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1 | /* | |
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/export.h> | |
19 | #include <linux/kernel.h> | |
20 | #include <linux/slab.h> | |
21 | #include <linux/fs.h> | |
22 | #include <linux/namei.h> | |
23 | #include <linux/pagemap.h> | |
24 | #include <linux/fsnotify.h> | |
25 | #include <linux/personality.h> | |
26 | #include <linux/security.h> | |
27 | #include <linux/ima.h> | |
28 | #include <linux/syscalls.h> | |
29 | #include <linux/mount.h> | |
30 | #include <linux/audit.h> | |
31 | #include <linux/capability.h> | |
32 | #include <linux/file.h> | |
33 | #include <linux/fcntl.h> | |
34 | #include <linux/device_cgroup.h> | |
35 | #include <linux/fs_struct.h> | |
36 | #include <linux/posix_acl.h> | |
37 | #include <linux/hash.h> | |
38 | #include <asm/uaccess.h> | |
39 | ||
40 | #include "internal.h" | |
41 | #include "mount.h" | |
42 | ||
43 | /* [Feb-1997 T. Schoebel-Theuer] | |
44 | * Fundamental changes in the pathname lookup mechanisms (namei) | |
45 | * were necessary because of omirr. The reason is that omirr needs | |
46 | * to know the _real_ pathname, not the user-supplied one, in case | |
47 | * of symlinks (and also when transname replacements occur). | |
48 | * | |
49 | * The new code replaces the old recursive symlink resolution with | |
50 | * an iterative one (in case of non-nested symlink chains). It does | |
51 | * this with calls to <fs>_follow_link(). | |
52 | * As a side effect, dir_namei(), _namei() and follow_link() are now | |
53 | * replaced with a single function lookup_dentry() that can handle all | |
54 | * the special cases of the former code. | |
55 | * | |
56 | * With the new dcache, the pathname is stored at each inode, at least as | |
57 | * long as the refcount of the inode is positive. As a side effect, the | |
58 | * size of the dcache depends on the inode cache and thus is dynamic. | |
59 | * | |
60 | * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink | |
61 | * resolution to correspond with current state of the code. | |
62 | * | |
63 | * Note that the symlink resolution is not *completely* iterative. | |
64 | * There is still a significant amount of tail- and mid- recursion in | |
65 | * the algorithm. Also, note that <fs>_readlink() is not used in | |
66 | * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink() | |
67 | * may return different results than <fs>_follow_link(). Many virtual | |
68 | * filesystems (including /proc) exhibit this behavior. | |
69 | */ | |
70 | ||
71 | /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation: | |
72 | * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL | |
73 | * and the name already exists in form of a symlink, try to create the new | |
74 | * name indicated by the symlink. The old code always complained that the | |
75 | * name already exists, due to not following the symlink even if its target | |
76 | * is nonexistent. The new semantics affects also mknod() and link() when | |
77 | * the name is a symlink pointing to a non-existent name. | |
78 | * | |
79 | * I don't know which semantics is the right one, since I have no access | |
80 | * to standards. But I found by trial that HP-UX 9.0 has the full "new" | |
81 | * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the | |
82 | * "old" one. Personally, I think the new semantics is much more logical. | |
83 | * Note that "ln old new" where "new" is a symlink pointing to a non-existing | |
84 | * file does succeed in both HP-UX and SunOs, but not in Solaris | |
85 | * and in the old Linux semantics. | |
86 | */ | |
87 | ||
88 | /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink | |
89 | * semantics. See the comments in "open_namei" and "do_link" below. | |
90 | * | |
91 | * [10-Sep-98 Alan Modra] Another symlink change. | |
92 | */ | |
93 | ||
94 | /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks: | |
95 | * inside the path - always follow. | |
96 | * in the last component in creation/removal/renaming - never follow. | |
97 | * if LOOKUP_FOLLOW passed - follow. | |
98 | * if the pathname has trailing slashes - follow. | |
99 | * otherwise - don't follow. | |
100 | * (applied in that order). | |
101 | * | |
102 | * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT | |
103 | * restored for 2.4. This is the last surviving part of old 4.2BSD bug. | |
104 | * During the 2.4 we need to fix the userland stuff depending on it - | |
105 | * hopefully we will be able to get rid of that wart in 2.5. So far only | |
106 | * XEmacs seems to be relying on it... | |
107 | */ | |
108 | /* | |
109 | * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland) | |
110 | * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives | |
111 | * any extra contention... | |
112 | */ | |
113 | ||
114 | /* In order to reduce some races, while at the same time doing additional | |
115 | * checking and hopefully speeding things up, we copy filenames to the | |
116 | * kernel data space before using them.. | |
117 | * | |
118 | * POSIX.1 2.4: an empty pathname is invalid (ENOENT). | |
119 | * PATH_MAX includes the nul terminator --RR. | |
120 | */ | |
121 | ||
122 | #define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname)) | |
123 | ||
124 | struct filename * | |
125 | getname_flags(const char __user *filename, int flags, int *empty) | |
126 | { | |
127 | struct filename *result; | |
128 | char *kname; | |
129 | int len; | |
130 | ||
131 | result = audit_reusename(filename); | |
132 | if (result) | |
133 | return result; | |
134 | ||
135 | result = __getname(); | |
136 | if (unlikely(!result)) | |
137 | return ERR_PTR(-ENOMEM); | |
138 | ||
139 | /* | |
140 | * First, try to embed the struct filename inside the names_cache | |
141 | * allocation | |
142 | */ | |
143 | kname = (char *)result->iname; | |
144 | result->name = kname; | |
145 | ||
146 | len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX); | |
147 | if (unlikely(len < 0)) { | |
148 | __putname(result); | |
149 | return ERR_PTR(len); | |
150 | } | |
151 | ||
152 | /* | |
153 | * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a | |
154 | * separate struct filename so we can dedicate the entire | |
155 | * names_cache allocation for the pathname, and re-do the copy from | |
156 | * userland. | |
157 | */ | |
158 | if (unlikely(len == EMBEDDED_NAME_MAX)) { | |
159 | const size_t size = offsetof(struct filename, iname[1]); | |
160 | kname = (char *)result; | |
161 | ||
162 | /* | |
163 | * size is chosen that way we to guarantee that | |
164 | * result->iname[0] is within the same object and that | |
165 | * kname can't be equal to result->iname, no matter what. | |
166 | */ | |
167 | result = kzalloc(size, GFP_KERNEL); | |
168 | if (unlikely(!result)) { | |
169 | __putname(kname); | |
170 | return ERR_PTR(-ENOMEM); | |
171 | } | |
172 | result->name = kname; | |
173 | len = strncpy_from_user(kname, filename, PATH_MAX); | |
174 | if (unlikely(len < 0)) { | |
175 | __putname(kname); | |
176 | kfree(result); | |
177 | return ERR_PTR(len); | |
178 | } | |
179 | if (unlikely(len == PATH_MAX)) { | |
180 | __putname(kname); | |
181 | kfree(result); | |
182 | return ERR_PTR(-ENAMETOOLONG); | |
183 | } | |
184 | } | |
185 | ||
186 | result->refcnt = 1; | |
187 | /* The empty path is special. */ | |
188 | if (unlikely(!len)) { | |
189 | if (empty) | |
190 | *empty = 1; | |
191 | if (!(flags & LOOKUP_EMPTY)) { | |
192 | putname(result); | |
193 | return ERR_PTR(-ENOENT); | |
194 | } | |
195 | } | |
196 | ||
197 | result->uptr = filename; | |
198 | result->aname = NULL; | |
199 | audit_getname(result); | |
200 | return result; | |
201 | } | |
202 | ||
203 | struct filename * | |
204 | getname(const char __user * filename) | |
205 | { | |
206 | return getname_flags(filename, 0, NULL); | |
207 | } | |
208 | ||
209 | struct filename * | |
210 | getname_kernel(const char * filename) | |
211 | { | |
212 | struct filename *result; | |
213 | int len = strlen(filename) + 1; | |
214 | ||
215 | result = __getname(); | |
216 | if (unlikely(!result)) | |
217 | return ERR_PTR(-ENOMEM); | |
218 | ||
219 | if (len <= EMBEDDED_NAME_MAX) { | |
220 | result->name = (char *)result->iname; | |
221 | } else if (len <= PATH_MAX) { | |
222 | struct filename *tmp; | |
223 | ||
224 | tmp = kmalloc(sizeof(*tmp), GFP_KERNEL); | |
225 | if (unlikely(!tmp)) { | |
226 | __putname(result); | |
227 | return ERR_PTR(-ENOMEM); | |
228 | } | |
229 | tmp->name = (char *)result; | |
230 | result = tmp; | |
231 | } else { | |
232 | __putname(result); | |
233 | return ERR_PTR(-ENAMETOOLONG); | |
234 | } | |
235 | memcpy((char *)result->name, filename, len); | |
236 | result->uptr = NULL; | |
237 | result->aname = NULL; | |
238 | result->refcnt = 1; | |
239 | audit_getname(result); | |
240 | ||
241 | return result; | |
242 | } | |
243 | ||
244 | void putname(struct filename *name) | |
245 | { | |
246 | BUG_ON(name->refcnt <= 0); | |
247 | ||
248 | if (--name->refcnt > 0) | |
249 | return; | |
250 | ||
251 | if (name->name != name->iname) { | |
252 | __putname(name->name); | |
253 | kfree(name); | |
254 | } else | |
255 | __putname(name); | |
256 | } | |
257 | ||
258 | static int check_acl(struct inode *inode, int mask) | |
259 | { | |
260 | #ifdef CONFIG_FS_POSIX_ACL | |
261 | struct posix_acl *acl; | |
262 | ||
263 | if (mask & MAY_NOT_BLOCK) { | |
264 | acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS); | |
265 | if (!acl) | |
266 | return -EAGAIN; | |
267 | /* no ->get_acl() calls in RCU mode... */ | |
268 | if (acl == ACL_NOT_CACHED) | |
269 | return -ECHILD; | |
270 | return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK); | |
271 | } | |
272 | ||
273 | acl = get_acl(inode, ACL_TYPE_ACCESS); | |
274 | if (IS_ERR(acl)) | |
275 | return PTR_ERR(acl); | |
276 | if (acl) { | |
277 | int error = posix_acl_permission(inode, acl, mask); | |
278 | posix_acl_release(acl); | |
279 | return error; | |
280 | } | |
281 | #endif | |
282 | ||
283 | return -EAGAIN; | |
284 | } | |
285 | ||
286 | /* | |
287 | * This does the basic permission checking | |
288 | */ | |
289 | static int acl_permission_check(struct inode *inode, int mask) | |
290 | { | |
291 | unsigned int mode = inode->i_mode; | |
292 | ||
293 | if (likely(uid_eq(current_fsuid(), inode->i_uid))) | |
294 | mode >>= 6; | |
295 | else { | |
296 | if (IS_POSIXACL(inode) && (mode & S_IRWXG)) { | |
297 | int error = check_acl(inode, mask); | |
298 | if (error != -EAGAIN) | |
299 | return error; | |
300 | } | |
301 | ||
302 | if (in_group_p(inode->i_gid)) | |
303 | mode >>= 3; | |
304 | } | |
305 | ||
306 | /* | |
307 | * If the DACs are ok we don't need any capability check. | |
308 | */ | |
309 | if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0) | |
310 | return 0; | |
311 | return -EACCES; | |
312 | } | |
313 | ||
314 | /** | |
315 | * generic_permission - check for access rights on a Posix-like filesystem | |
316 | * @inode: inode to check access rights for | |
317 | * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...) | |
318 | * | |
319 | * Used to check for read/write/execute permissions on a file. | |
320 | * We use "fsuid" for this, letting us set arbitrary permissions | |
321 | * for filesystem access without changing the "normal" uids which | |
322 | * are used for other things. | |
323 | * | |
324 | * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk | |
325 | * request cannot be satisfied (eg. requires blocking or too much complexity). | |
326 | * It would then be called again in ref-walk mode. | |
327 | */ | |
328 | int generic_permission(struct inode *inode, int mask) | |
329 | { | |
330 | int ret; | |
331 | ||
332 | /* | |
333 | * Do the basic permission checks. | |
334 | */ | |
335 | ret = acl_permission_check(inode, mask); | |
336 | if (ret != -EACCES) | |
337 | return ret; | |
338 | ||
339 | if (S_ISDIR(inode->i_mode)) { | |
340 | /* DACs are overridable for directories */ | |
341 | if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) | |
342 | return 0; | |
343 | if (!(mask & MAY_WRITE)) | |
344 | if (capable_wrt_inode_uidgid(inode, | |
345 | CAP_DAC_READ_SEARCH)) | |
346 | return 0; | |
347 | return -EACCES; | |
348 | } | |
349 | /* | |
350 | * Read/write DACs are always overridable. | |
351 | * Executable DACs are overridable when there is | |
352 | * at least one exec bit set. | |
353 | */ | |
354 | if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO)) | |
355 | if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) | |
356 | return 0; | |
357 | ||
358 | /* | |
359 | * Searching includes executable on directories, else just read. | |
360 | */ | |
361 | mask &= MAY_READ | MAY_WRITE | MAY_EXEC; | |
362 | if (mask == MAY_READ) | |
363 | if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH)) | |
364 | return 0; | |
365 | ||
366 | return -EACCES; | |
367 | } | |
368 | EXPORT_SYMBOL(generic_permission); | |
369 | ||
370 | /* | |
371 | * We _really_ want to just do "generic_permission()" without | |
372 | * even looking at the inode->i_op values. So we keep a cache | |
373 | * flag in inode->i_opflags, that says "this has not special | |
374 | * permission function, use the fast case". | |
375 | */ | |
376 | static inline int do_inode_permission(struct inode *inode, int mask) | |
377 | { | |
378 | if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) { | |
379 | if (likely(inode->i_op->permission)) | |
380 | return inode->i_op->permission(inode, mask); | |
381 | ||
382 | /* This gets set once for the inode lifetime */ | |
383 | spin_lock(&inode->i_lock); | |
384 | inode->i_opflags |= IOP_FASTPERM; | |
385 | spin_unlock(&inode->i_lock); | |
386 | } | |
387 | return generic_permission(inode, mask); | |
388 | } | |
389 | ||
390 | /** | |
391 | * __inode_permission - Check for access rights to a given inode | |
392 | * @inode: Inode to check permission on | |
393 | * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) | |
394 | * | |
395 | * Check for read/write/execute permissions on an inode. | |
396 | * | |
397 | * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. | |
398 | * | |
399 | * This does not check for a read-only file system. You probably want | |
400 | * inode_permission(). | |
401 | */ | |
402 | int __inode_permission(struct inode *inode, int mask) | |
403 | { | |
404 | int retval; | |
405 | ||
406 | if (unlikely(mask & MAY_WRITE)) { | |
407 | /* | |
408 | * Nobody gets write access to an immutable file. | |
409 | */ | |
410 | if (IS_IMMUTABLE(inode)) | |
411 | return -EACCES; | |
412 | } | |
413 | ||
414 | retval = do_inode_permission(inode, mask); | |
415 | if (retval) | |
416 | return retval; | |
417 | ||
418 | retval = devcgroup_inode_permission(inode, mask); | |
419 | if (retval) | |
420 | return retval; | |
421 | ||
422 | return security_inode_permission(inode, mask); | |
423 | } | |
424 | EXPORT_SYMBOL(__inode_permission); | |
425 | ||
426 | /** | |
427 | * sb_permission - Check superblock-level permissions | |
428 | * @sb: Superblock of inode to check permission on | |
429 | * @inode: Inode to check permission on | |
430 | * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) | |
431 | * | |
432 | * Separate out file-system wide checks from inode-specific permission checks. | |
433 | */ | |
434 | static int sb_permission(struct super_block *sb, struct inode *inode, int mask) | |
435 | { | |
436 | if (unlikely(mask & MAY_WRITE)) { | |
437 | umode_t mode = inode->i_mode; | |
438 | ||
439 | /* Nobody gets write access to a read-only fs. */ | |
440 | if ((sb->s_flags & MS_RDONLY) && | |
441 | (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) | |
442 | return -EROFS; | |
443 | } | |
444 | return 0; | |
445 | } | |
446 | ||
447 | /** | |
448 | * inode_permission - Check for access rights to a given inode | |
449 | * @inode: Inode to check permission on | |
450 | * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) | |
451 | * | |
452 | * Check for read/write/execute permissions on an inode. We use fs[ug]id for | |
453 | * this, letting us set arbitrary permissions for filesystem access without | |
454 | * changing the "normal" UIDs which are used for other things. | |
455 | * | |
456 | * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. | |
457 | */ | |
458 | int inode_permission(struct inode *inode, int mask) | |
459 | { | |
460 | int retval; | |
461 | ||
462 | retval = sb_permission(inode->i_sb, inode, mask); | |
463 | if (retval) | |
464 | return retval; | |
465 | return __inode_permission(inode, mask); | |
466 | } | |
467 | EXPORT_SYMBOL(inode_permission); | |
468 | ||
469 | /** | |
470 | * path_get - get a reference to a path | |
471 | * @path: path to get the reference to | |
472 | * | |
473 | * Given a path increment the reference count to the dentry and the vfsmount. | |
474 | */ | |
475 | void path_get(const struct path *path) | |
476 | { | |
477 | mntget(path->mnt); | |
478 | dget(path->dentry); | |
479 | } | |
480 | EXPORT_SYMBOL(path_get); | |
481 | ||
482 | /** | |
483 | * path_put - put a reference to a path | |
484 | * @path: path to put the reference to | |
485 | * | |
486 | * Given a path decrement the reference count to the dentry and the vfsmount. | |
487 | */ | |
488 | void path_put(const struct path *path) | |
489 | { | |
490 | dput(path->dentry); | |
491 | mntput(path->mnt); | |
492 | } | |
493 | EXPORT_SYMBOL(path_put); | |
494 | ||
495 | #define EMBEDDED_LEVELS 2 | |
496 | struct nameidata { | |
497 | struct path path; | |
498 | union { | |
499 | struct qstr last; | |
500 | struct path link; | |
501 | }; | |
502 | struct path root; | |
503 | struct inode *inode; /* path.dentry.d_inode */ | |
504 | unsigned int flags; | |
505 | unsigned seq, m_seq; | |
506 | int last_type; | |
507 | unsigned depth; | |
508 | struct file *base; | |
509 | struct saved { | |
510 | struct path link; | |
511 | void *cookie; | |
512 | const char *name; | |
513 | } *stack, internal[EMBEDDED_LEVELS]; | |
514 | }; | |
515 | ||
516 | static void set_nameidata(struct nameidata *nd) | |
517 | { | |
518 | nd->stack = nd->internal; | |
519 | } | |
520 | ||
521 | static void restore_nameidata(struct nameidata *nd) | |
522 | { | |
523 | if (nd->stack != nd->internal) { | |
524 | kfree(nd->stack); | |
525 | nd->stack = nd->internal; | |
526 | } | |
527 | } | |
528 | ||
529 | static int __nd_alloc_stack(struct nameidata *nd) | |
530 | { | |
531 | struct saved *p = kmalloc(MAXSYMLINKS * sizeof(struct saved), | |
532 | GFP_KERNEL); | |
533 | if (unlikely(!p)) | |
534 | return -ENOMEM; | |
535 | memcpy(p, nd->internal, sizeof(nd->internal)); | |
536 | nd->stack = p; | |
537 | return 0; | |
538 | } | |
539 | ||
540 | static inline int nd_alloc_stack(struct nameidata *nd) | |
541 | { | |
542 | if (likely(nd->depth != EMBEDDED_LEVELS)) | |
543 | return 0; | |
544 | if (likely(nd->stack != nd->internal)) | |
545 | return 0; | |
546 | return __nd_alloc_stack(nd); | |
547 | } | |
548 | ||
549 | /* | |
550 | * Path walking has 2 modes, rcu-walk and ref-walk (see | |
551 | * Documentation/filesystems/path-lookup.txt). In situations when we can't | |
552 | * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab | |
553 | * normal reference counts on dentries and vfsmounts to transition to rcu-walk | |
554 | * mode. Refcounts are grabbed at the last known good point before rcu-walk | |
555 | * got stuck, so ref-walk may continue from there. If this is not successful | |
556 | * (eg. a seqcount has changed), then failure is returned and it's up to caller | |
557 | * to restart the path walk from the beginning in ref-walk mode. | |
558 | */ | |
559 | ||
560 | /** | |
