error = mnt_want_write(nd.path.mnt);
2412 if (error)
2413 goto out_dput;
2414 error = security_path_symlink(&nd.path, dentry, from);
2415 if (error)
2416 goto out_drop_write;
2417 error = vfs_symlink(nd.path.dentry->d_inode, dentry, from);
2418 out_drop_write:
2419 mnt_drop_write(nd.path.mnt);
2420 out_dput:
2421 dput(dentry);
2422 out_unlock:
2423 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2424 path_put(&nd.path);
2425 putname(to);
2426 out_putname:
2427 putname(from);
2428 return error;
2431 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
2433 return sys_symlinkat(oldname, AT_FDCWD, newname);
2436 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
2438 struct inode *inode = old_dentry->d_inode;
2439 int error;
2441 if (!inode)
2442 return -ENOENT;
2444 error = may_create(dir, new_dentry);
2445 if (error)
2446 return error;
2448 if (dir->i_sb != inode->i_sb)
2449 return -EXDEV;
2452 * A link to an append-only or immutable file cannot be created.
2454 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
2455 return -EPERM;
2456 if (!dir->i_op->link)
2457 return -EPERM;
2458 if (S_ISDIR(inode->i_mode))
2459 return -EPERM;
2461 error = security_inode_link(old_dentry, dir, new_dentry);
2462 if (error)
2463 return error;
2465 mutex_lock(&inode->i_mutex);
2466 vfs_dq_init(dir);
2467 error = dir->i_op->link(old_dentry, dir, new_dentry);
2468 mutex_unlock(&inode->i_mutex);
2469 if (!error)
2470 fsnotify_link(dir, inode, new_dentry);
2471 return error;
2475 * Hardlinks are often used in delicate situations. We avoid
2476 * security-related surprises by not following symlinks on the
2477 * newname. --KAB
2479 * We don't follow them on the oldname either to be compatible
2480 * with linux 2.0, and to avoid hard-linking to directories
2481 * and other special files. --ADM
2483 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
2484 int, newdfd, const char __user *, newname, int, flags)
2486 struct dentry *new_dentry;
2487 struct nameidata nd;
2488 struct path old_path;
2489 int error;
2490 char *to;
2492 if ((flags & ~AT_SYMLINK_FOLLOW) != 0)
2493 return -EINVAL;
2495 error = user_path_at(olddfd, oldname,
2496 flags & AT_SYMLINK_FOLLOW ? LOOKUP_FOLLOW : 0,
2497 &old_path);
2498 if (error)
2499 return error;
2501 error = user_path_parent(newdfd, newname, &nd, &to);
2502 if (error)
2503 goto out;
2504 error = -EXDEV;
2505 if (old_path.mnt != nd.path.mnt)
2506 goto out_release;
2507 new_dentry = lookup_create(&nd, 0);
2508 error = PTR_ERR(new_dentry);
2509 if (IS_ERR(new_dentry))
2510 goto out_unlock;
2511 error = mnt_want_write(nd.path.mnt);
2512 if (error)
2513 goto out_dput;
2514 error = security_path_link(old_path.dentry, &nd.path, new_dentry);
2515 if (error)
2516 goto out_drop_write;
2517 error = vfs_link(old_path.dentry, nd.path.dentry->d_inode, new_dentry);
2518 out_drop_write:
2519 mnt_drop_write(nd.path.mnt);
2520 out_dput:
2521 dput(new_dentry);
2522 out_unlock:
2523 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2524 out_release:
2525 path_put(&nd.path);
2526 putname(to);
2527 out:
2528 path_put(&old_path);
2530 return error;
2533 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
2535 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
2539 * The worst of all namespace operations - renaming directory. "Perverted"
2540 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
2541 * Problems:
2542 * a) we can get into loop creation. Check is done in is_subdir().
2543 * b) race potential - two innocent renames can create a loop together.
2544 * That's where 4.4 screws up. Current fix: serialization on
2545 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
2546 * story.
2547 * c) we have to lock _three_ objects - parents and victim (if it exists).
