blob: 935b08d8dcd8220c6c0a0cb557308d659c6e21da [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/fs/namei.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7/*
8 * Some corrections by tytso.
9 */
10
11/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
12 * lookup logic.
13 */
14/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
15 */
16
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/dnotify.h>
25#include <linux/smp_lock.h>
26#include <linux/personality.h>
27#include <linux/security.h>
28#include <linux/syscalls.h>
29#include <linux/mount.h>
30#include <linux/audit.h>
31#include <asm/namei.h>
32#include <asm/uaccess.h>
33
34#define ACC_MODE(x) ("\000\004\002\006"[(x)&O_ACCMODE])
35
36/* [Feb-1997 T. Schoebel-Theuer]
37 * Fundamental changes in the pathname lookup mechanisms (namei)
38 * were necessary because of omirr. The reason is that omirr needs
39 * to know the _real_ pathname, not the user-supplied one, in case
40 * of symlinks (and also when transname replacements occur).
41 *
42 * The new code replaces the old recursive symlink resolution with
43 * an iterative one (in case of non-nested symlink chains). It does
44 * this with calls to <fs>_follow_link().
45 * As a side effect, dir_namei(), _namei() and follow_link() are now
46 * replaced with a single function lookup_dentry() that can handle all
47 * the special cases of the former code.
48 *
49 * With the new dcache, the pathname is stored at each inode, at least as
50 * long as the refcount of the inode is positive. As a side effect, the
51 * size of the dcache depends on the inode cache and thus is dynamic.
52 *
53 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
54 * resolution to correspond with current state of the code.
55 *
56 * Note that the symlink resolution is not *completely* iterative.
57 * There is still a significant amount of tail- and mid- recursion in
58 * the algorithm. Also, note that <fs>_readlink() is not used in
59 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
60 * may return different results than <fs>_follow_link(). Many virtual
61 * filesystems (including /proc) exhibit this behavior.
62 */
63
64/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
65 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
66 * and the name already exists in form of a symlink, try to create the new
67 * name indicated by the symlink. The old code always complained that the
68 * name already exists, due to not following the symlink even if its target
69 * is nonexistent. The new semantics affects also mknod() and link() when
70 * the name is a symlink pointing to a non-existant name.
71 *
72 * I don't know which semantics is the right one, since I have no access
73 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
74 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
75 * "old" one. Personally, I think the new semantics is much more logical.
76 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
77 * file does succeed in both HP-UX and SunOs, but not in Solaris
78 * and in the old Linux semantics.
79 */
80
81/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
82 * semantics. See the comments in "open_namei" and "do_link" below.
83 *
84 * [10-Sep-98 Alan Modra] Another symlink change.
85 */
86
87/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
88 * inside the path - always follow.
89 * in the last component in creation/removal/renaming - never follow.
90 * if LOOKUP_FOLLOW passed - follow.
91 * if the pathname has trailing slashes - follow.
92 * otherwise - don't follow.
93 * (applied in that order).
94 *
95 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
96 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
97 * During the 2.4 we need to fix the userland stuff depending on it -
98 * hopefully we will be able to get rid of that wart in 2.5. So far only
99 * XEmacs seems to be relying on it...
100 */
101/*
102 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
103 * implemented. Let's see if raised priority of ->s_vfs_rename_sem gives
104 * any extra contention...
105 */
106
107/* In order to reduce some races, while at the same time doing additional
108 * checking and hopefully speeding things up, we copy filenames to the
109 * kernel data space before using them..
110 *
111 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
112 * PATH_MAX includes the nul terminator --RR.
113 */
114static inline int do_getname(const char __user *filename, char *page)
115{
116 int retval;
117 unsigned long len = PATH_MAX;
118
119 if (!segment_eq(get_fs(), KERNEL_DS)) {
120 if ((unsigned long) filename >= TASK_SIZE)
121 return -EFAULT;
122 if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
123 len = TASK_SIZE - (unsigned long) filename;
124 }
125
126 retval = strncpy_from_user(page, filename, len);
127 if (retval > 0) {
128 if (retval < len)
129 return 0;
130 return -ENAMETOOLONG;
131 } else if (!retval)
132 retval = -ENOENT;
133 return retval;
134}
135
136char * getname(const char __user * filename)
137{
138 char *tmp, *result;
139
140 result = ERR_PTR(-ENOMEM);
141 tmp = __getname();
142 if (tmp) {
143 int retval = do_getname(filename, tmp);
144
145 result = tmp;
146 if (retval < 0) {
147 __putname(tmp);
148 result = ERR_PTR(retval);
149 }
150 }
151 audit_getname(result);
152 return result;
153}
154
155#ifdef CONFIG_AUDITSYSCALL
156void putname(const char *name)
157{
158 if (unlikely(current->audit_context))
159 audit_putname(name);
160 else
161 __putname(name);
162}
163EXPORT_SYMBOL(putname);
164#endif
165
166
167/**
168 * generic_permission - check for access rights on a Posix-like filesystem
169 * @inode: inode to check access rights for
170 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
171 * @check_acl: optional callback to check for Posix ACLs
172 *
173 * Used to check for read/write/execute permissions on a file.
174 * We use "fsuid" for this, letting us set arbitrary permissions
175 * for filesystem access without changing the "normal" uids which
176 * are used for other things..
177 */
178int generic_permission(struct inode *inode, int mask,
179 int (*check_acl)(struct inode *inode, int mask))
180{
181 umode_t mode = inode->i_mode;
182
183 if (current->fsuid == inode->i_uid)
184 mode >>= 6;
185 else {
186 if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
187 int error = check_acl(inode, mask);
188 if (error == -EACCES)
189 goto check_capabilities;
190 else if (error != -EAGAIN)
191 return error;
192 }
193
194 if (in_group_p(inode->i_gid))
195 mode >>= 3;
196 }
197
198 /*
199 * If the DACs are ok we don't need any capability check.
200 */
201 if (((mode & mask & (MAY_READ|MAY_WRITE|MAY_EXEC)) == mask))
202 return 0;
203
204 check_capabilities:
205 /*
206 * Read/write DACs are always overridable.
207 * Executable DACs are overridable if at least one exec bit is set.
208 */
209 if (!(mask & MAY_EXEC) ||
210 (inode->i_mode & S_IXUGO) || S_ISDIR(inode->i_mode))
211 if (capable(CAP_DAC_OVERRIDE))
212 return 0;
213
214 /*
215 * Searching includes executable on directories, else just read.
216 */
217 if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
218 if (capable(CAP_DAC_READ_SEARCH))
219 return 0;
220
221 return -EACCES;
222}
223
224int permission(struct inode *inode, int mask, struct nameidata *nd)
225{
226 int retval, submask;
227
228 if (mask & MAY_WRITE) {
229 umode_t mode = inode->i_mode;
230
231 /*
232 * Nobody gets write access to a read-only fs.
233 */
234 if (IS_RDONLY(inode) &&
235 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
236 return -EROFS;
237
238 /*
239 * Nobody gets write access to an immutable file.
240 */
241 if (IS_IMMUTABLE(inode))
242 return -EACCES;
243 }
244
245
246 /* Ordinary permission routines do not understand MAY_APPEND. */
247 submask = mask & ~MAY_APPEND;
248 if (inode->i_op && inode->i_op->permission)
249 retval = inode->i_op->permission(inode, submask, nd);
250 else
251 retval = generic_permission(inode, submask, NULL);
252 if (retval)
253 return retval;
254
255 return security_inode_permission(inode, mask, nd);
256}
257
258/*
259 * get_write_access() gets write permission for a file.
260 * put_write_access() releases this write permission.
261 * This is used for regular files.
262 * We cannot support write (and maybe mmap read-write shared) accesses and
263 * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
264 * can have the following values:
265 * 0: no writers, no VM_DENYWRITE mappings
266 * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
267 * > 0: (i_writecount) users are writing to the file.
268 *
269 * Normally we operate on that counter with atomic_{inc,dec} and it's safe
270 * except for the cases where we don't hold i_writecount yet. Then we need to
271 * use {get,deny}_write_access() - these functions check the sign and refuse
272 * to do the change if sign is wrong. Exclusion between them is provided by
273 * the inode->i_lock spinlock.
274 */
275
276int get_write_access(struct inode * inode)
277{
278 spin_lock(&inode->i_lock);
279 if (atomic_read(&inode->i_writecount) < 0) {
280 spin_unlock(&inode->i_lock);
281 return -ETXTBSY;
282 }
283 atomic_inc(&inode->i_writecount);
284 spin_unlock(&inode->i_lock);
285
286 return 0;
287}
288
289int deny_write_access(struct file * file)
290{
291 struct inode *inode = file->f_dentry->d_inode;
292
293 spin_lock(&inode->i_lock);
294 if (atomic_read(&inode->i_writecount) > 0) {
295 spin_unlock(&inode->i_lock);
296 return -ETXTBSY;
297 }
298 atomic_dec(&inode->i_writecount);
299 spin_unlock(&inode->i_lock);
300
301 return 0;
302}
303
304void path_release(struct nameidata *nd)
305{
306 dput(nd->dentry);
307 mntput(nd->mnt);
308}
309
310/*
311 * umount() mustn't call path_release()/mntput() as that would clear
312 * mnt_expiry_mark
313 */
314void path_release_on_umount(struct nameidata *nd)
315{
316 dput(nd->dentry);
317 _mntput(nd->mnt);
318}
319
320/*
321 * Internal lookup() using the new generic dcache.
322 * SMP-safe
323 */
324static struct dentry * cached_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
325{
326 struct dentry * dentry = __d_lookup(parent, name);
327
328 /* lockess __d_lookup may fail due to concurrent d_move()
329 * in some unrelated directory, so try with d_lookup
330 */
331 if (!dentry)
332 dentry = d_lookup(parent, name);
333
334 if (dentry && dentry->d_op && dentry->d_op->d_revalidate) {
335 if (!dentry->d_op->d_revalidate(dentry, nd) && !d_invalidate(dentry)) {
336 dput(dentry);
337 dentry = NULL;
338 }
339 }
340 return dentry;
341}
342
343/*
344 * Short-cut version of permission(), for calling by
345 * path_walk(), when dcache lock is held. Combines parts
346 * of permission() and generic_permission(), and tests ONLY for
347 * MAY_EXEC permission.