561 | * unlazy_walk - try to switch to ref-walk mode. | |
562 | * @nd: nameidata pathwalk data | |
563 | * @dentry: child of nd->path.dentry or NULL | |
564 | * Returns: 0 on success, -ECHILD on failure | |
565 | * | |
566 | * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry | |
567 | * for ref-walk mode. @dentry must be a path found by a do_lookup call on | |
568 | * @nd or NULL. Must be called from rcu-walk context. | |
569 | */ | |
570 | static int unlazy_walk(struct nameidata *nd, struct dentry *dentry) | |
571 | { | |
572 | struct fs_struct *fs = current->fs; | |
573 | struct dentry *parent = nd->path.dentry; | |
574 | ||
575 | BUG_ON(!(nd->flags & LOOKUP_RCU)); | |
576 | ||
577 | /* | |
578 | * After legitimizing the bastards, terminate_walk() | |
579 | * will do the right thing for non-RCU mode, and all our | |
580 | * subsequent exit cases should rcu_read_unlock() | |
581 | * before returning. Do vfsmount first; if dentry | |
582 | * can't be legitimized, just set nd->path.dentry to NULL | |
583 | * and rely on dput(NULL) being a no-op. | |
584 | */ | |
585 | if (!legitimize_mnt(nd->path.mnt, nd->m_seq)) | |
586 | return -ECHILD; | |
587 | nd->flags &= ~LOOKUP_RCU; | |
588 | ||
589 | if (!lockref_get_not_dead(&parent->d_lockref)) { | |
590 | nd->path.dentry = NULL; | |
591 | goto out; | |
592 | } | |
593 | ||
594 | /* | |
595 | * For a negative lookup, the lookup sequence point is the parents | |
596 | * sequence point, and it only needs to revalidate the parent dentry. | |
597 | * | |
598 | * For a positive lookup, we need to move both the parent and the | |
599 | * dentry from the RCU domain to be properly refcounted. And the | |
600 | * sequence number in the dentry validates *both* dentry counters, | |
601 | * since we checked the sequence number of the parent after we got | |
602 | * the child sequence number. So we know the parent must still | |
603 | * be valid if the child sequence number is still valid. | |
604 | */ | |
605 | if (!dentry) { | |
606 | if (read_seqcount_retry(&parent->d_seq, nd->seq)) | |
607 | goto out; | |
608 | BUG_ON(nd->inode != parent->d_inode); | |
609 | } else { | |
610 | if (!lockref_get_not_dead(&dentry->d_lockref)) | |
611 | goto out; | |
612 | if (read_seqcount_retry(&dentry->d_seq, nd->seq)) | |
613 | goto drop_dentry; | |
614 | } | |
615 | ||
616 | /* | |
617 | * Sequence counts matched. Now make sure that the root is | |
618 | * still valid and get it if required. | |
619 | */ | |
620 | if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { | |
621 | spin_lock(&fs->lock); | |
622 | if (nd->root.mnt != fs->root.mnt || nd->root.dentry != fs->root.dentry) | |
623 | goto unlock_and_drop_dentry; | |
624 | path_get(&nd->root); | |
625 | spin_unlock(&fs->lock); | |
626 | } | |
627 | ||
628 | rcu_read_unlock(); | |
629 | return 0; | |
630 | ||
631 | unlock_and_drop_dentry: | |
632 | spin_unlock(&fs->lock); | |
633 | drop_dentry: | |
634 | rcu_read_unlock(); | |
635 | dput(dentry); | |
636 | goto drop_root_mnt; | |
637 | out: | |
638 | rcu_read_unlock(); | |
639 | drop_root_mnt: | |
640 | if (!(nd->flags & LOOKUP_ROOT)) | |
641 | nd->root.mnt = NULL; | |
642 | return -ECHILD; | |
643 | } | |
644 | ||
645 | static inline int d_revalidate(struct dentry *dentry, unsigned int flags) | |
646 | { | |
647 | return dentry->d_op->d_revalidate(dentry, flags); | |
648 | } | |
649 | ||
650 | /** | |
651 | * complete_walk - successful completion of path walk | |
652 | * @nd: pointer nameidata | |
653 | * | |
654 | * If we had been in RCU mode, drop out of it and legitimize nd->path. | |
655 | * Revalidate the final result, unless we'd already done that during | |
656 | * the path walk or the filesystem doesn't ask for it. Return 0 on | |
657 | * success, -error on failure. In case of failure caller does not | |
658 | * need to drop nd->path. | |
659 | */ | |
660 | static int complete_walk(struct nameidata *nd) | |
661 | { | |
662 | struct dentry *dentry = nd->path.dentry; | |
663 | int status; | |
664 | ||
665 | if (nd->flags & LOOKUP_RCU) { | |
666 | nd->flags &= ~LOOKUP_RCU; | |
667 | if (!(nd->flags & LOOKUP_ROOT)) | |
668 | nd->root.mnt = NULL; | |
669 | ||
670 | if (!legitimize_mnt(nd->path.mnt, nd->m_seq)) { | |
671 | rcu_read_unlock(); | |
672 | return -ECHILD; | |
673 | } | |
674 | if (unlikely(!lockref_get_not_dead(&dentry->d_lockref))) { | |
675 | rcu_read_unlock(); | |
676 | mntput(nd->path.mnt); | |
677 | return -ECHILD; | |
678 | } | |
679 | if (read_seqcount_retry(&dentry->d_seq, nd->seq)) { | |
680 | rcu_read_unlock(); | |
681 | dput(dentry); | |
682 | mntput(nd->path.mnt); | |
683 | return -ECHILD; | |
684 | } | |
685 | rcu_read_unlock(); | |
686 | } | |
687 | ||
688 | if (likely(!(nd->flags & LOOKUP_JUMPED))) | |
689 | return 0; | |
690 | ||
691 | if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE))) | |
692 | return 0; | |
693 | ||
694 | status = dentry->d_op->d_weak_revalidate(dentry, nd->flags); | |
695 | if (status > 0) | |
696 | return 0; | |
697 | ||
698 | if (!status) | |
699 | status = -ESTALE; | |
700 | ||
701 | path_put(&nd->path); | |
702 | return status; | |
703 | } | |
704 | ||
705 | static __always_inline void set_root(struct nameidata *nd) | |
706 | { | |
707 | get_fs_root(current->fs, &nd->root); | |
708 | } | |
709 | ||
710 | static __always_inline unsigned set_root_rcu(struct nameidata *nd) | |
711 | { | |
712 | struct fs_struct *fs = current->fs; | |
713 | unsigned seq, res; | |
714 | ||
715 | do { | |
716 | seq = read_seqcount_begin(&fs->seq); | |
717 | nd->root = fs->root; | |
718 | res = __read_seqcount_begin(&nd->root.dentry->d_seq); | |
719 | } while (read_seqcount_retry(&fs->seq, seq)); | |
720 | return res; | |
721 | } | |
722 | ||
723 | static void path_put_conditional(struct path *path, struct nameidata *nd) | |
724 | { | |
725 | dput(path->dentry); | |
726 | if (path->mnt != nd->path.mnt) | |
727 | mntput(path->mnt); | |
728 | } | |
729 | ||
730 | static inline void path_to_nameidata(const struct path *path, | |
731 | struct nameidata *nd) | |
732 | { | |
733 | if (!(nd->flags & LOOKUP_RCU)) { | |
734 | dput(nd->path.dentry); | |
735 | if (nd->path.mnt != path->mnt) | |
736 | mntput(nd->path.mnt); | |
737 | } | |
738 | nd->path.mnt = path->mnt; | |
739 | nd->path.dentry = path->dentry; | |
740 | } | |
741 | ||
742 | /* | |
743 | * Helper to directly jump to a known parsed path from ->follow_link, | |
744 | * caller must have taken a reference to path beforehand. | |
745 | */ | |
746 | void nd_jump_link(struct nameidata *nd, struct path *path) | |
747 | { | |
748 | path_put(&nd->path); | |
749 | ||
750 | nd->path = *path; | |
751 | nd->inode = nd->path.dentry->d_inode; | |
752 | nd->flags |= LOOKUP_JUMPED; | |
753 | } | |
754 | ||
755 | static inline void put_link(struct nameidata *nd) | |
756 | { | |
757 | struct saved *last = nd->stack + --nd->depth; | |
758 | struct inode *inode = last->link.dentry->d_inode; | |
759 | if (last->cookie && inode->i_op->put_link) | |
760 | inode->i_op->put_link(last->link.dentry, last->cookie); | |
761 | path_put(&last->link); | |
762 | } | |
763 | ||
764 | int sysctl_protected_symlinks __read_mostly = 0; | |
765 | int sysctl_protected_hardlinks __read_mostly = 0; | |
766 | ||
767 | /** | |
768 | * may_follow_link - Check symlink following for unsafe situations | |
769 | * @link: The path of the symlink | |
770 | * @nd: nameidata pathwalk data | |
771 | * | |
772 | * In the case of the sysctl_protected_symlinks sysctl being enabled, | |
773 | * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is | |
774 | * in a sticky world-writable directory. This is to protect privileged | |
775 | * processes from failing races against path names that may change out | |
776 | * from under them by way of other users creating malicious symlinks. | |
777 | * It will permit symlinks to be followed only when outside a sticky | |
778 | * world-writable directory, or when the uid of the symlink and follower | |
779 | * match, or when the directory owner matches the symlink's owner. | |
780 | * | |
781 | * Returns 0 if following the symlink is allowed, -ve on error. | |
782 | */ | |
783 | static inline int may_follow_link(struct path *link, struct nameidata *nd) | |
784 | { | |
785 | const struct inode *inode; | |
786 | const struct inode *parent; | |
787 | ||
788 | if (!sysctl_protected_symlinks) | |
789 | return 0; | |
790 | ||
791 | /* Allowed if owner and follower match. */ | |
792 | inode = link->dentry->d_inode; | |
793 | if (uid_eq(current_cred()->fsuid, inode->i_uid)) | |
794 | return 0; | |
795 | ||
796 | /* Allowed if parent directory not sticky and world-writable. */ | |
797 | parent = nd->path.dentry->d_inode; | |
798 | if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH)) | |
799 | return 0; | |
800 | ||
801 | /* Allowed if parent directory and link owner match. */ | |
802 | if (uid_eq(parent->i_uid, inode->i_uid)) | |
803 | return 0; | |
804 | ||
805 | audit_log_link_denied("follow_link", link); | |
806 | path_put_conditional(link, nd); | |
807 | path_put(&nd->path); | |
808 | return -EACCES; | |
809 | } | |
810 | ||
811 | /** | |
812 | * safe_hardlink_source - Check for safe hardlink conditions | |
813 | * @inode: the source inode to hardlink from | |
814 | * | |
815 | * Return false if at least one of the following conditions: | |
816 | * - inode is not a regular file | |
817 | * - inode is setuid | |
818 | * - inode is setgid and group-exec | |
819 | * - access failure for read and write | |
820 | * | |
821 | * Otherwise returns true. | |
822 | */ | |
823 | static bool safe_hardlink_source(struct inode *inode) | |
824 | { | |
825 | umode_t mode = inode->i_mode; | |
826 | ||
827 | /* Special files should not get pinned to the filesystem. */ | |
828 | if (!S_ISREG(mode)) | |
829 | return false; | |
830 | ||
831 | /* Setuid files should not get pinned to the filesystem. */ | |
832 | if (mode & S_ISUID) | |
833 | return false; | |
834 | ||
835 | /* Executable setgid files should not get pinned to the filesystem. */ | |
836 | if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) | |
837 | return false; | |
838 | ||
839 | /* Hardlinking to unreadable or unwritable sources is dangerous. */ | |
840 | if (inode_permission(inode, MAY_READ | MAY_WRITE)) | |
841 | return false; | |
842 | ||
843 | return true; | |
844 | } | |
845 | ||
846 | /** | |
847 | * may_linkat - Check permissions for creating a hardlink | |
848 | * @link: the source to hardlink from | |
849 | * | |
850 | * Block hardlink when all of: | |
851 | * - sysctl_protected_hardlinks enabled | |
852 | * - fsuid does not match inode | |
853 | * - hardlink source is unsafe (see safe_hardlink_source() above) | |
854 | * - not CAP_FOWNER | |
855 | * | |
856 | * Returns 0 if successful, -ve on error. | |
857 | */ | |
858 | static int may_linkat(struct path *link) | |
859 | { | |
860 | const struct cred *cred; | |
861 | struct inode *inode; | |
862 | ||
863 | if (!sysctl_protected_hardlinks) | |
864 | return 0; | |
865 | ||
866 | cred = current_cred(); | |
867 | inode = link->dentry->d_inode; | |
868 | ||
869 | /* Source inode owner (or CAP_FOWNER) can hardlink all they like, | |
870 | * otherwise, it must be a safe source. | |
871 | */ | |
872 | if (uid_eq(cred->fsuid, inode->i_uid) || safe_hardlink_source(inode) || | |
873 | capable(CAP_FOWNER)) | |
874 | return 0; | |
875 | ||
876 | audit_log_link_denied("linkat", link); | |
877 | return -EPERM; | |
878 | } | |
879 | ||
880 | static __always_inline | |
881 | const char *get_link(struct nameidata *nd) | |
882 | { | |
883 | struct saved *last = nd->stack + nd->depth; | |
884 | struct dentry *dentry = nd->link.dentry; | |
885 | struct inode *inode = dentry->d_inode; | |
886 | int error; | |
887 | const char *res; | |
888 | ||
889 | BUG_ON(nd->flags & LOOKUP_RCU); | |
890 | ||
891 | if (nd->link.mnt == nd->path.mnt) | |
892 | mntget(nd->link.mnt); | |
893 | ||
894 | if (unlikely(current->total_link_count >= MAXSYMLINKS)) { | |
895 | path_put(&nd->path); | |
896 | path_put(&nd->link); | |
897 | return ERR_PTR(-ELOOP); | |
898 | } | |
899 | ||
900 | last->link = nd->link; | |
901 | last->cookie = NULL; | |
902 | ||
903 | cond_resched(); | |
904 | current->total_link_count++; | |
905 | ||
906 | touch_atime(&last->link); | |
907 | ||
908 | error = security_inode_follow_link(dentry); | |
909 | res = ERR_PTR(error); | |
910 | if (error) | |
911 | goto out; | |
912 | ||
913 | nd->last_type = LAST_BIND; | |
914 | res = inode->i_link; | |
915 | if (!res) { | |
916 | res = inode->i_op->follow_link(dentry, &last->cookie, nd); | |
917 | if (IS_ERR(res)) { | |
918 | out: | |
919 | path_put(&nd->path); | |
920 | path_put(&last->link); | |
921 | return res; | |
922 | } | |
923 | } | |
924 | nd->depth++; | |
925 | return res; | |
926 | } | |
927 | ||
928 | static int follow_up_rcu(struct path *path) | |
929 | { | |
930 | struct mount *mnt = real_mount(path->mnt); | |
931 | struct mount *parent; | |
932 | struct dentry *mountpoint; | |
933 | ||
934 | parent = mnt->mnt_parent; | |
935 | if (&parent->mnt == path->mnt) | |
936 | return 0; | |
937 | mountpoint = mnt->mnt_mountpoint; | |
938 | path->dentry = mountpoint; | |
939 | path->mnt = &parent->mnt; | |
940 | return 1; | |
941 | } | |
942 | ||
943 | /* | |
944 | * follow_up - Find the mountpoint of path's vfsmount | |
945 | * | |
946 | * Given a path, find the mountpoint of its source file system. | |
947 | * Replace @path with the path of the mountpoint in the parent mount. | |
948 | * Up is towards /. | |
949 | * | |
950 | * Return 1 if we went up a level and 0 if we were already at the | |
951 | * root. | |
952 | */ | |
953 | int follow_up(struct path *path) | |
954 | { | |
955 | struct mount *mnt = real_mount(path->mnt); | |
956 | struct mount *parent; | |
957 | struct dentry *mountpoint; | |
958 | ||
959 | read_seqlock_excl(&mount_lock); | |
960 | parent = mnt->mnt_parent; | |
961 | if (parent == mnt) { | |
962 | read_sequnlock_excl(&mount_lock); | |
963 | return 0; | |
964 | } | |
965 | mntget(&parent->mnt); | |
966 | mountpoint = dget(mnt->mnt_mountpoint); | |
967 | read_sequnlock_excl(&mount_lock); | |
968 | dput(path->dentry); | |
969 | path->dentry = mountpoint; | |
970 | mntput(path->mnt); | |
971 | path->mnt = &parent->mnt; | |
972 | return 1; | |
973 | } | |
974 | EXPORT_SYMBOL(follow_up); | |
975 | ||
976 | /* | |
977 | * Perform an automount | |
978 | * - return -EISDIR to tell follow_managed() to stop and return the path we | |
979 | * were called with. | |
980 | */ | |
981 | static int follow_automount(struct path *path, unsigned flags, | |
982 | bool *need_mntput) | |
983 | { | |
984 | struct vfsmount *mnt; | |
985 | int err; | |
986 | ||
987 | if (!path->dentry->d_op || !path->dentry->d_op->d_automount) | |
988 | return -EREMOTE; | |
989 | ||
990 | /* We don't want to mount if someone's just doing a stat - | |
991 | * unless they're stat'ing a directory and appended a '/' to | |
992 | * the name. | |
993 | * | |
994 | * We do, however, want to mount if someone wants to open or | |
995 | * create a file of any type under the mountpoint, wants to | |
996 | * traverse through the mountpoint or wants to open the | |
997 | * mounted directory. Also, autofs may mark negative dentries | |
998 | * as being automount points. These will need the attentions | |
999 | * of the daemon to instantiate them before they can be used. | |
1000 | */ | |
1001 | if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | | |
1002 | LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) && | |
1003 | path->dentry->d_inode) | |
1004 | return -EISDIR; | |
1005 | ||
1006 | current->total_link_count++; | |
1007 | if (current->total_link_count >= 40) | |
1008 | return -ELOOP; | |
1009 | ||
1010 | mnt = path->dentry->d_op->d_automount(path); | |
1011 | if (IS_ERR(mnt)) { | |
1012 | /* | |
1013 | * The filesystem is allowed to return -EISDIR here to indicate | |
1014 | * it doesn't want to automount. For instance, autofs would do | |
1015 | * this so that its userspace daemon can mount on this dentry. | |
1016 | * | |
1017 | * However, we can only permit this if it's a terminal point in | |
1018 | * the path being looked up; if it wasn't then the remainder of | |
1019 | * the path is inaccessible and we should say so. | |
1020 | */ | |
1021 | if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT)) | |
1022 | return -EREMOTE; | |
1023 | return PTR_ERR(mnt); | |
1024 | } | |
1025 | ||
1026 | if (!mnt) /* mount collision */ | |
1027 | return 0; | |
1028 | ||
1029 | if (!*need_mntput) { | |
1030 | /* lock_mount() may release path->mnt on error */ | |
1031 | mntget(path->mnt); | |
1032 | *need_mntput = true; | |
1033 | } | |
1034 | err = finish_automount(mnt, path); | |
1035 | ||
1036 | switch (err) { | |
1037 | case -EBUSY: | |
1038 | /* Someone else made a mount here whilst we were busy */ | |
1039 | return 0; | |
1040 | case 0: | |
1041 | path_put(path); | |
1042 | path->mnt = mnt; | |
1043 | path->dentry = dget(mnt->mnt_root); | |
1044 | return 0; | |
1045 | default: | |
1046 | return err; | |
1047 | } | |
1048 | ||
1049 | } | |
1050 | ||
1051 | /* | |
1052 | * Handle a dentry that is managed in some way. | |
1053 | * - Flagged for transit management (autofs) | |
1054 | * - Flagged as mountpoint | |
1055 | * - Flagged as automount point | |
1056 | * | |
1057 | * This may only be called in refwalk mode. | |
1058 | * | |
1059 | * Serialization is taken care of in namespace.c | |
1060 | */ | |
1061 | static int follow_managed(struct path *path, unsigned flags) | |
1062 | { | |
1063 | struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */ | |
1064 | unsigned managed; | |
1065 | bool need_mntput = false; | |
1066 | int ret = 0; | |
1067 | ||
1068 | /* Given that we're not holding a lock here, we retain the value in a | |
1069 | * local variable for each dentry as we look at it so that we don't see | |
1070 | * the components of that value change under us */ | |
1071 | while (managed = ACCESS_ONCE(path->dentry->d_flags), | |
1072 | managed &= DCACHE_MANAGED_DENTRY, | |
1073 | unlikely(managed != 0)) { | |
1074 | /* Allow the filesystem to manage the transit without i_mutex | |
1075 | * being held. */ | |
1076 | if (managed & DCACHE_MANAGE_TRANSIT) { | |
1077 | BUG_ON(!path->dentry->d_op); | |
1078 | BUG_ON(!path->dentry->d_op->d_manage); | |
1079 | ret = path->dentry->d_op->d_manage(path->dentry, false); | |
1080 | if (ret < 0) | |
1081 | break; | |
1082 | } | |
1083 | ||
1084 | /* Transit to a mounted filesystem. */ | |
1085 | if (managed & DCACHE_MOUNTED) { | |
1086 | struct vfsmount *mounted = lookup_mnt(path); | |
1087 | if (mounted) { | |
1088 | dput(path->dentry); | |
1089 | if (need_mntput) | |
1090 | mntput(path->mnt); | |
1091 | path->mnt = mounted; | |
1092 | path->dentry = dget(mounted->mnt_root); | |
1093 | need_mntput = true; | |
1094 | continue; | |
1095 | } | |
1096 | ||
1097 | /* Something is mounted on this dentry in another | |
1098 | * namespace and/or whatever was mounted there in this | |
1099 | * namespace got unmounted before lookup_mnt() could | |
1100 | * get it */ | |
1101 | } | |
1102 | ||
1103 | /* Handle an automount point */ | |
1104 | if (managed & DCACHE_NEED_AUTOMOUNT) { | |
1105 | ret = follow_automount(path, flags, &need_mntput); | |
1106 | if (ret < 0) | |
1107 | break; | |
1108 | continue; | |
1109 | } | |
1110 | ||
1111 | /* We didn't change the current path point */ | |
1112 | break; | |
1113 | } | |
1114 | ||
1115 | if (need_mntput && path->mnt == mnt) | |
1116 | mntput(path->mnt); | |
1117 | if (ret == -EISDIR) | |
1118 | ret = 0; | |
