blob: 6ec1f0fefc5b017aa321738f7d3581370a91fad3 [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>
Robert Love0eeca282005-07-12 17:06:03 -040024#include <linux/fsnotify.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070025#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);
Miklos Szeredi751c4042005-07-07 17:57:30 -0700317 mntput_no_expire(nd->mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700318}
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;
Linus Torvaldscc314ee2005-08-19 18:02:56 -0700504 void *cookie;
Al Virocd4e91d2005-06-06 13:36:03 -0700505 struct dentry *dentry = path->dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700506
Al Virod671a1c2005-06-06 13:36:14 -0700507 touch_atime(path->mnt, dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700508 nd_set_link(nd, NULL);
Al Virocd4e91d2005-06-06 13:36:03 -0700509
Al Viro39ca6d42005-06-06 13:36:12 -0700510 if (path->mnt == nd->mnt)
511 mntget(path->mnt);
Linus Torvaldscc314ee2005-08-19 18:02:56 -0700512 cookie = dentry->d_inode->i_op->follow_link(dentry, nd);
513 error = PTR_ERR(cookie);
514 if (!IS_ERR(cookie)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700515 char *s = nd_get_link(nd);
Linus Torvaldscc314ee2005-08-19 18:02:56 -0700516 error = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700517 if (s)
518 error = __vfs_follow_link(nd, s);
519 if (dentry->d_inode->i_op->put_link)
Linus Torvaldscc314ee2005-08-19 18:02:56 -0700520 dentry->d_inode->i_op->put_link(dentry, nd, cookie);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700521 }
Al Virocd4e91d2005-06-06 13:36:03 -0700522 dput(dentry);
523 mntput(path->mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700524
525 return error;
526}
527
528/*
529 * This limits recursive symlink follows to 8, while
530 * limiting consecutive symlinks to 40.
531 *
532 * Without that kind of total limit, nasty chains of consecutive
533 * symlinks can cause almost arbitrarily long lookups.
534 */
Al Viro90ebe562005-06-06 13:35:58 -0700535static inline int do_follow_link(struct path *path, struct nameidata *nd)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700536{
537 int err = -ELOOP;
538 if (current->link_count >= MAX_NESTED_LINKS)
539 goto loop;
540 if (current->total_link_count >= 40)
541 goto loop;
542 BUG_ON(nd->depth >= MAX_NESTED_LINKS);
543 cond_resched();
Al Viro90ebe562005-06-06 13:35:58 -0700544 err = security_inode_follow_link(path->dentry, nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700545 if (err)
546 goto loop;
547 current->link_count++;
548 current->total_link_count++;
549 nd->depth++;
Al Virocd4e91d2005-06-06 13:36:03 -0700550 err = __do_follow_link(path, nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700551 current->link_count--;
552 nd->depth--;
553 return err;
554loop:
Al Viro5f92b3bc2005-06-06 13:35:59 -0700555 dput(path->dentry);
Al Virod9d29a22005-06-06 13:36:11 -0700556 if (path->mnt != nd->mnt)
557 mntput(path->mnt);
Al Viro839d9f92005-06-06 13:36:02 -0700558 path_release(nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700559 return err;
560}
561
562int follow_up(struct vfsmount **mnt, struct dentry **dentry)
563{
564 struct vfsmount *parent;
565 struct dentry *mountpoint;
566 spin_lock(&vfsmount_lock);
567 parent=(*mnt)->mnt_parent;
568 if (parent == *mnt) {
569 spin_unlock(&vfsmount_lock);
570 return 0;
571 }
572 mntget(parent);
573 mountpoint=dget((*mnt)->mnt_mountpoint);
574 spin_unlock(&vfsmount_lock);
575 dput(*dentry);
576 *dentry = mountpoint;
577 mntput(*mnt);
578 *mnt = parent;
579 return 1;
580}
581
582/* no need for dcache_lock, as serialization is taken care in
583 * namespace.c
584 */
Al Viro463ffb22005-06-06 13:36:05 -0700585static int __follow_mount(struct path *path)
586{
587 int res = 0;
588 while (d_mountpoint(path->dentry)) {
589 struct vfsmount *mounted = lookup_mnt(path->mnt, path->dentry);
590 if (!mounted)
591 break;
592 dput(path->dentry);
593 if (res)
594 mntput(path->mnt);
595 path->mnt = mounted;
596 path->dentry = dget(mounted->mnt_root);
597 res = 1;
598 }
599 return res;
600}
601
Al Viro58c465e2005-06-06 13:36:13 -0700602static void follow_mount(struct vfsmount **mnt, struct dentry **dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700603{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700604 while (d_mountpoint(*dentry)) {
605 struct vfsmount *mounted = lookup_mnt(*mnt, *dentry);
606 if (!mounted)
607 break;
Al Viro58c465e2005-06-06 13:36:13 -0700608 dput(*dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700609 mntput(*mnt);
610 *mnt = mounted;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700611 *dentry = dget(mounted->mnt_root);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700612 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700613}
614
615/* no need for dcache_lock, as serialization is taken care in
616 * namespace.c
617 */
Al Viroe13b2102005-06-06 13:36:06 -0700618int follow_down(struct vfsmount **mnt, struct dentry **dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700619{
620 struct vfsmount *mounted;
621
622 mounted = lookup_mnt(*mnt, *dentry);
623 if (mounted) {
Al Viroe13b2102005-06-06 13:36:06 -0700624 dput(*dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700625 mntput(*mnt);
626 *mnt = mounted;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700627 *dentry = dget(mounted->mnt_root);
628 return 1;
629 }
630 return 0;
631}
632
Al Viro58c465e2005-06-06 13:36:13 -0700633static inline void follow_dotdot(struct nameidata *nd)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700634{
635 while(1) {
636 struct vfsmount *parent;
Al Viro58c465e2005-06-06 13:36:13 -0700637 struct dentry *old = nd->dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700638
639 read_lock(&current->fs->lock);
Al Viro58c465e2005-06-06 13:36:13 -0700640 if (nd->dentry == current->fs->root &&
641 nd->mnt == current->fs->rootmnt) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700642 read_unlock(&current->fs->lock);
643 break;
644 }
645 read_unlock(&current->fs->lock);
646 spin_lock(&dcache_lock);
Al Viro58c465e2005-06-06 13:36:13 -0700647 if (nd->dentry != nd->mnt->mnt_root) {
648 nd->dentry = dget(nd->dentry->d_parent);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700649 spin_unlock(&dcache_lock);
650 dput(old);
651 break;
652 }
653 spin_unlock(&dcache_lock);
654 spin_lock(&vfsmount_lock);
Al Viro58c465e2005-06-06 13:36:13 -0700655 parent = nd->mnt->mnt_parent;
656 if (parent == nd->mnt) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700657 spin_unlock(&vfsmount_lock);
658 break;
659 }
660 mntget(parent);
Al Viro58c465e2005-06-06 13:36:13 -0700661 nd->dentry = dget(nd->mnt->mnt_mountpoint);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700662 spin_unlock(&vfsmount_lock);
663 dput(old);
Al Viro58c465e2005-06-06 13:36:13 -0700664 mntput(nd->mnt);
665 nd->mnt = parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700666 }
Al Viro58c465e2005-06-06 13:36:13 -0700667 follow_mount(&nd->mnt, &nd->dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700668}
669
Linus Torvalds1da177e2005-04-16 15:20:36 -0700670/*
671 * It's more convoluted than I'd like it to be, but... it's still fairly
672 * small and for now I'd prefer to have fast path as straight as possible.
673 * It _is_ time-critical.
674 */
675static int do_lookup(struct nameidata *nd, struct qstr *name,
676 struct path *path)
677{
678 struct vfsmount *mnt = nd->mnt;
679 struct dentry *dentry = __d_lookup(nd->dentry, name);
680
681 if (!dentry)
682 goto need_lookup;
683 if (dentry->d_op && dentry->d_op->d_revalidate)
684 goto need_revalidate;
685done:
686 path->mnt = mnt;
687 path->dentry = dentry;
Al Viro634ee702005-06-06 13:36:13 -0700688 __follow_mount(path);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700689 return 0;
690
691need_lookup:
692 dentry = real_lookup(nd->dentry, name, nd);
693 if (IS_ERR(dentry))
694 goto fail;
695 goto done;
696
697need_revalidate:
698 if (dentry->d_op->d_revalidate(dentry, nd))
699 goto done;
700 if (d_invalidate(dentry))
701 goto done;
702 dput(dentry);
703 goto need_lookup;
704
705fail:
706 return PTR_ERR(dentry);
707}
708
709/*
710 * Name resolution.
Prasanna Medaea3834d2005-04-29 16:00:17 +0100711 * This is the basic name resolution function, turning a pathname into
712 * the final dentry. We expect 'base' to be positive and a directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700713 *
Prasanna Medaea3834d2005-04-29 16:00:17 +0100714 * Returns 0 and nd will have valid dentry and mnt on success.
