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1 /*
2 *
3 * Copyright (C) 2011 Novell Inc.
4 *
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 as published by
7 * the Free Software Foundation.
8 */
9
10 #include <linux/fs.h>
11 #include <linux/namei.h>
12 #include <linux/pagemap.h>
13 #include <linux/xattr.h>
14 #include <linux/security.h>
15 #include <linux/mount.h>
16 #include <linux/slab.h>
17 #include <linux/parser.h>
18 #include <linux/module.h>
19 #include <linux/pagemap.h>
20 #include <linux/sched.h>
21 #include <linux/statfs.h>
22 #include <linux/seq_file.h>
23 #include "overlayfs.h"
24
25 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
26 MODULE_DESCRIPTION("Overlay filesystem");
27 MODULE_LICENSE("GPL");
28
29 struct ovl_config {
30 char *lowerdir;
31 char *upperdir;
32 char *workdir;
33 bool default_permissions;
34 };
35
36 /* private information held for overlayfs's superblock */
37 struct ovl_fs {
38 struct vfsmount *upper_mnt;
39 unsigned numlower;
40 struct vfsmount **lower_mnt;
41 struct dentry *workdir;
42 long lower_namelen;
43 /* pathnames of lower and upper dirs, for show_options */
44 struct ovl_config config;
45 };
46
47 struct ovl_dir_cache;
48
49 /* private information held for every overlayfs dentry */
50 struct ovl_entry {
51 struct dentry *__upperdentry;
52 struct ovl_dir_cache *cache;
53 union {
54 struct {
55 u64 version;
56 bool opaque;
57 };
58 struct rcu_head rcu;
59 };
60 unsigned numlower;
61 struct path lowerstack[];
62 };
63
64 #define OVL_MAX_STACK 500
65
66 static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
67 {
68 return oe->numlower ? oe->lowerstack[0].dentry : NULL;
69 }
70
71 enum ovl_path_type ovl_path_type(struct dentry *dentry)
72 {
73 struct ovl_entry *oe = dentry->d_fsdata;
74 enum ovl_path_type type = 0;
75
76 if (oe->__upperdentry) {
77 type = __OVL_PATH_UPPER;
78
79 if (oe->numlower) {
80 if (S_ISDIR(dentry->d_inode->i_mode))
81 type |= __OVL_PATH_MERGE;
82 } else if (!oe->opaque) {
83 type |= __OVL_PATH_PURE;
84 }
85 } else {
86 if (oe->numlower > 1)
87 type |= __OVL_PATH_MERGE;
88 }
89 return type;
90 }
91
92 static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
93 {
94 return lockless_dereference(oe->__upperdentry);
95 }
96
97 void ovl_path_upper(struct dentry *dentry, struct path *path)
98 {
99 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
100 struct ovl_entry *oe = dentry->d_fsdata;
101
102 path->mnt = ofs->upper_mnt;
103 path->dentry = ovl_upperdentry_dereference(oe);
104 }
105
106 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
107 {
108 enum ovl_path_type type = ovl_path_type(dentry);
109
110 if (!OVL_TYPE_UPPER(type))
111 ovl_path_lower(dentry, path);
112 else
113 ovl_path_upper(dentry, path);
114
115 return type;
116 }
117
118 struct dentry *ovl_dentry_upper(struct dentry *dentry)
119 {
120 struct ovl_entry *oe = dentry->d_fsdata;
121
122 return ovl_upperdentry_dereference(oe);
123 }
124
125 struct dentry *ovl_dentry_lower(struct dentry *dentry)
126 {
127 struct ovl_entry *oe = dentry->d_fsdata;
128
129 return __ovl_dentry_lower(oe);
130 }
131
132 struct dentry *ovl_dentry_real(struct dentry *dentry)
133 {
134 struct ovl_entry *oe = dentry->d_fsdata;
135 struct dentry *realdentry;
136
137 realdentry = ovl_upperdentry_dereference(oe);
138 if (!realdentry)
139 realdentry = __ovl_dentry_lower(oe);
140
141 return realdentry;
142 }
143
144 struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper)
145 {
146 struct dentry *realdentry;
147
148 realdentry = ovl_upperdentry_dereference(oe);
149 if (realdentry) {
150 *is_upper = true;
151 } else {
152 realdentry = __ovl_dentry_lower(oe);
153 *is_upper = false;
154 }
155 return realdentry;
156 }
157
158 struct vfsmount *ovl_entry_mnt_real(struct ovl_entry *oe, struct inode *inode,
159 bool is_upper)
160 {
161 if (is_upper) {