348 *
349 * If appropriate, check DAC only. If not appropriate, or
350 * short-cut DAC fails, then call permission() to do more
351 * complete permission check.
352 */
353static inline int exec_permission_lite(struct inode *inode,
354 struct nameidata *nd)
355{
356 umode_t mode = inode->i_mode;
357
358 if (inode->i_op && inode->i_op->permission)
359 return -EAGAIN;
360
361 if (current->fsuid == inode->i_uid)
362 mode >>= 6;
363 else if (in_group_p(inode->i_gid))
364 mode >>= 3;
365
366 if (mode & MAY_EXEC)
367 goto ok;
368
369 if ((inode->i_mode & S_IXUGO) && capable(CAP_DAC_OVERRIDE))
370 goto ok;
371
372 if (S_ISDIR(inode->i_mode) && capable(CAP_DAC_OVERRIDE))
373 goto ok;
374
375 if (S_ISDIR(inode->i_mode) && capable(CAP_DAC_READ_SEARCH))
376 goto ok;
377
378 return -EACCES;
379ok:
380 return security_inode_permission(inode, MAY_EXEC, nd);
381}
382
383/*
384 * This is called when everything else fails, and we actually have
385 * to go to the low-level filesystem to find out what we should do..
386 *
387 * We get the directory semaphore, and after getting that we also
388 * make sure that nobody added the entry to the dcache in the meantime..
389 * SMP-safe
390 */
391static struct dentry * real_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
392{
393 struct dentry * result;
394 struct inode *dir = parent->d_inode;
395
396 down(&dir->i_sem);
397 /*
398 * First re-do the cached lookup just in case it was created
399 * while we waited for the directory semaphore..
400 *
401 * FIXME! This could use version numbering or similar to
402 * avoid unnecessary cache lookups.
403 *
404 * The "dcache_lock" is purely to protect the RCU list walker
405 * from concurrent renames at this point (we mustn't get false
406 * negatives from the RCU list walk here, unlike the optimistic
407 * fast walk).
408 *
409 * so doing d_lookup() (with seqlock), instead of lockfree __d_lookup
410 */
411 result = d_lookup(parent, name);
412 if (!result) {
413 struct dentry * dentry = d_alloc(parent, name);
414 result = ERR_PTR(-ENOMEM);
415 if (dentry) {
416 result = dir->i_op->lookup(dir, dentry, nd);
417 if (result)
418 dput(dentry);
419 else
420 result = dentry;
421 }
422 up(&dir->i_sem);
423 return result;
424 }
425
426 /*
427 * Uhhuh! Nasty case: the cache was re-populated while
428 * we waited on the semaphore. Need to revalidate.
429 */
430 up(&dir->i_sem);
431 if (result->d_op && result->d_op->d_revalidate) {
432 if (!result->d_op->d_revalidate(result, nd) && !d_invalidate(result)) {
433 dput(result);
434 result = ERR_PTR(-ENOENT);
435 }
436 }
437 return result;
438}
439
440static int __emul_lookup_dentry(const char *, struct nameidata *);
441
442/* SMP-safe */
443static inline int
444walk_init_root(const char *name, struct nameidata *nd)
445{
446 read_lock(&current->fs->lock);
447 if (current->fs->altroot && !(nd->flags & LOOKUP_NOALT)) {
448 nd->mnt = mntget(current->fs->altrootmnt);
449 nd->dentry = dget(current->fs->altroot);
450 read_unlock(&current->fs->lock);
451 if (__emul_lookup_dentry(name,nd))
452 return 0;
453 read_lock(&current->fs->lock);
454 }
455 nd->mnt = mntget(current->fs->rootmnt);
456 nd->dentry = dget(current->fs->root);
457 read_unlock(&current->fs->lock);
458 return 1;
459}
460
461static inline int __vfs_follow_link(struct nameidata *nd, const char *link)
462{
463 int res = 0;
464 char *name;
465 if (IS_ERR(link))
466 goto fail;
467
468 if (*link == '/') {
469 path_release(nd);
470 if (!walk_init_root(link, nd))
471 /* weird __emul_prefix() stuff did it */
472 goto out;
473 }
474 res = link_path_walk(link, nd);
475out:
476 if (nd->depth || res || nd->last_type!=LAST_NORM)
477 return res;
478 /*
479 * If it is an iterative symlinks resolution in open_namei() we
480 * have to copy the last component. And all that crap because of
481 * bloody create() on broken symlinks. Furrfu...
482 */
483 name = __getname();
484 if (unlikely(!name)) {
485 path_release(nd);
486 return -ENOMEM;
487 }
488 strcpy(name, nd->last.name);
489 nd->last.name = name;
490 return 0;
491fail:
492 path_release(nd);
493 return PTR_ERR(link);
494}
495
Al Viro90ebe562005-06-06 13:35:58 -0700496struct path {
497 struct vfsmount *mnt;
498 struct dentry *dentry;
499};
500
Al Virocd4e91d2005-06-06 13:36:03 -0700501static inline int __do_follow_link(struct path *path, struct nameidata *nd)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700502{
503 int error;
Al Virocd4e91d2005-06-06 13:36:03 -0700504 struct dentry *dentry = path->dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700505
506 touch_atime(nd->mnt, dentry);
507 nd_set_link(nd, NULL);
Al Virocd4e91d2005-06-06 13:36:03 -0700508
509 mntget(path->mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700510 error = dentry->d_inode->i_op->follow_link(dentry, nd);
511 if (!error) {
512 char *s = nd_get_link(nd);
513 if (s)
514 error = __vfs_follow_link(nd, s);
515 if (dentry->d_inode->i_op->put_link)
516 dentry->d_inode->i_op->put_link(dentry, nd);
517 }
Al Virocd4e91d2005-06-06 13:36:03 -0700518 dput(dentry);
519 mntput(path->mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700520
521 return error;
522}
523
524/*
525 * This limits recursive symlink follows to 8, while
526 * limiting consecutive symlinks to 40.
527 *
528 * Without that kind of total limit, nasty chains of consecutive
529 * symlinks can cause almost arbitrarily long lookups.
530 */
Al Viro90ebe562005-06-06 13:35:58 -0700531static inline int do_follow_link(struct path *path, struct nameidata *nd)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700532{
533 int err = -ELOOP;
534 if (current->link_count >= MAX_NESTED_LINKS)
535 goto loop;
536 if (current->total_link_count >= 40)
537 goto loop;
538 BUG_ON(nd->depth >= MAX_NESTED_LINKS);
539 cond_resched();
Al Viro90ebe562005-06-06 13:35:58 -0700540 err = security_inode_follow_link(path->dentry, nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700541 if (err)
542 goto loop;
543 current->link_count++;
544 current->total_link_count++;
545 nd->depth++;
Al Virocd4e91d2005-06-06 13:36:03 -0700546 err = __do_follow_link(path, nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700547 current->link_count--;
548 nd->depth--;
549 return err;
550loop:
Al Viro5f92b3bc2005-06-06 13:35:59 -0700551 dput(path->dentry);
Al Viro839d9f92005-06-06 13:36:02 -0700552 path_release(nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553 return err;
554}
555
556int follow_up(struct vfsmount **mnt, struct dentry **dentry)
557{
558 struct vfsmount *parent;
559 struct dentry *mountpoint;
560 spin_lock(&vfsmount_lock);
561 parent=(*mnt)->mnt_parent;
562 if (parent == *mnt) {
563 spin_unlock(&vfsmount_lock);
564 return 0;
565 }
566 mntget(parent);
567 mountpoint=dget((*mnt)->mnt_mountpoint);
568 spin_unlock(&vfsmount_lock);
569 dput(*dentry);
570 *dentry = mountpoint;
571 mntput(*mnt);
572 *mnt = parent;
573 return 1;
574}
575
576/* no need for dcache_lock, as serialization is taken care in
577 * namespace.c
578 */
Al Viro463ffb22005-06-06 13:36:05 -0700579static int __follow_mount(struct path *path)
580{
581 int res = 0;
582 while (d_mountpoint(path->dentry)) {
583 struct vfsmount *mounted = lookup_mnt(path->mnt, path->dentry);
584 if (!mounted)
585 break;
586 dput(path->dentry);
587 if (res)
588 mntput(path->mnt);
589 path->mnt = mounted;
590 path->dentry = dget(mounted->mnt_root);
591 res = 1;
592 }
593 return res;
594}
595
Linus Torvalds1da177e2005-04-16 15:20:36 -0700596static int follow_mount(struct vfsmount **mnt, struct dentry **dentry)
597{
598 int res = 0;
599 while (d_mountpoint(*dentry)) {
600 struct vfsmount *mounted = lookup_mnt(*mnt, *dentry);
601 if (!mounted)
602 break;
603 mntput(*mnt);
604 *mnt = mounted;
605 dput(*dentry);
606 *dentry = dget(mounted->mnt_root);
607 res = 1;
608 }
609 return res;
610}
611
612/* no need for dcache_lock, as serialization is taken care in
613 * namespace.c
614 */
Al Viroe13b2102005-06-06 13:36:06 -0700615int follow_down(struct vfsmount **mnt, struct dentry **dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700616{
617 struct vfsmount *mounted;
618
619 mounted = lookup_mnt(*mnt, *dentry);
620 if (mounted) {
Al Viroe13b2102005-06-06 13:36:06 -0700621 dput(*dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700622 mntput(*mnt);
623 *mnt = mounted;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700624 *dentry = dget(mounted->mnt_root);
625 return 1;
626 }
627 return 0;
628}
629
Linus Torvalds1da177e2005-04-16 15:20:36 -0700630static inline void follow_dotdot(struct vfsmount **mnt, struct dentry **dentry)
631{
632 while(1) {
633 struct vfsmount *parent;
634 struct dentry *old = *dentry;
635
636 read_lock(&current->fs->lock);
637 if (*dentry == current->fs->root &&
638 *mnt == current->fs->rootmnt) {
639 read_unlock(&current->fs->lock);
640 break;
641 }
642 read_unlock(&current->fs->lock);
643 spin_lock(&dcache_lock);
644 if (*dentry != (*mnt)->mnt_root) {
645 *dentry = dget((*dentry)->d_parent);
646 spin_unlock(&dcache_lock);
647 dput(old);
648 break;
649 }
650 spin_unlock(&dcache_lock);
651 spin_lock(&vfsmount_lock);
652 parent = (*mnt)->mnt_parent;
653 if (parent == *mnt) {
654 spin_unlock(&vfsmount_lock);
655 break;
656 }
657 mntget(parent);
658 *dentry = dget((*mnt)->mnt_mountpoint);
659 spin_unlock(&vfsmount_lock);
660 dput(old);
661 mntput(*mnt);
662 *mnt = parent;
663 }
664 follow_mount(mnt, dentry);
665}
666
Linus Torvalds1da177e2005-04-16 15:20:36 -0700667/*
668 * It's more convoluted than I'd like it to be, but... it's still fairly
669 * small and for now I'd prefer to have fast path as straight as possible.