715 * Returns error and drops reference to input namei data on failure.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700716 */
717static fastcall int __link_path_walk(const char * name, struct nameidata *nd)
718{
719 struct path next;
720 struct inode *inode;
721 int err;
722 unsigned int lookup_flags = nd->flags;
723
724 while (*name=='/')
725 name++;
726 if (!*name)
727 goto return_reval;
728
729 inode = nd->dentry->d_inode;
730 if (nd->depth)
731 lookup_flags = LOOKUP_FOLLOW;
732
733 /* At this point we know we have a real path component. */
734 for(;;) {
735 unsigned long hash;
736 struct qstr this;
737 unsigned int c;
738
739 err = exec_permission_lite(inode, nd);
740 if (err == -EAGAIN) {
741 err = permission(inode, MAY_EXEC, nd);
742 }
743 if (err)
744 break;
745
746 this.name = name;
747 c = *(const unsigned char *)name;
748
749 hash = init_name_hash();
750 do {
751 name++;
752 hash = partial_name_hash(c, hash);
753 c = *(const unsigned char *)name;
754 } while (c && (c != '/'));
755 this.len = name - (const char *) this.name;
756 this.hash = end_name_hash(hash);
757
758 /* remove trailing slashes? */
759 if (!c)
760 goto last_component;
761 while (*++name == '/');
762 if (!*name)
763 goto last_with_slashes;
764
765 /*
766 * "." and ".." are special - ".." especially so because it has
767 * to be able to know about the current root directory and
768 * parent relationships.
769 */
770 if (this.name[0] == '.') switch (this.len) {
771 default:
772 break;
773 case 2:
774 if (this.name[1] != '.')
775 break;
Al Viro58c465e2005-06-06 13:36:13 -0700776 follow_dotdot(nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700777 inode = nd->dentry->d_inode;
778 /* fallthrough */
779 case 1:
780 continue;
781 }
782 /*
783 * See if the low-level filesystem might want
784 * to use its own hash..
785 */
786 if (nd->dentry->d_op && nd->dentry->d_op->d_hash) {
787 err = nd->dentry->d_op->d_hash(nd->dentry, &this);
788 if (err < 0)
789 break;
790 }
791 nd->flags |= LOOKUP_CONTINUE;
792 /* This does the actual lookups.. */
793 err = do_lookup(nd, &this, &next);
794 if (err)
795 break;
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);
Al Viro2f12dbf2005-06-06 13:36:07 -0700818 if (nd->mnt != next.mnt)
819 mntput(nd->mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700820 nd->mnt = next.mnt;
821 nd->dentry = next.dentry;
822 }
823 err = -ENOTDIR;
824 if (!inode->i_op->lookup)
825 break;
826 continue;
827 /* here ends the main loop */
828
829last_with_slashes:
830 lookup_flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
831last_component:
832 nd->flags &= ~LOOKUP_CONTINUE;
833 if (lookup_flags & LOOKUP_PARENT)
834 goto lookup_parent;
835 if (this.name[0] == '.') switch (this.len) {
836 default:
837 break;
838 case 2:
839 if (this.name[1] != '.')
840 break;
Al Viro58c465e2005-06-06 13:36:13 -0700841 follow_dotdot(nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700842 inode = nd->dentry->d_inode;
843 /* fallthrough */
844 case 1:
845 goto return_reval;
846 }
847 if (nd->dentry->d_op && nd->dentry->d_op->d_hash) {
848 err = nd->dentry->d_op->d_hash(nd->dentry, &this);
849 if (err < 0)
850 break;
851 }
852 err = do_lookup(nd, &this, &next);
853 if (err)
854 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700855 inode = next.dentry->d_inode;
856 if ((lookup_flags & LOOKUP_FOLLOW)
857 && inode && inode->i_op && inode->i_op->follow_link) {
Al Viro90ebe562005-06-06 13:35:58 -0700858 err = do_follow_link(&next, nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700859 if (err)
860 goto return_err;
861 inode = nd->dentry->d_inode;
862 } else {
863 dput(nd->dentry);
Al Viro2f12dbf2005-06-06 13:36:07 -0700864 if (nd->mnt != next.mnt)
865 mntput(nd->mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700866 nd->mnt = next.mnt;
867 nd->dentry = next.dentry;
868 }
869 err = -ENOENT;
870 if (!inode)
871 break;
872 if (lookup_flags & LOOKUP_DIRECTORY) {
873 err = -ENOTDIR;
874 if (!inode->i_op || !inode->i_op->lookup)
875 break;
876 }
877 goto return_base;
878lookup_parent:
879 nd->last = this;
880 nd->last_type = LAST_NORM;
881 if (this.name[0] != '.')
882 goto return_base;
883 if (this.len == 1)
884 nd->last_type = LAST_DOT;
885 else if (this.len == 2 && this.name[1] == '.')
886 nd->last_type = LAST_DOTDOT;
887 else
888 goto return_base;
889return_reval:
890 /*
891 * We bypassed the ordinary revalidation routines.
892 * We may need to check the cached dentry for staleness.
893 */
894 if (nd->dentry && nd->dentry->d_sb &&
895 (nd->dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)) {
896 err = -ESTALE;
897 /* Note: we do not d_invalidate() */
898 if (!nd->dentry->d_op->d_revalidate(nd->dentry, nd))
899 break;
900 }
901return_base:
902 return 0;
903out_dput:
904 dput(next.dentry);
Al Viro2f12dbf2005-06-06 13:36:07 -0700905 if (nd->mnt != next.mnt)
Al Virod9d29a22005-06-06 13:36:11 -0700906 mntput(next.mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700907 break;
908 }
909 path_release(nd);
910return_err:
911 return err;
912}
913
914/*
915 * Wrapper to retry pathname resolution whenever the underlying
916 * file system returns an ESTALE.
917 *
918 * Retry the whole path once, forcing real lookup requests
919 * instead of relying on the dcache.
920 */
921int fastcall link_path_walk(const char *name, struct nameidata *nd)
922{
923 struct nameidata save = *nd;
924 int result;
925
926 /* make sure the stuff we saved doesn't go away */
927 dget(save.dentry);
928 mntget(save.mnt);
929
930 result = __link_path_walk(name, nd);
931 if (result == -ESTALE) {
932 *nd = save;
933 dget(nd->dentry);
934 mntget(nd->mnt);
935 nd->flags |= LOOKUP_REVAL;
936 result = __link_path_walk(name, nd);
937 }
938
939 dput(save.dentry);
940 mntput(save.mnt);
941
942 return result;
943}
944
945int fastcall path_walk(const char * name, struct nameidata *nd)
946{
947 current->total_link_count = 0;
948 return link_path_walk(name, nd);
949}
950
Prasanna Medaea3834d2005-04-29 16:00:17 +0100951/*
952 * SMP-safe: Returns 1 and nd will have valid dentry and mnt, if
953 * everything is done. Returns 0 and drops input nd, if lookup failed;
954 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700955static int __emul_lookup_dentry(const char *name, struct nameidata *nd)
956{
957 if (path_walk(name, nd))
958 return 0; /* something went wrong... */
959
960 if (!nd->dentry->d_inode || S_ISDIR(nd->dentry->d_inode->i_mode)) {
961 struct dentry *old_dentry = nd->dentry;
962 struct vfsmount *old_mnt = nd->mnt;
963 struct qstr last = nd->last;
964 int last_type = nd->last_type;
965 /*
966 * NAME was not found in alternate root or it's a directory. Try to find
967 * it in the normal root:
968 */
969 nd->last_type = LAST_ROOT;
970 read_lock(&current->fs->lock);
971 nd->mnt = mntget(current->fs->rootmnt);
972 nd->dentry = dget(current->fs->root);
973 read_unlock(&current->fs->lock);
974 if (path_walk(name, nd) == 0) {
975 if (nd->dentry->d_inode) {
976 dput(old_dentry);
977 mntput(old_mnt);
978 return 1;
979 }
980 path_release(nd);
981 }
982 nd->dentry = old_dentry;
983 nd->mnt = old_mnt;
984 nd->last = last;
985 nd->last_type = last_type;
986 }
987 return 1;
988}
989
990void set_fs_altroot(void)
991{
992 char *emul = __emul_prefix();
993 struct nameidata nd;
994 struct vfsmount *mnt = NULL, *oldmnt;
995 struct dentry *dentry = NULL, *olddentry;
996 int err;
997
998 if (!emul)
999 goto set_it;
1000 err = path_lookup(emul, LOOKUP_FOLLOW|LOOKUP_DIRECTORY|LOOKUP_NOALT, &nd);
1001 if (!err) {
1002 mnt = nd.mnt;
1003 dentry = nd.dentry;
1004 }
1005set_it:
1006 write_lock(&current->fs->lock);
1007 oldmnt = current->fs->altrootmnt;
1008 olddentry = current->fs->altroot;
1009 current->fs->altrootmnt = mnt;
1010 current->fs->altroot = dentry;
1011 write_unlock(&current->fs->lock);
1012 if (olddentry) {
1013 dput(olddentry);
1014 mntput(oldmnt);
1015 }
1016}
1017
Prasanna Medaea3834d2005-04-29 16:00:17 +01001018/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001019int fastcall path_lookup(const char *name, unsigned int flags, struct nameidata *nd)
1020{
Prasanna Medaea3834d2005-04-29 16:00:17 +01001021 int retval = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001022
1023 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1024 nd->flags = flags;
1025 nd->depth = 0;
1026
1027 read_lock(&current->fs->lock);
1028 if (*name=='/') {
1029 if (current->fs->altroot && !(nd->flags & LOOKUP_NOALT)) {
1030 nd->mnt = mntget(current->fs->altrootmnt);
1031 nd->dentry = dget(current->fs->altroot);
1032 read_unlock(&current->fs->lock);
1033 if (__emul_lookup_dentry(name,nd))
Prasanna Medaea3834d2005-04-29 16:00:17 +01001034 goto out; /* found in altroot */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001035 read_lock(&current->fs->lock);
1036 }
1037 nd->mnt = mntget(current->fs->rootmnt);
1038 nd->dentry = dget(current->fs->root);
1039 } else {
1040 nd->mnt = mntget(current->fs->pwdmnt);
1041 nd->dentry = dget(current->fs->pwd);
1042 }
1043 read_unlock(&current->fs->lock);
1044 current->total_link_count = 0;
1045 retval = link_path_walk(name, nd);
Prasanna Medaea3834d2005-04-29 16:00:17 +01001046out:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001047 if (unlikely(current->audit_context
1048 && nd && nd->dentry && nd->dentry->d_inode))
1049 audit_inode(name, nd->dentry->d_inode);
1050 return retval;
1051}
1052
1053/*
1054 * Restricted form of lookup. Doesn't follow links, single-component only,
1055 * needs parent already locked. Doesn't follow mounts.