2548 * And that - after we got ->i_mutex on parents (until then we don't know
2549 * whether the target exists). Solution: try to be smart with locking
2550 * order for inodes. We rely on the fact that tree topology may change
2551 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
2552 * move will be locked. Thus we can rank directories by the tree
2553 * (ancestors first) and rank all non-directories after them.
2554 * That works since everybody except rename does "lock parent, lookup,
2555 * lock child" and rename is under ->s_vfs_rename_mutex.
2556 * HOWEVER, it relies on the assumption that any object with ->lookup()
2557 * has no more than 1 dentry. If "hybrid" objects will ever appear,
2558 * we'd better make sure that there's no link(2) for them.
2559 * d) some filesystems don't support opened-but-unlinked directories,
2560 * either because of layout or because they are not ready to deal with
2561 * all cases correctly. The latter will be fixed (taking this sort of
2562 * stuff into VFS), but the former is not going away. Solution: the same
2563 * trick as in rmdir().
2564 * e) conversion from fhandle to dentry may come in the wrong moment - when
2565 * we are removing the target. Solution: we will have to grab ->i_mutex
2566 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
2567 * ->i_mutex on parents, which works but leads to some truely excessive
2568 * locking].
2570 static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
2571 struct inode *new_dir, struct dentry *new_dentry)
2573 int error = 0;
2574 struct inode *target;
2577 * If we are going to change the parent - check write permissions,
2578 * we'll need to flip '..'.
2580 if (new_dir != old_dir) {
2581 error = inode_permission(old_dentry->d_inode, MAY_WRITE);
2582 if (error)
2583 return error;
2586 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
2587 if (error)
2588 return error;
2590 target = new_dentry->d_inode;
2591 if (target) {
2592 mutex_lock(&target->i_mutex);
2593 dentry_unhash(new_dentry);
2595 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
2596 error = -EBUSY;
2597 else
2598 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
2599 if (target) {
2600 if (!error)
2601 target->i_flags |= S_DEAD;
2602 mutex_unlock(&target->i_mutex);
2603 if (d_unhashed(new_dentry))
2604 d_rehash(new_dentry);
2605 dput(new_dentry);
2607 if (!error)
2608 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
2609 d_move(old_dentry,new_dentry);
2610 return error;
2613 static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
2614 struct inode *new_dir, struct dentry *new_dentry)
2616 struct inode *target;
2617 int error;
2619 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
2620 if (error)
2621 return error;
2623 dget(new_dentry);
2624 target = new_dentry->d_inode;
2625 if (target)
2626 mutex_lock(&target->i_mutex);
2627 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
2628 error = -EBUSY;
2629 else
2630 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
2631 if (!error) {
2632 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
2633 d_move(old_dentry, new_dentry);
2635 if (target)
2636 mutex_unlock(&target->i_mutex);
2637 dput(new_dentry);
2638 return error;
2641 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
2642 struct inode *new_dir, struct dentry *new_dentry)
2644 int error;
2645 int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
2646 const char *old_name;
2648 if (old_dentry->d_inode == new_dentry->d_inode)
2649 return 0;
2651 error = may_delete(old_dir, old_dentry, is_dir);
2652 if (error)
2653 return error;
2655 if (!new_dentry->d_inode)
2656 error = may_create(new_dir, new_dentry);