162 struct ovl_fs *ofs = inode->i_sb->s_fs_info;
163
164 return ofs->upper_mnt;
165 } else {
166 return oe->numlower ? oe->lowerstack[0].mnt : NULL;
167 }
168 }
169
170 struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
171 {
172 struct ovl_entry *oe = dentry->d_fsdata;
173
174 return oe->cache;
175 }
176
177 bool ovl_is_default_permissions(struct inode *inode)
178 {
179 struct ovl_fs *ofs = inode->i_sb->s_fs_info;
180
181 return ofs->config.default_permissions;
182 }
183
184 void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
185 {
186 struct ovl_entry *oe = dentry->d_fsdata;
187
188 oe->cache = cache;
189 }
190
191 void ovl_path_lower(struct dentry *dentry, struct path *path)
192 {
193 struct ovl_entry *oe = dentry->d_fsdata;
194
195 *path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL };
196 }
197
198 int ovl_want_write(struct dentry *dentry)
199 {
200 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
201 return mnt_want_write(ofs->upper_mnt);
202 }
203
204 void ovl_drop_write(struct dentry *dentry)
205 {
206 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
207 mnt_drop_write(ofs->upper_mnt);
208 }
209
210 struct dentry *ovl_workdir(struct dentry *dentry)
211 {
212 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
213 return ofs->workdir;
214 }
215
216 bool ovl_dentry_is_opaque(struct dentry *dentry)
217 {
218 struct ovl_entry *oe = dentry->d_fsdata;
219 return oe->opaque;
220 }
221
222 void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
223 {
224 struct ovl_entry *oe = dentry->d_fsdata;
225 oe->opaque = opaque;
226 }
227
228 void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
229 {
230 struct ovl_entry *oe = dentry->d_fsdata;
231
232 WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
233 WARN_ON(oe->__upperdentry);
234 BUG_ON(!upperdentry->d_inode);
235 /*
236 * Make sure upperdentry is consistent before making it visible to
237 * ovl_upperdentry_dereference().
238 */
239 smp_wmb();
240 oe->__upperdentry = upperdentry;
241 }
242
243 void ovl_dentry_version_inc(struct dentry *dentry)
244 {
245 struct ovl_entry *oe = dentry->d_fsdata;
246
247 WARN_ON(!inode_is_locked(dentry->d_inode));
248 oe->version++;
249 }
250
251 u64 ovl_dentry_version_get(struct dentry *dentry)
252 {
253 struct ovl_entry *oe = dentry->d_fsdata;
254
255 WARN_ON(!inode_is_locked(dentry->d_inode));
256 return oe->version;
257 }
258
259 bool ovl_is_whiteout(struct dentry *dentry)
260 {
261 struct inode *inode = dentry->d_inode;
262
263 return inode && IS_WHITEOUT(inode);
264 }
265
266 static bool ovl_is_opaquedir(struct dentry *dentry)
267 {
268 int res;
269 char val;
270 struct inode *inode = dentry->d_inode;
271
272 if (!S_ISDIR(inode->i_mode) || !inode->i_op->getxattr)
273 return false;
274
275 res = inode->i_op->getxattr(dentry, OVL_XATTR_OPAQUE, &val, 1);
276 if (res == 1 && val == 'y')
277 return true;
278
279 return false;
280 }
281
282 static void ovl_dentry_release(struct dentry *dentry)
283 {
284 struct ovl_entry *oe = dentry->d_fsdata;
285
286 if (oe) {
287 unsigned int i;
288
289 dput(oe->__upperdentry);
290 for (i = 0; i < oe->numlower; i++)
291 dput(oe->lowerstack[i].dentry);
292 kfree_rcu(oe, rcu);
293 }
294 }
295
296 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
297 {
298 struct ovl_entry *oe = dentry->d_fsdata;
299 unsigned int i;
300 int ret = 1;
301
302 for (i = 0; i < oe->numlower; i++) {
303 struct dentry *d = oe->lowerstack[i].dentry;
304
305 if (d->d_flags & DCACHE_OP_REVALIDATE) {
306 ret = d->d_op->d_revalidate(d, flags);
307 if (ret < 0)
308 return ret;
309 if (!ret) {
310 if (!(flags & LOOKUP_RCU))
311 d_invalidate(d);
312 return -ESTALE;
313 }
314 }
315 }
316 return 1;
317 }
318
319 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
320 {
321 struct ovl_entry *oe = dentry->d_fsdata;
322 unsigned int i;
323 int ret = 1;