1056 * SMP-safe.
1057 */
1058static struct dentry * __lookup_hash(struct qstr *name, struct dentry * base, struct nameidata *nd)
1059{
1060 struct dentry * dentry;
1061 struct inode *inode;
1062 int err;
1063
1064 inode = base->d_inode;
1065 err = permission(inode, MAY_EXEC, nd);
1066 dentry = ERR_PTR(err);
1067 if (err)
1068 goto out;
1069
1070 /*
1071 * See if the low-level filesystem might want
1072 * to use its own hash..
1073 */
1074 if (base->d_op && base->d_op->d_hash) {
1075 err = base->d_op->d_hash(base, name);
1076 dentry = ERR_PTR(err);
1077 if (err < 0)
1078 goto out;
1079 }
1080
1081 dentry = cached_lookup(base, name, nd);
1082 if (!dentry) {
1083 struct dentry *new = d_alloc(base, name);
1084 dentry = ERR_PTR(-ENOMEM);
1085 if (!new)
1086 goto out;
1087 dentry = inode->i_op->lookup(inode, new, nd);
1088 if (!dentry)
1089 dentry = new;
1090 else
1091 dput(new);
1092 }
1093out:
1094 return dentry;
1095}
1096
1097struct dentry * lookup_hash(struct qstr *name, struct dentry * base)
1098{
1099 return __lookup_hash(name, base, NULL);
1100}
1101
1102/* SMP-safe */
1103struct dentry * lookup_one_len(const char * name, struct dentry * base, int len)
1104{
1105 unsigned long hash;
1106 struct qstr this;
1107 unsigned int c;
1108
1109 this.name = name;
1110 this.len = len;
1111 if (!len)
1112 goto access;
1113
1114 hash = init_name_hash();
1115 while (len--) {
1116 c = *(const unsigned char *)name++;
1117 if (c == '/' || c == '\0')
1118 goto access;
1119 hash = partial_name_hash(c, hash);
1120 }
1121 this.hash = end_name_hash(hash);
1122
1123 return lookup_hash(&this, base);
1124access:
1125 return ERR_PTR(-EACCES);
1126}
1127
1128/*
1129 * namei()
1130 *
1131 * is used by most simple commands to get the inode of a specified name.
1132 * Open, link etc use their own routines, but this is enough for things
1133 * like 'chmod' etc.
1134 *
1135 * namei exists in two versions: namei/lnamei. The only difference is
1136 * that namei follows links, while lnamei does not.
1137 * SMP-safe
1138 */
1139int fastcall __user_walk(const char __user *name, unsigned flags, struct nameidata *nd)
1140{
1141 char *tmp = getname(name);
1142 int err = PTR_ERR(tmp);
1143
1144 if (!IS_ERR(tmp)) {
1145 err = path_lookup(tmp, flags, nd);
1146 putname(tmp);
1147 }
1148 return err;
1149}
1150
1151/*
1152 * It's inline, so penalty for filesystems that don't use sticky bit is
1153 * minimal.
1154 */
1155static inline int check_sticky(struct inode *dir, struct inode *inode)
1156{
1157 if (!(dir->i_mode & S_ISVTX))
1158 return 0;
1159 if (inode->i_uid == current->fsuid)
1160 return 0;
1161 if (dir->i_uid == current->fsuid)
1162 return 0;
1163 return !capable(CAP_FOWNER);
1164}
1165
1166/*
1167 * Check whether we can remove a link victim from directory dir, check
1168 * whether the type of victim is right.
1169 * 1. We can't do it if dir is read-only (done in permission())
1170 * 2. We should have write and exec permissions on dir
1171 * 3. We can't remove anything from append-only dir
1172 * 4. We can't do anything with immutable dir (done in permission())
1173 * 5. If the sticky bit on dir is set we should either
1174 * a. be owner of dir, or
1175 * b. be owner of victim, or
1176 * c. have CAP_FOWNER capability
1177 * 6. If the victim is append-only or immutable we can't do antyhing with
1178 * links pointing to it.
1179 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
1180 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
1181 * 9. We can't remove a root or mountpoint.
1182 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
1183 * nfs_async_unlink().
1184 */
1185static inline int may_delete(struct inode *dir,struct dentry *victim,int isdir)
1186{
1187 int error;
1188
1189 if (!victim->d_inode)
1190 return -ENOENT;
1191
1192 BUG_ON(victim->d_parent->d_inode != dir);
1193
1194 error = permission(dir,MAY_WRITE | MAY_EXEC, NULL);
1195 if (error)
1196 return error;
1197 if (IS_APPEND(dir))
1198 return -EPERM;
1199 if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
1200 IS_IMMUTABLE(victim->d_inode))
1201 return -EPERM;
1202 if (isdir) {
1203 if (!S_ISDIR(victim->d_inode->i_mode))
1204 return -ENOTDIR;
1205 if (IS_ROOT(victim))
1206 return -EBUSY;
1207 } else if (S_ISDIR(victim->d_inode->i_mode))
1208 return -EISDIR;
1209 if (IS_DEADDIR(dir))
1210 return -ENOENT;
1211 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
1212 return -EBUSY;
1213 return 0;
1214}
1215
1216/* Check whether we can create an object with dentry child in directory
1217 * dir.
1218 * 1. We can't do it if child already exists (open has special treatment for
1219 * this case, but since we are inlined it's OK)
1220 * 2. We can't do it if dir is read-only (done in permission())
1221 * 3. We should have write and exec permissions on dir
1222 * 4. We can't do it if dir is immutable (done in permission())
1223 */
1224static inline int may_create(struct inode *dir, struct dentry *child,
1225 struct nameidata *nd)
1226{
1227 if (child->d_inode)
1228 return -EEXIST;
1229 if (IS_DEADDIR(dir))
1230 return -ENOENT;
1231 return permission(dir,MAY_WRITE | MAY_EXEC, nd);
1232}
1233
1234/*
1235 * Special case: O_CREAT|O_EXCL implies O_NOFOLLOW for security
1236 * reasons.
1237 *
1238 * O_DIRECTORY translates into forcing a directory lookup.
1239 */
1240static inline int lookup_flags(unsigned int f)
1241{
1242 unsigned long retval = LOOKUP_FOLLOW;
1243
1244 if (f & O_NOFOLLOW)
1245 retval &= ~LOOKUP_FOLLOW;
1246
1247 if ((f & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL))
1248 retval &= ~LOOKUP_FOLLOW;
1249
1250 if (f & O_DIRECTORY)
1251 retval |= LOOKUP_DIRECTORY;
1252
1253 return retval;
1254}
1255
1256/*
1257 * p1 and p2 should be directories on the same fs.