1119 | return ret < 0 ? ret : need_mntput; | |
1120 | } | |
1121 | ||
1122 | int follow_down_one(struct path *path) | |
1123 | { | |
1124 | struct vfsmount *mounted; | |
1125 | ||
1126 | mounted = lookup_mnt(path); | |
1127 | if (mounted) { | |
1128 | dput(path->dentry); | |
1129 | mntput(path->mnt); | |
1130 | path->mnt = mounted; | |
1131 | path->dentry = dget(mounted->mnt_root); | |
1132 | return 1; | |
1133 | } | |
1134 | return 0; | |
1135 | } | |
1136 | EXPORT_SYMBOL(follow_down_one); | |
1137 | ||
1138 | static inline int managed_dentry_rcu(struct dentry *dentry) | |
1139 | { | |
1140 | return (dentry->d_flags & DCACHE_MANAGE_TRANSIT) ? | |
1141 | dentry->d_op->d_manage(dentry, true) : 0; | |
1142 | } | |
1143 | ||
1144 | /* | |
1145 | * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if | |
1146 | * we meet a managed dentry that would need blocking. | |
1147 | */ | |
1148 | static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, | |
1149 | struct inode **inode) | |
1150 | { | |
1151 | for (;;) { | |
1152 | struct mount *mounted; | |
1153 | /* | |
1154 | * Don't forget we might have a non-mountpoint managed dentry | |
1155 | * that wants to block transit. | |
1156 | */ | |
1157 | switch (managed_dentry_rcu(path->dentry)) { | |
1158 | case -ECHILD: | |
1159 | default: | |
1160 | return false; | |
1161 | case -EISDIR: | |
1162 | return true; | |
1163 | case 0: | |
1164 | break; | |
1165 | } | |
1166 | ||
1167 | if (!d_mountpoint(path->dentry)) | |
1168 | return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT); | |
1169 | ||
1170 | mounted = __lookup_mnt(path->mnt, path->dentry); | |
1171 | if (!mounted) | |
1172 | break; | |
1173 | path->mnt = &mounted->mnt; | |
1174 | path->dentry = mounted->mnt.mnt_root; | |
1175 | nd->flags |= LOOKUP_JUMPED; | |
1176 | nd->seq = read_seqcount_begin(&path->dentry->d_seq); | |
1177 | /* | |
1178 | * Update the inode too. We don't need to re-check the | |
1179 | * dentry sequence number here after this d_inode read, | |
1180 | * because a mount-point is always pinned. | |
1181 | */ | |
1182 | *inode = path->dentry->d_inode; | |
1183 | } | |
1184 | return !read_seqretry(&mount_lock, nd->m_seq) && | |
1185 | !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT); | |
1186 | } | |
1187 | ||
1188 | static int follow_dotdot_rcu(struct nameidata *nd) | |
1189 | { | |
1190 | struct inode *inode = nd->inode; | |
1191 | if (!nd->root.mnt) | |
1192 | set_root_rcu(nd); | |
1193 | ||
1194 | while (1) { | |
1195 | if (nd->path.dentry == nd->root.dentry && | |
1196 | nd->path.mnt == nd->root.mnt) { | |
1197 | break; | |
1198 | } | |
1199 | if (nd->path.dentry != nd->path.mnt->mnt_root) { | |
1200 | struct dentry *old = nd->path.dentry; | |
1201 | struct dentry *parent = old->d_parent; | |
1202 | unsigned seq; | |
1203 | ||
1204 | inode = parent->d_inode; | |
1205 | seq = read_seqcount_begin(&parent->d_seq); | |
1206 | if (read_seqcount_retry(&old->d_seq, nd->seq)) | |
1207 | goto failed; | |
1208 | nd->path.dentry = parent; | |
1209 | nd->seq = seq; | |
1210 | break; | |
1211 | } | |
1212 | if (!follow_up_rcu(&nd->path)) | |
1213 | break; | |
1214 | inode = nd->path.dentry->d_inode; | |
1215 | nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); | |
1216 | } | |
1217 | while (d_mountpoint(nd->path.dentry)) { | |
1218 | struct mount *mounted; | |
1219 | mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry); | |
1220 | if (!mounted) | |
1221 | break; | |
1222 | nd->path.mnt = &mounted->mnt; | |
1223 | nd->path.dentry = mounted->mnt.mnt_root; | |
1224 | inode = nd->path.dentry->d_inode; | |
1225 | nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); | |
1226 | if (read_seqretry(&mount_lock, nd->m_seq)) | |
1227 | goto failed; | |
1228 | } | |
1229 | nd->inode = inode; | |
1230 | return 0; | |
1231 | ||
1232 | failed: | |
1233 | return -ECHILD; | |
1234 | } | |
1235 | ||
1236 | /* | |
1237 | * Follow down to the covering mount currently visible to userspace. At each | |
1238 | * point, the filesystem owning that dentry may be queried as to whether the | |
1239 | * caller is permitted to proceed or not. | |
1240 | */ | |
1241 | int follow_down(struct path *path) | |
1242 | { | |
1243 | unsigned managed; | |
1244 | int ret; | |
1245 | ||
1246 | while (managed = ACCESS_ONCE(path->dentry->d_flags), | |
1247 | unlikely(managed & DCACHE_MANAGED_DENTRY)) { | |
1248 | /* Allow the filesystem to manage the transit without i_mutex | |
1249 | * being held. | |
1250 | * | |
1251 | * We indicate to the filesystem if someone is trying to mount | |
1252 | * something here. This gives autofs the chance to deny anyone | |
1253 | * other than its daemon the right to mount on its | |
1254 | * superstructure. | |
1255 | * | |
1256 | * The filesystem may sleep at this point. | |
1257 | */ | |
1258 | if (managed & DCACHE_MANAGE_TRANSIT) { | |
1259 | BUG_ON(!path->dentry->d_op); | |
1260 | BUG_ON(!path->dentry->d_op->d_manage); | |
1261 | ret = path->dentry->d_op->d_manage( | |
1262 | path->dentry, false); | |
1263 | if (ret < 0) | |
1264 | return ret == -EISDIR ? 0 : ret; | |
1265 | } | |
1266 | ||
1267 | /* Transit to a mounted filesystem. */ | |
1268 | if (managed & DCACHE_MOUNTED) { | |
1269 | struct vfsmount *mounted = lookup_mnt(path); | |
1270 | if (!mounted) | |
1271 | break; | |
1272 | dput(path->dentry); | |
1273 | mntput(path->mnt); | |
1274 | path->mnt = mounted; | |
1275 | path->dentry = dget(mounted->mnt_root); | |
1276 | continue; | |
1277 | } | |
1278 | ||
1279 | /* Don't handle automount points here */ | |
1280 | break; | |
1281 | } | |
1282 | return 0; | |
1283 | } | |
1284 | EXPORT_SYMBOL(follow_down); | |
1285 | ||
1286 | /* | |
1287 | * Skip to top of mountpoint pile in refwalk mode for follow_dotdot() | |
1288 | */ | |
1289 | static void follow_mount(struct path *path) | |
1290 | { | |
1291 | while (d_mountpoint(path->dentry)) { | |
1292 | struct vfsmount *mounted = lookup_mnt(path); | |
1293 | if (!mounted) | |
1294 | break; | |
1295 | dput(path->dentry); | |
1296 | mntput(path->mnt); | |
1297 | path->mnt = mounted; | |
1298 | path->dentry = dget(mounted->mnt_root); | |
1299 | } | |
1300 | } | |
1301 | ||
1302 | static void follow_dotdot(struct nameidata *nd) | |
1303 | { | |
1304 | if (!nd->root.mnt) | |
1305 | set_root(nd); | |
1306 | ||
1307 | while(1) { | |
1308 | struct dentry *old = nd->path.dentry; | |
1309 | ||
1310 | if (nd->path.dentry == nd->root.dentry && | |
1311 | nd->path.mnt == nd->root.mnt) { | |
1312 | break; | |
1313 | } | |
1314 | if (nd->path.dentry != nd->path.mnt->mnt_root) { | |
1315 | /* rare case of legitimate dget_parent()... */ | |
1316 | nd->path.dentry = dget_parent(nd->path.dentry); | |
1317 | dput(old); | |
1318 | break; | |
1319 | } | |
1320 | if (!follow_up(&nd->path)) | |
1321 | break; | |
1322 | } | |
1323 | follow_mount(&nd->path); | |
1324 | nd->inode = nd->path.dentry->d_inode; | |
1325 | } | |
1326 | ||
1327 | /* | |
1328 | * This looks up the name in dcache, possibly revalidates the old dentry and | |
1329 | * allocates a new one if not found or not valid. In the need_lookup argument | |
1330 | * returns whether i_op->lookup is necessary. | |
1331 | * | |
1332 | * dir->d_inode->i_mutex must be held | |
1333 | */ | |
1334 | static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir, | |
1335 | unsigned int flags, bool *need_lookup) | |
1336 | { | |
1337 | struct dentry *dentry; | |
1338 | int error; | |
1339 | ||
1340 | *need_lookup = false; | |
1341 | dentry = d_lookup(dir, name); | |
1342 | if (dentry) { | |
1343 | if (dentry->d_flags & DCACHE_OP_REVALIDATE) { | |
1344 | error = d_revalidate(dentry, flags); | |
1345 | if (unlikely(error <= 0)) { | |
1346 | if (error < 0) { | |
1347 | dput(dentry); | |
1348 | return ERR_PTR(error); | |
1349 | } else { | |
1350 | d_invalidate(dentry); | |
1351 | dput(dentry); | |
1352 | dentry = NULL; | |
1353 | } | |
1354 | } | |
1355 | } | |
1356 | } | |
1357 | ||
1358 | if (!dentry) { | |
1359 | dentry = d_alloc(dir, name); | |
1360 | if (unlikely(!dentry)) | |
1361 | return ERR_PTR(-ENOMEM); | |
1362 | ||
1363 | *need_lookup = true; | |
1364 | } | |
1365 | return dentry; | |
1366 | } | |
1367 | ||
1368 | /* | |
1369 | * Call i_op->lookup on the dentry. The dentry must be negative and | |
1370 | * unhashed. | |
1371 | * | |
1372 | * dir->d_inode->i_mutex must be held | |
1373 | */ | |
1374 | static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry, | |
1375 | unsigned int flags) | |
1376 | { | |
1377 | struct dentry *old; | |
1378 | ||
1379 | /* Don't create child dentry for a dead directory. */ | |
1380 | if (unlikely(IS_DEADDIR(dir))) { | |
1381 | dput(dentry); | |
1382 | return ERR_PTR(-ENOENT); | |
1383 | } | |
1384 | ||
1385 | old = dir->i_op->lookup(dir, dentry, flags); | |
1386 | if (unlikely(old)) { | |
1387 | dput(dentry); | |
1388 | dentry = old; | |
1389 | } | |
1390 | return dentry; | |
1391 | } | |
1392 | ||
1393 | static struct dentry *__lookup_hash(struct qstr *name, | |
1394 | struct dentry *base, unsigned int flags) | |
1395 | { | |
1396 | bool need_lookup; | |
1397 | struct dentry *dentry; | |
1398 | ||
1399 | dentry = lookup_dcache(name, base, flags, &need_lookup); | |
1400 | if (!need_lookup) | |
1401 | return dentry; | |
1402 | ||
1403 | return lookup_real(base->d_inode, dentry, flags); | |
1404 | } | |
1405 | ||
1406 | /* | |
1407 | * It's more convoluted than I'd like it to be, but... it's still fairly | |
1408 | * small and for now I'd prefer to have fast path as straight as possible. | |
1409 | * It _is_ time-critical. | |
1410 | */ | |
1411 | static int lookup_fast(struct nameidata *nd, | |
1412 | struct path *path, struct inode **inode) | |
1413 | { | |
1414 | struct vfsmount *mnt = nd->path.mnt; | |
1415 | struct dentry *dentry, *parent = nd->path.dentry; | |
1416 | int need_reval = 1; | |
1417 | int status = 1; | |
1418 | int err; | |
1419 | ||
1420 | /* | |
1421 | * Rename seqlock is not required here because in the off chance | |
1422 | * of a false negative due to a concurrent rename, we're going to | |
1423 | * do the non-racy lookup, below. | |
1424 | */ | |
1425 | if (nd->flags & LOOKUP_RCU) { | |
1426 | unsigned seq; | |
1427 | bool negative; | |
1428 | dentry = __d_lookup_rcu(parent, &nd->last, &seq); | |
1429 | if (!dentry) | |
1430 | goto unlazy; | |
1431 | ||
1432 | /* | |
1433 | * This sequence count validates that the inode matches | |
1434 | * the dentry name information from lookup. | |
1435 | */ | |
1436 | *inode = dentry->d_inode; | |
1437 | negative = d_is_negative(dentry); | |
1438 | if (read_seqcount_retry(&dentry->d_seq, seq)) | |
1439 | return -ECHILD; | |
1440 | if (negative) | |
1441 | return -ENOENT; | |
1442 | ||
1443 | /* | |
1444 | * This sequence count validates that the parent had no | |
1445 | * changes while we did the lookup of the dentry above. | |
1446 | * | |
1447 | * The memory barrier in read_seqcount_begin of child is | |
1448 | * enough, we can use __read_seqcount_retry here. | |
1449 | */ | |
1450 | if (__read_seqcount_retry(&parent->d_seq, nd->seq)) | |
1451 | return -ECHILD; | |
1452 | nd->seq = seq; | |
1453 | ||
1454 | if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) { | |
1455 | status = d_revalidate(dentry, nd->flags); | |
1456 | if (unlikely(status <= 0)) { | |
1457 | if (status != -ECHILD) | |
1458 | need_reval = 0; | |
1459 | goto unlazy; | |
1460 | } | |
1461 | } | |
1462 | path->mnt = mnt; | |
1463 | path->dentry = dentry; | |
1464 | if (likely(__follow_mount_rcu(nd, path, inode))) | |
1465 | return 0; | |
1466 | unlazy: | |
1467 | if (unlazy_walk(nd, dentry)) | |
1468 | return -ECHILD; | |
1469 | } else { | |
1470 | dentry = __d_lookup(parent, &nd->last); | |
1471 | } | |
1472 | ||
1473 | if (unlikely(!dentry)) | |
1474 | goto need_lookup; | |
1475 | ||
1476 | if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval) | |
1477 | status = d_revalidate(dentry, nd->flags); | |
1478 | if (unlikely(status <= 0)) { | |
1479 | if (status < 0) { | |
1480 | dput(dentry); | |
1481 | return status; | |
1482 | } | |
1483 | d_invalidate(dentry); | |
1484 | dput(dentry); | |
1485 | goto need_lookup; | |
1486 | } | |
1487 | ||
1488 | if (unlikely(d_is_negative(dentry))) { | |
1489 | dput(dentry); | |
1490 | return -ENOENT; | |
1491 | } | |
1492 | path->mnt = mnt; | |
1493 | path->dentry = dentry; | |
1494 | err = follow_managed(path, nd->flags); | |
1495 | if (unlikely(err < 0)) { | |
1496 | path_put_conditional(path, nd); | |
1497 | return err; | |
1498 | } | |
1499 | if (err) | |
1500 | nd->flags |= LOOKUP_JUMPED; | |
1501 | *inode = path->dentry->d_inode; | |
1502 | return 0; | |
1503 | ||
1504 | need_lookup: | |
1505 | return 1; | |
1506 | } | |
1507 | ||
1508 | /* Fast lookup failed, do it the slow way */ | |
1509 | static int lookup_slow(struct nameidata *nd, struct path *path) | |
1510 | { | |
1511 | struct dentry *dentry, *parent; | |
1512 | int err; | |
1513 | ||
1514 | parent = nd->path.dentry; | |
1515 | BUG_ON(nd->inode != parent->d_inode); | |
1516 | ||
1517 | mutex_lock(&parent->d_inode->i_mutex); | |
1518 | dentry = __lookup_hash(&nd->last, parent, nd->flags); | |
1519 | mutex_unlock(&parent->d_inode->i_mutex); | |
1520 | if (IS_ERR(dentry)) | |
1521 | return PTR_ERR(dentry); | |
1522 | path->mnt = nd->path.mnt; | |
1523 | path->dentry = dentry; | |
1524 | err = follow_managed(path, nd->flags); | |
1525 | if (unlikely(err < 0)) { | |
1526 | path_put_conditional(path, nd); | |
1527 | return err; | |
1528 | } | |
1529 | if (err) | |
1530 | nd->flags |= LOOKUP_JUMPED; | |
1531 | return 0; | |
1532 | } | |
1533 | ||
1534 | static inline int may_lookup(struct nameidata *nd) | |
1535 | { | |
1536 | if (nd->flags & LOOKUP_RCU) { | |
1537 | int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK); | |
1538 | if (err != -ECHILD) | |
1539 | return err; | |
1540 | if (unlazy_walk(nd, NULL)) | |
1541 | return -ECHILD; | |
1542 | } | |
1543 | return inode_permission(nd->inode, MAY_EXEC); | |
1544 | } | |
1545 | ||
1546 | static inline int handle_dots(struct nameidata *nd, int type) | |
1547 | { | |
1548 | if (type == LAST_DOTDOT) { | |
1549 | if (nd->flags & LOOKUP_RCU) { | |
1550 | return follow_dotdot_rcu(nd); | |
1551 | } else | |
1552 | follow_dotdot(nd); | |
1553 | } | |
1554 | return 0; | |
1555 | } | |
1556 | ||
1557 | static void terminate_walk(struct nameidata *nd) | |
1558 | { | |
1559 | if (!(nd->flags & LOOKUP_RCU)) { | |
1560 | path_put(&nd->path); | |
1561 | } else { | |
1562 | nd->flags &= ~LOOKUP_RCU; | |
1563 | if (!(nd->flags & LOOKUP_ROOT)) | |
1564 | nd->root.mnt = NULL; | |
1565 | rcu_read_unlock(); | |
1566 | } | |
1567 | } | |
1568 | ||
1569 | /* | |
1570 | * Do we need to follow links? We _really_ want to be able | |
1571 | * to do this check without having to look at inode->i_op, | |
1572 | * so we keep a cache of "no, this doesn't need follow_link" | |
1573 | * for the common case. | |
1574 | */ | |
1575 | static inline int should_follow_link(struct dentry *dentry, int follow) | |
1576 | { | |
1577 | return unlikely(d_is_symlink(dentry)) ? follow : 0; | |
1578 | } | |
1579 | ||
1580 | static int walk_component(struct nameidata *nd, int follow) | |
1581 | { | |
1582 | struct path path; | |
1583 | struct inode *inode; | |
1584 | int err; | |
1585 | /* | |
1586 | * "." and ".." are special - ".." especially so because it has | |
1587 | * to be able to know about the current root directory and | |
1588 | * parent relationships. | |
1589 | */ | |
1590 | if (unlikely(nd->last_type != LAST_NORM)) { | |
1591 | err = handle_dots(nd, nd->last_type); | |
1592 | if (err) | |
1593 | goto out_err; | |
1594 | return 0; | |
1595 | } | |
1596 | err = lookup_fast(nd, &path, &inode); | |
1597 | if (unlikely(err)) { | |
1598 | if (err < 0) | |
1599 | goto out_err; | |
1600 | ||
1601 | err = lookup_slow(nd, &path); | |
1602 | if (err < 0) | |
1603 | goto out_err; | |
1604 | ||
1605 | inode = path.dentry->d_inode; | |
1606 | err = -ENOENT; | |
1607 | if (d_is_negative(path.dentry)) | |
1608 | goto out_path_put; | |
1609 | } | |
1610 | ||
1611 | if (should_follow_link(path.dentry, follow)) { | |
1612 | if (nd->flags & LOOKUP_RCU) { | |
1613 | if (unlikely(nd->path.mnt != path.mnt || | |
1614 | unlazy_walk(nd, path.dentry))) { | |
1615 | err = -ECHILD; | |
1616 | goto out_err; | |
1617 | } | |
1618 | } | |
1619 | BUG_ON(inode != path.dentry->d_inode); | |
1620 | nd->link = path; | |
1621 | return 1; | |
1622 | } | |
1623 | path_to_nameidata(&path, nd); | |
1624 | nd->inode = inode; | |
1625 | return 0; | |
1626 | ||
1627 | out_path_put: | |
1628 | path_to_nameidata(&path, nd); | |
1629 | out_err: | |
1630 | terminate_walk(nd); | |
1631 | return err; | |
1632 | } | |
1633 | ||
1634 | /* | |
1635 | * We can do the critical dentry name comparison and hashing | |
1636 | * operations one word at a time, but we are limited to: | |
1637 | * | |
1638 | * - Architectures with fast unaligned word accesses. We could | |
1639 | * do a "get_unaligned()" if this helps and is sufficiently | |
1640 | * fast. | |
1641 | * | |
1642 | * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we | |
1643 | * do not trap on the (extremely unlikely) case of a page | |
1644 | * crossing operation. | |
1645 | * | |
1646 | * - Furthermore, we need an efficient 64-bit compile for the | |
1647 | * 64-bit case in order to generate the "number of bytes in | |
1648 | * the final mask". Again, that could be replaced with a | |
1649 | * efficient population count instruction or similar. | |
1650 | */ | |
1651 | #ifdef CONFIG_DCACHE_WORD_ACCESS | |
1652 | ||
1653 | #include <asm/word-at-a-time.h> | |
1654 | ||
1655 | #ifdef CONFIG_64BIT | |
1656 | ||
1657 | static inline unsigned int fold_hash(unsigned long hash) | |
1658 | { | |
1659 | return hash_64(hash, 32); | |
1660 | } | |
1661 | ||
1662 | #else /* 32-bit case */ | |
1663 | ||
1664 | #define fold_hash(x) (x) | |
1665 | ||
1666 | #endif | |
1667 | ||
1668 | unsigned int full_name_hash(const unsigned char *name, unsigned int len) | |
1669 | { | |
1670 | unsigned long a, mask; | |
1671 | unsigned long hash = 0; | |
1672 | ||
1673 | for (;;) { | |
1674 | a = load_unaligned_zeropad(name); | |
1675 | if (len < sizeof(unsigned long)) | |
1676 | break; | |
1677 | hash += a; | |
1678 | hash *= 9; | |
1679 | name += sizeof(unsigned long); | |
1680 | len -= sizeof(unsigned long); | |
1681 | if (!len) | |
1682 | goto done; | |
1683 | } | |
1684 | mask = bytemask_from_count(len); | |
1685 | hash += mask & a; | |
1686 | done: | |
1687 | return fold_hash(hash); | |
1688 | } | |
1689 | EXPORT_SYMBOL(full_name_hash); | |
1690 | ||
1691 | /* | |
1692 | * Calculate the length and hash of the path component, and | |
1693 | * return the "hash_len" as the result. | |
1694 | */ | |
1695 | static inline u64 hash_name(const char *name) | |
1696 | { | |
1697 | unsigned long a, b, adata, bdata, mask, hash, len; | |
1698 | const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; | |
1699 | ||
1700 | hash = a = 0; | |
1701 | len = -sizeof(unsigned long); | |
1702 | do { | |
1703 | hash = (hash + a) * 9; | |
1704 | len += sizeof(unsigned long); | |
1705 | a = load_unaligned_zeropad(name+len); | |
1706 | b = a ^ REPEAT_BYTE('/'); | |
1707 | } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants))); | |
1708 | ||
1709 | adata = prep_zero_mask(a, adata, &constants); | |
1710 | bdata = prep_zero_mask(b, bdata, &constants); | |
1711 | ||
1712 | mask = create_zero_mask(adata | bdata); | |
1713 | ||
1714 | hash += a & zero_bytemask(mask); | |
1715 | len += find_zero(mask); | |
1716 | return hashlen_create(fold_hash(hash), len); | |