324
325 for (i = 0; i < oe->numlower; i++) {
326 struct dentry *d = oe->lowerstack[i].dentry;
327
328 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
329 ret = d->d_op->d_weak_revalidate(d, flags);
330 if (ret <= 0)
331 break;
332 }
333 }
334 return ret;
335 }
336
337 static const struct dentry_operations ovl_dentry_operations = {
338 .d_release = ovl_dentry_release,
339 .d_select_inode = ovl_d_select_inode,
340 };
341
342 static const struct dentry_operations ovl_reval_dentry_operations = {
343 .d_release = ovl_dentry_release,
344 .d_revalidate = ovl_dentry_revalidate,
345 .d_weak_revalidate = ovl_dentry_weak_revalidate,
346 };
347
348 static struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
349 {
350 size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
351 struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
352
353 if (oe)
354 oe->numlower = numlower;
355
356 return oe;
357 }
358
359 static bool ovl_dentry_remote(struct dentry *dentry)
360 {
361 return dentry->d_flags &
362 (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
363 }
364
365 static bool ovl_dentry_weird(struct dentry *dentry)
366 {
367 return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
368 DCACHE_MANAGE_TRANSIT |
369 DCACHE_OP_HASH |
370 DCACHE_OP_COMPARE);
371 }
372
373 static inline struct dentry *ovl_lookup_real(struct dentry *dir,
374 struct qstr *name)
375 {
376 struct dentry *dentry;
377
378 inode_lock(dir->d_inode);
379 dentry = lookup_one_len(name->name, dir, name->len);
380 inode_unlock(dir->d_inode);
381
382 if (IS_ERR(dentry)) {
383 if (PTR_ERR(dentry) == -ENOENT)
384 dentry = NULL;
385 } else if (!dentry->d_inode) {
386 dput(dentry);
387 dentry = NULL;
388 } else if (ovl_dentry_weird(dentry)) {
389 dput(dentry);
390 /* Don't support traversing automounts and other weirdness */
391 dentry = ERR_PTR(-EREMOTE);
392 }
393 return dentry;
394 }
395
396 /*
397 * Returns next layer in stack starting from top.
398 * Returns -1 if this is the last layer.
399 */
400 int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
401 {
402 struct ovl_entry *oe = dentry->d_fsdata;
403
404 BUG_ON(idx < 0);
405 if (idx == 0) {
406 ovl_path_upper(dentry, path);
407 if (path->dentry)
408 return oe->numlower ? 1 : -1;
409 idx++;
410 }
411 BUG_ON(idx > oe->numlower);
412 *path = oe->lowerstack[idx - 1];
413
414 return (idx < oe->numlower) ? idx + 1 : -1;
415 }
416
417 struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
418 unsigned int flags)
419 {
420 struct ovl_entry *oe;
421 struct ovl_entry *poe = dentry->d_parent->d_fsdata;
422 struct path *stack = NULL;
423 struct dentry *upperdir, *upperdentry = NULL;
424 unsigned int ctr = 0;
425 struct inode *inode = NULL;
426 bool upperopaque = false;
427 struct dentry *this, *prev = NULL;
428 unsigned int i;
429 int err;
430
431 upperdir = ovl_upperdentry_dereference(poe);
432 if (upperdir) {
433 this = ovl_lookup_real(upperdir, &dentry->d_name);
434 err = PTR_ERR(this);
435 if (IS_ERR(this))
436 goto out;
437
438 if (this) {
439 if (unlikely(ovl_dentry_remote(this))) {
440 dput(this);
441 err = -EREMOTE;
442 goto out;
443 }
444 if (ovl_is_whiteout(this)) {
445 dput(this);
446 this = NULL;
447 upperopaque = true;
448 } else if (poe->numlower && ovl_is_opaquedir(this)) {
449 upperopaque = true;
450 }
451 }
452 upperdentry = prev = this;
453 }
454
455 if (!upperopaque && poe->numlower) {
456 err = -ENOMEM;
457 stack = kcalloc(poe->numlower, sizeof(struct path), GFP_KERNEL);
458 if (!stack)
459 goto out_put_upper;
460 }
461
462 for (i = 0; !upperopaque && i < poe->numlower; i++) {
463 bool opaque = false;
464 struct path lowerpath = poe->lowerstack[i];
465
466 this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
467 err = PTR_ERR(this);
468 if (IS_ERR(this)) {
469 /*
470 * If it's positive, then treat ENAMETOOLONG as ENOENT.