1258 */
1259struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
1260{
1261 struct dentry *p;
1262
1263 if (p1 == p2) {
1264 down(&p1->d_inode->i_sem);
1265 return NULL;
1266 }
1267
1268 down(&p1->d_inode->i_sb->s_vfs_rename_sem);
1269
1270 for (p = p1; p->d_parent != p; p = p->d_parent) {
1271 if (p->d_parent == p2) {
1272 down(&p2->d_inode->i_sem);
1273 down(&p1->d_inode->i_sem);
1274 return p;
1275 }
1276 }
1277
1278 for (p = p2; p->d_parent != p; p = p->d_parent) {
1279 if (p->d_parent == p1) {
1280 down(&p1->d_inode->i_sem);
1281 down(&p2->d_inode->i_sem);
1282 return p;
1283 }
1284 }
1285
1286 down(&p1->d_inode->i_sem);
1287 down(&p2->d_inode->i_sem);
1288 return NULL;
1289}
1290
1291void unlock_rename(struct dentry *p1, struct dentry *p2)
1292{
1293 up(&p1->d_inode->i_sem);
1294 if (p1 != p2) {
1295 up(&p2->d_inode->i_sem);
1296 up(&p1->d_inode->i_sb->s_vfs_rename_sem);
1297 }
1298}
1299
1300int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
1301 struct nameidata *nd)
1302{
1303 int error = may_create(dir, dentry, nd);
1304
1305 if (error)
1306 return error;
1307
1308 if (!dir->i_op || !dir->i_op->create)
1309 return -EACCES; /* shouldn't it be ENOSYS? */
1310 mode &= S_IALLUGO;
1311 mode |= S_IFREG;
1312 error = security_inode_create(dir, dentry, mode);
1313 if (error)
1314 return error;
1315 DQUOT_INIT(dir);
1316 error = dir->i_op->create(dir, dentry, mode, nd);
1317 if (!error) {
Robert Love0eeca282005-07-12 17:06:03 -04001318 fsnotify_create(dir, dentry->d_name.name);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001319 security_inode_post_create(dir, dentry, mode);
1320 }
1321 return error;
1322}
1323
1324int may_open(struct nameidata *nd, int acc_mode, int flag)
1325{
1326 struct dentry *dentry = nd->dentry;
1327 struct inode *inode = dentry->d_inode;
1328 int error;
1329
1330 if (!inode)
1331 return -ENOENT;
1332
1333 if (S_ISLNK(inode->i_mode))
1334 return -ELOOP;
1335
1336 if (S_ISDIR(inode->i_mode) && (flag & FMODE_WRITE))
1337 return -EISDIR;
1338
1339 error = permission(inode, acc_mode, nd);
1340 if (error)
1341 return error;
1342
1343 /*
1344 * FIFO's, sockets and device files are special: they don't
1345 * actually live on the filesystem itself, and as such you
1346 * can write to them even if the filesystem is read-only.
1347 */
1348 if (S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
1349 flag &= ~O_TRUNC;
1350 } else if (S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode)) {
1351 if (nd->mnt->mnt_flags & MNT_NODEV)
1352 return -EACCES;
1353
1354 flag &= ~O_TRUNC;
1355 } else if (IS_RDONLY(inode) && (flag & FMODE_WRITE))
1356 return -EROFS;
1357 /*
1358 * An append-only file must be opened in append mode for writing.
1359 */
1360 if (IS_APPEND(inode)) {
1361 if ((flag & FMODE_WRITE) && !(flag & O_APPEND))
1362 return -EPERM;
1363 if (flag & O_TRUNC)
1364 return -EPERM;
1365 }
1366
1367 /* O_NOATIME can only be set by the owner or superuser */
1368 if (flag & O_NOATIME)
1369 if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
1370 return -EPERM;
1371
1372 /*
1373 * Ensure there are no outstanding leases on the file.
1374 */
1375 error = break_lease(inode, flag);
1376 if (error)
1377 return error;
1378
1379 if (flag & O_TRUNC) {
1380 error = get_write_access(inode);
1381 if (error)
1382 return error;
1383
1384 /*
1385 * Refuse to truncate files with mandatory locks held on them.
1386 */
1387 error = locks_verify_locked(inode);
1388 if (!error) {
1389 DQUOT_INIT(inode);
1390
1391 error = do_truncate(dentry, 0);
1392 }
1393 put_write_access(inode);
1394 if (error)
1395 return error;
1396 } else
1397 if (flag & FMODE_WRITE)
1398 DQUOT_INIT(inode);
1399
1400 return 0;
1401}
1402
1403/*
1404 * open_namei()
1405 *
1406 * namei for open - this is in fact almost the whole open-routine.
1407 *
1408 * Note that the low bits of "flag" aren't the same as in the open
1409 * system call - they are 00 - no permissions needed
1410 * 01 - read permission needed
1411 * 10 - write permission needed
1412 * 11 - read/write permissions needed
1413 * which is a lot more logical, and also allows the "no perm" needed
1414 * for symlinks (where the permissions are checked later).
1415 * SMP-safe
1416 */
1417int open_namei(const char * pathname, int flag, int mode, struct nameidata *nd)
1418{
1419 int acc_mode, error = 0;
Al Viro4e7506e2005-06-06 13:36:00 -07001420 struct path path;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001421 struct dentry *dir;
1422 int count = 0;
1423
1424 acc_mode = ACC_MODE(flag);
1425
1426 /* Allow the LSM permission hook to distinguish append
1427 access from general write access. */
1428 if (flag & O_APPEND)
1429 acc_mode |= MAY_APPEND;
1430
1431 /* Fill in the open() intent data */
1432 nd->intent.open.flags = flag;
1433 nd->intent.open.create_mode = mode;
1434
1435 /*
1436 * The simplest case - just a plain lookup.
1437 */
1438 if (!(flag & O_CREAT)) {
1439 error = path_lookup(pathname, lookup_flags(flag)|LOOKUP_OPEN, nd);
1440 if (error)
1441 return error;
1442 goto ok;
1443 }
1444
1445 /*
1446 * Create - we need to know the parent.
1447 */
1448 error = path_lookup(pathname, LOOKUP_PARENT|LOOKUP_OPEN|LOOKUP_CREATE, nd);
1449 if (error)
1450 return error;
1451
1452 /*
1453 * We have the parent and last component. First of all, check
1454 * that we are not asked to creat(2) an obvious directory - that
1455 * will not do.
1456 */
1457 error = -EISDIR;
1458 if (nd->last_type != LAST_NORM || nd->last.name[nd->last.len])
1459 goto exit;
1460
1461 dir = nd->dentry;
1462 nd->flags &= ~LOOKUP_PARENT;
1463 down(&dir->d_inode->i_sem);
Al Viro4e7506e2005-06-06 13:36:00 -07001464 path.dentry = __lookup_hash(&nd->last, nd->dentry, nd);
Al Virod73ffe12005-06-06 13:36:01 -07001465 path.mnt = nd->mnt;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001466
1467do_last:
Al Viro4e7506e2005-06-06 13:36:00 -07001468 error = PTR_ERR(path.dentry);
1469 if (IS_ERR(path.dentry)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001470 up(&dir->d_inode->i_sem);
1471 goto exit;
1472 }
1473
1474 /* Negative dentry, just create the file */
Al Viro4e7506e2005-06-06 13:36:00 -07001475 if (!path.dentry->d_inode) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001476 if (!IS_POSIXACL(dir->d_inode))
1477 mode &= ~current->fs->umask;
Al Viro4e7506e2005-06-06 13:36:00 -07001478 error = vfs_create(dir->d_inode, path.dentry, mode, nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001479 up(&dir->d_inode->i_sem);
1480 dput(nd->dentry);
Al Viro4e7506e2005-06-06 13:36:00 -07001481 nd->dentry = path.dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001482 if (error)
1483 goto exit;
1484 /* Don't check for write permission, don't truncate */
1485 acc_mode = 0;
1486 flag &= ~O_TRUNC;
1487 goto ok;
1488 }
1489
1490 /*
1491 * It already exists.