1717 | } | |
1718 | ||
1719 | #else | |
1720 | ||
1721 | unsigned int full_name_hash(const unsigned char *name, unsigned int len) | |
1722 | { | |
1723 | unsigned long hash = init_name_hash(); | |
1724 | while (len--) | |
1725 | hash = partial_name_hash(*name++, hash); | |
1726 | return end_name_hash(hash); | |
1727 | } | |
1728 | EXPORT_SYMBOL(full_name_hash); | |
1729 | ||
1730 | /* | |
1731 | * We know there's a real path component here of at least | |
1732 | * one character. | |
1733 | */ | |
1734 | static inline u64 hash_name(const char *name) | |
1735 | { | |
1736 | unsigned long hash = init_name_hash(); | |
1737 | unsigned long len = 0, c; | |
1738 | ||
1739 | c = (unsigned char)*name; | |
1740 | do { | |
1741 | len++; | |
1742 | hash = partial_name_hash(c, hash); | |
1743 | c = (unsigned char)name[len]; | |
1744 | } while (c && c != '/'); | |
1745 | return hashlen_create(end_name_hash(hash), len); | |
1746 | } | |
1747 | ||
1748 | #endif | |
1749 | ||
1750 | /* | |
1751 | * Name resolution. | |
1752 | * This is the basic name resolution function, turning a pathname into | |
1753 | * the final dentry. We expect 'base' to be positive and a directory. | |
1754 | * | |
1755 | * Returns 0 and nd will have valid dentry and mnt on success. | |
1756 | * Returns error and drops reference to input namei data on failure. | |
1757 | */ | |
1758 | static int link_path_walk(const char *name, struct nameidata *nd) | |
1759 | { | |
1760 | int err; | |
1761 | ||
1762 | while (*name=='/') | |
1763 | name++; | |
1764 | if (!*name) | |
1765 | return 0; | |
1766 | ||
1767 | /* At this point we know we have a real path component. */ | |
1768 | for(;;) { | |
1769 | u64 hash_len; | |
1770 | int type; | |
1771 | ||
1772 | err = may_lookup(nd); | |
1773 | if (err) | |
1774 | break; | |
1775 | ||
1776 | hash_len = hash_name(name); | |
1777 | ||
1778 | type = LAST_NORM; | |
1779 | if (name[0] == '.') switch (hashlen_len(hash_len)) { | |
1780 | case 2: | |
1781 | if (name[1] == '.') { | |
1782 | type = LAST_DOTDOT; | |
1783 | nd->flags |= LOOKUP_JUMPED; | |
1784 | } | |
1785 | break; | |
1786 | case 1: | |
1787 | type = LAST_DOT; | |
1788 | } | |
1789 | if (likely(type == LAST_NORM)) { | |
1790 | struct dentry *parent = nd->path.dentry; | |
1791 | nd->flags &= ~LOOKUP_JUMPED; | |
1792 | if (unlikely(parent->d_flags & DCACHE_OP_HASH)) { | |
1793 | struct qstr this = { { .hash_len = hash_len }, .name = name }; | |
1794 | err = parent->d_op->d_hash(parent, &this); | |
1795 | if (err < 0) | |
1796 | break; | |
1797 | hash_len = this.hash_len; | |
1798 | name = this.name; | |
1799 | } | |
1800 | } | |
1801 | ||
1802 | nd->last.hash_len = hash_len; | |
1803 | nd->last.name = name; | |
1804 | nd->last_type = type; | |
1805 | ||
1806 | name += hashlen_len(hash_len); | |
1807 | if (!*name) | |
1808 | goto OK; | |
1809 | /* | |
1810 | * If it wasn't NUL, we know it was '/'. Skip that | |
1811 | * slash, and continue until no more slashes. | |
1812 | */ | |
1813 | do { | |
1814 | name++; | |
1815 | } while (unlikely(*name == '/')); | |
1816 | if (!*name) | |
1817 | goto OK; | |
1818 | ||
1819 | err = walk_component(nd, LOOKUP_FOLLOW); | |
1820 | Walked: | |
1821 | if (err < 0) | |
1822 | goto Err; | |
1823 | ||
1824 | if (err) { | |
1825 | const char *s; | |
1826 | ||
1827 | err = nd_alloc_stack(nd); | |
1828 | if (unlikely(err)) { | |
1829 | path_to_nameidata(&nd->link, nd); | |
1830 | break; | |
1831 | } | |
1832 | ||
1833 | s = get_link(nd); | |
1834 | ||
1835 | if (unlikely(IS_ERR(s))) { | |
1836 | err = PTR_ERR(s); | |
1837 | goto Err; | |
1838 | } | |
1839 | err = 0; | |
1840 | if (unlikely(!s)) { | |
1841 | /* jumped */ | |
1842 | put_link(nd); | |
1843 | } else { | |
1844 | if (*s == '/') { | |
1845 | if (!nd->root.mnt) | |
1846 | set_root(nd); | |
1847 | path_put(&nd->path); | |
1848 | nd->path = nd->root; | |
1849 | path_get(&nd->root); | |
1850 | nd->flags |= LOOKUP_JUMPED; | |
1851 | while (unlikely(*++s == '/')) | |
1852 | ; | |
1853 | } | |
1854 | nd->inode = nd->path.dentry->d_inode; | |
1855 | nd->stack[nd->depth - 1].name = name; | |
1856 | if (!*s) | |
1857 | goto OK; | |
1858 | name = s; | |
1859 | continue; | |
1860 | } | |
1861 | } | |
1862 | if (!d_can_lookup(nd->path.dentry)) { | |
1863 | err = -ENOTDIR; | |
1864 | break; | |
1865 | } | |
1866 | } | |
1867 | terminate_walk(nd); | |
1868 | Err: | |
1869 | while (unlikely(nd->depth)) | |
1870 | put_link(nd); | |
1871 | return err; | |
1872 | OK: | |
1873 | if (!nd->depth) /* called from path_init(), done */ | |
1874 | return 0; | |
1875 | name = nd->stack[nd->depth - 1].name; | |
1876 | if (!name) /* called from trailing_symlink(), done */ | |
1877 | return 0; | |
1878 | ||
1879 | err = walk_component(nd, LOOKUP_FOLLOW); | |
1880 | put_link(nd); | |
1881 | goto Walked; | |
1882 | } | |
1883 | ||
1884 | static int path_init(int dfd, const struct filename *name, unsigned int flags, | |
1885 | struct nameidata *nd) | |
1886 | { | |
1887 | int retval = 0; | |
1888 | const char *s = name->name; | |
1889 | ||
1890 | nd->last_type = LAST_ROOT; /* if there are only slashes... */ | |
1891 | nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT; | |
1892 | nd->depth = 0; | |
1893 | nd->base = NULL; | |
1894 | if (flags & LOOKUP_ROOT) { | |
1895 | struct dentry *root = nd->root.dentry; | |
1896 | struct inode *inode = root->d_inode; | |
1897 | if (*s) { | |
1898 | if (!d_can_lookup(root)) | |
1899 | return -ENOTDIR; | |
1900 | retval = inode_permission(inode, MAY_EXEC); | |
1901 | if (retval) | |
1902 | return retval; | |
1903 | } | |
1904 | nd->path = nd->root; | |
1905 | nd->inode = inode; | |
1906 | if (flags & LOOKUP_RCU) { | |
1907 | rcu_read_lock(); | |
1908 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); | |
1909 | nd->m_seq = read_seqbegin(&mount_lock); | |
1910 | } else { | |
1911 | path_get(&nd->path); | |
1912 | } | |
1913 | goto done; | |
1914 | } | |
1915 | ||
1916 | nd->root.mnt = NULL; | |
1917 | ||
1918 | nd->m_seq = read_seqbegin(&mount_lock); | |
1919 | if (*s == '/') { | |
1920 | if (flags & LOOKUP_RCU) { | |
1921 | rcu_read_lock(); | |
1922 | nd->seq = set_root_rcu(nd); | |
1923 | } else { | |
1924 | set_root(nd); | |
1925 | path_get(&nd->root); | |
1926 | } | |
1927 | nd->path = nd->root; | |
1928 | } else if (dfd == AT_FDCWD) { | |
1929 | if (flags & LOOKUP_RCU) { | |
1930 | struct fs_struct *fs = current->fs; | |
1931 | unsigned seq; | |
1932 | ||
1933 | rcu_read_lock(); | |
1934 | ||
1935 | do { | |
1936 | seq = read_seqcount_begin(&fs->seq); | |
1937 | nd->path = fs->pwd; | |
1938 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); | |
1939 | } while (read_seqcount_retry(&fs->seq, seq)); | |
1940 | } else { | |
1941 | get_fs_pwd(current->fs, &nd->path); | |
1942 | } | |
1943 | } else { | |
1944 | /* Caller must check execute permissions on the starting path component */ | |
1945 | struct fd f = fdget_raw(dfd); | |
1946 | struct dentry *dentry; | |
1947 | ||
1948 | if (!f.file) | |
1949 | return -EBADF; | |
1950 | ||
1951 | dentry = f.file->f_path.dentry; | |
1952 | ||
1953 | if (*s) { | |
1954 | if (!d_can_lookup(dentry)) { | |
1955 | fdput(f); | |
1956 | return -ENOTDIR; | |
1957 | } | |
1958 | } | |
1959 | ||
1960 | nd->path = f.file->f_path; | |
1961 | if (flags & LOOKUP_RCU) { | |
1962 | if (f.flags & FDPUT_FPUT) | |
1963 | nd->base = f.file; | |
1964 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); | |
1965 | rcu_read_lock(); | |
1966 | } else { | |
1967 | path_get(&nd->path); | |
1968 | fdput(f); | |
1969 | } | |
1970 | } | |
1971 | ||
1972 | nd->inode = nd->path.dentry->d_inode; | |
1973 | if (!(flags & LOOKUP_RCU)) | |
1974 | goto done; | |
1975 | if (likely(!read_seqcount_retry(&nd->path.dentry->d_seq, nd->seq))) | |
1976 | goto done; | |
1977 | if (!(nd->flags & LOOKUP_ROOT)) | |
1978 | nd->root.mnt = NULL; | |
1979 | rcu_read_unlock(); | |
1980 | return -ECHILD; | |
1981 | done: | |
1982 | current->total_link_count = 0; | |
1983 | return link_path_walk(s, nd); | |
1984 | } | |
1985 | ||
1986 | static void path_cleanup(struct nameidata *nd) | |
1987 | { | |
1988 | if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { | |
1989 | path_put(&nd->root); | |
1990 | nd->root.mnt = NULL; | |
1991 | } | |
1992 | if (unlikely(nd->base)) | |
1993 | fput(nd->base); | |
1994 | } | |
1995 | ||
1996 | static int trailing_symlink(struct nameidata *nd) | |
1997 | { | |
1998 | const char *s; | |
1999 | int error = may_follow_link(&nd->link, nd); | |
2000 | if (unlikely(error)) | |
2001 | return error; | |
2002 | nd->flags |= LOOKUP_PARENT; | |
2003 | s = get_link(nd); | |
2004 | if (unlikely(IS_ERR(s))) | |
2005 | return PTR_ERR(s); | |
2006 | if (unlikely(!s)) | |
2007 | return 0; | |
2008 | if (*s == '/') { | |
2009 | if (!nd->root.mnt) | |
2010 | set_root(nd); | |
2011 | path_put(&nd->path); | |
2012 | nd->path = nd->root; | |
2013 | path_get(&nd->root); | |
2014 | nd->flags |= LOOKUP_JUMPED; | |
2015 | } | |
2016 | nd->inode = nd->path.dentry->d_inode; | |
2017 | nd->stack[0].name = NULL; | |
2018 | return link_path_walk(s, nd); | |
2019 | } | |
2020 | ||
2021 | static inline int lookup_last(struct nameidata *nd) | |
2022 | { | |
2023 | if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len]) | |
2024 | nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; | |
2025 | ||
2026 | nd->flags &= ~LOOKUP_PARENT; | |
2027 | return walk_component(nd, nd->flags & LOOKUP_FOLLOW); | |
2028 | } | |
2029 | ||
2030 | /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ | |
2031 | static int path_lookupat(int dfd, const struct filename *name, | |
2032 | unsigned int flags, struct nameidata *nd) | |
2033 | { | |
2034 | int err; | |
2035 | ||
2036 | /* | |
2037 | * Path walking is largely split up into 2 different synchronisation | |
2038 | * schemes, rcu-walk and ref-walk (explained in | |
2039 | * Documentation/filesystems/path-lookup.txt). These share much of the | |
2040 | * path walk code, but some things particularly setup, cleanup, and | |
2041 | * following mounts are sufficiently divergent that functions are | |
2042 | * duplicated. Typically there is a function foo(), and its RCU | |
2043 | * analogue, foo_rcu(). | |
2044 | * | |
2045 | * -ECHILD is the error number of choice (just to avoid clashes) that | |
2046 | * is returned if some aspect of an rcu-walk fails. Such an error must | |
2047 | * be handled by restarting a traditional ref-walk (which will always | |
2048 | * be able to complete). | |
2049 | */ | |
2050 | err = path_init(dfd, name, flags, nd); | |
2051 | if (!err && !(flags & LOOKUP_PARENT)) { | |
2052 | err = lookup_last(nd); | |
2053 | while (err > 0) { | |
2054 | err = trailing_symlink(nd); | |
2055 | if (err) | |
2056 | break; | |
2057 | err = lookup_last(nd); | |
2058 | put_link(nd); | |
2059 | } | |
2060 | } | |
2061 | ||
2062 | if (!err) | |
2063 | err = complete_walk(nd); | |
2064 | ||
2065 | if (!err && nd->flags & LOOKUP_DIRECTORY) { | |
2066 | if (!d_can_lookup(nd->path.dentry)) { | |
2067 | path_put(&nd->path); | |
2068 | err = -ENOTDIR; | |
2069 | } | |
2070 | } | |
2071 | ||
2072 | path_cleanup(nd); | |
2073 | return err; | |
2074 | } | |
2075 | ||
2076 | static int filename_lookup(int dfd, struct filename *name, | |
2077 | unsigned int flags, struct nameidata *nd) | |
2078 | { | |
2079 | int retval; | |
2080 | ||
2081 | set_nameidata(nd); | |
2082 | retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd); | |
2083 | ||
2084 | if (unlikely(retval == -ECHILD)) | |
2085 | retval = path_lookupat(dfd, name, flags, nd); | |
2086 | if (unlikely(retval == -ESTALE)) | |
2087 | retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd); | |
2088 | ||
2089 | if (likely(!retval)) | |
2090 | audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT); | |
2091 | restore_nameidata(nd); | |
2092 | return retval; | |
2093 | } | |
2094 | ||
2095 | /* does lookup, returns the object with parent locked */ | |
2096 | struct dentry *kern_path_locked(const char *name, struct path *path) | |
2097 | { | |
2098 | struct filename *filename = getname_kernel(name); | |
2099 | struct nameidata nd; | |
2100 | struct dentry *d; | |
2101 | int err; | |
2102 | ||
2103 | if (IS_ERR(filename)) | |
2104 | return ERR_CAST(filename); | |
2105 | ||
2106 | err = filename_lookup(AT_FDCWD, filename, LOOKUP_PARENT, &nd); | |
2107 | if (err) { | |
2108 | d = ERR_PTR(err); | |
2109 | goto out; | |
2110 | } | |
2111 | if (nd.last_type != LAST_NORM) { | |
2112 | path_put(&nd.path); | |
2113 | d = ERR_PTR(-EINVAL); | |
2114 | goto out; | |
2115 | } | |
2116 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
2117 | d = __lookup_hash(&nd.last, nd.path.dentry, 0); | |
2118 | if (IS_ERR(d)) { | |
2119 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
2120 | path_put(&nd.path); | |
2121 | goto out; | |
2122 | } | |
2123 | *path = nd.path; | |
2124 | out: | |
2125 | putname(filename); | |
2126 | return d; | |
2127 | } | |
2128 | ||
2129 | int kern_path(const char *name, unsigned int flags, struct path *path) | |
2130 | { | |
2131 | struct nameidata nd; | |
2132 | struct filename *filename = getname_kernel(name); | |
2133 | int res = PTR_ERR(filename); | |
2134 | ||
2135 | if (!IS_ERR(filename)) { | |
2136 | res = filename_lookup(AT_FDCWD, filename, flags, &nd); | |
2137 | putname(filename); | |
2138 | if (!res) | |
2139 | *path = nd.path; | |
2140 | } | |
2141 | return res; | |
2142 | } | |
2143 | EXPORT_SYMBOL(kern_path); | |
2144 | ||
2145 | /** | |
2146 | * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair | |
2147 | * @dentry: pointer to dentry of the base directory | |
2148 | * @mnt: pointer to vfs mount of the base directory | |
2149 | * @name: pointer to file name | |
2150 | * @flags: lookup flags | |
2151 | * @path: pointer to struct path to fill | |
2152 | */ | |
2153 | int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, | |
2154 | const char *name, unsigned int flags, | |
2155 | struct path *path) | |
2156 | { | |
2157 | struct filename *filename = getname_kernel(name); | |
2158 | int err = PTR_ERR(filename); | |
2159 | ||
2160 | BUG_ON(flags & LOOKUP_PARENT); | |
2161 | ||
2162 | /* the first argument of filename_lookup() is ignored with LOOKUP_ROOT */ | |
2163 | if (!IS_ERR(filename)) { | |
2164 | struct nameidata nd; | |
2165 | nd.root.dentry = dentry; | |
2166 | nd.root.mnt = mnt; | |
2167 | err = filename_lookup(AT_FDCWD, filename, | |
2168 | flags | LOOKUP_ROOT, &nd); | |
2169 | if (!err) | |
2170 | *path = nd.path; | |
2171 | putname(filename); | |
2172 | } | |
2173 | return err; | |
2174 | } | |
2175 | EXPORT_SYMBOL(vfs_path_lookup); | |
2176 | ||
2177 | /** | |
2178 | * lookup_one_len - filesystem helper to lookup single pathname component | |
2179 | * @name: pathname component to lookup | |
2180 | * @base: base directory to lookup from | |
2181 | * @len: maximum length @len should be interpreted to | |
2182 | * | |
2183 | * Note that this routine is purely a helper for filesystem usage and should | |
2184 | * not be called by generic code. | |
2185 | */ | |
2186 | struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) | |
2187 | { | |
2188 | struct qstr this; | |
2189 | unsigned int c; | |
2190 | int err; | |
2191 | ||
2192 | WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex)); | |
2193 | ||
2194 | this.name = name; | |
2195 | this.len = len; | |
2196 | this.hash = full_name_hash(name, len); | |
2197 | if (!len) | |
2198 | return ERR_PTR(-EACCES); | |
2199 | ||
2200 | if (unlikely(name[0] == '.')) { | |
2201 | if (len < 2 || (len == 2 && name[1] == '.')) | |
2202 | return ERR_PTR(-EACCES); | |
2203 | } | |
2204 | ||
2205 | while (len--) { | |
2206 | c = *(const unsigned char *)name++; | |
2207 | if (c == '/' || c == '\0') | |
2208 | return ERR_PTR(-EACCES); | |
2209 | } | |
2210 | /* | |
2211 | * See if the low-level filesystem might want | |
2212 | * to use its own hash.. | |
2213 | */ | |
2214 | if (base->d_flags & DCACHE_OP_HASH) { | |
2215 | int err = base->d_op->d_hash(base, &this); | |
2216 | if (err < 0) | |
2217 | return ERR_PTR(err); | |
2218 | } | |
2219 | ||
2220 | err = inode_permission(base->d_inode, MAY_EXEC); | |
2221 | if (err) | |
2222 | return ERR_PTR(err); | |
2223 | ||
2224 | return __lookup_hash(&this, base, 0); | |
2225 | } | |
2226 | EXPORT_SYMBOL(lookup_one_len); | |
2227 | ||
2228 | int user_path_at_empty(int dfd, const char __user *name, unsigned flags, | |
2229 | struct path *path, int *empty) | |
2230 | { | |
2231 | struct nameidata nd; | |
2232 | struct filename *tmp = getname_flags(name, flags, empty); | |
2233 | int err = PTR_ERR(tmp); | |
2234 | if (!IS_ERR(tmp)) { | |
2235 | ||
2236 | BUG_ON(flags & LOOKUP_PARENT); | |
2237 | ||
2238 | err = filename_lookup(dfd, tmp, flags, &nd); | |
2239 | putname(tmp); | |
2240 | if (!err) | |
2241 | *path = nd.path; | |
2242 | } | |
2243 | return err; | |
2244 | } | |
2245 | ||
2246 | int user_path_at(int dfd, const char __user *name, unsigned flags, | |
2247 | struct path *path) | |
2248 | { | |
2249 | return user_path_at_empty(dfd, name, flags, path, NULL); | |
2250 | } | |
2251 | EXPORT_SYMBOL(user_path_at); | |
2252 | ||
2253 | /* | |
2254 | * NB: most callers don't do anything directly with the reference to the | |
2255 | * to struct filename, but the nd->last pointer points into the name string | |
2256 | * allocated by getname. So we must hold the reference to it until all | |
2257 | * path-walking is complete. | |
2258 | */ | |
2259 | static struct filename * | |
2260 | user_path_parent(int dfd, const char __user *path, | |
2261 | struct path *parent, | |
2262 | struct qstr *last, | |
2263 | int *type, | |
2264 | unsigned int flags) | |
2265 | { | |
2266 | struct nameidata nd; | |
2267 | struct filename *s = getname(path); | |
2268 | int error; | |
2269 | ||
2270 | /* only LOOKUP_REVAL is allowed in extra flags */ | |
2271 | flags &= LOOKUP_REVAL; | |
2272 | ||
2273 | if (IS_ERR(s)) | |
2274 | return s; | |
2275 | ||
2276 | error = filename_lookup(dfd, s, flags | LOOKUP_PARENT, &nd); | |
2277 | if (error) { | |
2278 | putname(s); | |
2279 | return ERR_PTR(error); | |
2280 | } | |
2281 | *parent = nd.path; | |
2282 | *last = nd.last; | |
2283 | *type = nd.last_type; | |
2284 | ||
2285 | return s; | |
2286 | } | |
2287 | ||
2288 | /** | |
2289 | * mountpoint_last - look up last component for umount | |
2290 | * @nd: pathwalk nameidata - currently pointing at parent directory of "last" | |
2291 | * @path: pointer to container for result | |
2292 | * | |
2293 | * This is a special lookup_last function just for umount. In this case, we | |
2294 | * need to resolve the path without doing any revalidation. | |
2295 | * | |
2296 | * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since | |
2297 | * mountpoints are always pinned in the dcache, their ancestors are too. Thus, | |
2298 | * in almost all cases, this lookup will be served out of the dcache. The only | |
2299 | * cases where it won't are if nd->last refers to a symlink or the path is | |
2300 | * bogus and it doesn't exist. | |
2301 | * | |
2302 | * Returns: | |
2303 | * -error: if there was an error during lookup. This includes -ENOENT if the | |
2304 | * lookup found a negative dentry. The nd->path reference will also be | |
2305 | * put in this case. | |
2306 | * | |
2307 | * 0: if we successfully resolved nd->path and found it to not to be a | |
2308 | * symlink that needs to be followed. "path" will also be populated. | |
2309 | * The nd->path reference will also be put. | |
2310 | * | |
2311 | * 1: if we successfully resolved nd->last and found it to be a symlink | |