471 */
472 if (err == -ENAMETOOLONG && (upperdentry || ctr))
473 continue;
474 goto out_put;
475 }
476 if (!this)
477 continue;
478 if (ovl_is_whiteout(this)) {
479 dput(this);
480 break;
481 }
482 /*
483 * Only makes sense to check opaque dir if this is not the
484 * lowermost layer.
485 */
486 if (i < poe->numlower - 1 && ovl_is_opaquedir(this))
487 opaque = true;
488
489 if (prev && (!S_ISDIR(prev->d_inode->i_mode) ||
490 !S_ISDIR(this->d_inode->i_mode))) {
491 /*
492 * FIXME: check for upper-opaqueness maybe better done
493 * in remove code.
494 */
495 if (prev == upperdentry)
496 upperopaque = true;
497 dput(this);
498 break;
499 }
500 /*
501 * If this is a non-directory then stop here.
502 */
503 if (!S_ISDIR(this->d_inode->i_mode))
504 opaque = true;
505
506 stack[ctr].dentry = this;
507 stack[ctr].mnt = lowerpath.mnt;
508 ctr++;
509 prev = this;
510 if (opaque)
511 break;
512 }
513
514 oe = ovl_alloc_entry(ctr);
515 err = -ENOMEM;
516 if (!oe)
517 goto out_put;
518
519 if (upperdentry || ctr) {
520 struct dentry *realdentry;
521
522 realdentry = upperdentry ? upperdentry : stack[0].dentry;
523
524 err = -ENOMEM;
525 inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode,
526 oe);
527 if (!inode)
528 goto out_free_oe;
529 ovl_copyattr(realdentry->d_inode, inode);
530 }
531
532 oe->opaque = upperopaque;
533 oe->__upperdentry = upperdentry;
534 memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
535 kfree(stack);
536 dentry->d_fsdata = oe;
537 d_add(dentry, inode);
538
539 return NULL;
540
541 out_free_oe:
542 kfree(oe);
543 out_put:
544 for (i = 0; i < ctr; i++)
545 dput(stack[i].dentry);
546 kfree(stack);
547 out_put_upper:
548 dput(upperdentry);
549 out:
550 return ERR_PTR(err);
551 }
552
553 struct file *ovl_path_open(struct path *path, int flags)
554 {
555 return dentry_open(path, flags, current_cred());
556 }
557
558 static void ovl_put_super(struct super_block *sb)
559 {
560 struct ovl_fs *ufs = sb->s_fs_info;
561 unsigned i;
562
563 dput(ufs->workdir);
564 mntput(ufs->upper_mnt);
565 for (i = 0; i < ufs->numlower; i++)
566 mntput(ufs->lower_mnt[i]);
567 kfree(ufs->lower_mnt);
568
569 kfree(ufs->config.lowerdir);
570 kfree(ufs->config.upperdir);
571 kfree(ufs->config.workdir);
572 kfree(ufs);
573 }
574
575 /**
576 * ovl_statfs
577 * @sb: The overlayfs super block
578 * @buf: The struct kstatfs to fill in with stats
579 *
580 * Get the filesystem statistics. As writes always target the upper layer
581 * filesystem pass the statfs to the upper filesystem (if it exists)
582 */
583 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
584 {
585 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
586 struct dentry *root_dentry = dentry->d_sb->s_root;
587 struct path path;
588 int err;
589
590 ovl_path_real(root_dentry, &path);
591
592 err = vfs_statfs(&path, buf);
593 if (!err) {
594 buf->f_namelen = max(buf->f_namelen, ofs->lower_namelen);
595 buf->f_type = OVERLAYFS_SUPER_MAGIC;
596 }
597
598 return err;
599 }
600
601 /**
602 * ovl_show_options
603 *
604 * Prints the mount options for a given superblock.