670 * It _is_ time-critical.
671 */
672static int do_lookup(struct nameidata *nd, struct qstr *name,
673 struct path *path)
674{
675 struct vfsmount *mnt = nd->mnt;
676 struct dentry *dentry = __d_lookup(nd->dentry, name);
677
678 if (!dentry)
679 goto need_lookup;
680 if (dentry->d_op && dentry->d_op->d_revalidate)
681 goto need_revalidate;
682done:
683 path->mnt = mnt;
684 path->dentry = dentry;
685 return 0;
686
687need_lookup:
688 dentry = real_lookup(nd->dentry, name, nd);
689 if (IS_ERR(dentry))
690 goto fail;
691 goto done;
692
693need_revalidate:
694 if (dentry->d_op->d_revalidate(dentry, nd))
695 goto done;
696 if (d_invalidate(dentry))
697 goto done;
698 dput(dentry);
699 goto need_lookup;
700
701fail:
702 return PTR_ERR(dentry);
703}
704
705/*
706 * Name resolution.
Prasanna Medaea3834d2005-04-29 16:00:17 +0100707 * This is the basic name resolution function, turning a pathname into
708 * the final dentry. We expect 'base' to be positive and a directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700709 *
Prasanna Medaea3834d2005-04-29 16:00:17 +0100710 * Returns 0 and nd will have valid dentry and mnt on success.
711 * Returns error and drops reference to input namei data on failure.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700712 */
713static fastcall int __link_path_walk(const char * name, struct nameidata *nd)
714{
715 struct path next;
716 struct inode *inode;
717 int err;
718 unsigned int lookup_flags = nd->flags;
719
720 while (*name=='/')
721 name++;
722 if (!*name)
723 goto return_reval;
724
725 inode = nd->dentry->d_inode;
726 if (nd->depth)
727 lookup_flags = LOOKUP_FOLLOW;
728
729 /* At this point we know we have a real path component. */
730 for(;;) {
731 unsigned long hash;
732 struct qstr this;
733 unsigned int c;
734
735 err = exec_permission_lite(inode, nd);
736 if (err == -EAGAIN) {
737 err = permission(inode, MAY_EXEC, nd);
738 }
739 if (err)
740 break;
741
742 this.name = name;
743 c = *(const unsigned char *)name;
744
745 hash = init_name_hash();
746 do {
747 name++;
748 hash = partial_name_hash(c, hash);
749 c = *(const unsigned char *)name;
750 } while (c && (c != '/'));
751 this.len = name - (const char *) this.name;
752 this.hash = end_name_hash(hash);
753
754 /* remove trailing slashes? */
755 if (!c)
756 goto last_component;
757 while (*++name == '/');
758 if (!*name)
759 goto last_with_slashes;
760
761 /*
762 * "." and ".." are special - ".." especially so because it has
763 * to be able to know about the current root directory and
764 * parent relationships.
765 */
766 if (this.name[0] == '.') switch (this.len) {
767 default:
768 break;
769 case 2:
770 if (this.name[1] != '.')
771 break;
772 follow_dotdot(&nd->mnt, &nd->dentry);
773 inode = nd->dentry->d_inode;
774 /* fallthrough */
775 case 1:
776 continue;
777 }
778 /*
779 * See if the low-level filesystem might want
780 * to use its own hash..
781 */
782 if (nd->dentry->d_op && nd->dentry->d_op->d_hash) {
783 err = nd->dentry->d_op->d_hash(nd->dentry, &this);
784 if (err < 0)
785 break;
786 }
787 nd->flags |= LOOKUP_CONTINUE;
788 /* This does the actual lookups.. */
789 err = do_lookup(nd, &this, &next);
790 if (err)
791 break;
792 /* Check mountpoints.. */
Al Viro463ffb22005-06-06 13:36:05 -0700793 __follow_mount(&next);
794 if (nd->mnt != next.mnt)
795 mntput(nd->mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700796
797 err = -ENOENT;
798 inode = next.dentry->d_inode;
799 if (!inode)
800 goto out_dput;
801 err = -ENOTDIR;
802 if (!inode->i_op)
803 goto out_dput;
804
805 if (inode->i_op->follow_link) {
Al Viro90ebe562005-06-06 13:35:58 -0700806 err = do_follow_link(&next, nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700807 if (err)
808 goto return_err;
809 err = -ENOENT;
810 inode = nd->dentry->d_inode;
811 if (!inode)
812 break;
813 err = -ENOTDIR;
814 if (!inode->i_op)
815 break;
816 } else {
817 dput(nd->dentry);
818 nd->mnt = next.mnt;
819 nd->dentry = next.dentry;
820 }
821 err = -ENOTDIR;
822 if (!inode->i_op->lookup)
823 break;
824 continue;
825 /* here ends the main loop */
826
827last_with_slashes:
828 lookup_flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
829last_component:
830 nd->flags &= ~LOOKUP_CONTINUE;
831 if (lookup_flags & LOOKUP_PARENT)
832 goto lookup_parent;
833 if (this.name[0] == '.') switch (this.len) {
834 default:
835 break;
836 case 2:
837 if (this.name[1] != '.')
838 break;
839 follow_dotdot(&nd->mnt, &nd->dentry);
840 inode = nd->dentry->d_inode;
841 /* fallthrough */
842 case 1:
843 goto return_reval;
844 }
845 if (nd->dentry->d_op && nd->dentry->d_op->d_hash) {
846 err = nd->dentry->d_op->d_hash(nd->dentry, &this);
847 if (err < 0)
848 break;
849 }
850 err = do_lookup(nd, &this, &next);
851 if (err)
852 break;
Al Viro463ffb22005-06-06 13:36:05 -0700853 __follow_mount(&next);
854 if (nd->mnt != next.mnt)
855 mntput(nd->mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700856 inode = next.dentry->d_inode;
857 if ((lookup_flags & LOOKUP_FOLLOW)
858 && inode && inode->i_op && inode->i_op->follow_link) {
Al Viro90ebe562005-06-06 13:35:58 -0700859 err = do_follow_link(&next, nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700860 if (err)
861 goto return_err;
862 inode = nd->dentry->d_inode;
863 } else {
864 dput(nd->dentry);
865 nd->mnt = next.mnt;
866 nd->dentry = next.dentry;
867 }
868 err = -ENOENT;
869 if (!inode)
870 break;
871 if (lookup_flags & LOOKUP_DIRECTORY) {
872 err = -ENOTDIR;
873 if (!inode->i_op || !inode->i_op->lookup)
874 break;
875 }
876 goto return_base;
877lookup_parent:
878 nd->last = this;
879 nd->last_type = LAST_NORM;
880 if (this.name[0] != '.')
881 goto return_base;
882 if (this.len == 1)
883 nd->last_type = LAST_DOT;
884 else if (this.len == 2 && this.name[1] == '.')
885 nd->last_type = LAST_DOTDOT;
886 else
887 goto return_base;
888return_reval:
889 /*
890 * We bypassed the ordinary revalidation routines.
891 * We may need to check the cached dentry for staleness.
892 */
893 if (nd->dentry && nd->dentry->d_sb &&
894 (nd->dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)) {
895 err = -ESTALE;
896 /* Note: we do not d_invalidate() */
897 if (!nd->dentry->d_op->d_revalidate(nd->dentry, nd))
898 break;
899 }
900return_base:
901 return 0;
902out_dput:
903 dput(next.dentry);
904 break;
905 }
906 path_release(nd);
907return_err:
908 return err;
909}
910
911/*
912 * Wrapper to retry pathname resolution whenever the underlying
913 * file system returns an ESTALE.
914 *
915 * Retry the whole path once, forcing real lookup requests
916 * instead of relying on the dcache.