2312 | * that needs to be followed. "path" will be populated with the path | |
2313 | * to the link, and nd->path will *not* be put. | |
2314 | */ | |
2315 | static int | |
2316 | mountpoint_last(struct nameidata *nd, struct path *path) | |
2317 | { | |
2318 | int error = 0; | |
2319 | struct dentry *dentry; | |
2320 | struct dentry *dir = nd->path.dentry; | |
2321 | ||
2322 | /* If we're in rcuwalk, drop out of it to handle last component */ | |
2323 | if (nd->flags & LOOKUP_RCU) { | |
2324 | if (unlazy_walk(nd, NULL)) { | |
2325 | error = -ECHILD; | |
2326 | goto out; | |
2327 | } | |
2328 | } | |
2329 | ||
2330 | nd->flags &= ~LOOKUP_PARENT; | |
2331 | ||
2332 | if (unlikely(nd->last_type != LAST_NORM)) { | |
2333 | error = handle_dots(nd, nd->last_type); | |
2334 | if (error) | |
2335 | goto out; | |
2336 | dentry = dget(nd->path.dentry); | |
2337 | goto done; | |
2338 | } | |
2339 | ||
2340 | mutex_lock(&dir->d_inode->i_mutex); | |
2341 | dentry = d_lookup(dir, &nd->last); | |
2342 | if (!dentry) { | |
2343 | /* | |
2344 | * No cached dentry. Mounted dentries are pinned in the cache, | |
2345 | * so that means that this dentry is probably a symlink or the | |
2346 | * path doesn't actually point to a mounted dentry. | |
2347 | */ | |
2348 | dentry = d_alloc(dir, &nd->last); | |
2349 | if (!dentry) { | |
2350 | error = -ENOMEM; | |
2351 | mutex_unlock(&dir->d_inode->i_mutex); | |
2352 | goto out; | |
2353 | } | |
2354 | dentry = lookup_real(dir->d_inode, dentry, nd->flags); | |
2355 | error = PTR_ERR(dentry); | |
2356 | if (IS_ERR(dentry)) { | |
2357 | mutex_unlock(&dir->d_inode->i_mutex); | |
2358 | goto out; | |
2359 | } | |
2360 | } | |
2361 | mutex_unlock(&dir->d_inode->i_mutex); | |
2362 | ||
2363 | done: | |
2364 | if (d_is_negative(dentry)) { | |
2365 | error = -ENOENT; | |
2366 | dput(dentry); | |
2367 | goto out; | |
2368 | } | |
2369 | path->dentry = dentry; | |
2370 | path->mnt = nd->path.mnt; | |
2371 | if (should_follow_link(dentry, nd->flags & LOOKUP_FOLLOW)) { | |
2372 | nd->link = *path; | |
2373 | return 1; | |
2374 | } | |
2375 | mntget(path->mnt); | |
2376 | follow_mount(path); | |
2377 | error = 0; | |
2378 | out: | |
2379 | terminate_walk(nd); | |
2380 | return error; | |
2381 | } | |
2382 | ||
2383 | /** | |
2384 | * path_mountpoint - look up a path to be umounted | |
2385 | * @dfd: directory file descriptor to start walk from | |
2386 | * @name: full pathname to walk | |
2387 | * @path: pointer to container for result | |
2388 | * @flags: lookup flags | |
2389 | * | |
2390 | * Look up the given name, but don't attempt to revalidate the last component. | |
2391 | * Returns 0 and "path" will be valid on success; Returns error otherwise. | |
2392 | */ | |
2393 | static int | |
2394 | path_mountpoint(int dfd, const struct filename *name, struct path *path, | |
2395 | struct nameidata *nd, unsigned int flags) | |
2396 | { | |
2397 | int err = path_init(dfd, name, flags, nd); | |
2398 | if (unlikely(err)) | |
2399 | goto out; | |
2400 | ||
2401 | err = mountpoint_last(nd, path); | |
2402 | while (err > 0) { | |
2403 | err = trailing_symlink(nd); | |
2404 | if (err) | |
2405 | break; | |
2406 | err = mountpoint_last(nd, path); | |
2407 | put_link(nd); | |
2408 | } | |
2409 | out: | |
2410 | path_cleanup(nd); | |
2411 | return err; | |
2412 | } | |
2413 | ||
2414 | static int | |
2415 | filename_mountpoint(int dfd, struct filename *name, struct path *path, | |
2416 | unsigned int flags) | |
2417 | { | |
2418 | struct nameidata nd; | |
2419 | int error; | |
2420 | if (IS_ERR(name)) | |
2421 | return PTR_ERR(name); | |
2422 | set_nameidata(&nd); | |
2423 | error = path_mountpoint(dfd, name, path, &nd, flags | LOOKUP_RCU); | |
2424 | if (unlikely(error == -ECHILD)) | |
2425 | error = path_mountpoint(dfd, name, path, &nd, flags); | |
2426 | if (unlikely(error == -ESTALE)) | |
2427 | error = path_mountpoint(dfd, name, path, &nd, flags | LOOKUP_REVAL); | |
2428 | if (likely(!error)) | |
2429 | audit_inode(name, path->dentry, 0); | |
2430 | restore_nameidata(&nd); | |
2431 | putname(name); | |
2432 | return error; | |
2433 | } | |
2434 | ||
2435 | /** | |
2436 | * user_path_mountpoint_at - lookup a path from userland in order to umount it | |
2437 | * @dfd: directory file descriptor | |
2438 | * @name: pathname from userland | |
2439 | * @flags: lookup flags | |
2440 | * @path: pointer to container to hold result | |
2441 | * | |
2442 | * A umount is a special case for path walking. We're not actually interested | |
2443 | * in the inode in this situation, and ESTALE errors can be a problem. We | |
2444 | * simply want track down the dentry and vfsmount attached at the mountpoint | |
2445 | * and avoid revalidating the last component. | |
2446 | * | |
2447 | * Returns 0 and populates "path" on success. | |
2448 | */ | |
2449 | int | |
2450 | user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags, | |
2451 | struct path *path) | |
2452 | { | |
2453 | return filename_mountpoint(dfd, getname(name), path, flags); | |
2454 | } | |
2455 | ||
2456 | int | |
2457 | kern_path_mountpoint(int dfd, const char *name, struct path *path, | |
2458 | unsigned int flags) | |
2459 | { | |
2460 | return filename_mountpoint(dfd, getname_kernel(name), path, flags); | |
2461 | } | |
2462 | EXPORT_SYMBOL(kern_path_mountpoint); | |
2463 | ||
2464 | int __check_sticky(struct inode *dir, struct inode *inode) | |
2465 | { | |
2466 | kuid_t fsuid = current_fsuid(); | |
2467 | ||
2468 | if (uid_eq(inode->i_uid, fsuid)) | |
2469 | return 0; | |
2470 | if (uid_eq(dir->i_uid, fsuid)) | |
2471 | return 0; | |
2472 | return !capable_wrt_inode_uidgid(inode, CAP_FOWNER); | |
2473 | } | |
2474 | EXPORT_SYMBOL(__check_sticky); | |
2475 | ||
2476 | /* | |
2477 | * Check whether we can remove a link victim from directory dir, check | |
2478 | * whether the type of victim is right. | |
2479 | * 1. We can't do it if dir is read-only (done in permission()) | |
2480 | * 2. We should have write and exec permissions on dir | |
2481 | * 3. We can't remove anything from append-only dir | |
2482 | * 4. We can't do anything with immutable dir (done in permission()) | |
2483 | * 5. If the sticky bit on dir is set we should either | |
2484 | * a. be owner of dir, or | |
2485 | * b. be owner of victim, or | |
2486 | * c. have CAP_FOWNER capability | |
2487 | * 6. If the victim is append-only or immutable we can't do antyhing with | |
2488 | * links pointing to it. | |
2489 | * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR. | |
2490 | * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR. | |
2491 | * 9. We can't remove a root or mountpoint. | |
2492 | * 10. We don't allow removal of NFS sillyrenamed files; it's handled by | |
2493 | * nfs_async_unlink(). | |
2494 | */ | |
2495 | static int may_delete(struct inode *dir, struct dentry *victim, bool isdir) | |
2496 | { | |
2497 | struct inode *inode = victim->d_inode; | |
2498 | int error; | |
2499 | ||
2500 | if (d_is_negative(victim)) | |
2501 | return -ENOENT; | |
2502 | BUG_ON(!inode); | |
2503 | ||
2504 | BUG_ON(victim->d_parent->d_inode != dir); | |
2505 | audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE); | |
2506 | ||
2507 | error = inode_permission(dir, MAY_WRITE | MAY_EXEC); | |
2508 | if (error) | |
2509 | return error; | |
2510 | if (IS_APPEND(dir)) | |
2511 | return -EPERM; | |
2512 | ||
2513 | if (check_sticky(dir, inode) || IS_APPEND(inode) || | |
2514 | IS_IMMUTABLE(inode) || IS_SWAPFILE(inode)) | |
2515 | return -EPERM; | |
2516 | if (isdir) { | |
2517 | if (!d_is_dir(victim)) | |
2518 | return -ENOTDIR; | |
2519 | if (IS_ROOT(victim)) | |
2520 | return -EBUSY; | |
2521 | } else if (d_is_dir(victim)) | |
2522 | return -EISDIR; | |
2523 | if (IS_DEADDIR(dir)) | |
2524 | return -ENOENT; | |
2525 | if (victim->d_flags & DCACHE_NFSFS_RENAMED) | |
2526 | return -EBUSY; | |
2527 | return 0; | |
2528 | } | |
2529 | ||
2530 | /* Check whether we can create an object with dentry child in directory | |
2531 | * dir. | |
2532 | * 1. We can't do it if child already exists (open has special treatment for | |
2533 | * this case, but since we are inlined it's OK) | |
2534 | * 2. We can't do it if dir is read-only (done in permission()) | |
2535 | * 3. We should have write and exec permissions on dir | |
2536 | * 4. We can't do it if dir is immutable (done in permission()) | |
2537 | */ | |
2538 | static inline int may_create(struct inode *dir, struct dentry *child) | |
2539 | { | |
2540 | audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE); | |
2541 | if (child->d_inode) | |
2542 | return -EEXIST; | |
2543 | if (IS_DEADDIR(dir)) | |
2544 | return -ENOENT; | |
2545 | return inode_permission(dir, MAY_WRITE | MAY_EXEC); | |
2546 | } | |
2547 | ||
2548 | /* | |
2549 | * p1 and p2 should be directories on the same fs. | |
2550 | */ | |
2551 | struct dentry *lock_rename(struct dentry *p1, struct dentry *p2) | |
2552 | { | |
2553 | struct dentry *p; | |
2554 | ||
2555 | if (p1 == p2) { | |
2556 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); | |
2557 | return NULL; | |
2558 | } | |
2559 | ||
2560 | mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex); | |
2561 | ||
2562 | p = d_ancestor(p2, p1); | |
2563 | if (p) { | |
2564 | mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT); | |
2565 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD); | |
2566 | return p; | |
2567 | } | |
2568 | ||
2569 | p = d_ancestor(p1, p2); | |
2570 | if (p) { | |
2571 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); | |
2572 | mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD); | |
2573 | return p; | |
2574 | } | |
2575 | ||
2576 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); | |
2577 | mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT2); | |
2578 | return NULL; | |
2579 | } | |
2580 | EXPORT_SYMBOL(lock_rename); | |
2581 | ||
2582 | void unlock_rename(struct dentry *p1, struct dentry *p2) | |
2583 | { | |
2584 | mutex_unlock(&p1->d_inode->i_mutex); | |
2585 | if (p1 != p2) { | |
2586 | mutex_unlock(&p2->d_inode->i_mutex); | |
2587 | mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex); | |
2588 | } | |
2589 | } | |
2590 | EXPORT_SYMBOL(unlock_rename); | |
2591 | ||
2592 | int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, | |
2593 | bool want_excl) | |
2594 | { | |
2595 | int error = may_create(dir, dentry); | |
2596 | if (error) | |
2597 | return error; | |
2598 | ||
2599 | if (!dir->i_op->create) | |
2600 | return -EACCES; /* shouldn't it be ENOSYS? */ | |
2601 | mode &= S_IALLUGO; | |
2602 | mode |= S_IFREG; | |
2603 | error = security_inode_create(dir, dentry, mode); | |
2604 | if (error) | |
2605 | return error; | |
2606 | error = dir->i_op->create(dir, dentry, mode, want_excl); | |
2607 | if (!error) | |
2608 | fsnotify_create(dir, dentry); | |
2609 | return error; | |
2610 | } | |
2611 | EXPORT_SYMBOL(vfs_create); | |
2612 | ||
2613 | static int may_open(struct path *path, int acc_mode, int flag) | |
2614 | { | |
2615 | struct dentry *dentry = path->dentry; | |
2616 | struct inode *inode = dentry->d_inode; | |
2617 | int error; | |
2618 | ||
2619 | /* O_PATH? */ | |
2620 | if (!acc_mode) | |
2621 | return 0; | |
2622 | ||
2623 | if (!inode) | |
2624 | return -ENOENT; | |
2625 | ||
2626 | switch (inode->i_mode & S_IFMT) { | |
2627 | case S_IFLNK: | |
2628 | return -ELOOP; | |
2629 | case S_IFDIR: | |
2630 | if (acc_mode & MAY_WRITE) | |
2631 | return -EISDIR; | |
2632 | break; | |
2633 | case S_IFBLK: | |
2634 | case S_IFCHR: | |
2635 | if (path->mnt->mnt_flags & MNT_NODEV) | |
2636 | return -EACCES; | |
2637 | /*FALLTHRU*/ | |
2638 | case S_IFIFO: | |
2639 | case S_IFSOCK: | |
2640 | flag &= ~O_TRUNC; | |
2641 | break; | |
2642 | } | |
2643 | ||
2644 | error = inode_permission(inode, acc_mode); | |
2645 | if (error) | |
2646 | return error; | |
2647 | ||
2648 | /* | |
2649 | * An append-only file must be opened in append mode for writing. | |
2650 | */ | |
2651 | if (IS_APPEND(inode)) { | |
2652 | if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) | |
2653 | return -EPERM; | |
2654 | if (flag & O_TRUNC) | |
2655 | return -EPERM; | |
2656 | } | |
2657 | ||
2658 | /* O_NOATIME can only be set by the owner or superuser */ | |
2659 | if (flag & O_NOATIME && !inode_owner_or_capable(inode)) | |
2660 | return -EPERM; | |
2661 | ||
2662 | return 0; | |
2663 | } | |
2664 | ||
2665 | static int handle_truncate(struct file *filp) | |
2666 | { | |
2667 | struct path *path = &filp->f_path; | |
2668 | struct inode *inode = path->dentry->d_inode; | |
2669 | int error = get_write_access(inode); | |
2670 | if (error) | |
2671 | return error; | |
2672 | /* | |
2673 | * Refuse to truncate files with mandatory locks held on them. | |
2674 | */ | |
2675 | error = locks_verify_locked(filp); | |
2676 | if (!error) | |
2677 | error = security_path_truncate(path); | |
2678 | if (!error) { | |
2679 | error = do_truncate(path->dentry, 0, | |
2680 | ATTR_MTIME|ATTR_CTIME|ATTR_OPEN, | |
2681 | filp); | |
2682 | } | |
2683 | put_write_access(inode); | |
2684 | return error; | |
2685 | } | |
2686 | ||
2687 | static inline int open_to_namei_flags(int flag) | |
2688 | { | |
2689 | if ((flag & O_ACCMODE) == 3) | |
2690 | flag--; | |
2691 | return flag; | |
2692 | } | |
2693 | ||
2694 | static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode) | |
2695 | { | |
2696 | int error = security_path_mknod(dir, dentry, mode, 0); | |
2697 | if (error) | |
2698 | return error; | |
2699 | ||
2700 | error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC); | |
2701 | if (error) | |
2702 | return error; | |
2703 | ||
2704 | return security_inode_create(dir->dentry->d_inode, dentry, mode); | |
2705 | } | |
2706 | ||
2707 | /* | |
2708 | * Attempt to atomically look up, create and open a file from a negative | |
2709 | * dentry. | |
2710 | * | |
2711 | * Returns 0 if successful. The file will have been created and attached to | |
2712 | * @file by the filesystem calling finish_open(). | |
2713 | * | |
2714 | * Returns 1 if the file was looked up only or didn't need creating. The | |
2715 | * caller will need to perform the open themselves. @path will have been | |
2716 | * updated to point to the new dentry. This may be negative. | |
2717 | * | |
2718 | * Returns an error code otherwise. | |
2719 | */ | |
2720 | static int atomic_open(struct nameidata *nd, struct dentry *dentry, | |
2721 | struct path *path, struct file *file, | |
2722 | const struct open_flags *op, | |
2723 | bool got_write, bool need_lookup, | |
2724 | int *opened) | |
2725 | { | |
2726 | struct inode *dir = nd->path.dentry->d_inode; | |
2727 | unsigned open_flag = open_to_namei_flags(op->open_flag); | |
2728 | umode_t mode; | |
2729 | int error; | |
2730 | int acc_mode; | |
2731 | int create_error = 0; | |
2732 | struct dentry *const DENTRY_NOT_SET = (void *) -1UL; | |
2733 | bool excl; | |
2734 | ||
2735 | BUG_ON(dentry->d_inode); | |
2736 | ||
2737 | /* Don't create child dentry for a dead directory. */ | |
2738 | if (unlikely(IS_DEADDIR(dir))) { | |
2739 | error = -ENOENT; | |
2740 | goto out; | |
2741 | } | |
2742 | ||
2743 | mode = op->mode; | |
2744 | if ((open_flag & O_CREAT) && !IS_POSIXACL(dir)) | |
2745 | mode &= ~current_umask(); | |
2746 | ||
2747 | excl = (open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT); | |
2748 | if (excl) | |
2749 | open_flag &= ~O_TRUNC; | |
2750 | ||
2751 | /* | |
2752 | * Checking write permission is tricky, bacuse we don't know if we are | |
2753 | * going to actually need it: O_CREAT opens should work as long as the | |
2754 | * file exists. But checking existence breaks atomicity. The trick is | |
2755 | * to check access and if not granted clear O_CREAT from the flags. | |
2756 | * | |
2757 | * Another problem is returing the "right" error value (e.g. for an | |
2758 | * O_EXCL open we want to return EEXIST not EROFS). | |
2759 | */ | |
2760 | if (((open_flag & (O_CREAT | O_TRUNC)) || | |
2761 | (open_flag & O_ACCMODE) != O_RDONLY) && unlikely(!got_write)) { | |
2762 | if (!(open_flag & O_CREAT)) { | |
2763 | /* | |
2764 | * No O_CREATE -> atomicity not a requirement -> fall | |
2765 | * back to lookup + open | |
2766 | */ | |
2767 | goto no_open; | |
2768 | } else if (open_flag & (O_EXCL | O_TRUNC)) { | |
2769 | /* Fall back and fail with the right error */ | |
2770 | create_error = -EROFS; | |
2771 | goto no_open; | |
2772 | } else { | |
2773 | /* No side effects, safe to clear O_CREAT */ | |
2774 | create_error = -EROFS; | |
2775 | open_flag &= ~O_CREAT; | |
2776 | } | |
2777 | } | |
2778 | ||
2779 | if (open_flag & O_CREAT) { | |
2780 | error = may_o_create(&nd->path, dentry, mode); | |
2781 | if (error) { | |
2782 | create_error = error; | |
2783 | if (open_flag & O_EXCL) | |
2784 | goto no_open; | |
2785 | open_flag &= ~O_CREAT; | |
2786 | } | |
2787 | } | |
2788 | ||
2789 | if (nd->flags & LOOKUP_DIRECTORY) | |
2790 | open_flag |= O_DIRECTORY; | |
2791 | ||
2792 | file->f_path.dentry = DENTRY_NOT_SET; | |
2793 | file->f_path.mnt = nd->path.mnt; | |
2794 | error = dir->i_op->atomic_open(dir, dentry, file, open_flag, mode, | |
2795 | opened); | |
2796 | if (error < 0) { | |
2797 | if (create_error && error == -ENOENT) | |
2798 | error = create_error; | |
2799 | goto out; | |
2800 | } | |
2801 | ||
2802 | if (error) { /* returned 1, that is */ | |
2803 | if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) { | |
2804 | error = -EIO; | |
2805 | goto out; | |
2806 | } | |
2807 | if (file->f_path.dentry) { | |
2808 | dput(dentry); | |
2809 | dentry = file->f_path.dentry; | |
2810 | } | |
2811 | if (*opened & FILE_CREATED) | |
2812 | fsnotify_create(dir, dentry); | |
2813 | if (!dentry->d_inode) { | |
2814 | WARN_ON(*opened & FILE_CREATED); | |
2815 | if (create_error) { | |
2816 | error = create_error; | |
2817 | goto out; | |
2818 | } | |
2819 | } else { | |
2820 | if (excl && !(*opened & FILE_CREATED)) { | |
2821 | error = -EEXIST; | |
2822 | goto out; | |
2823 | } | |
2824 | } | |
2825 | goto looked_up; | |
2826 | } | |
2827 | ||
2828 | /* | |
2829 | * We didn't have the inode before the open, so check open permission | |
2830 | * here. | |
2831 | */ | |
2832 | acc_mode = op->acc_mode; | |
2833 | if (*opened & FILE_CREATED) { | |
2834 | WARN_ON(!(open_flag & O_CREAT)); | |
2835 | fsnotify_create(dir, dentry); | |
2836 | acc_mode = MAY_OPEN; | |
2837 | } | |
2838 | error = may_open(&file->f_path, acc_mode, open_flag); | |
2839 | if (error) | |
2840 | fput(file); | |
2841 | ||
2842 | out: | |
2843 | dput(dentry); | |
2844 | return error; | |
2845 | ||
2846 | no_open: | |
2847 | if (need_lookup) { | |
2848 | dentry = lookup_real(dir, dentry, nd->flags); | |
2849 | if (IS_ERR(dentry)) | |
2850 | return PTR_ERR(dentry); | |
2851 | ||
2852 | if (create_error) { | |
2853 | int open_flag = op->open_flag; | |
2854 | ||
2855 | error = create_error; | |
2856 | if ((open_flag & O_EXCL)) { | |
2857 | if (!dentry->d_inode) | |
2858 | goto out; | |
2859 | } else if (!dentry->d_inode) { | |
2860 | goto out; | |
2861 | } else if ((open_flag & O_TRUNC) && | |
2862 | d_is_reg(dentry)) { | |
2863 | goto out; | |
2864 | } | |
2865 | /* will fail later, go on to get the right error */ | |
2866 | } | |
2867 | } | |
2868 | looked_up: | |
2869 | path->dentry = dentry; | |
2870 | path->mnt = nd->path.mnt; | |
2871 | return 1; | |
2872 | } | |
2873 | ||
2874 | /* | |
2875 | * Look up and maybe create and open the last component. | |
2876 | * | |
2877 | * Must be called with i_mutex held on parent. | |
2878 | * | |