605 * Returns zero; does not fail.
606 */
607 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
608 {
609 struct super_block *sb = dentry->d_sb;
610 struct ovl_fs *ufs = sb->s_fs_info;
611
612 seq_show_option(m, "lowerdir", ufs->config.lowerdir);
613 if (ufs->config.upperdir) {
614 seq_show_option(m, "upperdir", ufs->config.upperdir);
615 seq_show_option(m, "workdir", ufs->config.workdir);
616 }
617 if (ufs->config.default_permissions)
618 seq_puts(m, ",default_permissions");
619 return 0;
620 }
621
622 static int ovl_remount(struct super_block *sb, int *flags, char *data)
623 {
624 struct ovl_fs *ufs = sb->s_fs_info;
625
626 if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir))
627 return -EROFS;
628
629 return 0;
630 }
631
632 static const struct super_operations ovl_super_operations = {
633 .put_super = ovl_put_super,
634 .statfs = ovl_statfs,
635 .show_options = ovl_show_options,
636 .remount_fs = ovl_remount,
637 };
638
639 enum {
640 OPT_LOWERDIR,
641 OPT_UPPERDIR,
642 OPT_WORKDIR,
643 OPT_DEFAULT_PERMISSIONS,
644 OPT_ERR,
645 };
646
647 static const match_table_t ovl_tokens = {
648 {OPT_LOWERDIR, "lowerdir=%s"},
649 {OPT_UPPERDIR, "upperdir=%s"},
650 {OPT_WORKDIR, "workdir=%s"},
651 {OPT_DEFAULT_PERMISSIONS, "default_permissions"},
652 {OPT_ERR, NULL}
653 };
654
655 static char *ovl_next_opt(char **s)
656 {
657 char *sbegin = *s;
658 char *p;
659
660 if (sbegin == NULL)
661 return NULL;
662
663 for (p = sbegin; *p; p++) {
664 if (*p == '\\') {
665 p++;
666 if (!*p)
667 break;
668 } else if (*p == ',') {
669 *p = '\0';
670 *s = p + 1;
671 return sbegin;
672 }
673 }
674 *s = NULL;
675 return sbegin;
676 }
677
678 static int ovl_parse_opt(char *opt, struct ovl_config *config)
679 {
680 char *p;
681
682 while ((p = ovl_next_opt(&opt)) != NULL) {
683 int token;
684 substring_t args[MAX_OPT_ARGS];
685
686 if (!*p)
687 continue;
688
689 token = match_token(p, ovl_tokens, args);
690 switch (token) {
691 case OPT_UPPERDIR:
692 kfree(config->upperdir);
693 config->upperdir = match_strdup(&args[0]);
694 if (!config->upperdir)
695 return -ENOMEM;
696 break;
697
698 case OPT_LOWERDIR:
699 kfree(config->lowerdir);
700 config->lowerdir = match_strdup(&args[0]);
701 if (!config->lowerdir)
702 return -ENOMEM;
703 break;
704
705 case OPT_WORKDIR:
706 kfree(config->workdir);
707 config->workdir = match_strdup(&args[0]);
708 if (!config->workdir)
709 return -ENOMEM;
710 break;
711
712 case OPT_DEFAULT_PERMISSIONS:
713 config->default_permissions = true;
714 break;
715
716 default:
717 pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
718 return -EINVAL;
719 }
720 }
721
722 /* Workdir is useless in non-upper mount */
723 if (!config->upperdir && config->workdir) {
724 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
725 config->workdir);
726 kfree(config->workdir);
727 config->workdir = NULL;
728 }
729
730 return 0;
731 }
732
733 #define OVL_WORKDIR_NAME "work"
734
735 static struct dentry *ovl_workdir_create(struct vfsmount *mnt,
736 struct dentry *dentry)
737 {
738 struct inode *dir = dentry->d_inode;
739 struct dentry *work;
740 int err;
741 bool retried = false;
742
743 err = mnt_want_write(mnt);
744 if (err)
745 return ERR_PTR(err);
746
747 inode_lock_nested(dir, I_MUTEX_PARENT);
748 retry:
749 work = lookup_one_len(OVL_WORKDIR_NAME, dentry,
750 strlen(OVL_WORKDIR_NAME));
751
752 if (!IS_ERR(work)) {
753 struct kstat stat = {
754 .mode = S_IFDIR | 0,
755 };
756
757 if (work->d_inode) {