2657 else
2658 error = may_delete(new_dir, new_dentry, is_dir);
2659 if (error)
2660 return error;
2662 if (!old_dir->i_op->rename)
2663 return -EPERM;
2665 vfs_dq_init(old_dir);
2666 vfs_dq_init(new_dir);
2668 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
2670 if (is_dir)
2671 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
2672 else
2673 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
2674 if (!error) {
2675 const char *new_name = old_dentry->d_name.name;
2676 fsnotify_move(old_dir, new_dir, old_name, new_name, is_dir,
2677 new_dentry->d_inode, old_dentry);
2679 fsnotify_oldname_free(old_name);
2681 return error;
2684 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
2685 int, newdfd, const char __user *, newname)
2687 struct dentry *old_dir, *new_dir;
2688 struct dentry *old_dentry, *new_dentry;
2689 struct dentry *trap;
2690 struct nameidata oldnd, newnd;
2691 char *from;
2692 char *to;
2693 int error;
2695 error = user_path_parent(olddfd, oldname, &oldnd, &from);
2696 if (error)
2697 goto exit;
2699 error = user_path_parent(newdfd, newname, &newnd, &to);
2700 if (error)
2701 goto exit1;
2703 error = -EXDEV;
2704 if (oldnd.path.mnt != newnd.path.mnt)
2705 goto exit2;
2707 old_dir = oldnd.path.dentry;
2708 error = -EBUSY;
2709 if (oldnd.last_type != LAST_NORM)
2710 goto exit2;
2712 new_dir = newnd.path.dentry;
2713 if (newnd.last_type != LAST_NORM)
2714 goto exit2;
2716 oldnd.flags &= ~LOOKUP_PARENT;
2717 newnd.flags &= ~LOOKUP_PARENT;
2718 newnd.flags |= LOOKUP_RENAME_TARGET;
2720 trap = lock_rename(new_dir, old_dir);
2722 old_dentry = lookup_hash(&oldnd);
2723 error = PTR_ERR(old_dentry);
2724 if (IS_ERR(old_dentry))
2725 goto exit3;
2726 /* source must exist */
2727 error = -ENOENT;
2728 if (!old_dentry->d_inode)
2729 goto exit4;
2730 /* unless the source is a directory trailing slashes give -ENOTDIR */
2731 if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
2732 error = -ENOTDIR;
2733 if (oldnd.last.name[oldnd.last.len])
2734 goto exit4;
2735 if (newnd.last.name[newnd.last.len])
2736 goto exit4;
2738 /* source should not be ancestor of target */
2739 error = -EINVAL;
2740 if (old_dentry == trap)
2741 goto exit4;
2742 new_dentry = lookup_hash(&newnd);
2743 error = PTR_ERR(new_dentry);
2744 if (IS_ERR(new_dentry))
2745 goto exit4;
2746 /* target should not be an ancestor of source */
2747 error = -ENOTEMPTY;
2748 if (new_dentry == trap)
2749 goto exit5;
2751 error = mnt_want_write(oldnd.path.mnt);
2752 if (error)
2753 goto exit5;
2754 error = security_path_rename(&oldnd.path, old_dentry,
2755 &newnd.path, new_dentry);
2756 if (error)
2757 goto exit6;
2758 error = vfs_rename(old_dir->d_inode, old_dentry,
2759 new_dir->d_inode, new_dentry);
2760 exit6:
2761 mnt_drop_write(oldnd.path.mnt);
2762 exit5:
2763 dput(new_dentry);
2764 exit4:
2765 dput(old_dentry);
2766 exit3:
2767 unlock_rename(new_dir, old_dir);
2768 exit2:
2769 path_put(&newnd.path);
2770 putname(to);
2771 exit1:
2772 path_put(&oldnd.path);
2773 putname(from);
2774 exit:
2775 return error;
2778 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
2780 return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
2783 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
2785 int len;
2787 len = PTR_ERR(link);
2788 if (IS_ERR(link))
2789 goto out;
2791 len = strlen(link);
2792 if (len > (unsigned) buflen)
2793 len = buflen;
2794 if (copy_to_user(buffer, link, len))
2795 len = -EFAULT;
2796 out:
2797 return len;
2801 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
2802 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
2803 * using) it for any given inode is up to filesystem.