917 */
918int fastcall link_path_walk(const char *name, struct nameidata *nd)
919{
920 struct nameidata save = *nd;
921 int result;
922
923 /* make sure the stuff we saved doesn't go away */
924 dget(save.dentry);
925 mntget(save.mnt);
926
927 result = __link_path_walk(name, nd);
928 if (result == -ESTALE) {
929 *nd = save;
930 dget(nd->dentry);
931 mntget(nd->mnt);
932 nd->flags |= LOOKUP_REVAL;
933 result = __link_path_walk(name, nd);
934 }
935
936 dput(save.dentry);
937 mntput(save.mnt);
938
939 return result;
940}
941
942int fastcall path_walk(const char * name, struct nameidata *nd)
943{
944 current->total_link_count = 0;
945 return link_path_walk(name, nd);
946}
947
Prasanna Medaea3834d2005-04-29 16:00:17 +0100948/*
949 * SMP-safe: Returns 1 and nd will have valid dentry and mnt, if
950 * everything is done. Returns 0 and drops input nd, if lookup failed;
951 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700952static int __emul_lookup_dentry(const char *name, struct nameidata *nd)
953{
954 if (path_walk(name, nd))
955 return 0; /* something went wrong... */
956
957 if (!nd->dentry->d_inode || S_ISDIR(nd->dentry->d_inode->i_mode)) {
958 struct dentry *old_dentry = nd->dentry;
959 struct vfsmount *old_mnt = nd->mnt;
960 struct qstr last = nd->last;
961 int last_type = nd->last_type;
962 /*
963 * NAME was not found in alternate root or it's a directory. Try to find
964 * it in the normal root:
965 */
966 nd->last_type = LAST_ROOT;
967 read_lock(&current->fs->lock);
968 nd->mnt = mntget(current->fs->rootmnt);
969 nd->dentry = dget(current->fs->root);
970 read_unlock(&current->fs->lock);
971 if (path_walk(name, nd) == 0) {
972 if (nd->dentry->d_inode) {
973 dput(old_dentry);
974 mntput(old_mnt);
975 return 1;
976 }
977 path_release(nd);
978 }
979 nd->dentry = old_dentry;
980 nd->mnt = old_mnt;
981 nd->last = last;
982 nd->last_type = last_type;
983 }
984 return 1;
985}
986
987void set_fs_altroot(void)
988{
989 char *emul = __emul_prefix();
990 struct nameidata nd;
991 struct vfsmount *mnt = NULL, *oldmnt;
992 struct dentry *dentry = NULL, *olddentry;
993 int err;
994
995 if (!emul)
996 goto set_it;
997 err = path_lookup(emul, LOOKUP_FOLLOW|LOOKUP_DIRECTORY|LOOKUP_NOALT, &nd);
998 if (!err) {
999 mnt = nd.mnt;
1000 dentry = nd.dentry;
1001 }
1002set_it:
1003 write_lock(&current->fs->lock);
1004 oldmnt = current->fs->altrootmnt;
1005 olddentry = current->fs->altroot;
1006 current->fs->altrootmnt = mnt;
1007 current->fs->altroot = dentry;
1008 write_unlock(&current->fs->lock);
1009 if (olddentry) {
1010 dput(olddentry);
1011 mntput(oldmnt);
1012 }
1013}
1014
Prasanna Medaea3834d2005-04-29 16:00:17 +01001015/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001016int fastcall path_lookup(const char *name, unsigned int flags, struct nameidata *nd)
1017{
Prasanna Medaea3834d2005-04-29 16:00:17 +01001018 int retval = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001019
1020 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1021 nd->flags = flags;
1022 nd->depth = 0;
1023
1024 read_lock(&current->fs->lock);
1025 if (*name=='/') {
1026 if (current->fs->altroot && !(nd->flags & LOOKUP_NOALT)) {
1027 nd->mnt = mntget(current->fs->altrootmnt);
1028 nd->dentry = dget(current->fs->altroot);
1029 read_unlock(&current->fs->lock);
1030 if (__emul_lookup_dentry(name,nd))
Prasanna Medaea3834d2005-04-29 16:00:17 +01001031 goto out; /* found in altroot */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001032 read_lock(&current->fs->lock);
1033 }
1034 nd->mnt = mntget(current->fs->rootmnt);
1035 nd->dentry = dget(current->fs->root);
1036 } else {
1037 nd->mnt = mntget(current->fs->pwdmnt);
1038 nd->dentry = dget(current->fs->pwd);
1039 }
1040 read_unlock(&current->fs->lock);
1041 current->total_link_count = 0;
1042 retval = link_path_walk(name, nd);
Prasanna Medaea3834d2005-04-29 16:00:17 +01001043out:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001044 if (unlikely(current->audit_context
1045 && nd && nd->dentry && nd->dentry->d_inode))
1046 audit_inode(name, nd->dentry->d_inode);
1047 return retval;
1048}
1049
1050/*
1051 * Restricted form of lookup. Doesn't follow links, single-component only,
1052 * needs parent already locked. Doesn't follow mounts.
1053 * SMP-safe.
1054 */
1055static struct dentry * __lookup_hash(struct qstr *name, struct dentry * base, struct nameidata *nd)
1056{
1057 struct dentry * dentry;
1058 struct inode *inode;
1059 int err;
1060
1061 inode = base->d_inode;
1062 err = permission(inode, MAY_EXEC, nd);
1063 dentry = ERR_PTR(err);
1064 if (err)
1065 goto out;
1066
1067 /*
1068 * See if the low-level filesystem might want
1069 * to use its own hash..
1070 */
1071 if (base->d_op && base->d_op->d_hash) {
1072 err = base->d_op->d_hash(base, name);
1073 dentry = ERR_PTR(err);
1074 if (err < 0)
1075 goto out;
1076 }
1077
1078 dentry = cached_lookup(base, name, nd);
1079 if (!dentry) {
1080 struct dentry *new = d_alloc(base, name);
1081 dentry = ERR_PTR(-ENOMEM);
1082 if (!new)
1083 goto out;
1084 dentry = inode->i_op->lookup(inode, new, nd);
1085 if (!dentry)
1086 dentry = new;
1087 else
1088 dput(new);
1089 }
1090out:
1091 return dentry;
1092}
1093
1094struct dentry * lookup_hash(struct qstr *name, struct dentry * base)
1095{
1096 return __lookup_hash(name, base, NULL);
1097}
1098
1099/* SMP-safe */
1100struct dentry * lookup_one_len(const char * name, struct dentry * base, int len)
1101{
1102 unsigned long hash;
1103 struct qstr this;
1104 unsigned int c;
1105
1106 this.name = name;
1107 this.len = len;
1108 if (!len)
1109 goto access;
1110
1111 hash = init_name_hash();
1112 while (len--) {
1113 c = *(const unsigned char *)name++;
1114 if (c == '/' || c == '\0')
1115 goto access;
1116 hash = partial_name_hash(c, hash);
1117 }
1118 this.hash = end_name_hash(hash);
1119
1120 return lookup_hash(&this, base);
1121access:
1122 return ERR_PTR(-EACCES);
1123}
1124
1125/*
1126 * namei()
1127 *
1128 * is used by most simple commands to get the inode of a specified name.
1129 * Open, link etc use their own routines, but this is enough for things
1130 * like 'chmod' etc.
1131 *
1132 * namei exists in two versions: namei/lnamei. The only difference is
1133 * that namei follows links, while lnamei does not.
1134 * SMP-safe
1135 */
1136int fastcall __user_walk(const char __user *name, unsigned flags, struct nameidata *nd)
1137{
1138 char *tmp = getname(name);
1139 int err = PTR_ERR(tmp);
1140
1141 if (!IS_ERR(tmp)) {
1142 err = path_lookup(tmp, flags, nd);
1143 putname(tmp);
1144 }
1145 return err;
1146}
1147
1148/*
1149 * It's inline, so penalty for filesystems that don't use sticky bit is
1150 * minimal.
1151 */
1152static inline int check_sticky(struct inode *dir, struct inode *inode)
1153{
1154 if (!(dir->i_mode & S_ISVTX))
1155 return 0;
1156 if (inode->i_uid == current->fsuid)
1157 return 0;
1158 if (dir->i_uid == current->fsuid)
1159 return 0;
1160 return !capable(CAP_FOWNER);
1161}
1162
1163/*
1164 * Check whether we can remove a link victim from directory dir, check
1165 * whether the type of victim is right.
1166 * 1. We can't do it if dir is read-only (done in permission())
1167 * 2. We should have write and exec permissions on dir
1168 * 3. We can't remove anything from append-only dir
1169 * 4. We can't do anything with immutable dir (done in permission())
1170 * 5. If the sticky bit on dir is set we should either
1171 * a. be owner of dir, or
1172 * b. be owner of victim, or
1173 * c. have CAP_FOWNER capability
1174 * 6. If the victim is append-only or immutable we can't do antyhing with
1175 * links pointing to it.
1176 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
1177 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
1178 * 9. We can't remove a root or mountpoint.
1179 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
1180 * nfs_async_unlink().
1181 */
1182static inline int may_delete(struct inode *dir,struct dentry *victim,int isdir)
1183{
1184 int error;
1185
1186 if (!victim->d_inode)
1187 return -ENOENT;
1188
1189 BUG_ON(victim->d_parent->d_inode != dir);
1190
1191 error = permission(dir,MAY_WRITE | MAY_EXEC, NULL);
1192 if (error)
1193 return error;
1194 if (IS_APPEND(dir))
1195 return -EPERM;
1196 if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
1197 IS_IMMUTABLE(victim->d_inode))
1198 return -EPERM;
1199 if (isdir) {
1200 if (!S_ISDIR(victim->d_inode->i_mode))
1201 return -ENOTDIR;
1202 if (IS_ROOT(victim))
1203 return -EBUSY;
1204 } else if (S_ISDIR(victim->d_inode->i_mode))
1205 return -EISDIR;
1206 if (IS_DEADDIR(dir))
1207 return -ENOENT;
1208 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
1209 return -EBUSY;
1210 return 0;
1211}
1212
1213/* Check whether we can create an object with dentry child in directory
1214 * dir.
1215 * 1. We can't do it if child already exists (open has special treatment for
1216 * this case, but since we are inlined it's OK)
1217 * 2. We can't do it if dir is read-only (done in permission())
1218 * 3. We should have write and exec permissions on dir
1219 * 4. We can't do it if dir is immutable (done in permission())
1220 */
1221static inline int may_create(struct inode *dir, struct dentry *child,
1222 struct nameidata *nd)
1223{
1224 if (child->d_inode)
1225 return -EEXIST;
1226 if (IS_DEADDIR(dir))
1227 return -ENOENT;
1228 return permission(dir,MAY_WRITE | MAY_EXEC, nd);
1229}
1230
1231/*
1232 * Special case: O_CREAT|O_EXCL implies O_NOFOLLOW for security
1233 * reasons.
1234 *
1235 * O_DIRECTORY translates into forcing a directory lookup.
1236 */
1237static inline int lookup_flags(unsigned int f)
1238{
1239 unsigned long retval = LOOKUP_FOLLOW;
1240
1241 if (f & O_NOFOLLOW)
1242 retval &= ~LOOKUP_FOLLOW;
1243
1244 if ((f & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL))
1245 retval &= ~LOOKUP_FOLLOW;
1246
1247 if (f & O_DIRECTORY)
1248 retval |= LOOKUP_DIRECTORY;
1249
1250 return retval;
1251}
1252
1253/*
1254 * p1 and p2 should be directories on the same fs.