1492 */
1493 up(&dir->d_inode->i_sem);
1494
1495 error = -EEXIST;
1496 if (flag & O_EXCL)
1497 goto exit_dput;
1498
Al Viroe13b2102005-06-06 13:36:06 -07001499 if (__follow_mount(&path)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001500 error = -ELOOP;
Al Viroba7a4c12005-06-06 13:36:08 -07001501 if (flag & O_NOFOLLOW)
1502 goto exit_dput;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001503 }
1504 error = -ENOENT;
Al Viro4e7506e2005-06-06 13:36:00 -07001505 if (!path.dentry->d_inode)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001506 goto exit_dput;
Al Viro4e7506e2005-06-06 13:36:00 -07001507 if (path.dentry->d_inode->i_op && path.dentry->d_inode->i_op->follow_link)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001508 goto do_link;
1509
1510 dput(nd->dentry);
Al Viro4e7506e2005-06-06 13:36:00 -07001511 nd->dentry = path.dentry;
Al Viroa15a3f62005-06-06 13:36:08 -07001512 if (nd->mnt != path.mnt)
1513 mntput(nd->mnt);
1514 nd->mnt = path.mnt;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001515 error = -EISDIR;
Al Viro4e7506e2005-06-06 13:36:00 -07001516 if (path.dentry->d_inode && S_ISDIR(path.dentry->d_inode->i_mode))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001517 goto exit;
1518ok:
1519 error = may_open(nd, acc_mode, flag);
1520 if (error)
1521 goto exit;
1522 return 0;
1523
1524exit_dput:
Al Viro4e7506e2005-06-06 13:36:00 -07001525 dput(path.dentry);
Al Viroa15a3f62005-06-06 13:36:08 -07001526 if (nd->mnt != path.mnt)
Al Viroba7a4c12005-06-06 13:36:08 -07001527 mntput(path.mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001528exit:
1529 path_release(nd);
1530 return error;
1531
1532do_link:
1533 error = -ELOOP;
1534 if (flag & O_NOFOLLOW)
1535 goto exit_dput;
1536 /*
1537 * This is subtle. Instead of calling do_follow_link() we do the
1538 * thing by hands. The reason is that this way we have zero link_count
1539 * and path_walk() (called from ->follow_link) honoring LOOKUP_PARENT.
1540 * After that we have the parent and last component, i.e.
1541 * we are in the same situation as after the first path_walk().
1542 * Well, almost - if the last component is normal we get its copy
1543 * stored in nd->last.name and we will have to putname() it when we
1544 * are done. Procfs-like symlinks just set LAST_BIND.
1545 */
1546 nd->flags |= LOOKUP_PARENT;
Al Viro4e7506e2005-06-06 13:36:00 -07001547 error = security_inode_follow_link(path.dentry, nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001548 if (error)
1549 goto exit_dput;
Al Virocd4e91d2005-06-06 13:36:03 -07001550 error = __do_follow_link(&path, nd);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001551 if (error)
1552 return error;
1553 nd->flags &= ~LOOKUP_PARENT;
Al Virod671d5e2005-06-06 13:36:04 -07001554 if (nd->last_type == LAST_BIND)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001555 goto ok;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001556 error = -EISDIR;
1557 if (nd->last_type != LAST_NORM)
1558 goto exit;
1559 if (nd->last.name[nd->last.len]) {
1560 putname(nd->last.name);
1561 goto exit;
1562 }
1563 error = -ELOOP;
1564 if (count++==32) {
1565 putname(nd->last.name);
1566 goto exit;
1567 }
1568 dir = nd->dentry;
1569 down(&dir->d_inode->i_sem);
Al Viro4e7506e2005-06-06 13:36:00 -07001570 path.dentry = __lookup_hash(&nd->last, nd->dentry, nd);
Al Virod671d5e2005-06-06 13:36:04 -07001571 path.mnt = nd->mnt;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001572 putname(nd->last.name);
1573 goto do_last;
1574}
1575
1576/**
1577 * lookup_create - lookup a dentry, creating it if it doesn't exist
1578 * @nd: nameidata info
1579 * @is_dir: directory flag
1580 *
1581 * Simple function to lookup and return a dentry and create it
1582 * if it doesn't exist. Is SMP-safe.
Christoph Hellwigc663e5d2005-06-23 00:09:49 -07001583 *
1584 * Returns with nd->dentry->d_inode->i_sem locked.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001585 */
1586struct dentry *lookup_create(struct nameidata *nd, int is_dir)
1587{
Christoph Hellwigc663e5d2005-06-23 00:09:49 -07001588 struct dentry *dentry = ERR_PTR(-EEXIST);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001589
1590 down(&nd->dentry->d_inode->i_sem);
Christoph Hellwigc663e5d2005-06-23 00:09:49 -07001591 /*
1592 * Yucky last component or no last component at all?
1593 * (foo/., foo/.., /////)
1594 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001595 if (nd->last_type != LAST_NORM)
1596 goto fail;
1597 nd->flags &= ~LOOKUP_PARENT;
Christoph Hellwigc663e5d2005-06-23 00:09:49 -07001598
1599 /*
1600 * Do the final lookup.
1601 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001602 dentry = lookup_hash(&nd->last, nd->dentry);
1603 if (IS_ERR(dentry))
1604 goto fail;
Christoph Hellwigc663e5d2005-06-23 00:09:49 -07001605
1606 /*
1607 * Special case - lookup gave negative, but... we had foo/bar/
1608 * From the vfs_mknod() POV we just have a negative dentry -
1609 * all is fine. Let's be bastards - you had / on the end, you've
1610 * been asking for (non-existent) directory. -ENOENT for you.
1611 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001612 if (!is_dir && nd->last.name[nd->last.len] && !dentry->d_inode)
1613 goto enoent;
1614 return dentry;
1615enoent:
1616 dput(dentry);
1617 dentry = ERR_PTR(-ENOENT);
1618fail:
1619 return dentry;
1620}
Christoph Hellwigf81a0bf2005-05-19 12:26:43 -07001621EXPORT_SYMBOL_GPL(lookup_create);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001622
1623int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1624{
1625 int error = may_create(dir, dentry, NULL);
1626
1627 if (error)
1628 return error;
1629
1630 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
1631 return -EPERM;
1632
1633 if (!dir->i_op || !dir->i_op->mknod)
1634 return -EPERM;
1635
1636 error = security_inode_mknod(dir, dentry, mode, dev);
1637 if (error)
1638 return error;
1639
1640 DQUOT_INIT(dir);
1641 error = dir->i_op->mknod(dir, dentry, mode, dev);
1642 if (!error) {
Robert Love0eeca282005-07-12 17:06:03 -04001643 fsnotify_create(dir, dentry->d_name.name);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001644 security_inode_post_mknod(dir, dentry, mode, dev);
1645 }
1646 return error;
1647}
1648
1649asmlinkage long sys_mknod(const char __user * filename, int mode, unsigned dev)
1650{
1651 int error = 0;
1652 char * tmp;
1653 struct dentry * dentry;
1654 struct nameidata nd;
1655
1656 if (S_ISDIR(mode))
1657 return -EPERM;
1658 tmp = getname(filename);
1659 if (IS_ERR(tmp))
1660 return PTR_ERR(tmp);
1661
1662 error = path_lookup(tmp, LOOKUP_PARENT, &nd);
1663 if (error)
1664 goto out;
1665 dentry = lookup_create(&nd, 0);
1666 error = PTR_ERR(dentry);
1667
1668 if (!IS_POSIXACL(nd.dentry->d_inode))
1669 mode &= ~current->fs->umask;
1670 if (!IS_ERR(dentry)) {
1671 switch (mode & S_IFMT) {
1672 case 0: case S_IFREG:
1673 error = vfs_create(nd.dentry->d_inode,dentry,mode,&nd);
1674 break;
1675 case S_IFCHR: case S_IFBLK:
1676 error = vfs_mknod(nd.dentry->d_inode,dentry,mode,
1677 new_decode_dev(dev));
1678 break;
1679 case S_IFIFO: case S_IFSOCK:
1680 error = vfs_mknod(nd.dentry->d_inode,dentry,mode,0);
1681 break;
1682 case S_IFDIR:
1683 error = -EPERM;
1684 break;
1685 default:
1686 error = -EINVAL;
1687 }
1688 dput(dentry);
1689 }
1690 up(&nd.dentry->d_inode->i_sem);
1691 path_release(&nd);
1692out:
1693 putname(tmp);
1694
1695 return error;
1696}
1697
1698int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1699{
1700 int error = may_create(dir, dentry, NULL);
1701
1702 if (error)
1703 return error;
1704
1705 if (!dir->i_op || !dir->i_op->mkdir)
1706 return -EPERM;
1707
1708 mode &= (S_IRWXUGO|S_ISVTX);
1709 error = security_inode_mkdir(dir, dentry, mode);
1710 if (error)
1711 return error;
1712
1713 DQUOT_INIT(dir);
1714 error = dir->i_op->mkdir(dir, dentry, mode);
1715 if (!error) {
Robert Love0eeca282005-07-12 17:06:03 -04001716 fsnotify_mkdir(dir, dentry->d_name.name);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001717 security_inode_post_mkdir(dir,dentry, mode);
1718 }
1719 return error;
1720}
1721
1722asmlinkage long sys_mkdir(const char __user * pathname, int mode)
1723{
1724 int error = 0;
1725 char * tmp;
1726
1727 tmp = getname(pathname);
1728 error = PTR_ERR(tmp);
1729 if (!IS_ERR(tmp)) {
1730 struct dentry *dentry;
1731 struct nameidata nd;
1732
1733 error = path_lookup(tmp, LOOKUP_PARENT, &nd);
1734 if (error)
1735 goto out;
1736 dentry = lookup_create(&nd, 1);
1737 error = PTR_ERR(dentry);
1738 if (!IS_ERR(dentry)) {
1739 if (!IS_POSIXACL(nd.dentry->d_inode))
1740 mode &= ~current->fs->umask;
1741 error = vfs_mkdir(nd.dentry->d_inode, dentry, mode);
1742 dput(dentry);
1743 }
1744 up(&nd.dentry->d_inode->i_sem);
1745 path_release(&nd);
1746out:
1747 putname(tmp);
1748 }
1749
1750 return error;
1751}
1752
1753/*
1754 * We try to drop the dentry early: we should have
1755 * a usage count of 2 if we're the only user of this
1756 * dentry, and if that is true (possibly after pruning
1757 * the dcache), then we drop the dentry now.