758 err = -EEXIST;
759 if (retried)
760 goto out_dput;
761
762 retried = true;
763 ovl_cleanup(dir, work);
764 dput(work);
765 goto retry;
766 }
767
768 err = ovl_create_real(dir, work, &stat, NULL, NULL, true);
769 if (err)
770 goto out_dput;
771 }
772 out_unlock:
773 inode_unlock(dir);
774 mnt_drop_write(mnt);
775
776 return work;
777
778 out_dput:
779 dput(work);
780 work = ERR_PTR(err);
781 goto out_unlock;
782 }
783
784 static void ovl_unescape(char *s)
785 {
786 char *d = s;
787
788 for (;; s++, d++) {
789 if (*s == '\\')
790 s++;
791 *d = *s;
792 if (!*s)
793 break;
794 }
795 }
796
797 static int ovl_mount_dir_noesc(const char *name, struct path *path)
798 {
799 int err = -EINVAL;
800
801 if (!*name) {
802 pr_err("overlayfs: empty lowerdir\n");
803 goto out;
804 }
805 err = kern_path(name, LOOKUP_FOLLOW, path);
806 if (err) {
807 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
808 goto out;
809 }
810 err = -EINVAL;
811 if (ovl_dentry_weird(path->dentry)) {
812 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
813 goto out_put;
814 }
815 if (!S_ISDIR(path->dentry->d_inode->i_mode)) {
816 pr_err("overlayfs: '%s' not a directory\n", name);
817 goto out_put;
818 }
819 return 0;
820
821 out_put:
822 path_put(path);
823 out:
824 return err;
825 }
826
827 static int ovl_mount_dir(const char *name, struct path *path)
828 {
829 int err = -ENOMEM;
830 char *tmp = kstrdup(name, GFP_KERNEL);
831
832 if (tmp) {
833 ovl_unescape(tmp);
834 err = ovl_mount_dir_noesc(tmp, path);
835
836 if (!err)
837 if (ovl_dentry_remote(path->dentry)) {
838 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
839 tmp);
840 path_put(path);
841 err = -EINVAL;
842 }
843 kfree(tmp);
844 }
845 return err;
846 }
847
848 static int ovl_lower_dir(const char *name, struct path *path, long *namelen,
849 int *stack_depth, bool *remote)
850 {
851 int err;
852 struct kstatfs statfs;
853
854 err = ovl_mount_dir_noesc(name, path);
855 if (err)
856 goto out;
857
858 err = vfs_statfs(path, &statfs);
859 if (err) {
860 pr_err("overlayfs: statfs failed on '%s'\n", name);
861 goto out_put;
862 }
863 *namelen = max(*namelen, statfs.f_namelen);
864 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
865
866 if (ovl_dentry_remote(path->dentry))
867 *remote = true;
868
869 return 0;
870
871 out_put:
872 path_put(path);
873 out:
874 return err;
875 }
876
877 /* Workdir should not be subdir of upperdir and vice versa */
878 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
879 {
880 bool ok = false;
881
882 if (workdir != upperdir) {
883 ok = (lock_rename(workdir, upperdir) == NULL);
884 unlock_rename(workdir, upperdir);
885 }
886 return ok;
887 }
888
889 static unsigned int ovl_split_lowerdirs(char *str)
890 {
891 unsigned int ctr = 1;
892 char *s, *d;
893
894 for (s = d = str;; s++, d++) {
895 if (*s == '\\') {
896 s++;
897 } else if (*s == ':') {
898 *d = '\0';
899 ctr++;
900 continue;
901 }
902 *d = *s;
903 if (!*s)
904 break;
905 }
906 return ctr;
907 }
908
909 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
910 {
911 struct path upperpath = { NULL, NULL };
912 struct path workpath = { NULL, NULL };
913 struct dentry *root_dentry;
914 struct ovl_entry *oe;
915 struct ovl_fs *ufs;
916 struct path *stack = NULL;
917 char *lowertmp;
918 char *lower;
919 unsigned int numlower;
920 unsigned int stacklen = 0;
921 unsigned int i;
922 bool remote = false;
923 int err;
924
925 err = -ENOMEM;