1255 */
1256struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
1257{
1258 struct dentry *p;
1259
1260 if (p1 == p2) {
1261 down(&p1->d_inode->i_sem);
1262 return NULL;
1263 }
1264
1265 down(&p1->d_inode->i_sb->s_vfs_rename_sem);
1266
1267 for (p = p1; p->d_parent != p; p = p->d_parent) {
1268 if (p->d_parent == p2) {
1269 down(&p2->d_inode->i_sem);
1270 down(&p1->d_inode->i_sem);
1271 return p;
1272 }
1273 }
1274
1275 for (p = p2; p->d_parent != p; p = p->d_parent) {
1276 if (p->d_parent == p1) {
1277 down(&p1->d_inode->i_sem);
1278 down(&p2->d_inode->i_sem);
1279 return p;
1280 }
1281 }
1282
1283 down(&p1->d_inode->i_sem);
1284 down(&p2->d_inode->i_sem);
1285 return NULL;
1286}
1287
1288void unlock_rename(struct dentry *p1, struct dentry *p2)
1289{
1290 up(&p1->d_inode->i_sem);
1291 if (p1 != p2) {
1292 up(&p2->d_inode->i_sem);
1293 up(&p1->d_inode->i_sb->s_vfs_rename_sem);
1294 }
1295}
1296
1297int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
1298 struct nameidata *nd)
1299{
1300 int error = may_create(dir, dentry, nd);
1301
1302 if (error)
1303 return error;
1304
1305 if (!dir->i_op || !dir->i_op->create)
1306 return -EACCES; /* shouldn't it be ENOSYS? */
1307 mode &= S_IALLUGO;
1308 mode |= S_IFREG;
1309 error = security_inode_create(dir, dentry, mode);
1310 if (error)
1311 return error;
1312 DQUOT_INIT(dir);
1313 error = dir->i_op->create(dir, dentry, mode, nd);
1314 if (!error) {
1315 inode_dir_notify(dir, DN_CREATE);
1316 security_inode_post_create(dir, dentry, mode);
1317 }
1318 return error;
1319}
1320
1321int may_open(struct nameidata *nd, int acc_mode, int flag)
1322{
1323 struct dentry *dentry = nd->dentry;
1324 struct inode *inode = dentry->d_inode;
1325 int error;
1326
1327 if (!inode)
1328 return -ENOENT;
1329
1330 if (S_ISLNK(inode->i_mode))
1331 return -ELOOP;
1332
1333 if (S_ISDIR(inode->i_mode) && (flag & FMODE_WRITE))
1334 return -EISDIR;
1335
1336 error = permission(inode, acc_mode, nd);
1337 if (error)
1338 return error;
1339
1340 /*
1341 * FIFO's, sockets and device files are special: they don't
1342 * actually live on the filesystem itself, and as such you
1343 * can write to them even if the filesystem is read-only.
1344 */
1345 if (S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
1346 flag &= ~O_TRUNC;
1347 } else if (S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode)) {
1348 if (nd->mnt->mnt_flags & MNT_NODEV)
1349 return -EACCES;
1350
1351 flag &= ~O_TRUNC;
1352 } else if (IS_RDONLY(inode) && (flag & FMODE_WRITE))
1353 return -EROFS;
1354 /*
1355 * An append-only file must be opened in append mode for writing.
1356 */
1357 if (IS_APPEND(inode)) {
1358 if ((flag & FMODE_WRITE) && !(flag & O_APPEND))
1359 return -EPERM;
1360 if (flag & O_TRUNC)
1361 return -EPERM;
1362 }
1363
1364 /* O_NOATIME can only be set by the owner or superuser */
1365 if (flag & O_NOATIME)
1366 if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
1367 return -EPERM;
1368
1369 /*
1370 * Ensure there are no outstanding leases on the file.
1371 */
1372 error = break_lease(inode, flag);
1373 if (error)
1374 return error;
1375
1376 if (flag & O_TRUNC) {
1377 error = get_write_access(inode);
1378 if (error)
1379 return error;
1380
1381 /*
1382 * Refuse to truncate files with mandatory locks held on them.
1383 */
1384 error = locks_verify_locked(inode);
1385 if (!error) {
1386 DQUOT_INIT(inode);
1387
1388 error = do_truncate(dentry, 0);
1389 }
1390 put_write_access(inode);
1391 if (error)
1392 return error;
1393 } else
1394 if (flag & FMODE_WRITE)
1395 DQUOT_INIT(inode);
1396
1397 return 0;
1398}
1399
1400/*
1401 * open_namei()
1402 *
1403 * namei for open - this is in fact almost the whole open-routine.
1404 *
1405 * Note that the low bits of "flag" aren't the same as in the open
1406 * system call - they are 00 - no permissions needed
1407 * 01 - read permission needed
1408 * 10 - write permission needed
1409 * 11 - read/write permissions needed
1410 * which is a lot more logical, and also allows the "no perm" needed
1411 * for symlinks (where the permissions are checked later).
1412 * SMP-safe
1413 */
1414int open_namei(const char * pathname, int flag, int mode, struct nameidata *nd)
1415{
1416 int acc_mode, error = 0;
Al Viro4e7506e2005-06-06 13:36:00 -07001417 struct path path;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001418 struct dentry *dir;
1419 int count = 0;
1420
1421 acc_mode = ACC_MODE(flag);
1422
1423 /* Allow the LSM permission hook to distinguish append
1424 access from general write access. */
1425 if (flag & O_APPEND)
1426 acc_mode |= MAY_APPEND;
1427
1428 /* Fill in the open() intent data */
1429 nd->intent.open.flags = flag;
1430 nd->intent.open.create_mode = mode;
1431
1432 /*
1433 * The simplest case - just a plain lookup.
1434 */
1435 if (!(flag & O_CREAT)) {
1436 error = path_lookup(pathname, lookup_flags(flag)|LOOKUP_OPEN, nd);
1437 if (error)
1438 return error;
1439 goto ok;
1440 }
1441
1442 /*
1443 * Create - we need to know the parent.
1444 */
1445 error = path_lookup(pathname, LOOKUP_PARENT|LOOKUP_OPEN|LOOKUP_CREATE, nd);
1446 if (error)
1447 return error;
1448
1449 /*
1450 * We have the parent and last component. First of all, check
1451 * that we are not asked to creat(2) an obvious directory - that
1452 * will not do.
1453 */
1454 error = -EISDIR;
1455 if (nd->last_type != LAST_NORM || nd->last.name[nd->last.len])
1456 goto exit;
1457
1458 dir = nd->dentry;
1459 nd->flags &= ~LOOKUP_PARENT;
1460 down(&dir->d_inode->i_sem);
Al Viro4e7506e2005-06-06 13:36:00 -07001461 path.dentry = __lookup_hash(&nd->last, nd->dentry, nd);
Al Virod73ffe12005-06-06 13:36:01 -07001462 path.mnt = nd->mnt;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001463
1464do_last:
Al Viro4e7506e2005-06-06 13:36:00 -07001465 error = PTR_ERR(path.dentry);
1466 if (IS_ERR(path.dentry)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001467 up(&dir->d_inode->i_sem);
1468 goto exit;
1469 }
1470
1471 /* Negative dentry, just create the file */
Al Viro4e7506e2005-06-06 13:36:00 -07001472 if (!path.dentry->d_inode) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001473 if (!IS_POSIXACL(dir->d_inode))
1474 mode &= ~current->fs->umask;
Al Viro4e7506e2005-06-06 13:36:00 -07001475 error = vfs_create(dir->d_inode, path.dentry, mode, nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001476 up(&dir->d_inode->i_sem);
1477 dput(nd->dentry);
Al Viro4e7506e2005-06-06 13:36:00 -07001478 nd->dentry = path.dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001479 if (error)
1480 goto exit;
1481 /* Don't check for write permission, don't truncate */
1482 acc_mode = 0;
1483 flag &= ~O_TRUNC;
1484 goto ok;
1485 }
1486
1487 /*
1488 * It already exists.
1489 */
1490 up(&dir->d_inode->i_sem);
1491
1492 error = -EEXIST;
1493 if (flag & O_EXCL)
1494 goto exit_dput;
1495
Al Viroe13b2102005-06-06 13:36:06 -07001496 if (__follow_mount(&path)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001497 error = -ELOOP;
Al Viroe13b2102005-06-06 13:36:06 -07001498 if (flag & O_NOFOLLOW) {
1499 dput(path.dentry);
1500 mntput(path.mnt);
1501 goto exit;
1502 }
1503 mntput(nd->mnt);
Al Virod73ffe12005-06-06 13:36:01 -07001504 nd->mnt = path.mnt;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001505 }
1506 error = -ENOENT;
Al Viro4e7506e2005-06-06 13:36:00 -07001507 if (!path.dentry->d_inode)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001508 goto exit_dput;
Al Viro4e7506e2005-06-06 13:36:00 -07001509 if (path.dentry->d_inode->i_op && path.dentry->d_inode->i_op->follow_link)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001510 goto do_link;
1511
1512 dput(nd->dentry);
Al Viro4e7506e2005-06-06 13:36:00 -07001513 nd->dentry = path.dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001514 error = -EISDIR;
Al Viro4e7506e2005-06-06 13:36:00 -07001515 if (path.dentry->d_inode && S_ISDIR(path.dentry->d_inode->i_mode))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001516 goto exit;
1517ok:
1518 error = may_open(nd, acc_mode, flag);
1519 if (error)
1520 goto exit;
1521 return 0;
1522
1523exit_dput:
Al Viro4e7506e2005-06-06 13:36:00 -07001524 dput(path.dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001525exit:
1526 path_release(nd);
1527 return error;
1528
1529do_link:
1530 error = -ELOOP;
1531 if (flag & O_NOFOLLOW)
1532 goto exit_dput;
1533 /*
1534 * This is subtle. Instead of calling do_follow_link() we do the
1535 * thing by hands. The reason is that this way we have zero link_count
1536 * and path_walk() (called from ->follow_link) honoring LOOKUP_PARENT.
1537 * After that we have the parent and last component, i.e.
1538 * we are in the same situation as after the first path_walk().
1539 * Well, almost - if the last component is normal we get its copy
1540 * stored in nd->last.name and we will have to putname() it when we
1541 * are done. Procfs-like symlinks just set LAST_BIND.