2879 | * Returns 0 if the file was successfully atomically created (if necessary) and | |
2880 | * opened. In this case the file will be returned attached to @file. | |
2881 | * | |
2882 | * Returns 1 if the file was not completely opened at this time, though lookups | |
2883 | * and creations will have been performed and the dentry returned in @path will | |
2884 | * be positive upon return if O_CREAT was specified. If O_CREAT wasn't | |
2885 | * specified then a negative dentry may be returned. | |
2886 | * | |
2887 | * An error code is returned otherwise. | |
2888 | * | |
2889 | * FILE_CREATE will be set in @*opened if the dentry was created and will be | |
2890 | * cleared otherwise prior to returning. | |
2891 | */ | |
2892 | static int lookup_open(struct nameidata *nd, struct path *path, | |
2893 | struct file *file, | |
2894 | const struct open_flags *op, | |
2895 | bool got_write, int *opened) | |
2896 | { | |
2897 | struct dentry *dir = nd->path.dentry; | |
2898 | struct inode *dir_inode = dir->d_inode; | |
2899 | struct dentry *dentry; | |
2900 | int error; | |
2901 | bool need_lookup; | |
2902 | ||
2903 | *opened &= ~FILE_CREATED; | |
2904 | dentry = lookup_dcache(&nd->last, dir, nd->flags, &need_lookup); | |
2905 | if (IS_ERR(dentry)) | |
2906 | return PTR_ERR(dentry); | |
2907 | ||
2908 | /* Cached positive dentry: will open in f_op->open */ | |
2909 | if (!need_lookup && dentry->d_inode) | |
2910 | goto out_no_open; | |
2911 | ||
2912 | if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) { | |
2913 | return atomic_open(nd, dentry, path, file, op, got_write, | |
2914 | need_lookup, opened); | |
2915 | } | |
2916 | ||
2917 | if (need_lookup) { | |
2918 | BUG_ON(dentry->d_inode); | |
2919 | ||
2920 | dentry = lookup_real(dir_inode, dentry, nd->flags); | |
2921 | if (IS_ERR(dentry)) | |
2922 | return PTR_ERR(dentry); | |
2923 | } | |
2924 | ||
2925 | /* Negative dentry, just create the file */ | |
2926 | if (!dentry->d_inode && (op->open_flag & O_CREAT)) { | |
2927 | umode_t mode = op->mode; | |
2928 | if (!IS_POSIXACL(dir->d_inode)) | |
2929 | mode &= ~current_umask(); | |
2930 | /* | |
2931 | * This write is needed to ensure that a | |
2932 | * rw->ro transition does not occur between | |
2933 | * the time when the file is created and when | |
2934 | * a permanent write count is taken through | |
2935 | * the 'struct file' in finish_open(). | |
2936 | */ | |
2937 | if (!got_write) { | |
2938 | error = -EROFS; | |
2939 | goto out_dput; | |
2940 | } | |
2941 | *opened |= FILE_CREATED; | |
2942 | error = security_path_mknod(&nd->path, dentry, mode, 0); | |
2943 | if (error) | |
2944 | goto out_dput; | |
2945 | error = vfs_create(dir->d_inode, dentry, mode, | |
2946 | nd->flags & LOOKUP_EXCL); | |
2947 | if (error) | |
2948 | goto out_dput; | |
2949 | } | |
2950 | out_no_open: | |
2951 | path->dentry = dentry; | |
2952 | path->mnt = nd->path.mnt; | |
2953 | return 1; | |
2954 | ||
2955 | out_dput: | |
2956 | dput(dentry); | |
2957 | return error; | |
2958 | } | |
2959 | ||
2960 | /* | |
2961 | * Handle the last step of open() | |
2962 | */ | |
2963 | static int do_last(struct nameidata *nd, | |
2964 | struct file *file, const struct open_flags *op, | |
2965 | int *opened, struct filename *name) | |
2966 | { | |
2967 | struct dentry *dir = nd->path.dentry; | |
2968 | int open_flag = op->open_flag; | |
2969 | bool will_truncate = (open_flag & O_TRUNC) != 0; | |
2970 | bool got_write = false; | |
2971 | int acc_mode = op->acc_mode; | |
2972 | struct inode *inode; | |
2973 | struct path save_parent = { .dentry = NULL, .mnt = NULL }; | |
2974 | struct path path; | |
2975 | bool retried = false; | |
2976 | int error; | |
2977 | ||
2978 | nd->flags &= ~LOOKUP_PARENT; | |
2979 | nd->flags |= op->intent; | |
2980 | ||
2981 | if (nd->last_type != LAST_NORM) { | |
2982 | error = handle_dots(nd, nd->last_type); | |
2983 | if (unlikely(error)) { | |
2984 | terminate_walk(nd); | |
2985 | return error; | |
2986 | } | |
2987 | goto finish_open; | |
2988 | } | |
2989 | ||
2990 | if (!(open_flag & O_CREAT)) { | |
2991 | if (nd->last.name[nd->last.len]) | |
2992 | nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; | |
2993 | /* we _can_ be in RCU mode here */ | |
2994 | error = lookup_fast(nd, &path, &inode); | |
2995 | if (likely(!error)) | |
2996 | goto finish_lookup; | |
2997 | ||
2998 | if (error < 0) | |
2999 | goto out; | |
3000 | ||
3001 | BUG_ON(nd->inode != dir->d_inode); | |
3002 | } else { | |
3003 | /* create side of things */ | |
3004 | /* | |
3005 | * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED | |
3006 | * has been cleared when we got to the last component we are | |
3007 | * about to look up | |
3008 | */ | |
3009 | error = complete_walk(nd); | |
3010 | if (error) | |
3011 | return error; | |
3012 | ||
3013 | audit_inode(name, dir, LOOKUP_PARENT); | |
3014 | error = -EISDIR; | |
3015 | /* trailing slashes? */ | |
3016 | if (nd->last.name[nd->last.len]) | |
3017 | goto out; | |
3018 | } | |
3019 | ||
3020 | retry_lookup: | |
3021 | if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) { | |
3022 | error = mnt_want_write(nd->path.mnt); | |
3023 | if (!error) | |
3024 | got_write = true; | |
3025 | /* | |
3026 | * do _not_ fail yet - we might not need that or fail with | |
3027 | * a different error; let lookup_open() decide; we'll be | |
3028 | * dropping this one anyway. | |
3029 | */ | |
3030 | } | |
3031 | mutex_lock(&dir->d_inode->i_mutex); | |
3032 | error = lookup_open(nd, &path, file, op, got_write, opened); | |
3033 | mutex_unlock(&dir->d_inode->i_mutex); | |
3034 | ||
3035 | if (error <= 0) { | |
3036 | if (error) | |
3037 | goto out; | |
3038 | ||
3039 | if ((*opened & FILE_CREATED) || | |
3040 | !S_ISREG(file_inode(file)->i_mode)) | |
3041 | will_truncate = false; | |
3042 | ||
3043 | audit_inode(name, file->f_path.dentry, 0); | |
3044 | goto opened; | |
3045 | } | |
3046 | ||
3047 | if (*opened & FILE_CREATED) { | |
3048 | /* Don't check for write permission, don't truncate */ | |
3049 | open_flag &= ~O_TRUNC; | |
3050 | will_truncate = false; | |
3051 | acc_mode = MAY_OPEN; | |
3052 | path_to_nameidata(&path, nd); | |
3053 | goto finish_open_created; | |
3054 | } | |
3055 | ||
3056 | /* | |
3057 | * create/update audit record if it already exists. | |
3058 | */ | |
3059 | if (d_is_positive(path.dentry)) | |
3060 | audit_inode(name, path.dentry, 0); | |
3061 | ||
3062 | /* | |
3063 | * If atomic_open() acquired write access it is dropped now due to | |
3064 | * possible mount and symlink following (this might be optimized away if | |
3065 | * necessary...) | |
3066 | */ | |
3067 | if (got_write) { | |
3068 | mnt_drop_write(nd->path.mnt); | |
3069 | got_write = false; | |
3070 | } | |
3071 | ||
3072 | error = -EEXIST; | |
3073 | if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT)) | |
3074 | goto exit_dput; | |
3075 | ||
3076 | error = follow_managed(&path, nd->flags); | |
3077 | if (error < 0) | |
3078 | goto exit_dput; | |
3079 | ||
3080 | if (error) | |
3081 | nd->flags |= LOOKUP_JUMPED; | |
3082 | ||
3083 | BUG_ON(nd->flags & LOOKUP_RCU); | |
3084 | inode = path.dentry->d_inode; | |
3085 | error = -ENOENT; | |
3086 | if (d_is_negative(path.dentry)) { | |
3087 | path_to_nameidata(&path, nd); | |
3088 | goto out; | |
3089 | } | |
3090 | finish_lookup: | |
3091 | if (should_follow_link(path.dentry, nd->flags & LOOKUP_FOLLOW)) { | |
3092 | if (nd->flags & LOOKUP_RCU) { | |
3093 | if (unlikely(nd->path.mnt != path.mnt || | |
3094 | unlazy_walk(nd, path.dentry))) { | |
3095 | error = -ECHILD; | |
3096 | goto out; | |
3097 | } | |
3098 | } | |
3099 | BUG_ON(inode != path.dentry->d_inode); | |
3100 | nd->link = path; | |
3101 | return 1; | |
3102 | } | |
3103 | ||
3104 | if (unlikely(d_is_symlink(path.dentry)) && !(open_flag & O_PATH)) { | |
3105 | path_to_nameidata(&path, nd); | |
3106 | error = -ELOOP; | |
3107 | goto out; | |
3108 | } | |
3109 | ||
3110 | if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path.mnt) { | |
3111 | path_to_nameidata(&path, nd); | |
3112 | } else { | |
3113 | save_parent.dentry = nd->path.dentry; | |
3114 | save_parent.mnt = mntget(path.mnt); | |
3115 | nd->path.dentry = path.dentry; | |
3116 | ||
3117 | } | |
3118 | nd->inode = inode; | |
3119 | /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */ | |
3120 | finish_open: | |
3121 | error = complete_walk(nd); | |
3122 | if (error) { | |
3123 | path_put(&save_parent); | |
3124 | return error; | |
3125 | } | |
3126 | audit_inode(name, nd->path.dentry, 0); | |
3127 | error = -EISDIR; | |
3128 | if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry)) | |
3129 | goto out; | |
3130 | error = -ENOTDIR; | |
3131 | if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry)) | |
3132 | goto out; | |
3133 | if (!d_is_reg(nd->path.dentry)) | |
3134 | will_truncate = false; | |
3135 | ||
3136 | if (will_truncate) { | |
3137 | error = mnt_want_write(nd->path.mnt); | |
3138 | if (error) | |
3139 | goto out; | |
3140 | got_write = true; | |
3141 | } | |
3142 | finish_open_created: | |
3143 | error = may_open(&nd->path, acc_mode, open_flag); | |
3144 | if (error) | |
3145 | goto out; | |
3146 | ||
3147 | BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */ | |
3148 | error = vfs_open(&nd->path, file, current_cred()); | |
3149 | if (!error) { | |
3150 | *opened |= FILE_OPENED; | |
3151 | } else { | |
3152 | if (error == -EOPENSTALE) | |
3153 | goto stale_open; | |
3154 | goto out; | |
3155 | } | |
3156 | opened: | |
3157 | error = open_check_o_direct(file); | |
3158 | if (error) | |
3159 | goto exit_fput; | |
3160 | error = ima_file_check(file, op->acc_mode, *opened); | |
3161 | if (error) | |
3162 | goto exit_fput; | |
3163 | ||
3164 | if (will_truncate) { | |
3165 | error = handle_truncate(file); | |
3166 | if (error) | |
3167 | goto exit_fput; | |
3168 | } | |
3169 | out: | |
3170 | if (got_write) | |
3171 | mnt_drop_write(nd->path.mnt); | |
3172 | path_put(&save_parent); | |
3173 | terminate_walk(nd); | |
3174 | return error; | |
3175 | ||
3176 | exit_dput: | |
3177 | path_put_conditional(&path, nd); | |
3178 | goto out; | |
3179 | exit_fput: | |
3180 | fput(file); | |
3181 | goto out; | |
3182 | ||
3183 | stale_open: | |
3184 | /* If no saved parent or already retried then can't retry */ | |
3185 | if (!save_parent.dentry || retried) | |
3186 | goto out; | |
3187 | ||
3188 | BUG_ON(save_parent.dentry != dir); | |
3189 | path_put(&nd->path); | |
3190 | nd->path = save_parent; | |
3191 | nd->inode = dir->d_inode; | |
3192 | save_parent.mnt = NULL; | |
3193 | save_parent.dentry = NULL; | |
3194 | if (got_write) { | |
3195 | mnt_drop_write(nd->path.mnt); | |
3196 | got_write = false; | |
3197 | } | |
3198 | retried = true; | |
3199 | goto retry_lookup; | |
3200 | } | |
3201 | ||
3202 | static int do_tmpfile(int dfd, struct filename *pathname, | |
3203 | struct nameidata *nd, int flags, | |
3204 | const struct open_flags *op, | |
3205 | struct file *file, int *opened) | |
3206 | { | |
3207 | static const struct qstr name = QSTR_INIT("/", 1); | |
3208 | struct dentry *dentry, *child; | |
3209 | struct inode *dir; | |
3210 | int error = path_lookupat(dfd, pathname, | |
3211 | flags | LOOKUP_DIRECTORY, nd); | |
3212 | if (unlikely(error)) | |
3213 | return error; | |
3214 | error = mnt_want_write(nd->path.mnt); | |
3215 | if (unlikely(error)) | |
3216 | goto out; | |
3217 | /* we want directory to be writable */ | |
3218 | error = inode_permission(nd->inode, MAY_WRITE | MAY_EXEC); | |
3219 | if (error) | |
3220 | goto out2; | |
3221 | dentry = nd->path.dentry; | |
3222 | dir = dentry->d_inode; | |
3223 | if (!dir->i_op->tmpfile) { | |
3224 | error = -EOPNOTSUPP; | |
3225 | goto out2; | |
3226 | } | |
3227 | child = d_alloc(dentry, &name); | |
3228 | if (unlikely(!child)) { | |
3229 | error = -ENOMEM; | |
3230 | goto out2; | |
3231 | } | |
3232 | nd->flags &= ~LOOKUP_DIRECTORY; | |
3233 | nd->flags |= op->intent; | |
3234 | dput(nd->path.dentry); | |
3235 | nd->path.dentry = child; | |
3236 | error = dir->i_op->tmpfile(dir, nd->path.dentry, op->mode); | |
3237 | if (error) | |
3238 | goto out2; | |
3239 | audit_inode(pathname, nd->path.dentry, 0); | |
3240 | /* Don't check for other permissions, the inode was just created */ | |
3241 | error = may_open(&nd->path, MAY_OPEN, op->open_flag); | |
3242 | if (error) | |
3243 | goto out2; | |
3244 | file->f_path.mnt = nd->path.mnt; | |
3245 | error = finish_open(file, nd->path.dentry, NULL, opened); | |
3246 | if (error) | |
3247 | goto out2; | |
3248 | error = open_check_o_direct(file); | |
3249 | if (error) { | |
3250 | fput(file); | |
3251 | } else if (!(op->open_flag & O_EXCL)) { | |
3252 | struct inode *inode = file_inode(file); | |
3253 | spin_lock(&inode->i_lock); | |
3254 | inode->i_state |= I_LINKABLE; | |
3255 | spin_unlock(&inode->i_lock); | |
3256 | } | |
3257 | out2: | |
3258 | mnt_drop_write(nd->path.mnt); | |
3259 | out: | |
3260 | path_put(&nd->path); | |
3261 | return error; | |
3262 | } | |
3263 | ||
3264 | static struct file *path_openat(int dfd, struct filename *pathname, | |
3265 | struct nameidata *nd, const struct open_flags *op, int flags) | |
3266 | { | |
3267 | struct file *file; | |
3268 | int opened = 0; | |
3269 | int error; | |
3270 | ||
3271 | file = get_empty_filp(); | |
3272 | if (IS_ERR(file)) | |
3273 | return file; | |
3274 | ||
3275 | file->f_flags = op->open_flag; | |
3276 | ||
3277 | if (unlikely(file->f_flags & __O_TMPFILE)) { | |
3278 | error = do_tmpfile(dfd, pathname, nd, flags, op, file, &opened); | |
3279 | goto out2; | |
3280 | } | |
3281 | ||
3282 | error = path_init(dfd, pathname, flags, nd); | |
3283 | if (unlikely(error)) | |
3284 | goto out; | |
3285 | ||
3286 | error = do_last(nd, file, op, &opened, pathname); | |
3287 | while (unlikely(error > 0)) { /* trailing symlink */ | |
3288 | nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL); | |
3289 | error = trailing_symlink(nd); | |
3290 | if (unlikely(error)) | |
3291 | break; | |
3292 | error = do_last(nd, file, op, &opened, pathname); | |
3293 | put_link(nd); | |
3294 | } | |
3295 | out: | |
3296 | path_cleanup(nd); | |
3297 | out2: | |
3298 | if (!(opened & FILE_OPENED)) { | |
3299 | BUG_ON(!error); | |
3300 | put_filp(file); | |
3301 | } | |
3302 | if (unlikely(error)) { | |
3303 | if (error == -EOPENSTALE) { | |
3304 | if (flags & LOOKUP_RCU) | |
3305 | error = -ECHILD; | |
3306 | else | |
3307 | error = -ESTALE; | |
3308 | } | |
3309 | file = ERR_PTR(error); | |
3310 | } | |
3311 | return file; | |
3312 | } | |
3313 | ||
3314 | struct file *do_filp_open(int dfd, struct filename *pathname, | |
3315 | const struct open_flags *op) | |
3316 | { | |
3317 | struct nameidata nd; | |
3318 | int flags = op->lookup_flags; | |
3319 | struct file *filp; | |
3320 | ||
3321 | set_nameidata(&nd); | |
3322 | filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU); | |
3323 | if (unlikely(filp == ERR_PTR(-ECHILD))) | |
3324 | filp = path_openat(dfd, pathname, &nd, op, flags); | |
3325 | if (unlikely(filp == ERR_PTR(-ESTALE))) | |
3326 | filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL); | |
3327 | restore_nameidata(&nd); | |
3328 | return filp; | |
3329 | } | |
3330 | ||
3331 | struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt, | |
3332 | const char *name, const struct open_flags *op) | |
3333 | { | |
3334 | struct nameidata nd; | |
3335 | struct file *file; | |
3336 | struct filename *filename; | |
3337 | int flags = op->lookup_flags | LOOKUP_ROOT; | |
3338 | ||
3339 | nd.root.mnt = mnt; | |
3340 | nd.root.dentry = dentry; | |
3341 | set_nameidata(&nd); | |
3342 | ||
3343 | if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN) | |
3344 | return ERR_PTR(-ELOOP); | |
3345 | ||
3346 | filename = getname_kernel(name); | |
3347 | if (unlikely(IS_ERR(filename))) | |
3348 | return ERR_CAST(filename); | |
3349 | ||
3350 | file = path_openat(-1, filename, &nd, op, flags | LOOKUP_RCU); | |
3351 | if (unlikely(file == ERR_PTR(-ECHILD))) | |
3352 | file = path_openat(-1, filename, &nd, op, flags); | |
3353 | if (unlikely(file == ERR_PTR(-ESTALE))) | |
3354 | file = path_openat(-1, filename, &nd, op, flags | LOOKUP_REVAL); | |
3355 | restore_nameidata(&nd); | |
3356 | putname(filename); | |
3357 | return file; | |
3358 | } | |
3359 | ||
3360 | static struct dentry *filename_create(int dfd, struct filename *name, | |
3361 | struct path *path, unsigned int lookup_flags) | |
3362 | { | |
3363 | struct dentry *dentry = ERR_PTR(-EEXIST); | |
3364 | struct nameidata nd; | |
3365 | int err2; | |
3366 | int error; | |
3367 | bool is_dir = (lookup_flags & LOOKUP_DIRECTORY); | |
3368 | ||
3369 | /* | |
3370 | * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any | |
3371 | * other flags passed in are ignored! | |
3372 | */ | |
3373 | lookup_flags &= LOOKUP_REVAL; | |
3374 | ||
3375 | error = filename_lookup(dfd, name, LOOKUP_PARENT|lookup_flags, &nd); | |
3376 | if (error) | |
3377 | return ERR_PTR(error); | |
3378 | ||
3379 | /* | |
3380 | * Yucky last component or no last component at all? | |
3381 | * (foo/., foo/.., /////) | |
3382 | */ | |
3383 | if (nd.last_type != LAST_NORM) | |
3384 | goto out; | |
3385 | nd.flags &= ~LOOKUP_PARENT; | |
3386 | nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL; | |
3387 | ||
3388 | /* don't fail immediately if it's r/o, at least try to report other errors */ | |
3389 | err2 = mnt_want_write(nd.path.mnt); | |
3390 | /* | |
3391 | * Do the final lookup. | |
3392 | */ | |
3393 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
3394 | dentry = __lookup_hash(&nd.last, nd.path.dentry, nd.flags); | |
3395 | if (IS_ERR(dentry)) | |
3396 | goto unlock; | |
3397 | ||
3398 | error = -EEXIST; | |
3399 | if (d_is_positive(dentry)) | |
3400 | goto fail; | |
3401 | ||
3402 | /* | |
3403 | * Special case - lookup gave negative, but... we had foo/bar/ | |
3404 | * From the vfs_mknod() POV we just have a negative dentry - | |
3405 | * all is fine. Let's be bastards - you had / on the end, you've | |
3406 | * been asking for (non-existent) directory. -ENOENT for you. | |
3407 | */ | |
3408 | if (unlikely(!is_dir && nd.last.name[nd.last.len])) { | |
3409 | error = -ENOENT; | |
3410 | goto fail; | |
3411 | } | |
3412 | if (unlikely(err2)) { | |
3413 | error = err2; | |
3414 | goto fail; | |
3415 | } | |
3416 | *path = nd.path; | |
3417 | return dentry; | |
3418 | fail: | |
3419 | dput(dentry); | |
3420 | dentry = ERR_PTR(error); | |
3421 | unlock: | |
3422 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
3423 | if (!err2) | |
3424 | mnt_drop_write(nd.path.mnt); | |
3425 | out: | |
3426 | path_put(&nd.path); | |
3427 | return dentry; | |
3428 | } | |
3429 | ||
3430 | struct dentry *kern_path_create(int dfd, const char *pathname, | |
3431 | struct path *path, unsigned int lookup_flags) | |
3432 | { | |
3433 | struct filename *filename = getname_kernel(pathname); | |
3434 | struct dentry *res; | |
3435 | ||
3436 | if (IS_ERR(filename)) | |
3437 | return ERR_CAST(filename); | |
3438 | res = filename_create(dfd, filename, path, lookup_flags); | |
3439 | putname(filename); | |
3440 | return res; | |
3441 | } | |
3442 | EXPORT_SYMBOL(kern_path_create); | |
3443 | ||
3444 | void done_path_create(struct path *path, struct dentry *dentry) | |
3445 | { | |
3446 | dput(dentry); | |
3447 | mutex_unlock(&path->dentry->d_inode->i_mutex); | |
3448 | mnt_drop_write(path->mnt); | |
3449 | path_put(path); | |
3450 | } | |
3451 | EXPORT_SYMBOL(done_path_create); | |
3452 | ||
3453 | struct dentry *user_path_create(int dfd, const char __user *pathname, | |