926 ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
927 if (!ufs)
928 goto out;
929
930 err = ovl_parse_opt((char *) data, &ufs->config);
931 if (err)
932 goto out_free_config;
933
934 err = -EINVAL;
935 if (!ufs->config.lowerdir) {
936 pr_err("overlayfs: missing 'lowerdir'\n");
937 goto out_free_config;
938 }
939
940 sb->s_stack_depth = 0;
941 sb->s_maxbytes = MAX_LFS_FILESIZE;
942 if (ufs->config.upperdir) {
943 if (!ufs->config.workdir) {
944 pr_err("overlayfs: missing 'workdir'\n");
945 goto out_free_config;
946 }
947
948 err = ovl_mount_dir(ufs->config.upperdir, &upperpath);
949 if (err)
950 goto out_free_config;
951
952 /* Upper fs should not be r/o */
953 if (upperpath.mnt->mnt_sb->s_flags & MS_RDONLY) {
954 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
955 err = -EINVAL;
956 goto out_put_upperpath;
957 }
958
959 err = ovl_mount_dir(ufs->config.workdir, &workpath);
960 if (err)
961 goto out_put_upperpath;
962
963 err = -EINVAL;
964 if (upperpath.mnt != workpath.mnt) {
965 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
966 goto out_put_workpath;
967 }
968 if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry)) {
969 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
970 goto out_put_workpath;
971 }
972 sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
973 }
974 err = -ENOMEM;
975 lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL);
976 if (!lowertmp)
977 goto out_put_workpath;
978
979 err = -EINVAL;
980 stacklen = ovl_split_lowerdirs(lowertmp);
981 if (stacklen > OVL_MAX_STACK) {
982 pr_err("overlayfs: too many lower directries, limit is %d\n",
983 OVL_MAX_STACK);
984 goto out_free_lowertmp;
985 } else if (!ufs->config.upperdir && stacklen == 1) {
986 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
987 goto out_free_lowertmp;
988 }
989
990 stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
991 if (!stack)
992 goto out_free_lowertmp;
993
994 lower = lowertmp;
995 for (numlower = 0; numlower < stacklen; numlower++) {
996 err = ovl_lower_dir(lower, &stack[numlower],
997 &ufs->lower_namelen, &sb->s_stack_depth,
998 &remote);
999 if (err)
1000 goto out_put_lowerpath;
1001
1002 lower = strchr(lower, '\0') + 1;
1003 }
1004
1005 err = -EINVAL;
1006 sb->s_stack_depth++;
1007 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1008 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1009 goto out_put_lowerpath;
1010 }
1011
1012 if (ufs->config.upperdir) {
1013 ufs->upper_mnt = clone_private_mount(&upperpath);
1014 err = PTR_ERR(ufs->upper_mnt);
1015 if (IS_ERR(ufs->upper_mnt)) {
1016 pr_err("overlayfs: failed to clone upperpath\n");
1017 goto out_put_lowerpath;
1018 }
1019
1020 ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
1021 err = PTR_ERR(ufs->workdir);
1022 if (IS_ERR(ufs->workdir)) {
1023 pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
1024 ufs->config.workdir, OVL_WORKDIR_NAME, -err);
1025 sb->s_flags |= MS_RDONLY;
1026 ufs->workdir = NULL;
1027 }
1028 }
1029
1030 err = -ENOMEM;
1031 ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL);
1032 if (ufs->lower_mnt == NULL)
1033 goto out_put_workdir;
1034 for (i = 0; i < numlower; i++) {
1035 struct vfsmount *mnt = clone_private_mount(&stack[i]);
1036
1037 err = PTR_ERR(mnt);
1038 if (IS_ERR(mnt)) {
1039 pr_err("overlayfs: failed to clone lowerpath\n");
1040 goto out_put_lower_mnt;
1041 }
1042 /*
1043 * Make lower_mnt R/O. That way fchmod/fchown on lower file
1044 * will fail instead of modifying lower fs.