1542 */
1543 nd->flags |= LOOKUP_PARENT;
Al Viro4e7506e2005-06-06 13:36:00 -07001544 error = security_inode_follow_link(path.dentry, nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001545 if (error)
1546 goto exit_dput;
Al Virocd4e91d2005-06-06 13:36:03 -07001547 error = __do_follow_link(&path, nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001548 if (error)
1549 return error;
1550 nd->flags &= ~LOOKUP_PARENT;
Al Virod671d5e2005-06-06 13:36:04 -07001551 if (nd->last_type == LAST_BIND)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001552 goto ok;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001553 error = -EISDIR;
1554 if (nd->last_type != LAST_NORM)
1555 goto exit;
1556 if (nd->last.name[nd->last.len]) {
1557 putname(nd->last.name);
1558 goto exit;
1559 }
1560 error = -ELOOP;
1561 if (count++==32) {
1562 putname(nd->last.name);
1563 goto exit;
1564 }
1565 dir = nd->dentry;
1566 down(&dir->d_inode->i_sem);
Al Viro4e7506e2005-06-06 13:36:00 -07001567 path.dentry = __lookup_hash(&nd->last, nd->dentry, nd);
Al Virod671d5e2005-06-06 13:36:04 -07001568 path.mnt = nd->mnt;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001569 putname(nd->last.name);
1570 goto do_last;
1571}
1572
1573/**
1574 * lookup_create - lookup a dentry, creating it if it doesn't exist
1575 * @nd: nameidata info
1576 * @is_dir: directory flag
1577 *
1578 * Simple function to lookup and return a dentry and create it
1579 * if it doesn't exist. Is SMP-safe.
1580 */
1581struct dentry *lookup_create(struct nameidata *nd, int is_dir)
1582{
1583 struct dentry *dentry;
1584
1585 down(&nd->dentry->d_inode->i_sem);
1586 dentry = ERR_PTR(-EEXIST);
1587 if (nd->last_type != LAST_NORM)
1588 goto fail;
1589 nd->flags &= ~LOOKUP_PARENT;
1590 dentry = lookup_hash(&nd->last, nd->dentry);
1591 if (IS_ERR(dentry))
1592 goto fail;
1593 if (!is_dir && nd->last.name[nd->last.len] && !dentry->d_inode)
1594 goto enoent;
1595 return dentry;
1596enoent:
1597 dput(dentry);
1598 dentry = ERR_PTR(-ENOENT);
1599fail:
1600 return dentry;
1601}
Christoph Hellwigf81a0bf2005-05-19 12:26:43 -07001602EXPORT_SYMBOL_GPL(lookup_create);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001603
1604int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1605{
1606 int error = may_create(dir, dentry, NULL);
1607
1608 if (error)
1609 return error;
1610
1611 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
1612 return -EPERM;
1613
1614 if (!dir->i_op || !dir->i_op->mknod)
1615 return -EPERM;
1616
1617 error = security_inode_mknod(dir, dentry, mode, dev);
1618 if (error)
1619 return error;
1620
1621 DQUOT_INIT(dir);
1622 error = dir->i_op->mknod(dir, dentry, mode, dev);
1623 if (!error) {
1624 inode_dir_notify(dir, DN_CREATE);
1625 security_inode_post_mknod(dir, dentry, mode, dev);
1626 }
1627 return error;
1628}
1629
1630asmlinkage long sys_mknod(const char __user * filename, int mode, unsigned dev)
1631{
1632 int error = 0;
1633 char * tmp;
1634 struct dentry * dentry;
1635 struct nameidata nd;
1636
1637 if (S_ISDIR(mode))
1638 return -EPERM;
1639 tmp = getname(filename);
1640 if (IS_ERR(tmp))
1641 return PTR_ERR(tmp);
1642
1643 error = path_lookup(tmp, LOOKUP_PARENT, &nd);
1644 if (error)
1645 goto out;
1646 dentry = lookup_create(&nd, 0);
1647 error = PTR_ERR(dentry);
1648
1649 if (!IS_POSIXACL(nd.dentry->d_inode))
1650 mode &= ~current->fs->umask;
1651 if (!IS_ERR(dentry)) {
1652 switch (mode & S_IFMT) {
1653 case 0: case S_IFREG:
1654 error = vfs_create(nd.dentry->d_inode,dentry,mode,&nd);
1655 break;
1656 case S_IFCHR: case S_IFBLK:
1657 error = vfs_mknod(nd.dentry->d_inode,dentry,mode,
1658 new_decode_dev(dev));
1659 break;
1660 case S_IFIFO: case S_IFSOCK:
1661 error = vfs_mknod(nd.dentry->d_inode,dentry,mode,0);
1662 break;
1663 case S_IFDIR:
1664 error = -EPERM;
1665 break;
1666 default:
1667 error = -EINVAL;
1668 }
1669 dput(dentry);
1670 }
1671 up(&nd.dentry->d_inode->i_sem);
1672 path_release(&nd);
1673out:
1674 putname(tmp);
1675
1676 return error;
1677}
1678
1679int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1680{
1681 int error = may_create(dir, dentry, NULL);
1682
1683 if (error)
1684 return error;
1685
1686 if (!dir->i_op || !dir->i_op->mkdir)
1687 return -EPERM;
1688
1689 mode &= (S_IRWXUGO|S_ISVTX);
1690 error = security_inode_mkdir(dir, dentry, mode);
1691 if (error)
1692 return error;
1693
1694 DQUOT_INIT(dir);
1695 error = dir->i_op->mkdir(dir, dentry, mode);
1696 if (!error) {
1697 inode_dir_notify(dir, DN_CREATE);
1698 security_inode_post_mkdir(dir,dentry, mode);
1699 }
1700 return error;
1701}
1702
1703asmlinkage long sys_mkdir(const char __user * pathname, int mode)
1704{
1705 int error = 0;
1706 char * tmp;
1707
1708 tmp = getname(pathname);
1709 error = PTR_ERR(tmp);
1710 if (!IS_ERR(tmp)) {
1711 struct dentry *dentry;
1712 struct nameidata nd;
1713
1714 error = path_lookup(tmp, LOOKUP_PARENT, &nd);
1715 if (error)
1716 goto out;
1717 dentry = lookup_create(&nd, 1);
1718 error = PTR_ERR(dentry);
1719 if (!IS_ERR(dentry)) {
1720 if (!IS_POSIXACL(nd.dentry->d_inode))
1721 mode &= ~current->fs->umask;
1722 error = vfs_mkdir(nd.dentry->d_inode, dentry, mode);
1723 dput(dentry);
1724 }
1725 up(&nd.dentry->d_inode->i_sem);
1726 path_release(&nd);
1727out:
1728 putname(tmp);
1729 }
1730
1731 return error;
1732}
1733
1734/*
1735 * We try to drop the dentry early: we should have
1736 * a usage count of 2 if we're the only user of this
1737 * dentry, and if that is true (possibly after pruning
1738 * the dcache), then we drop the dentry now.
1739 *
1740 * A low-level filesystem can, if it choses, legally
1741 * do a
1742 *
1743 * if (!d_unhashed(dentry))
1744 * return -EBUSY;
1745 *
1746 * if it cannot handle the case of removing a directory
1747 * that is still in use by something else..
1748 */
1749void dentry_unhash(struct dentry *dentry)
1750{
1751 dget(dentry);
1752 if (atomic_read(&dentry->d_count))
1753 shrink_dcache_parent(dentry);
1754 spin_lock(&dcache_lock);
1755 spin_lock(&dentry->d_lock);
1756 if (atomic_read(&dentry->d_count) == 2)
1757 __d_drop(dentry);
1758 spin_unlock(&dentry->d_lock);
1759 spin_unlock(&dcache_lock);
1760}
1761
1762int vfs_rmdir(struct inode *dir, struct dentry *dentry)
1763{
1764 int error = may_delete(dir, dentry, 1);
1765
1766 if (error)
1767 return error;
1768
1769 if (!dir->i_op || !dir->i_op->rmdir)
1770 return -EPERM;
1771
1772 DQUOT_INIT(dir);
1773
1774 down(&dentry->d_inode->i_sem);
1775 dentry_unhash(dentry);
1776 if (d_mountpoint(dentry))
1777 error = -EBUSY;
1778 else {
1779 error = security_inode_rmdir(dir, dentry);
1780 if (!error) {
1781 error = dir->i_op->rmdir(dir, dentry);
1782 if (!error)
1783 dentry->d_inode->i_flags |= S_DEAD;
1784 }
1785 }
1786 up(&dentry->d_inode->i_sem);
1787 if (!error) {
1788 inode_dir_notify(dir, DN_DELETE);
1789 d_delete(dentry);
1790 }
1791 dput(dentry);
1792
1793 return error;
1794}
1795
1796asmlinkage long sys_rmdir(const char __user * pathname)
1797{
1798 int error = 0;
1799 char * name;
1800 struct dentry *dentry;
1801 struct nameidata nd;
1802
1803 name = getname(pathname);
1804 if(IS_ERR(name))
1805 return PTR_ERR(name);
1806
1807 error = path_lookup(name, LOOKUP_PARENT, &nd);
1808 if (error)
1809 goto exit;
1810
1811 switch(nd.last_type) {
1812 case LAST_DOTDOT:
1813 error = -ENOTEMPTY;
1814 goto exit1;
1815 case LAST_DOT:
1816 error = -EINVAL;
1817 goto exit1;
1818 case LAST_ROOT:
1819 error = -EBUSY;
1820 goto exit1;
1821 }
1822 down(&nd.dentry->d_inode->i_sem);
1823 dentry = lookup_hash(&nd.last, nd.dentry);
1824 error = PTR_ERR(dentry);
1825 if (!IS_ERR(dentry)) {
1826 error = vfs_rmdir(nd.dentry->d_inode, dentry);
1827 dput(dentry);
1828 }
1829 up(&nd.dentry->d_inode->i_sem);
1830exit1:
1831 path_release(&nd);
1832exit:
1833 putname(name);
1834 return error;
1835}
1836
1837int vfs_unlink(struct inode *dir, struct dentry *dentry)
1838{
1839 int error = may_delete(dir, dentry, 0);
1840
1841 if (error)
1842 return error;
1843
1844 if (!dir->i_op || !dir->i_op->unlink)
1845 return -EPERM;
1846
1847 DQUOT_INIT(dir);
1848
1849 down(&dentry->d_inode->i_sem);
1850 if (d_mountpoint(dentry))
1851 error = -EBUSY;
1852 else {
1853 error = security_inode_unlink(dir, dentry);
1854 if (!error)
1855 error = dir->i_op->unlink(dir, dentry);
1856 }
1857 up(&dentry->d_inode->i_sem);
1858
1859 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
1860 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
1861 d_delete(dentry);
1862 inode_dir_notify(dir, DN_DELETE);
1863 }
1864 return error;
1865}
1866
1867/*
1868 * Make sure that the actual truncation of the file will occur outside its
1869 * directory's i_sem. Truncate can take a long time if there is a lot of
1870 * writeout happening, and we don't want to prevent access to the directory
1871 * while waiting on the I/O.