1758 *
1759 * A low-level filesystem can, if it choses, legally
1760 * do a
1761 *
1762 * if (!d_unhashed(dentry))
1763 * return -EBUSY;
1764 *
1765 * if it cannot handle the case of removing a directory
1766 * that is still in use by something else..
1767 */
1768void dentry_unhash(struct dentry *dentry)
1769{
1770 dget(dentry);
1771 if (atomic_read(&dentry->d_count))
1772 shrink_dcache_parent(dentry);
1773 spin_lock(&dcache_lock);
1774 spin_lock(&dentry->d_lock);
1775 if (atomic_read(&dentry->d_count) == 2)
1776 __d_drop(dentry);
1777 spin_unlock(&dentry->d_lock);
1778 spin_unlock(&dcache_lock);
1779}
1780
1781int vfs_rmdir(struct inode *dir, struct dentry *dentry)
1782{
1783 int error = may_delete(dir, dentry, 1);
1784
1785 if (error)
1786 return error;
1787
1788 if (!dir->i_op || !dir->i_op->rmdir)
1789 return -EPERM;
1790
1791 DQUOT_INIT(dir);
1792
1793 down(&dentry->d_inode->i_sem);
1794 dentry_unhash(dentry);
1795 if (d_mountpoint(dentry))
1796 error = -EBUSY;
1797 else {
1798 error = security_inode_rmdir(dir, dentry);
1799 if (!error) {
1800 error = dir->i_op->rmdir(dir, dentry);
1801 if (!error)
1802 dentry->d_inode->i_flags |= S_DEAD;
1803 }
1804 }
1805 up(&dentry->d_inode->i_sem);
1806 if (!error) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001807 d_delete(dentry);
1808 }
1809 dput(dentry);
1810
1811 return error;
1812}
1813
1814asmlinkage long sys_rmdir(const char __user * pathname)
1815{
1816 int error = 0;
1817 char * name;
1818 struct dentry *dentry;
1819 struct nameidata nd;
1820
1821 name = getname(pathname);
1822 if(IS_ERR(name))
1823 return PTR_ERR(name);
1824
1825 error = path_lookup(name, LOOKUP_PARENT, &nd);
1826 if (error)
1827 goto exit;
1828
1829 switch(nd.last_type) {
1830 case LAST_DOTDOT:
1831 error = -ENOTEMPTY;
1832 goto exit1;
1833 case LAST_DOT:
1834 error = -EINVAL;
1835 goto exit1;
1836 case LAST_ROOT:
1837 error = -EBUSY;
1838 goto exit1;
1839 }
1840 down(&nd.dentry->d_inode->i_sem);
1841 dentry = lookup_hash(&nd.last, nd.dentry);
1842 error = PTR_ERR(dentry);
1843 if (!IS_ERR(dentry)) {
1844 error = vfs_rmdir(nd.dentry->d_inode, dentry);
1845 dput(dentry);
1846 }
1847 up(&nd.dentry->d_inode->i_sem);
1848exit1:
1849 path_release(&nd);
1850exit:
1851 putname(name);
1852 return error;
1853}
1854
1855int vfs_unlink(struct inode *dir, struct dentry *dentry)
1856{
1857 int error = may_delete(dir, dentry, 0);
1858
1859 if (error)
1860 return error;
1861
1862 if (!dir->i_op || !dir->i_op->unlink)
1863 return -EPERM;
1864
1865 DQUOT_INIT(dir);
1866
1867 down(&dentry->d_inode->i_sem);
1868 if (d_mountpoint(dentry))
1869 error = -EBUSY;
1870 else {
1871 error = security_inode_unlink(dir, dentry);
1872 if (!error)
1873 error = dir->i_op->unlink(dir, dentry);
1874 }
1875 up(&dentry->d_inode->i_sem);
1876
1877 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
1878 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
1879 d_delete(dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001880 }
Robert Love0eeca282005-07-12 17:06:03 -04001881
Linus Torvalds1da177e2005-04-16 15:20:36 -07001882 return error;
1883}
1884
1885/*
1886 * Make sure that the actual truncation of the file will occur outside its
1887 * directory's i_sem. Truncate can take a long time if there is a lot of
1888 * writeout happening, and we don't want to prevent access to the directory
1889 * while waiting on the I/O.
1890 */
1891asmlinkage long sys_unlink(const char __user * pathname)
1892{
1893 int error = 0;
1894 char * name;
1895 struct dentry *dentry;
1896 struct nameidata nd;
1897 struct inode *inode = NULL;
1898
1899 name = getname(pathname);
1900 if(IS_ERR(name))
1901 return PTR_ERR(name);
1902
1903 error = path_lookup(name, LOOKUP_PARENT, &nd);
1904 if (error)
1905 goto exit;
1906 error = -EISDIR;
1907 if (nd.last_type != LAST_NORM)
1908 goto exit1;
1909 down(&nd.dentry->d_inode->i_sem);
1910 dentry = lookup_hash(&nd.last, nd.dentry);
1911 error = PTR_ERR(dentry);
1912 if (!IS_ERR(dentry)) {
1913 /* Why not before? Because we want correct error value */
1914 if (nd.last.name[nd.last.len])
1915 goto slashes;
1916 inode = dentry->d_inode;
1917 if (inode)
1918 atomic_inc(&inode->i_count);
1919 error = vfs_unlink(nd.dentry->d_inode, dentry);
1920 exit2:
1921 dput(dentry);
1922 }
1923 up(&nd.dentry->d_inode->i_sem);
1924 if (inode)
1925 iput(inode); /* truncate the inode here */
1926exit1:
1927 path_release(&nd);
1928exit:
1929 putname(name);
1930 return error;
1931
1932slashes:
1933 error = !dentry->d_inode ? -ENOENT :
1934 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
1935 goto exit2;
1936}
1937
1938int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname, int mode)
1939{
1940 int error = may_create(dir, dentry, NULL);
1941
1942 if (error)
1943 return error;
1944
1945 if (!dir->i_op || !dir->i_op->symlink)
1946 return -EPERM;
1947
1948 error = security_inode_symlink(dir, dentry, oldname);
1949 if (error)
1950 return error;
1951
1952 DQUOT_INIT(dir);
1953 error = dir->i_op->symlink(dir, dentry, oldname);
1954 if (!error) {
Robert Love0eeca282005-07-12 17:06:03 -04001955 fsnotify_create(dir, dentry->d_name.name);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001956 security_inode_post_symlink(dir, dentry, oldname);
1957 }
1958 return error;
1959}
1960
1961asmlinkage long sys_symlink(const char __user * oldname, const char __user * newname)
1962{
1963 int error = 0;
1964 char * from;
1965 char * to;
1966
1967 from = getname(oldname);
1968 if(IS_ERR(from))
1969 return PTR_ERR(from);
1970 to = getname(newname);
1971 error = PTR_ERR(to);
1972 if (!IS_ERR(to)) {
1973 struct dentry *dentry;
1974 struct nameidata nd;
1975
1976 error = path_lookup(to, LOOKUP_PARENT, &nd);
1977 if (error)
1978 goto out;
1979 dentry = lookup_create(&nd, 0);
1980 error = PTR_ERR(dentry);
1981 if (!IS_ERR(dentry)) {
1982 error = vfs_symlink(nd.dentry->d_inode, dentry, from, S_IALLUGO);
1983 dput(dentry);
1984 }
1985 up(&nd.dentry->d_inode->i_sem);
1986 path_release(&nd);
1987out:
1988 putname(to);
1989 }
1990 putname(from);
1991 return error;
1992}
1993
1994int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
1995{
1996 struct inode *inode = old_dentry->d_inode;
1997 int error;
1998
1999 if (!inode)
2000 return -ENOENT;
2001
2002 error = may_create(dir, new_dentry, NULL);
2003 if (error)
2004 return error;
2005
2006 if (dir->i_sb != inode->i_sb)
2007 return -EXDEV;
2008
2009 /*
2010 * A link to an append-only or immutable file cannot be created.