2805 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
2807 struct nameidata nd;
2808 void *cookie;
2809 int res;
2811 nd.depth = 0;
2812 cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
2813 if (IS_ERR(cookie))
2814 return PTR_ERR(cookie);
2816 res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
2817 if (dentry->d_inode->i_op->put_link)
2818 dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
2819 return res;
2822 int vfs_follow_link(struct nameidata *nd, const char *link)
2824 return __vfs_follow_link(nd, link);
2827 /* get the link contents into pagecache */
2828 static char *page_getlink(struct dentry * dentry, struct page **ppage)
2830 char *kaddr;
2831 struct page *page;
2832 struct address_space *mapping = dentry->d_inode->i_mapping;
2833 page = read_mapping_page(mapping, 0, NULL);
2834 if (IS_ERR(page))
2835 return (char*)page;
2836 *ppage = page;
2837 kaddr = kmap(page);
2838 nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
2839 return kaddr;
2842 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
2844 struct page *page = NULL;
2845 char *s = page_getlink(dentry, &page);
2846 int res = vfs_readlink(dentry,buffer,buflen,s);
2847 if (page) {
2848 kunmap(page);
2849 page_cache_release(page);
2851 return res;
2854 void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
2856 struct page *page = NULL;
2857 nd_set_link(nd, page_getlink(dentry, &page));
2858 return page;
2861 void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2863 struct page *page = cookie;
2865 if (page) {
2866 kunmap(page);
2867 page_cache_release(page);
2872 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
2874 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
2876 struct address_space *mapping = inode->i_mapping;
2877 struct page *page;
2878 void *fsdata;
2879 int err;
2880 char *kaddr;
2881 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
2882 if (nofs)
2883 flags |= AOP_FLAG_NOFS;
2885 retry:
2886 err = pagecache_write_begin(NULL, mapping, 0, len-1,
2887 flags, &page, &fsdata);
2888 if (err)
2889 goto fail;
2891 kaddr = kmap_atomic(page, KM_USER0);
2892 memcpy(kaddr, symname, len-1);
2893 kunmap_atomic(kaddr, KM_USER0);
2895 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
2896 page, fsdata);
2897 if (err < 0)
2898 goto fail;
2899 if (err < len-1)
2900 goto retry;
2902 mark_inode_dirty(inode);
2903 return 0;
2904 fail:
2905 return err;
2908 int page_symlink(struct inode *inode, const char *symname, int len)
2910 return __page_symlink(inode, symname, len,
2911 !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
2914 const struct inode_operations page_symlink_inode_operations = {
2915 .readlink = generic_readlink,
2916 .follow_link = page_follow_link_light,
2917 .put_link = page_put_link,
2920 EXPORT_SYMBOL(user_path_at);
2921 EXPORT_SYMBOL(follow_down);
2922 EXPORT_SYMBOL(follow_up);
2923 EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
2924 EXPORT_SYMBOL(getname);
2925 EXPORT_SYMBOL(lock_rename);
2926 EXPORT_SYMBOL(lookup_one_len);
2927 EXPORT_SYMBOL(page_follow_link_light);
2928 EXPORT_SYMBOL(page_put_link);
2929 EXPORT_SYMBOL(page_readlink);
2930 EXPORT_SYMBOL(__page_symlink);
2931 EXPORT_SYMBOL(page_symlink);
2932 EXPORT_SYMBOL(page_symlink_inode_operations);
2933 EXPORT_SYMBOL(path_lookup);
2934 EXPORT_SYMBOL(kern_path);
2935 EXPORT_SYMBOL(vfs_path_lookup);
2936 EXPORT_SYMBOL(inode_permission);
2937 EXPORT_SYMBOL(file_permission);
2938 EXPORT_SYMBOL(unlock_rename);
2939 EXPORT_SYMBOL(vfs_create);
2940 EXPORT_SYMBOL(vfs_follow_link);
2941 EXPORT_SYMBOL(vfs_link);
2942 EXPORT_SYMBOL(vfs_mkdir);
2943 EXPORT_SYMBOL(vfs_mknod);
2944 EXPORT_SYMBOL(generic_permission);
2945 EXPORT_SYMBOL(vfs_readlink);
2946 EXPORT_SYMBOL(vfs_rename);
2947 EXPORT_SYMBOL(vfs_rmdir);
2948 EXPORT_SYMBOL(vfs_symlink);
2949 EXPORT_SYMBOL(vfs_unlink);
2950 EXPORT_SYMBOL(dentry_unhash);
2951 EXPORT_SYMBOL(generic_readlink);