1872 */
1873asmlinkage long sys_unlink(const char __user * pathname)
1874{
1875 int error = 0;
1876 char * name;
1877 struct dentry *dentry;
1878 struct nameidata nd;
1879 struct inode *inode = NULL;
1880
1881 name = getname(pathname);
1882 if(IS_ERR(name))
1883 return PTR_ERR(name);
1884
1885 error = path_lookup(name, LOOKUP_PARENT, &nd);
1886 if (error)
1887 goto exit;
1888 error = -EISDIR;
1889 if (nd.last_type != LAST_NORM)
1890 goto exit1;
1891 down(&nd.dentry->d_inode->i_sem);
1892 dentry = lookup_hash(&nd.last, nd.dentry);
1893 error = PTR_ERR(dentry);
1894 if (!IS_ERR(dentry)) {
1895 /* Why not before? Because we want correct error value */
1896 if (nd.last.name[nd.last.len])
1897 goto slashes;
1898 inode = dentry->d_inode;
1899 if (inode)
1900 atomic_inc(&inode->i_count);
1901 error = vfs_unlink(nd.dentry->d_inode, dentry);
1902 exit2:
1903 dput(dentry);
1904 }
1905 up(&nd.dentry->d_inode->i_sem);
1906 if (inode)
1907 iput(inode); /* truncate the inode here */
1908exit1:
1909 path_release(&nd);
1910exit:
1911 putname(name);
1912 return error;
1913
1914slashes:
1915 error = !dentry->d_inode ? -ENOENT :
1916 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
1917 goto exit2;
1918}
1919
1920int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname, int mode)
1921{
1922 int error = may_create(dir, dentry, NULL);
1923
1924 if (error)
1925 return error;
1926
1927 if (!dir->i_op || !dir->i_op->symlink)
1928 return -EPERM;
1929
1930 error = security_inode_symlink(dir, dentry, oldname);
1931 if (error)
1932 return error;
1933
1934 DQUOT_INIT(dir);
1935 error = dir->i_op->symlink(dir, dentry, oldname);
1936 if (!error) {
1937 inode_dir_notify(dir, DN_CREATE);
1938 security_inode_post_symlink(dir, dentry, oldname);
1939 }
1940 return error;
1941}
1942
1943asmlinkage long sys_symlink(const char __user * oldname, const char __user * newname)
1944{
1945 int error = 0;
1946 char * from;
1947 char * to;
1948
1949 from = getname(oldname);
1950 if(IS_ERR(from))
1951 return PTR_ERR(from);
1952 to = getname(newname);
1953 error = PTR_ERR(to);
1954 if (!IS_ERR(to)) {
1955 struct dentry *dentry;
1956 struct nameidata nd;
1957
1958 error = path_lookup(to, LOOKUP_PARENT, &nd);
1959 if (error)
1960 goto out;
1961 dentry = lookup_create(&nd, 0);
1962 error = PTR_ERR(dentry);
1963 if (!IS_ERR(dentry)) {
1964 error = vfs_symlink(nd.dentry->d_inode, dentry, from, S_IALLUGO);
1965 dput(dentry);
1966 }
1967 up(&nd.dentry->d_inode->i_sem);
1968 path_release(&nd);
1969out:
1970 putname(to);
1971 }
1972 putname(from);
1973 return error;
1974}
1975
1976int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
1977{
1978 struct inode *inode = old_dentry->d_inode;
1979 int error;
1980
1981 if (!inode)
1982 return -ENOENT;
1983
1984 error = may_create(dir, new_dentry, NULL);
1985 if (error)
1986 return error;
1987
1988 if (dir->i_sb != inode->i_sb)
1989 return -EXDEV;
1990
1991 /*
1992 * A link to an append-only or immutable file cannot be created.
1993 */
1994 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
1995 return -EPERM;
1996 if (!dir->i_op || !dir->i_op->link)
1997 return -EPERM;
1998 if (S_ISDIR(old_dentry->d_inode->i_mode))
1999 return -EPERM;
2000
2001 error = security_inode_link(old_dentry, dir, new_dentry);
2002 if (error)
2003 return error;
2004
2005 down(&old_dentry->d_inode->i_sem);
2006 DQUOT_INIT(dir);
2007 error = dir->i_op->link(old_dentry, dir, new_dentry);
2008 up(&old_dentry->d_inode->i_sem);
2009 if (!error) {
2010 inode_dir_notify(dir, DN_CREATE);
2011 security_inode_post_link(old_dentry, dir, new_dentry);
2012 }
2013 return error;
2014}
2015
2016/*
2017 * Hardlinks are often used in delicate situations. We avoid
2018 * security-related surprises by not following symlinks on the
2019 * newname. --KAB
2020 *
2021 * We don't follow them on the oldname either to be compatible
2022 * with linux 2.0, and to avoid hard-linking to directories
2023 * and other special files. --ADM
2024 */
2025asmlinkage long sys_link(const char __user * oldname, const char __user * newname)
2026{
2027 struct dentry *new_dentry;
2028 struct nameidata nd, old_nd;
2029 int error;
2030 char * to;
2031
2032 to = getname(newname);
2033 if (IS_ERR(to))
2034 return PTR_ERR(to);
2035
2036 error = __user_walk(oldname, 0, &old_nd);
2037 if (error)
2038 goto exit;
2039 error = path_lookup(to, LOOKUP_PARENT, &nd);
2040 if (error)
2041 goto out;
2042 error = -EXDEV;
2043 if (old_nd.mnt != nd.mnt)
2044 goto out_release;
2045 new_dentry = lookup_create(&nd, 0);
2046 error = PTR_ERR(new_dentry);
2047 if (!IS_ERR(new_dentry)) {
2048 error = vfs_link(old_nd.dentry, nd.dentry->d_inode, new_dentry);
2049 dput(new_dentry);
2050 }
2051 up(&nd.dentry->d_inode->i_sem);
2052out_release:
2053 path_release(&nd);
2054out:
2055 path_release(&old_nd);
2056exit:
2057 putname(to);
2058
2059 return error;
2060}
2061
2062/*
2063 * The worst of all namespace operations - renaming directory. "Perverted"
2064 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
2065 * Problems:
2066 * a) we can get into loop creation. Check is done in is_subdir().
2067 * b) race potential - two innocent renames can create a loop together.
2068 * That's where 4.4 screws up. Current fix: serialization on
2069 * sb->s_vfs_rename_sem. We might be more accurate, but that's another
2070 * story.
2071 * c) we have to lock _three_ objects - parents and victim (if it exists).
2072 * And that - after we got ->i_sem on parents (until then we don't know
2073 * whether the target exists). Solution: try to be smart with locking
2074 * order for inodes. We rely on the fact that tree topology may change
2075 * only under ->s_vfs_rename_sem _and_ that parent of the object we
2076 * move will be locked. Thus we can rank directories by the tree
2077 * (ancestors first) and rank all non-directories after them.
2078 * That works since everybody except rename does "lock parent, lookup,
2079 * lock child" and rename is under ->s_vfs_rename_sem.
2080 * HOWEVER, it relies on the assumption that any object with ->lookup()
2081 * has no more than 1 dentry. If "hybrid" objects will ever appear,
2082 * we'd better make sure that there's no link(2) for them.
2083 * d) some filesystems don't support opened-but-unlinked directories,
2084 * either because of layout or because they are not ready to deal with
2085 * all cases correctly. The latter will be fixed (taking this sort of
2086 * stuff into VFS), but the former is not going away. Solution: the same
2087 * trick as in rmdir().
2088 * e) conversion from fhandle to dentry may come in the wrong moment - when
2089 * we are removing the target. Solution: we will have to grab ->i_sem
2090 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
2091 * ->i_sem on parents, which works but leads to some truely excessive
2092 * locking].
2093 */
Adrian Bunk75c96f82005-05-05 16:16:09 -07002094static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
2095 struct inode *new_dir, struct dentry *new_dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002096{
2097 int error = 0;
2098 struct inode *target;
2099
2100 /*
2101 * If we are going to change the parent - check write permissions,
2102 * we'll need to flip '..'.