2011 */
2012 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
2013 return -EPERM;
2014 if (!dir->i_op || !dir->i_op->link)
2015 return -EPERM;
2016 if (S_ISDIR(old_dentry->d_inode->i_mode))
2017 return -EPERM;
2018
2019 error = security_inode_link(old_dentry, dir, new_dentry);
2020 if (error)
2021 return error;
2022
2023 down(&old_dentry->d_inode->i_sem);
2024 DQUOT_INIT(dir);
2025 error = dir->i_op->link(old_dentry, dir, new_dentry);
2026 up(&old_dentry->d_inode->i_sem);
2027 if (!error) {
Robert Love0eeca282005-07-12 17:06:03 -04002028 fsnotify_create(dir, new_dentry->d_name.name);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002029 security_inode_post_link(old_dentry, dir, new_dentry);
2030 }
2031 return error;
2032}
2033
2034/*
2035 * Hardlinks are often used in delicate situations. We avoid
2036 * security-related surprises by not following symlinks on the
2037 * newname. --KAB
2038 *
2039 * We don't follow them on the oldname either to be compatible
2040 * with linux 2.0, and to avoid hard-linking to directories
2041 * and other special files. --ADM
2042 */
2043asmlinkage long sys_link(const char __user * oldname, const char __user * newname)
2044{
2045 struct dentry *new_dentry;
2046 struct nameidata nd, old_nd;
2047 int error;
2048 char * to;
2049
2050 to = getname(newname);
2051 if (IS_ERR(to))
2052 return PTR_ERR(to);
2053
2054 error = __user_walk(oldname, 0, &old_nd);
2055 if (error)
2056 goto exit;
2057 error = path_lookup(to, LOOKUP_PARENT, &nd);
2058 if (error)
2059 goto out;
2060 error = -EXDEV;
2061 if (old_nd.mnt != nd.mnt)
2062 goto out_release;
2063 new_dentry = lookup_create(&nd, 0);
2064 error = PTR_ERR(new_dentry);
2065 if (!IS_ERR(new_dentry)) {
2066 error = vfs_link(old_nd.dentry, nd.dentry->d_inode, new_dentry);
2067 dput(new_dentry);
2068 }
2069 up(&nd.dentry->d_inode->i_sem);
2070out_release:
2071 path_release(&nd);
2072out:
2073 path_release(&old_nd);
2074exit:
2075 putname(to);
2076
2077 return error;
2078}
2079
2080/*
2081 * The worst of all namespace operations - renaming directory. "Perverted"
2082 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
2083 * Problems:
2084 * a) we can get into loop creation. Check is done in is_subdir().
2085 * b) race potential - two innocent renames can create a loop together.
2086 * That's where 4.4 screws up. Current fix: serialization on
2087 * sb->s_vfs_rename_sem. We might be more accurate, but that's another
2088 * story.
2089 * c) we have to lock _three_ objects - parents and victim (if it exists).
2090 * And that - after we got ->i_sem on parents (until then we don't know
2091 * whether the target exists). Solution: try to be smart with locking
2092 * order for inodes. We rely on the fact that tree topology may change
2093 * only under ->s_vfs_rename_sem _and_ that parent of the object we
2094 * move will be locked. Thus we can rank directories by the tree
2095 * (ancestors first) and rank all non-directories after them.
2096 * That works since everybody except rename does "lock parent, lookup,
2097 * lock child" and rename is under ->s_vfs_rename_sem.
2098 * HOWEVER, it relies on the assumption that any object with ->lookup()
2099 * has no more than 1 dentry. If "hybrid" objects will ever appear,
2100 * we'd better make sure that there's no link(2) for them.
2101 * d) some filesystems don't support opened-but-unlinked directories,
2102 * either because of layout or because they are not ready to deal with
2103 * all cases correctly. The latter will be fixed (taking this sort of
2104 * stuff into VFS), but the former is not going away. Solution: the same
2105 * trick as in rmdir().
2106 * e) conversion from fhandle to dentry may come in the wrong moment - when
2107 * we are removing the target. Solution: we will have to grab ->i_sem
2108 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
2109 * ->i_sem on parents, which works but leads to some truely excessive
2110 * locking].
2111 */
Adrian Bunk75c96f82005-05-05 16:16:09 -07002112static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
2113 struct inode *new_dir, struct dentry *new_dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002114{
2115 int error = 0;
2116 struct inode *target;
2117
2118 /*
2119 * If we are going to change the parent - check write permissions,
2120 * we'll need to flip '..'.
2121 */
2122 if (new_dir != old_dir) {
2123 error = permission(old_dentry->d_inode, MAY_WRITE, NULL);
2124 if (error)
2125 return error;
2126 }
2127
2128 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
2129 if (error)
2130 return error;
2131
2132 target = new_dentry->d_inode;
2133 if (target) {
2134 down(&target->i_sem);
2135 dentry_unhash(new_dentry);
2136 }
2137 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
2138 error = -EBUSY;
2139 else
2140 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
2141 if (target) {
2142 if (!error)
2143 target->i_flags |= S_DEAD;
2144 up(&target->i_sem);
2145 if (d_unhashed(new_dentry))
2146 d_rehash(new_dentry);
2147 dput(new_dentry);
2148 }
2149 if (!error) {
2150 d_move(old_dentry,new_dentry);
2151 security_inode_post_rename(old_dir, old_dentry,
2152 new_dir, new_dentry);
2153 }
2154 return error;
2155}
2156
Adrian Bunk75c96f82005-05-05 16:16:09 -07002157static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
2158 struct inode *new_dir, struct dentry *new_dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002159{
2160 struct inode *target;
2161 int error;
2162
2163 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
2164 if (error)
2165 return error;
2166
2167 dget(new_dentry);
2168 target = new_dentry->d_inode;
2169 if (target)
2170 down(&target->i_sem);
2171 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
2172 error = -EBUSY;
2173 else
2174 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
2175 if (!error) {
2176 /* The following d_move() should become unconditional */
2177 if (!(old_dir->i_sb->s_type->fs_flags & FS_ODD_RENAME))
2178 d_move(old_dentry, new_dentry);
2179 security_inode_post_rename(old_dir, old_dentry, new_dir, new_dentry);
2180 }
2181 if (target)
2182 up(&target->i_sem);
2183 dput(new_dentry);
2184 return error;
2185}
2186
2187int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
2188 struct inode *new_dir, struct dentry *new_dentry)
2189{
2190 int error;
2191 int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
Robert Love0eeca282005-07-12 17:06:03 -04002192 const char *old_name;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002193
2194 if (old_dentry->d_inode == new_dentry->d_inode)
2195 return 0;
2196
2197 error = may_delete(old_dir, old_dentry, is_dir);
2198 if (error)
2199 return error;
2200
2201 if (!new_dentry->d_inode)
2202 error = may_create(new_dir, new_dentry, NULL);
2203 else
2204 error = may_delete(new_dir, new_dentry, is_dir);
2205 if (error)
2206 return error;
2207
2208 if (!old_dir->i_op || !old_dir->i_op->rename)
2209 return -EPERM;
2210
2211 DQUOT_INIT(old_dir);
2212 DQUOT_INIT(new_dir);
2213
Robert Love0eeca282005-07-12 17:06:03 -04002214 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
2215
Linus Torvalds1da177e2005-04-16 15:20:36 -07002216 if (is_dir)
2217 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
2218 else
2219 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
2220 if (!error) {
Robert Love0eeca282005-07-12 17:06:03 -04002221 const char *new_name = old_dentry->d_name.name;
John McCutchan89204c42005-08-15 12:13:28 -04002222 fsnotify_move(old_dir, new_dir, old_name, new_name, is_dir,
2223 new_dentry->d_inode, old_dentry->d_inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002224 }
Robert Love0eeca282005-07-12 17:06:03 -04002225 fsnotify_oldname_free(old_name);
2226
Linus Torvalds1da177e2005-04-16 15:20:36 -07002227 return error;
2228}
2229
2230static inline int do_rename(const char * oldname, const char * newname)
2231{
2232 int error = 0;
2233 struct dentry * old_dir, * new_dir;