1045 */
1046 mnt->mnt_flags |= MNT_READONLY;
1047
1048 ufs->lower_mnt[ufs->numlower] = mnt;
1049 ufs->numlower++;
1050 }
1051
1052 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1053 if (!ufs->upper_mnt)
1054 sb->s_flags |= MS_RDONLY;
1055
1056 if (remote)
1057 sb->s_d_op = &ovl_reval_dentry_operations;
1058 else
1059 sb->s_d_op = &ovl_dentry_operations;
1060
1061 err = -ENOMEM;
1062 oe = ovl_alloc_entry(numlower);
1063 if (!oe)
1064 goto out_put_lower_mnt;
1065
1066 root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, oe));
1067 if (!root_dentry)
1068 goto out_free_oe;
1069
1070 mntput(upperpath.mnt);
1071 for (i = 0; i < numlower; i++)
1072 mntput(stack[i].mnt);
1073 path_put(&workpath);
1074 kfree(lowertmp);
1075
1076 oe->__upperdentry = upperpath.dentry;
1077 for (i = 0; i < numlower; i++) {
1078 oe->lowerstack[i].dentry = stack[i].dentry;
1079 oe->lowerstack[i].mnt = ufs->lower_mnt[i];
1080 }
1081 kfree(stack);
1082
1083 root_dentry->d_fsdata = oe;
1084
1085 ovl_copyattr(ovl_dentry_real(root_dentry)->d_inode,
1086 root_dentry->d_inode);
1087
1088 sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1089 sb->s_op = &ovl_super_operations;
1090 sb->s_root = root_dentry;
1091 sb->s_fs_info = ufs;
1092
1093 return 0;
1094
1095 out_free_oe:
1096 kfree(oe);
1097 out_put_lower_mnt:
1098 for (i = 0; i < ufs->numlower; i++)
1099 mntput(ufs->lower_mnt[i]);
1100 kfree(ufs->lower_mnt);
1101 out_put_workdir:
1102 dput(ufs->workdir);
1103 mntput(ufs->upper_mnt);
1104 out_put_lowerpath:
1105 for (i = 0; i < numlower; i++)
1106 path_put(&stack[i]);
1107 kfree(stack);
1108 out_free_lowertmp:
1109 kfree(lowertmp);
1110 out_put_workpath:
1111 path_put(&workpath);
1112 out_put_upperpath:
1113 path_put(&upperpath);
1114 out_free_config:
1115 kfree(ufs->config.lowerdir);
1116 kfree(ufs->config.upperdir);
1117 kfree(ufs->config.workdir);
1118 kfree(ufs);
1119 out:
1120 return err;
1121 }
1122
1123 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1124 const char *dev_name, void *raw_data)
1125 {
1126 return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1127 }
1128
1129 static struct file_system_type ovl_fs_type = {
1130 .owner = THIS_MODULE,
1131 .name = "overlay",
1132 .mount = ovl_mount,
1133 .kill_sb = kill_anon_super,
1134 };
1135 MODULE_ALIAS_FS("overlay");
1136
1137 static int __init ovl_init(void)
1138 {
1139 return register_filesystem(&ovl_fs_type);
1140 }
1141
1142 static void __exit ovl_exit(void)
1143 {
1144 unregister_filesystem(&ovl_fs_type);
1145 }
1146
1147 module_init(ovl_init);
1148 module_exit(ovl_exit);