2103 */
2104 if (new_dir != old_dir) {
2105 error = permission(old_dentry->d_inode, MAY_WRITE, NULL);
2106 if (error)
2107 return error;
2108 }
2109
2110 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
2111 if (error)
2112 return error;
2113
2114 target = new_dentry->d_inode;
2115 if (target) {
2116 down(&target->i_sem);
2117 dentry_unhash(new_dentry);
2118 }
2119 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
2120 error = -EBUSY;
2121 else
2122 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
2123 if (target) {
2124 if (!error)
2125 target->i_flags |= S_DEAD;
2126 up(&target->i_sem);
2127 if (d_unhashed(new_dentry))
2128 d_rehash(new_dentry);
2129 dput(new_dentry);
2130 }
2131 if (!error) {
2132 d_move(old_dentry,new_dentry);
2133 security_inode_post_rename(old_dir, old_dentry,
2134 new_dir, new_dentry);
2135 }
2136 return error;
2137}
2138
Adrian Bunk75c96f82005-05-05 16:16:09 -07002139static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
2140 struct inode *new_dir, struct dentry *new_dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002141{
2142 struct inode *target;
2143 int error;
2144
2145 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
2146 if (error)
2147 return error;
2148
2149 dget(new_dentry);
2150 target = new_dentry->d_inode;
2151 if (target)
2152 down(&target->i_sem);
2153 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
2154 error = -EBUSY;
2155 else
2156 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
2157 if (!error) {
2158 /* The following d_move() should become unconditional */
2159 if (!(old_dir->i_sb->s_type->fs_flags & FS_ODD_RENAME))
2160 d_move(old_dentry, new_dentry);
2161 security_inode_post_rename(old_dir, old_dentry, new_dir, new_dentry);
2162 }
2163 if (target)
2164 up(&target->i_sem);
2165 dput(new_dentry);
2166 return error;
2167}
2168
2169int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
2170 struct inode *new_dir, struct dentry *new_dentry)
2171{
2172 int error;
2173 int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
2174
2175 if (old_dentry->d_inode == new_dentry->d_inode)
2176 return 0;
2177
2178 error = may_delete(old_dir, old_dentry, is_dir);
2179 if (error)
2180 return error;
2181
2182 if (!new_dentry->d_inode)
2183 error = may_create(new_dir, new_dentry, NULL);
2184 else
2185 error = may_delete(new_dir, new_dentry, is_dir);
2186 if (error)
2187 return error;
2188
2189 if (!old_dir->i_op || !old_dir->i_op->rename)
2190 return -EPERM;
2191
2192 DQUOT_INIT(old_dir);
2193 DQUOT_INIT(new_dir);
2194
2195 if (is_dir)
2196 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
2197 else
2198 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
2199 if (!error) {
2200 if (old_dir == new_dir)
2201 inode_dir_notify(old_dir, DN_RENAME);
2202 else {
2203 inode_dir_notify(old_dir, DN_DELETE);
2204 inode_dir_notify(new_dir, DN_CREATE);
2205 }
2206 }
2207 return error;
2208}
2209
2210static inline int do_rename(const char * oldname, const char * newname)
2211{
2212 int error = 0;
2213 struct dentry * old_dir, * new_dir;
2214 struct dentry * old_dentry, *new_dentry;
2215 struct dentry * trap;
2216 struct nameidata oldnd, newnd;
2217
2218 error = path_lookup(oldname, LOOKUP_PARENT, &oldnd);
2219 if (error)
2220 goto exit;
2221
2222 error = path_lookup(newname, LOOKUP_PARENT, &newnd);
2223 if (error)
2224 goto exit1;
2225
2226 error = -EXDEV;
2227 if (oldnd.mnt != newnd.mnt)
2228 goto exit2;
2229
2230 old_dir = oldnd.dentry;
2231 error = -EBUSY;
2232 if (oldnd.last_type != LAST_NORM)
2233 goto exit2;
2234
2235 new_dir = newnd.dentry;
2236 if (newnd.last_type != LAST_NORM)
2237 goto exit2;
2238
2239 trap = lock_rename(new_dir, old_dir);
2240
2241 old_dentry = lookup_hash(&oldnd.last, old_dir);
2242 error = PTR_ERR(old_dentry);
2243 if (IS_ERR(old_dentry))
2244 goto exit3;
2245 /* source must exist */
2246 error = -ENOENT;
2247 if (!old_dentry->d_inode)
2248 goto exit4;
2249 /* unless the source is a directory trailing slashes give -ENOTDIR */
2250 if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
2251 error = -ENOTDIR;
2252 if (oldnd.last.name[oldnd.last.len])
2253 goto exit4;
2254 if (newnd.last.name[newnd.last.len])
2255 goto exit4;
2256 }
2257 /* source should not be ancestor of target */
2258 error = -EINVAL;
2259 if (old_dentry == trap)
2260 goto exit4;
2261 new_dentry = lookup_hash(&newnd.last, new_dir);
2262 error = PTR_ERR(new_dentry);
2263 if (IS_ERR(new_dentry))
2264 goto exit4;
2265 /* target should not be an ancestor of source */
2266 error = -ENOTEMPTY;
2267 if (new_dentry == trap)
2268 goto exit5;
2269
2270 error = vfs_rename(old_dir->d_inode, old_dentry,
2271 new_dir->d_inode, new_dentry);
2272exit5:
2273 dput(new_dentry);
2274exit4:
2275 dput(old_dentry);
2276exit3:
2277 unlock_rename(new_dir, old_dir);
2278exit2:
2279 path_release(&newnd);
2280exit1:
2281 path_release(&oldnd);
2282exit:
2283 return error;
2284}
2285
2286asmlinkage long sys_rename(const char __user * oldname, const char __user * newname)
2287{
2288 int error;
2289 char * from;
2290 char * to;
2291
2292 from = getname(oldname);
2293 if(IS_ERR(from))
2294 return PTR_ERR(from);
2295 to = getname(newname);
2296 error = PTR_ERR(to);
2297 if (!IS_ERR(to)) {
2298 error = do_rename(from,to);
2299 putname(to);
2300 }
2301 putname(from);
2302 return error;
2303}
2304
2305int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
2306{
2307 int len;
2308
2309 len = PTR_ERR(link);
2310 if (IS_ERR(link))
2311 goto out;
2312
2313 len = strlen(link);
2314 if (len > (unsigned) buflen)
2315 len = buflen;
2316 if (copy_to_user(buffer, link, len))
2317 len = -EFAULT;
2318out:
2319 return len;
2320}
2321
2322/*
2323 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
2324 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
2325 * using) it for any given inode is up to filesystem.
2326 */
2327int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
2328{
2329 struct nameidata nd;
2330 int res;
2331 nd.depth = 0;
2332 res = dentry->d_inode->i_op->follow_link(dentry, &nd);
2333 if (!res) {
2334 res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
2335 if (dentry->d_inode->i_op->put_link)
2336 dentry->d_inode->i_op->put_link(dentry, &nd);
2337 }
2338 return res;
2339}
2340
2341int vfs_follow_link(struct nameidata *nd, const char *link)
2342{
2343 return __vfs_follow_link(nd, link);
2344}
2345
2346/* get the link contents into pagecache */
2347static char *page_getlink(struct dentry * dentry, struct page **ppage)
2348{
2349 struct page * page;
2350 struct address_space *mapping = dentry->d_inode->i_mapping;
2351 page = read_cache_page(mapping, 0, (filler_t *)mapping->a_ops->readpage,
2352 NULL);
2353 if (IS_ERR(page))
2354 goto sync_fail;
2355 wait_on_page_locked(page);
2356 if (!PageUptodate(page))
2357 goto async_fail;
2358 *ppage = page;
2359 return kmap(page);
2360
2361async_fail:
2362 page_cache_release(page);
2363 return ERR_PTR(-EIO);
2364
2365sync_fail:
2366 return (char*)page;
2367}
2368
2369int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
2370{
2371 struct page *page = NULL;
2372 char *s = page_getlink(dentry, &page);
2373 int res = vfs_readlink(dentry,buffer,buflen,s);
2374 if (page) {
2375 kunmap(page);
2376 page_cache_release(page);
2377 }
2378 return res;
2379}
2380
2381int page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
2382{
2383 struct page *page;
2384 nd_set_link(nd, page_getlink(dentry, &page));
2385 return 0;
2386}
2387
2388void page_put_link(struct dentry *dentry, struct nameidata *nd)
2389{
2390 if (!IS_ERR(nd_get_link(nd))) {
2391 struct page *page;
2392 page = find_get_page(dentry->d_inode->i_mapping, 0);
2393 if (!page)
2394 BUG();
2395 kunmap(page);
2396 page_cache_release(page);
2397 page_cache_release(page);
2398 }
2399}
2400
2401int page_symlink(struct inode *inode, const char *symname, int len)
2402{
2403 struct address_space *mapping = inode->i_mapping;
2404 struct page *page = grab_cache_page(mapping, 0);
2405 int err = -ENOMEM;
2406 char *kaddr;
2407
2408 if (!page)
2409 goto fail;
2410 err = mapping->a_ops->prepare_write(NULL, page, 0, len-1);
2411 if (err)
2412 goto fail_map;
2413 kaddr = kmap_atomic(page, KM_USER0);
2414 memcpy(kaddr, symname, len-1);
2415 kunmap_atomic(kaddr, KM_USER0);
2416 mapping->a_ops->commit_write(NULL, page, 0, len-1);
2417 /*
2418 * Notice that we are _not_ going to block here - end of page is
2419 * unmapped, so this will only try to map the rest of page, see
2420 * that it is unmapped (typically even will not look into inode -
2421 * ->i_size will be enough for everything) and zero it out.
2422 * OTOH it's obviously correct and should make the page up-to-date.
2423 */
2424 if (!PageUptodate(page)) {
2425 err = mapping->a_ops->readpage(NULL, page);
2426 wait_on_page_locked(page);
2427 } else {
2428 unlock_page(page);
2429 }
2430 page_cache_release(page);
2431 if (err < 0)
2432 goto fail;
2433 mark_inode_dirty(inode);
2434 return 0;
2435fail_map:
2436 unlock_page(page);
2437 page_cache_release(page);
2438fail:
2439 return err;
2440}
2441
2442struct inode_operations page_symlink_inode_operations = {
2443 .readlink = generic_readlink,
2444 .follow_link = page_follow_link_light,
2445 .put_link = page_put_link,
2446};
2447
2448EXPORT_SYMBOL(__user_walk);
2449EXPORT_SYMBOL(follow_down);
2450EXPORT_SYMBOL(follow_up);
2451EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
2452EXPORT_SYMBOL(getname);
2453EXPORT_SYMBOL(lock_rename);
2454EXPORT_SYMBOL(lookup_hash);
2455EXPORT_SYMBOL(lookup_one_len);
2456EXPORT_SYMBOL(page_follow_link_light);
2457EXPORT_SYMBOL(page_put_link);
2458EXPORT_SYMBOL(page_readlink);
2459EXPORT_SYMBOL(page_symlink);
2460EXPORT_SYMBOL(page_symlink_inode_operations);
2461EXPORT_SYMBOL(path_lookup);
2462EXPORT_SYMBOL(path_release);
2463EXPORT_SYMBOL(path_walk);
2464EXPORT_SYMBOL(permission);
2465EXPORT_SYMBOL(unlock_rename);
2466EXPORT_SYMBOL(vfs_create);
2467EXPORT_SYMBOL(vfs_follow_link);
2468EXPORT_SYMBOL(vfs_link);
2469EXPORT_SYMBOL(vfs_mkdir);
2470EXPORT_SYMBOL(vfs_mknod);
2471EXPORT_SYMBOL(generic_permission);
2472EXPORT_SYMBOL(vfs_readlink);
2473EXPORT_SYMBOL(vfs_rename);
2474EXPORT_SYMBOL(vfs_rmdir);
2475EXPORT_SYMBOL(vfs_symlink);
2476EXPORT_SYMBOL(vfs_unlink);
2477EXPORT_SYMBOL(dentry_unhash);
2478EXPORT_SYMBOL(generic_readlink);