2234 struct dentry * old_dentry, *new_dentry;
2235 struct dentry * trap;
2236 struct nameidata oldnd, newnd;
2237
2238 error = path_lookup(oldname, LOOKUP_PARENT, &oldnd);
2239 if (error)
2240 goto exit;
2241
2242 error = path_lookup(newname, LOOKUP_PARENT, &newnd);
2243 if (error)
2244 goto exit1;
2245
2246 error = -EXDEV;
2247 if (oldnd.mnt != newnd.mnt)
2248 goto exit2;
2249
2250 old_dir = oldnd.dentry;
2251 error = -EBUSY;
2252 if (oldnd.last_type != LAST_NORM)
2253 goto exit2;
2254
2255 new_dir = newnd.dentry;
2256 if (newnd.last_type != LAST_NORM)
2257 goto exit2;
2258
2259 trap = lock_rename(new_dir, old_dir);
2260
2261 old_dentry = lookup_hash(&oldnd.last, old_dir);
2262 error = PTR_ERR(old_dentry);
2263 if (IS_ERR(old_dentry))
2264 goto exit3;
2265 /* source must exist */
2266 error = -ENOENT;
2267 if (!old_dentry->d_inode)
2268 goto exit4;
2269 /* unless the source is a directory trailing slashes give -ENOTDIR */
2270 if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
2271 error = -ENOTDIR;
2272 if (oldnd.last.name[oldnd.last.len])
2273 goto exit4;
2274 if (newnd.last.name[newnd.last.len])
2275 goto exit4;
2276 }
2277 /* source should not be ancestor of target */
2278 error = -EINVAL;
2279 if (old_dentry == trap)
2280 goto exit4;
2281 new_dentry = lookup_hash(&newnd.last, new_dir);
2282 error = PTR_ERR(new_dentry);
2283 if (IS_ERR(new_dentry))
2284 goto exit4;
2285 /* target should not be an ancestor of source */
2286 error = -ENOTEMPTY;
2287 if (new_dentry == trap)
2288 goto exit5;
2289
2290 error = vfs_rename(old_dir->d_inode, old_dentry,
2291 new_dir->d_inode, new_dentry);
2292exit5:
2293 dput(new_dentry);
2294exit4:
2295 dput(old_dentry);
2296exit3:
2297 unlock_rename(new_dir, old_dir);
2298exit2:
2299 path_release(&newnd);
2300exit1:
2301 path_release(&oldnd);
2302exit:
2303 return error;
2304}
2305
2306asmlinkage long sys_rename(const char __user * oldname, const char __user * newname)
2307{
2308 int error;
2309 char * from;
2310 char * to;
2311
2312 from = getname(oldname);
2313 if(IS_ERR(from))
2314 return PTR_ERR(from);
2315 to = getname(newname);
2316 error = PTR_ERR(to);
2317 if (!IS_ERR(to)) {
2318 error = do_rename(from,to);
2319 putname(to);
2320 }
2321 putname(from);
2322 return error;
2323}
2324
2325int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
2326{
2327 int len;
2328
2329 len = PTR_ERR(link);
2330 if (IS_ERR(link))
2331 goto out;
2332
2333 len = strlen(link);
2334 if (len > (unsigned) buflen)
2335 len = buflen;
2336 if (copy_to_user(buffer, link, len))
2337 len = -EFAULT;
2338out:
2339 return len;
2340}
2341
2342/*
2343 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
2344 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
2345 * using) it for any given inode is up to filesystem.
2346 */
2347int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
2348{
2349 struct nameidata nd;
Linus Torvaldscc314ee2005-08-19 18:02:56 -07002350 void *cookie;
2351
Linus Torvalds1da177e2005-04-16 15:20:36 -07002352 nd.depth = 0;
Linus Torvaldscc314ee2005-08-19 18:02:56 -07002353 cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
2354 if (!IS_ERR(cookie)) {
2355 int res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002356 if (dentry->d_inode->i_op->put_link)
Linus Torvaldscc314ee2005-08-19 18:02:56 -07002357 dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
2358 cookie = ERR_PTR(res);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002359 }
Linus Torvaldscc314ee2005-08-19 18:02:56 -07002360 return PTR_ERR(cookie);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002361}
2362
2363int vfs_follow_link(struct nameidata *nd, const char *link)
2364{
2365 return __vfs_follow_link(nd, link);
2366}
2367
2368/* get the link contents into pagecache */
2369static char *page_getlink(struct dentry * dentry, struct page **ppage)
2370{
2371 struct page * page;
2372 struct address_space *mapping = dentry->d_inode->i_mapping;
2373 page = read_cache_page(mapping, 0, (filler_t *)mapping->a_ops->readpage,
2374 NULL);
2375 if (IS_ERR(page))
2376 goto sync_fail;
2377 wait_on_page_locked(page);
2378 if (!PageUptodate(page))
2379 goto async_fail;
2380 *ppage = page;
2381 return kmap(page);
2382
2383async_fail:
2384 page_cache_release(page);
2385 return ERR_PTR(-EIO);
2386
2387sync_fail:
2388 return (char*)page;
2389}
2390
2391int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
2392{
2393 struct page *page = NULL;
2394 char *s = page_getlink(dentry, &page);
2395 int res = vfs_readlink(dentry,buffer,buflen,s);
2396 if (page) {
2397 kunmap(page);
2398 page_cache_release(page);
2399 }
2400 return res;
2401}
2402
Linus Torvaldscc314ee2005-08-19 18:02:56 -07002403void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002404{
Linus Torvaldscc314ee2005-08-19 18:02:56 -07002405 struct page *page = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002406 nd_set_link(nd, page_getlink(dentry, &page));
Linus Torvaldscc314ee2005-08-19 18:02:56 -07002407 return page;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002408}
2409
Linus Torvaldscc314ee2005-08-19 18:02:56 -07002410void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002411{
Linus Torvaldscc314ee2005-08-19 18:02:56 -07002412 struct page *page = cookie;
2413
2414 if (page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002415 kunmap(page);
2416 page_cache_release(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002417 }
2418}
2419
2420int page_symlink(struct inode *inode, const char *symname, int len)
2421{
2422 struct address_space *mapping = inode->i_mapping;
2423 struct page *page = grab_cache_page(mapping, 0);
2424 int err = -ENOMEM;
2425 char *kaddr;
2426
2427 if (!page)
2428 goto fail;
2429 err = mapping->a_ops->prepare_write(NULL, page, 0, len-1);
2430 if (err)
2431 goto fail_map;
2432 kaddr = kmap_atomic(page, KM_USER0);
2433 memcpy(kaddr, symname, len-1);
2434 kunmap_atomic(kaddr, KM_USER0);
2435 mapping->a_ops->commit_write(NULL, page, 0, len-1);
2436 /*
2437 * Notice that we are _not_ going to block here - end of page is
2438 * unmapped, so this will only try to map the rest of page, see
2439 * that it is unmapped (typically even will not look into inode -
2440 * ->i_size will be enough for everything) and zero it out.
2441 * OTOH it's obviously correct and should make the page up-to-date.
2442 */
2443 if (!PageUptodate(page)) {
2444 err = mapping->a_ops->readpage(NULL, page);
2445 wait_on_page_locked(page);
2446 } else {
2447 unlock_page(page);
2448 }
2449 page_cache_release(page);
2450 if (err < 0)
2451 goto fail;
2452 mark_inode_dirty(inode);
2453 return 0;
2454fail_map:
2455 unlock_page(page);
2456 page_cache_release(page);
2457fail:
2458 return err;
2459}
2460
2461struct inode_operations page_symlink_inode_operations = {
2462 .readlink = generic_readlink,
2463 .follow_link = page_follow_link_light,
2464 .put_link = page_put_link,
2465};
2466
2467EXPORT_SYMBOL(__user_walk);
2468EXPORT_SYMBOL(follow_down);
2469EXPORT_SYMBOL(follow_up);
2470EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
2471EXPORT_SYMBOL(getname);
2472EXPORT_SYMBOL(lock_rename);
2473EXPORT_SYMBOL(lookup_hash);
2474EXPORT_SYMBOL(lookup_one_len);
2475EXPORT_SYMBOL(page_follow_link_light);
2476EXPORT_SYMBOL(page_put_link);
2477EXPORT_SYMBOL(page_readlink);
2478EXPORT_SYMBOL(page_symlink);
2479EXPORT_SYMBOL(page_symlink_inode_operations);
2480EXPORT_SYMBOL(path_lookup);
2481EXPORT_SYMBOL(path_release);
2482EXPORT_SYMBOL(path_walk);
2483EXPORT_SYMBOL(permission);
2484EXPORT_SYMBOL(unlock_rename);
2485EXPORT_SYMBOL(vfs_create);
2486EXPORT_SYMBOL(vfs_follow_link);
2487EXPORT_SYMBOL(vfs_link);
2488EXPORT_SYMBOL(vfs_mkdir);
2489EXPORT_SYMBOL(vfs_mknod);
2490EXPORT_SYMBOL(generic_permission);
2491EXPORT_SYMBOL(vfs_readlink);
2492EXPORT_SYMBOL(vfs_rename);
2493EXPORT_SYMBOL(vfs_rmdir);
2494EXPORT_SYMBOL(vfs_symlink);
2495EXPORT_SYMBOL(vfs_unlink);
2496EXPORT_SYMBOL(dentry_unhash);
2497EXPORT_SYMBOL(generic_readlink);