3454 | struct path *path, unsigned int lookup_flags) | |
3455 | { | |
3456 | struct filename *tmp = getname(pathname); | |
3457 | struct dentry *res; | |
3458 | if (IS_ERR(tmp)) | |
3459 | return ERR_CAST(tmp); | |
3460 | res = filename_create(dfd, tmp, path, lookup_flags); | |
3461 | putname(tmp); | |
3462 | return res; | |
3463 | } | |
3464 | EXPORT_SYMBOL(user_path_create); | |
3465 | ||
3466 | int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) | |
3467 | { | |
3468 | int error = may_create(dir, dentry); | |
3469 | ||
3470 | if (error) | |
3471 | return error; | |
3472 | ||
3473 | if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD)) | |
3474 | return -EPERM; | |
3475 | ||
3476 | if (!dir->i_op->mknod) | |
3477 | return -EPERM; | |
3478 | ||
3479 | error = devcgroup_inode_mknod(mode, dev); | |
3480 | if (error) | |
3481 | return error; | |
3482 | ||
3483 | error = security_inode_mknod(dir, dentry, mode, dev); | |
3484 | if (error) | |
3485 | return error; | |
3486 | ||
3487 | error = dir->i_op->mknod(dir, dentry, mode, dev); | |
3488 | if (!error) | |
3489 | fsnotify_create(dir, dentry); | |
3490 | return error; | |
3491 | } | |
3492 | EXPORT_SYMBOL(vfs_mknod); | |
3493 | ||
3494 | static int may_mknod(umode_t mode) | |
3495 | { | |
3496 | switch (mode & S_IFMT) { | |
3497 | case S_IFREG: | |
3498 | case S_IFCHR: | |
3499 | case S_IFBLK: | |
3500 | case S_IFIFO: | |
3501 | case S_IFSOCK: | |
3502 | case 0: /* zero mode translates to S_IFREG */ | |
3503 | return 0; | |
3504 | case S_IFDIR: | |
3505 | return -EPERM; | |
3506 | default: | |
3507 | return -EINVAL; | |
3508 | } | |
3509 | } | |
3510 | ||
3511 | SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode, | |
3512 | unsigned, dev) | |
3513 | { | |
3514 | struct dentry *dentry; | |
3515 | struct path path; | |
3516 | int error; | |
3517 | unsigned int lookup_flags = 0; | |
3518 | ||
3519 | error = may_mknod(mode); | |
3520 | if (error) | |
3521 | return error; | |
3522 | retry: | |
3523 | dentry = user_path_create(dfd, filename, &path, lookup_flags); | |
3524 | if (IS_ERR(dentry)) | |
3525 | return PTR_ERR(dentry); | |
3526 | ||
3527 | if (!IS_POSIXACL(path.dentry->d_inode)) | |
3528 | mode &= ~current_umask(); | |
3529 | error = security_path_mknod(&path, dentry, mode, dev); | |
3530 | if (error) | |
3531 | goto out; | |
3532 | switch (mode & S_IFMT) { | |
3533 | case 0: case S_IFREG: | |
3534 | error = vfs_create(path.dentry->d_inode,dentry,mode,true); | |
3535 | break; | |
3536 | case S_IFCHR: case S_IFBLK: | |
3537 | error = vfs_mknod(path.dentry->d_inode,dentry,mode, | |
3538 | new_decode_dev(dev)); | |
3539 | break; | |
3540 | case S_IFIFO: case S_IFSOCK: | |
3541 | error = vfs_mknod(path.dentry->d_inode,dentry,mode,0); | |
3542 | break; | |
3543 | } | |
3544 | out: | |
3545 | done_path_create(&path, dentry); | |
3546 | if (retry_estale(error, lookup_flags)) { | |
3547 | lookup_flags |= LOOKUP_REVAL; | |
3548 | goto retry; | |
3549 | } | |
3550 | return error; | |
3551 | } | |
3552 | ||
3553 | SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev) | |
3554 | { | |
3555 | return sys_mknodat(AT_FDCWD, filename, mode, dev); | |
3556 | } | |
3557 | ||
3558 | int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) | |
3559 | { | |
3560 | int error = may_create(dir, dentry); | |
3561 | unsigned max_links = dir->i_sb->s_max_links; | |
3562 | ||
3563 | if (error) | |
3564 | return error; | |
3565 | ||
3566 | if (!dir->i_op->mkdir) | |
3567 | return -EPERM; | |
3568 | ||
3569 | mode &= (S_IRWXUGO|S_ISVTX); | |
3570 | error = security_inode_mkdir(dir, dentry, mode); | |
3571 | if (error) | |
3572 | return error; | |
3573 | ||
3574 | if (max_links && dir->i_nlink >= max_links) | |
3575 | return -EMLINK; | |
3576 | ||
3577 | error = dir->i_op->mkdir(dir, dentry, mode); | |
3578 | if (!error) | |
3579 | fsnotify_mkdir(dir, dentry); | |
3580 | return error; | |
3581 | } | |
3582 | EXPORT_SYMBOL(vfs_mkdir); | |
3583 | ||
3584 | SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode) | |
3585 | { | |
3586 | struct dentry *dentry; | |
3587 | struct path path; | |
3588 | int error; | |
3589 | unsigned int lookup_flags = LOOKUP_DIRECTORY; | |
3590 | ||
3591 | retry: | |
3592 | dentry = user_path_create(dfd, pathname, &path, lookup_flags); | |
3593 | if (IS_ERR(dentry)) | |
3594 | return PTR_ERR(dentry); | |
3595 | ||
3596 | if (!IS_POSIXACL(path.dentry->d_inode)) | |
3597 | mode &= ~current_umask(); | |
3598 | error = security_path_mkdir(&path, dentry, mode); | |
3599 | if (!error) | |
3600 | error = vfs_mkdir(path.dentry->d_inode, dentry, mode); | |
3601 | done_path_create(&path, dentry); | |
3602 | if (retry_estale(error, lookup_flags)) { | |
3603 | lookup_flags |= LOOKUP_REVAL; | |
3604 | goto retry; | |
3605 | } | |
3606 | return error; | |
3607 | } | |
3608 | ||
3609 | SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode) | |
3610 | { | |
3611 | return sys_mkdirat(AT_FDCWD, pathname, mode); | |
3612 | } | |
3613 | ||
3614 | /* | |
3615 | * The dentry_unhash() helper will try to drop the dentry early: we | |
3616 | * should have a usage count of 1 if we're the only user of this | |
3617 | * dentry, and if that is true (possibly after pruning the dcache), | |
3618 | * then we drop the dentry now. | |
3619 | * | |
3620 | * A low-level filesystem can, if it choses, legally | |
3621 | * do a | |
3622 | * | |
3623 | * if (!d_unhashed(dentry)) | |
3624 | * return -EBUSY; | |
3625 | * | |
3626 | * if it cannot handle the case of removing a directory | |
3627 | * that is still in use by something else.. | |
3628 | */ | |
3629 | void dentry_unhash(struct dentry *dentry) | |
3630 | { | |
3631 | shrink_dcache_parent(dentry); | |
3632 | spin_lock(&dentry->d_lock); | |
3633 | if (dentry->d_lockref.count == 1) | |
3634 | __d_drop(dentry); | |
3635 | spin_unlock(&dentry->d_lock); | |
3636 | } | |
3637 | EXPORT_SYMBOL(dentry_unhash); | |
3638 | ||
3639 | int vfs_rmdir(struct inode *dir, struct dentry *dentry) | |
3640 | { | |
3641 | int error = may_delete(dir, dentry, 1); | |
3642 | ||
3643 | if (error) | |
3644 | return error; | |
3645 | ||
3646 | if (!dir->i_op->rmdir) | |
3647 | return -EPERM; | |
3648 | ||
3649 | dget(dentry); | |
3650 | mutex_lock(&dentry->d_inode->i_mutex); | |
3651 | ||
3652 | error = -EBUSY; | |
3653 | if (is_local_mountpoint(dentry)) | |
3654 | goto out; | |
3655 | ||
3656 | error = security_inode_rmdir(dir, dentry); | |
3657 | if (error) | |
3658 | goto out; | |
3659 | ||
3660 | shrink_dcache_parent(dentry); | |
3661 | error = dir->i_op->rmdir(dir, dentry); | |
3662 | if (error) | |
3663 | goto out; | |
3664 | ||
3665 | dentry->d_inode->i_flags |= S_DEAD; | |
3666 | dont_mount(dentry); | |
3667 | detach_mounts(dentry); | |
3668 | ||
3669 | out: | |
3670 | mutex_unlock(&dentry->d_inode->i_mutex); | |
3671 | dput(dentry); | |
3672 | if (!error) | |
3673 | d_delete(dentry); | |
3674 | return error; | |
3675 | } | |
3676 | EXPORT_SYMBOL(vfs_rmdir); | |
3677 | ||
3678 | static long do_rmdir(int dfd, const char __user *pathname) | |
3679 | { | |
3680 | int error = 0; | |
3681 | struct filename *name; | |
3682 | struct dentry *dentry; | |
3683 | struct path path; | |
3684 | struct qstr last; | |
3685 | int type; | |
3686 | unsigned int lookup_flags = 0; | |
3687 | retry: | |
3688 | name = user_path_parent(dfd, pathname, | |
3689 | &path, &last, &type, lookup_flags); | |
3690 | if (IS_ERR(name)) | |
3691 | return PTR_ERR(name); | |
3692 | ||
3693 | switch (type) { | |
3694 | case LAST_DOTDOT: | |
3695 | error = -ENOTEMPTY; | |
3696 | goto exit1; | |
3697 | case LAST_DOT: | |
3698 | error = -EINVAL; | |
3699 | goto exit1; | |
3700 | case LAST_ROOT: | |
3701 | error = -EBUSY; | |
3702 | goto exit1; | |
3703 | } | |
3704 | ||
3705 | error = mnt_want_write(path.mnt); | |
3706 | if (error) | |
3707 | goto exit1; | |
3708 | ||
3709 | mutex_lock_nested(&path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
3710 | dentry = __lookup_hash(&last, path.dentry, lookup_flags); | |
3711 | error = PTR_ERR(dentry); | |
3712 | if (IS_ERR(dentry)) | |
3713 | goto exit2; | |
3714 | if (!dentry->d_inode) { | |
3715 | error = -ENOENT; | |
3716 | goto exit3; | |
3717 | } | |
3718 | error = security_path_rmdir(&path, dentry); | |
3719 | if (error) | |
3720 | goto exit3; | |
3721 | error = vfs_rmdir(path.dentry->d_inode, dentry); | |
3722 | exit3: | |
3723 | dput(dentry); | |
3724 | exit2: | |
3725 | mutex_unlock(&path.dentry->d_inode->i_mutex); | |
3726 | mnt_drop_write(path.mnt); | |
3727 | exit1: | |
3728 | path_put(&path); | |
3729 | putname(name); | |
3730 | if (retry_estale(error, lookup_flags)) { | |
3731 | lookup_flags |= LOOKUP_REVAL; | |
3732 | goto retry; | |
3733 | } | |
3734 | return error; | |
3735 | } | |
3736 | ||
3737 | SYSCALL_DEFINE1(rmdir, const char __user *, pathname) | |
3738 | { | |
3739 | return do_rmdir(AT_FDCWD, pathname); | |
3740 | } | |
3741 | ||
3742 | /** | |
3743 | * vfs_unlink - unlink a filesystem object | |
3744 | * @dir: parent directory | |
3745 | * @dentry: victim | |
3746 | * @delegated_inode: returns victim inode, if the inode is delegated. | |
3747 | * | |
3748 | * The caller must hold dir->i_mutex. | |
3749 | * | |
3750 | * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and | |
3751 | * return a reference to the inode in delegated_inode. The caller | |
3752 | * should then break the delegation on that inode and retry. Because | |
3753 | * breaking a delegation may take a long time, the caller should drop | |
3754 | * dir->i_mutex before doing so. | |
3755 | * | |
3756 | * Alternatively, a caller may pass NULL for delegated_inode. This may | |
3757 | * be appropriate for callers that expect the underlying filesystem not | |
3758 | * to be NFS exported. | |
3759 | */ | |
3760 | int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode) | |
3761 | { | |
3762 | struct inode *target = dentry->d_inode; | |
3763 | int error = may_delete(dir, dentry, 0); | |
3764 | ||
3765 | if (error) | |
3766 | return error; | |
3767 | ||
3768 | if (!dir->i_op->unlink) | |
3769 | return -EPERM; | |
3770 | ||
3771 | mutex_lock(&target->i_mutex); | |
3772 | if (is_local_mountpoint(dentry)) | |
3773 | error = -EBUSY; | |
3774 | else { | |
3775 | error = security_inode_unlink(dir, dentry); | |
3776 | if (!error) { | |
3777 | error = try_break_deleg(target, delegated_inode); | |
3778 | if (error) | |
3779 | goto out; | |
3780 | error = dir->i_op->unlink(dir, dentry); | |
3781 | if (!error) { | |
3782 | dont_mount(dentry); | |
3783 | detach_mounts(dentry); | |
3784 | } | |
3785 | } | |
3786 | } | |
3787 | out: | |
3788 | mutex_unlock(&target->i_mutex); | |
3789 | ||
3790 | /* We don't d_delete() NFS sillyrenamed files--they still exist. */ | |
3791 | if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) { | |
3792 | fsnotify_link_count(target); | |
3793 | d_delete(dentry); | |
3794 | } | |
3795 | ||
3796 | return error; | |
3797 | } | |
3798 | EXPORT_SYMBOL(vfs_unlink); | |
3799 | ||
3800 | /* | |
3801 | * Make sure that the actual truncation of the file will occur outside its | |
3802 | * directory's i_mutex. Truncate can take a long time if there is a lot of | |
3803 | * writeout happening, and we don't want to prevent access to the directory | |
3804 | * while waiting on the I/O. | |
3805 | */ | |
3806 | static long do_unlinkat(int dfd, const char __user *pathname) | |
3807 | { | |
3808 | int error; | |
3809 | struct filename *name; | |
3810 | struct dentry *dentry; | |
3811 | struct path path; | |
3812 | struct qstr last; | |
3813 | int type; | |
3814 | struct inode *inode = NULL; | |
3815 | struct inode *delegated_inode = NULL; | |
3816 | unsigned int lookup_flags = 0; | |
3817 | retry: | |
3818 | name = user_path_parent(dfd, pathname, | |
3819 | &path, &last, &type, lookup_flags); | |
3820 | if (IS_ERR(name)) | |
3821 | return PTR_ERR(name); | |
3822 | ||
3823 | error = -EISDIR; | |
3824 | if (type != LAST_NORM) | |
3825 | goto exit1; | |
3826 | ||
3827 | error = mnt_want_write(path.mnt); | |
3828 | if (error) | |
3829 | goto exit1; | |
3830 | retry_deleg: | |
3831 | mutex_lock_nested(&path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
3832 | dentry = __lookup_hash(&last, path.dentry, lookup_flags); | |
3833 | error = PTR_ERR(dentry); | |
3834 | if (!IS_ERR(dentry)) { | |
3835 | /* Why not before? Because we want correct error value */ | |
3836 | if (last.name[last.len]) | |
3837 | goto slashes; | |
3838 | inode = dentry->d_inode; | |
3839 | if (d_is_negative(dentry)) | |
3840 | goto slashes; | |
3841 | ihold(inode); | |
3842 | error = security_path_unlink(&path, dentry); | |
3843 | if (error) | |
3844 | goto exit2; | |
3845 | error = vfs_unlink(path.dentry->d_inode, dentry, &delegated_inode); | |
3846 | exit2: | |
3847 | dput(dentry); | |
3848 | } | |
3849 | mutex_unlock(&path.dentry->d_inode->i_mutex); | |
3850 | if (inode) | |
3851 | iput(inode); /* truncate the inode here */ | |
3852 | inode = NULL; | |
3853 | if (delegated_inode) { | |
3854 | error = break_deleg_wait(&delegated_inode); | |
3855 | if (!error) | |
3856 | goto retry_deleg; | |
3857 | } | |
3858 | mnt_drop_write(path.mnt); | |
3859 | exit1: | |
3860 | path_put(&path); | |
3861 | putname(name); | |
3862 | if (retry_estale(error, lookup_flags)) { | |
3863 | lookup_flags |= LOOKUP_REVAL; | |
3864 | inode = NULL; | |
3865 | goto retry; | |
3866 | } | |
3867 | return error; | |
3868 | ||
3869 | slashes: | |
3870 | if (d_is_negative(dentry)) | |
3871 | error = -ENOENT; | |
3872 | else if (d_is_dir(dentry)) | |
3873 | error = -EISDIR; | |
3874 | else | |
3875 | error = -ENOTDIR; | |
3876 | goto exit2; | |
3877 | } | |
3878 | ||
3879 | SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag) | |
3880 | { | |
3881 | if ((flag & ~AT_REMOVEDIR) != 0) | |
3882 | return -EINVAL; | |
3883 | ||
3884 | if (flag & AT_REMOVEDIR) | |
3885 | return do_rmdir(dfd, pathname); | |
3886 | ||
3887 | return do_unlinkat(dfd, pathname); | |
3888 | } | |
3889 | ||
3890 | SYSCALL_DEFINE1(unlink, const char __user *, pathname) | |
3891 | { | |
3892 | return do_unlinkat(AT_FDCWD, pathname); | |
3893 | } | |
3894 | ||
3895 | int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname) | |
3896 | { | |
3897 | int error = may_create(dir, dentry); | |
3898 | ||
3899 | if (error) | |
3900 | return error; | |
3901 | ||
3902 | if (!dir->i_op->symlink) | |
3903 | return -EPERM; | |
3904 | ||
3905 | error = security_inode_symlink(dir, dentry, oldname); | |
3906 | if (error) | |
3907 | return error; | |
3908 | ||
3909 | error = dir->i_op->symlink(dir, dentry, oldname); | |
3910 | if (!error) | |
3911 | fsnotify_create(dir, dentry); | |
3912 | return error; | |
3913 | } | |
3914 | EXPORT_SYMBOL(vfs_symlink); | |
3915 | ||
3916 | SYSCALL_DEFINE3(symlinkat, const char __user *, oldname, | |
3917 | int, newdfd, const char __user *, newname) | |
3918 | { | |
3919 | int error; | |
3920 | struct filename *from; | |
3921 | struct dentry *dentry; | |
3922 | struct path path; | |
3923 | unsigned int lookup_flags = 0; | |
3924 | ||
3925 | from = getname(oldname); | |
3926 | if (IS_ERR(from)) | |
3927 | return PTR_ERR(from); | |
3928 | retry: | |
3929 | dentry = user_path_create(newdfd, newname, &path, lookup_flags); | |
3930 | error = PTR_ERR(dentry); | |
3931 | if (IS_ERR(dentry)) | |
3932 | goto out_putname; | |
3933 | ||
3934 | error = security_path_symlink(&path, dentry, from->name); | |
3935 | if (!error) | |
3936 | error = vfs_symlink(path.dentry->d_inode, dentry, from->name); | |
3937 | done_path_create(&path, dentry); | |
3938 | if (retry_estale(error, lookup_flags)) { | |
3939 | lookup_flags |= LOOKUP_REVAL; | |
3940 | goto retry; | |
3941 | } | |
3942 | out_putname: | |
3943 | putname(from); | |
3944 | return error; | |
3945 | } | |
3946 | ||
3947 | SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname) | |
3948 | { | |
3949 | return sys_symlinkat(oldname, AT_FDCWD, newname); | |
3950 | } | |
3951 | ||
3952 | /** | |
3953 | * vfs_link - create a new link | |
3954 | * @old_dentry: object to be linked | |
3955 | * @dir: new parent | |
3956 | * @new_dentry: where to create the new link | |
3957 | * @delegated_inode: returns inode needing a delegation break | |
3958 | * | |
3959 | * The caller must hold dir->i_mutex | |
3960 | * | |
3961 | * If vfs_link discovers a delegation on the to-be-linked file in need | |
3962 | * of breaking, it will return -EWOULDBLOCK and return a reference to the | |
3963 | * inode in delegated_inode. The caller should then break the delegation | |
3964 | * and retry. Because breaking a delegation may take a long time, the | |
3965 | * caller should drop the i_mutex before doing so. | |
3966 | * | |
3967 | * Alternatively, a caller may pass NULL for delegated_inode. This may | |
3968 | * be appropriate for callers that expect the underlying filesystem not | |
3969 | * to be NFS exported. | |
3970 | */ | |
3971 | int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode) | |
3972 | { | |
3973 | struct inode *inode = old_dentry->d_inode; | |
3974 | unsigned max_links = dir->i_sb->s_max_links; | |
3975 | int error; | |
3976 | ||
3977 | if (!inode) | |
3978 | return -ENOENT; | |
3979 | ||
3980 | error = may_create(dir, new_dentry); | |
3981 | if (error) | |
3982 | return error; | |
3983 | ||
3984 | if (dir->i_sb != inode->i_sb) | |
3985 | return -EXDEV; | |
3986 | ||
3987 | /* | |
3988 | * A link to an append-only or immutable file cannot be created. | |
3989 | */ | |
3990 | if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) | |
3991 | return -EPERM; | |
3992 | if (!dir->i_op->link) | |
3993 | return -EPERM; | |
3994 | if (S_ISDIR(inode->i_mode)) | |
3995 | return -EPERM; | |
3996 | ||
3997 | error = security_inode_link(old_dentry, dir, new_dentry); | |
3998 | if (error) | |
3999 | return error; | |
4000 | ||
4001 | mutex_lock(&inode->i_mutex); | |
4002 | /* Make sure we don't allow creating hardlink to an unlinked file */ | |
4003 | if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE)) | |
4004 | error = -ENOENT; | |
4005 | else if (max_links && inode->i_nlink >= max_links) | |
4006 | error = -EMLINK; | |
4007 | else { | |
4008 | error = try_break_deleg(inode, delegated_inode); | |
4009 | if (!error) | |
4010 | error = dir->i_op->link(old_dentry, dir, new_dentry); | |
4011 | } | |
4012 | ||
4013 | if (!error && (inode->i_state & I_LINKABLE)) { | |
4014 | spin_lock(&inode->i_lock); | |
4015 | inode->i_state &= ~I_LINKABLE; | |
4016 | spin_unlock(&inode->i_lock); | |
4017 | } | |
4018 | mutex_unlock(&inode->i_mutex); | |
4019 | if (!error) | |
4020 | fsnotify_link(dir, inode, new_dentry); | |
4021 | return error; | |
4022 | } | |
4023 | EXPORT_SYMBOL(vfs_link); | |
4024 | ||
4025 | /* | |
4026 | * Hardlinks are often used in delicate situations. We avoid | |
4027 | * security-related surprises by not following symlinks on the | |
4028 | * newname. --KAB | |
4029 | * | |
4030 | * We don't follow them on the oldname either to be compatible | |
4031 | * with linux 2.0, and to avoid hard-linking to directories | |
4032 | * and other special files. --ADM | |
4033 | */ | |
4034 | SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname, | |
4035 | int, newdfd, const char __user *, newname, int, flags) | |
4036 | { | |
4037 | struct dentry *new_dentry; | |
4038 | struct path old_path, new_path; | |
4039 | struct inode *delegated_inode = NULL; | |
4040 | int how = 0; | |
4041 | int error; | |
4042 | ||
4043 | if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) | |
4044 | return -EINVAL; | |
4045 | /* | |
4046 | * To use null names we require CAP_DAC_READ_SEARCH | |
4047 | * This ensures that not everyone will be able to create | |
4048 | * handlink using the passed filedescriptor. | |
4049 | */ | |
4050 | if (flags & AT_EMPTY_PATH) { | |
4051 | if (!capable(CAP_DAC_READ_SEARCH)) | |
4052 | return -ENOENT; | |
4053 | how = LOOKUP_EMPTY; | |
4054 | } | |
4055 | ||
4056 | if (flags & AT_SYMLINK_FOLLOW) | |
4057 | how |= LOOKUP_FOLLOW; | |
4058 | retry: | |
4059 | error = user_path_at(olddfd, oldname, how, &old_path); | |
4060 | if (error) | |
4061 | return error; | |
4062 | ||
4063 | new_dentry = user_path_create(newdfd, newname, &new_path, | |
4064 | (how & LOOKUP_REVAL)); | |
4065 | error = PTR_ERR(new_dentry); | |
4066 | if (IS_ERR(new_dentry)) | |
4067 | goto out; | |
4068 | ||
4069 | error = -EXDEV; | |
4070 | if (old_path.mnt != new_path.mnt) | |
4071 | goto out_dput; | |
4072 | error = may_linkat(&old_path); | |
4073 | if (unlikely(error)) | |
4074 | goto out_dput; | |
4075 | error = security_path_link(old_path.dentry, &new_path, new_dentry); | |
4076 | if (error) | |
4077 | goto out_dput; | |
4078 | error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, &delegated_inode); | |
4079 | out_dput: | |
4080 | done_path_create(&new_path, new_dentry); | |
4081 | if (delegated_inode) { | |
4082 | error = break_deleg_wait(&delegated_inode); | |
4083 | if (!error) { | |
4084 | path_put(&old_path); | |
4085 | goto retry; | |
4086 | } | |
4087 | } | |
4088 | if (retry_estale(error, how)) { | |
4089 | path_put(&old_path); | |
4090 | how |= LOOKUP_REVAL; | |
4091 | goto retry; | |
4092 | } | |
4093 | out: | |
4094 | path_put(&old_path); | |
4095 | ||
4096 | return error; | |
4097 | } | |
4098 | ||
4099 | SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname) | |
4100 | { | |
4101 | return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0); | |
4102 | } | |
4103 | ||
4104 | /** | |
4105 | * vfs_rename - rename a filesystem object | |
4106 | * @old_dir: parent of source | |
4107 | * @old_dentry: source | |
4108 | * @new_dir: parent of destination | |
4109 | * @new_dentry: destination | |
4110 | * @delegated_inode: returns an inode needing a delegation break | |
4111 | * @flags: rename flags | |
4112 | * | |
4113 | * The caller must hold multiple mutexes--see lock_rename()). | |
4114 | * | |
4115 | * If vfs_rename discovers a delegation in need of breaking at either | |
4116 | * the source or destination, it will return -EWOULDBLOCK and return a | |
4117 | * reference to the inode in delegated_inode. The caller should then | |
4118 | * break the delegation and retry. Because breaking a delegation may | |
4119 | * take a long time, the caller should drop all locks before doing | |
4120 | * so. | |
4121 | * | |
4122 | * Alternatively, a caller may pass NULL for delegated_inode. This may | |
4123 | * be appropriate for callers that expect the underlying filesystem not | |
4124 | * to be NFS exported. | |
4125 | * | |
4126 | * The worst of all namespace operations - renaming directory. "Perverted" | |
4127 | * doesn't even start to describe it. Somebody in UCB had a heck of a trip... | |
4128 | * Problems: | |
4129 | * a) we can get into loop creation. | |
4130 | * b) race potential - two innocent renames can create a loop together. | |
4131 | * That's where 4.4 screws up. Current fix: serialization on | |
4132 | * sb->s_vfs_rename_mutex. We might be more accurate, but that's another | |
4133 | * story. | |
4134 | * c) we have to lock _four_ objects - parents and victim (if it exists), | |
4135 | * and source (if it is not a directory). | |
4136 | * And that - after we got ->i_mutex on parents (until then we don't know | |
4137 | * whether the target exists). Solution: try to be smart with locking | |
4138 | * order for inodes. We rely on the fact that tree topology may change | |
4139 | * only under ->s_vfs_rename_mutex _and_ that parent of the object we | |
4140 | * move will be locked. Thus we can rank directories by the tree | |
4141 | * (ancestors first) and rank all non-directories after them. | |
4142 | * That works since everybody except rename does "lock parent, lookup, | |
4143 | * lock child" and rename is under ->s_vfs_rename_mutex. | |
4144 | * HOWEVER, it relies on the assumption that any object with ->lookup() | |
4145 | * has no more than 1 dentry. If "hybrid" objects will ever appear, | |
4146 | * we'd better make sure that there's no link(2) for them. | |
4147 | * d) conversion from fhandle to dentry may come in the wrong moment - when | |
4148 | * we are removing the target. Solution: we will have to grab ->i_mutex | |
4149 | * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on | |
4150 | * ->i_mutex on parents, which works but leads to some truly excessive | |
4151 | * locking]. | |
4152 | */ | |
4153 | int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, | |
4154 | struct inode *new_dir, struct dentry *new_dentry, | |
4155 | struct inode **delegated_inode, unsigned int flags) | |
4156 | { | |
4157 | int error; | |
4158 | bool is_dir = d_is_dir(old_dentry); | |
4159 | const unsigned char *old_name; | |
4160 | struct inode *source = old_dentry->d_inode; | |
4161 | struct inode *target = new_dentry->d_inode; | |
4162 | bool new_is_dir = false; | |
4163 | unsigned max_links = new_dir->i_sb->s_max_links; | |
4164 | ||
4165 | if (source == target) | |
4166 | return 0; | |
4167 | ||
4168 | error = may_delete(old_dir, old_dentry, is_dir); | |
4169 | if (error) | |
4170 | return error; | |
4171 | ||
4172 | if (!target) { | |
4173 | error = may_create(new_dir, new_dentry); | |
4174 | } else { | |
4175 | new_is_dir = d_is_dir(new_dentry); | |
4176 | ||
4177 | if (!(flags & RENAME_EXCHANGE)) | |
4178 | error = may_delete(new_dir, new_dentry, is_dir); | |
4179 | else | |
4180 | error = may_delete(new_dir, new_dentry, new_is_dir); | |
4181 | } | |
4182 | if (error) | |
4183 | return error; | |
4184 | ||
4185 | if (!old_dir->i_op->rename && !old_dir->i_op->rename2) | |
4186 | return -EPERM; | |
4187 | ||
4188 | if (flags && !old_dir->i_op->rename2) | |
4189 | return -EINVAL; | |
4190 | ||
4191 | /* | |
4192 | * If we are going to change the parent - check write permissions, | |
4193 | * we'll need to flip '..'. | |
4194 | */ | |
4195 | if (new_dir != old_dir) { | |
4196 | if (is_dir) { | |
4197 | error = inode_permission(source, MAY_WRITE); | |
4198 | if (error) | |
4199 | return error; | |
4200 | } | |
4201 | if ((flags & RENAME_EXCHANGE) && new_is_dir) { | |
4202 | error = inode_permission(target, MAY_WRITE); | |
4203 | if (error) | |
4204 | return error; | |
4205 | } | |
4206 | } | |
4207 | ||
4208 | error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry, | |
4209 | flags); | |
4210 | if (error) | |
4211 | return error; | |
4212 | ||
4213 | old_name = fsnotify_oldname_init(old_dentry->d_name.name); | |
4214 | dget(new_dentry); | |
4215 | if (!is_dir || (flags & RENAME_EXCHANGE)) | |
4216 | lock_two_nondirectories(source, target); | |
4217 | else if (target) | |
4218 | mutex_lock(&target->i_mutex); | |
4219 | ||
4220 | error = -EBUSY; | |
4221 | if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry)) | |
4222 | goto out; | |
4223 | ||
4224 | if (max_links && new_dir != old_dir) { | |
4225 | error = -EMLINK; | |
4226 | if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links) | |
4227 | goto out; | |
4228 | if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir && | |
4229 | old_dir->i_nlink >= max_links) | |
4230 | goto out; | |
4231 | } | |
4232 | if (is_dir && !(flags & RENAME_EXCHANGE) && target) | |
4233 | shrink_dcache_parent(new_dentry); | |
4234 | if (!is_dir) { | |
4235 | error = try_break_deleg(source, delegated_inode); | |
4236 | if (error) | |
4237 | goto out; | |
4238 | } | |
4239 | if (target && !new_is_dir) { | |
4240 | error = try_break_deleg(target, delegated_inode); | |
4241 | if (error) | |
4242 | goto out; | |
4243 | } | |
4244 | if (!old_dir->i_op->rename2) { | |
4245 | error = old_dir->i_op->rename(old_dir, old_dentry, | |
4246 | new_dir, new_dentry); | |
4247 | } else { | |
4248 | WARN_ON(old_dir->i_op->rename != NULL); | |
4249 | error = old_dir->i_op->rename2(old_dir, old_dentry, | |
4250 | new_dir, new_dentry, flags); | |
4251 | } | |
4252 | if (error) | |
4253 | goto out; | |
4254 | ||
4255 | if (!(flags & RENAME_EXCHANGE) && target) { | |
4256 | if (is_dir) | |
4257 | target->i_flags |= S_DEAD; | |
4258 | dont_mount(new_dentry); | |
4259 | detach_mounts(new_dentry); | |
4260 | } | |
4261 | if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) { | |
4262 | if (!(flags & RENAME_EXCHANGE)) | |
4263 | d_move(old_dentry, new_dentry); | |
4264 | else | |
4265 | d_exchange(old_dentry, new_dentry); | |
4266 | } | |
4267 | out: | |
4268 | if (!is_dir || (flags & RENAME_EXCHANGE)) | |
4269 | unlock_two_nondirectories(source, target); | |
4270 | else if (target) | |
4271 | mutex_unlock(&target->i_mutex); | |
4272 | dput(new_dentry); | |
4273 | if (!error) { | |
4274 | fsnotify_move(old_dir, new_dir, old_name, is_dir, | |
4275 | !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry); | |
4276 | if (flags & RENAME_EXCHANGE) { | |
4277 | fsnotify_move(new_dir, old_dir, old_dentry->d_name.name, | |
4278 | new_is_dir, NULL, new_dentry); | |
4279 | } | |
4280 | } | |
4281 | fsnotify_oldname_free(old_name); | |
4282 | ||
4283 | return error; | |
4284 | } | |
4285 | EXPORT_SYMBOL(vfs_rename); | |
4286 | ||
4287 | SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname, | |
4288 | int, newdfd, const char __user *, newname, unsigned int, flags) | |
4289 | { | |
4290 | struct dentry *old_dentry, *new_dentry; | |
4291 | struct dentry *trap; | |
4292 | struct path old_path, new_path; | |
4293 | struct qstr old_last, new_last; | |
4294 | int old_type, new_type; | |
4295 | struct inode *delegated_inode = NULL; | |
4296 | struct filename *from; | |
4297 | struct filename *to; | |
4298 | unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET; | |
4299 | bool should_retry = false; | |
4300 | int error; | |
4301 | ||
4302 | if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT)) | |
4303 | return -EINVAL; | |
4304 | ||
4305 | if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) && | |
4306 | (flags & RENAME_EXCHANGE)) | |
4307 | return -EINVAL; | |
4308 | ||
4309 | if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD)) | |
4310 | return -EPERM; | |
4311 | ||
4312 | if (flags & RENAME_EXCHANGE) | |
4313 | target_flags = 0; | |
4314 | ||
4315 | retry: | |
4316 | from = user_path_parent(olddfd, oldname, | |
4317 | &old_path, &old_last, &old_type, lookup_flags); | |
4318 | if (IS_ERR(from)) { | |
4319 | error = PTR_ERR(from); | |
4320 | goto exit; | |
4321 | } | |
4322 | ||
4323 | to = user_path_parent(newdfd, newname, | |
4324 | &new_path, &new_last, &new_type, lookup_flags); | |
4325 | if (IS_ERR(to)) { | |
4326 | error = PTR_ERR(to); | |
4327 | goto exit1; | |
4328 | } | |
4329 | ||
4330 | error = -EXDEV; | |
4331 | if (old_path.mnt != new_path.mnt) | |
4332 | goto exit2; | |
4333 | ||
4334 | error = -EBUSY; | |
4335 | if (old_type != LAST_NORM) | |
4336 | goto exit2; | |
4337 | ||
4338 | if (flags & RENAME_NOREPLACE) | |
4339 | error = -EEXIST; | |
4340 | if (new_type != LAST_NORM) | |
4341 | goto exit2; | |
4342 | ||
4343 | error = mnt_want_write(old_path.mnt); | |
4344 | if (error) | |
4345 | goto exit2; | |
4346 | ||
4347 | retry_deleg: | |
4348 | trap = lock_rename(new_path.dentry, old_path.dentry); | |
4349 | ||
4350 | old_dentry = __lookup_hash(&old_last, old_path.dentry, lookup_flags); | |
4351 | error = PTR_ERR(old_dentry); | |
4352 | if (IS_ERR(old_dentry)) | |
4353 | goto exit3; | |
4354 | /* source must exist */ | |
4355 | error = -ENOENT; | |
4356 | if (d_is_negative(old_dentry)) | |
4357 | goto exit4; | |
4358 | new_dentry = __lookup_hash(&new_last, new_path.dentry, lookup_flags | target_flags); | |
4359 | error = PTR_ERR(new_dentry); | |
4360 | if (IS_ERR(new_dentry)) | |
4361 | goto exit4; | |
4362 | error = -EEXIST; | |
4363 | if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry)) | |
4364 | goto exit5; | |
4365 | if (flags & RENAME_EXCHANGE) { | |
4366 | error = -ENOENT; | |
4367 | if (d_is_negative(new_dentry)) | |
4368 | goto exit5; | |
4369 | ||
4370 | if (!d_is_dir(new_dentry)) { | |
4371 | error = -ENOTDIR; | |
4372 | if (new_last.name[new_last.len]) | |
4373 | goto exit5; | |
4374 | } | |
4375 | } | |
4376 | /* unless the source is a directory trailing slashes give -ENOTDIR */ | |
4377 | if (!d_is_dir(old_dentry)) { | |
4378 | error = -ENOTDIR; | |
4379 | if (old_last.name[old_last.len]) | |
4380 | goto exit5; | |
4381 | if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len]) | |
4382 | goto exit5; | |
4383 | } | |
4384 | /* source should not be ancestor of target */ | |
4385 | error = -EINVAL; | |
4386 | if (old_dentry == trap) | |
4387 | goto exit5; | |
4388 | /* target should not be an ancestor of source */ | |
4389 | if (!(flags & RENAME_EXCHANGE)) | |
4390 | error = -ENOTEMPTY; | |
4391 | if (new_dentry == trap) | |
4392 | goto exit5; | |
4393 | ||
4394 | error = security_path_rename(&old_path, old_dentry, | |
4395 | &new_path, new_dentry, flags); | |
4396 | if (error) | |
4397 | goto exit5; | |
4398 | error = vfs_rename(old_path.dentry->d_inode, old_dentry, | |
4399 | new_path.dentry->d_inode, new_dentry, | |
4400 | &delegated_inode, flags); | |
4401 | exit5: | |
4402 | dput(new_dentry); | |
4403 | exit4: | |
4404 | dput(old_dentry); | |
4405 | exit3: | |
4406 | unlock_rename(new_path.dentry, old_path.dentry); | |
4407 | if (delegated_inode) { | |
4408 | error = break_deleg_wait(&delegated_inode); | |
4409 | if (!error) | |
4410 | goto retry_deleg; | |
4411 | } | |
4412 | mnt_drop_write(old_path.mnt); | |
4413 | exit2: | |
4414 | if (retry_estale(error, lookup_flags)) | |
4415 | should_retry = true; | |
4416 | path_put(&new_path); | |
4417 | putname(to); | |
4418 | exit1: | |
4419 | path_put(&old_path); | |
4420 | putname(from); | |
4421 | if (should_retry) { | |
4422 | should_retry = false; | |
4423 | lookup_flags |= LOOKUP_REVAL; | |
4424 | goto retry; | |
4425 | } | |
4426 | exit: | |
4427 | return error; | |
4428 | } | |
4429 | ||
4430 | SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname, | |
4431 | int, newdfd, const char __user *, newname) | |
4432 | { | |
4433 | return sys_renameat2(olddfd, oldname, newdfd, newname, 0); | |
4434 | } | |
4435 | ||
4436 | SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname) | |
4437 | { | |
4438 | return sys_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0); | |
4439 | } | |
4440 | ||
4441 | int vfs_whiteout(struct inode *dir, struct dentry *dentry) | |
4442 | { | |
4443 | int error = may_create(dir, dentry); | |
4444 | if (error) | |
4445 | return error; | |
4446 | ||
4447 | if (!dir->i_op->mknod) | |
4448 | return -EPERM; | |
4449 | ||
4450 | return dir->i_op->mknod(dir, dentry, | |
4451 | S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV); | |
4452 | } | |
4453 | EXPORT_SYMBOL(vfs_whiteout); | |
4454 | ||
4455 | int readlink_copy(char __user *buffer, int buflen, const char *link) | |
4456 | { | |
4457 | int len = PTR_ERR(link); | |
4458 | if (IS_ERR(link)) | |
4459 | goto out; | |
4460 | ||
4461 | len = strlen(link); | |
4462 | if (len > (unsigned) buflen) | |
4463 | len = buflen; | |
4464 | if (copy_to_user(buffer, link, len)) | |
4465 | len = -EFAULT; | |
4466 | out: | |
4467 | return len; | |
4468 | } | |
4469 | EXPORT_SYMBOL(readlink_copy); | |
4470 | ||
4471 | /* | |
4472 | * A helper for ->readlink(). This should be used *ONLY* for symlinks that | |
4473 | * have ->follow_link() touching nd only in nd_set_link(). Using (or not | |
4474 | * using) it for any given inode is up to filesystem. | |
4475 | */ | |
4476 | int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen) | |
4477 | { | |
4478 | void *cookie; | |
4479 | const char *link = dentry->d_inode->i_link; | |
4480 | int res; | |
4481 | ||
4482 | if (!link) { | |
4483 | link = dentry->d_inode->i_op->follow_link(dentry, &cookie, NULL); | |
4484 | if (IS_ERR(link)) | |
4485 | return PTR_ERR(link); | |
4486 | } | |
4487 | res = readlink_copy(buffer, buflen, link); | |
4488 | if (cookie && dentry->d_inode->i_op->put_link) | |
4489 | dentry->d_inode->i_op->put_link(dentry, cookie); | |
4490 | return res; | |
4491 | } | |
4492 | EXPORT_SYMBOL(generic_readlink); | |
4493 | ||
4494 | /* get the link contents into pagecache */ | |
4495 | static char *page_getlink(struct dentry * dentry, struct page **ppage) | |
4496 | { | |
4497 | char *kaddr; | |
4498 | struct page *page; | |
4499 | struct address_space *mapping = dentry->d_inode->i_mapping; | |
4500 | page = read_mapping_page(mapping, 0, NULL); | |
4501 | if (IS_ERR(page)) | |
4502 | return (char*)page; | |
4503 | *ppage = page; | |
4504 | kaddr = kmap(page); | |
4505 | nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1); | |
4506 | return kaddr; | |
4507 | } | |
4508 | ||
4509 | int page_readlink(struct dentry *dentry, char __user *buffer, int buflen) | |
4510 | { | |
4511 | struct page *page = NULL; | |
4512 | int res = readlink_copy(buffer, buflen, page_getlink(dentry, &page)); | |
4513 | if (page) { | |
4514 | kunmap(page); | |
4515 | page_cache_release(page); | |
4516 | } | |
4517 | return res; | |
4518 | } | |
4519 | EXPORT_SYMBOL(page_readlink); | |
4520 | ||
4521 | const char *page_follow_link_light(struct dentry *dentry, void **cookie, struct nameidata *nd) | |
4522 | { | |
4523 | struct page *page = NULL; | |
4524 | char *res = page_getlink(dentry, &page); | |
4525 | if (!IS_ERR(res)) | |
4526 | *cookie = page; | |
4527 | return res; | |
4528 | } | |
4529 | EXPORT_SYMBOL(page_follow_link_light); | |
4530 | ||
4531 | void page_put_link(struct dentry *dentry, void *cookie) | |
4532 | { | |
4533 | struct page *page = cookie; | |
4534 | kunmap(page); | |
4535 | page_cache_release(page); | |
4536 | } | |
4537 | EXPORT_SYMBOL(page_put_link); | |
4538 | ||
4539 | /* | |
4540 | * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS | |
4541 | */ | |
4542 | int __page_symlink(struct inode *inode, const char *symname, int len, int nofs) | |
4543 | { | |
4544 | struct address_space *mapping = inode->i_mapping; | |
4545 | struct page *page; | |
4546 | void *fsdata; | |
4547 | int err; | |
4548 | char *kaddr; | |
4549 | unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE; | |
4550 | if (nofs) | |
4551 | flags |= AOP_FLAG_NOFS; | |
4552 | ||
4553 | retry: | |
4554 | err = pagecache_write_begin(NULL, mapping, 0, len-1, | |
4555 | flags, &page, &fsdata); | |
4556 | if (err) | |
4557 | goto fail; | |
4558 | ||
4559 | kaddr = kmap_atomic(page); | |
4560 | memcpy(kaddr, symname, len-1); | |
4561 | kunmap_atomic(kaddr); | |
4562 | ||
4563 | err = pagecache_write_end(NULL, mapping, 0, len-1, len-1, | |
4564 | page, fsdata); | |
4565 | if (err < 0) | |
4566 | goto fail; | |
4567 | if (err < len-1) | |
4568 | goto retry; | |
4569 | ||
4570 | mark_inode_dirty(inode); | |
4571 | return 0; | |
4572 | fail: | |
4573 | return err; | |
4574 | } | |
4575 | EXPORT_SYMBOL(__page_symlink); | |
4576 | ||
4577 | int page_symlink(struct inode *inode, const char *symname, int len) | |
4578 | { | |
4579 | return __page_symlink(inode, symname, len, | |
4580 | !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS)); | |
4581 | } | |
4582 | EXPORT_SYMBOL(page_symlink); | |
4583 | ||
4584 | const struct inode_operations page_symlink_inode_operations = { | |
4585 | .readlink = generic_readlink, | |
4586 | .follow_link = page_follow_link_light, | |
4587 | .put_link = page_put_link, | |
4588 | }; | |
4589 | EXPORT_SYMBOL(page_symlink_inode_operations); |