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bus: mhi: core: Fix some error return code
[linux/fpc-iii.git] / fs / overlayfs / super.c
blob732ad5495c9219c5ef43939bd92ce9a4cf65f251
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 *
4 * Copyright (C) 2011 Novell Inc.
5 */
6
7 #include <uapi/linux/magic.h>
8 #include <linux/fs.h>
9 #include <linux/namei.h>
10 #include <linux/xattr.h>
11 #include <linux/mount.h>
12 #include <linux/parser.h>
13 #include <linux/module.h>
14 #include <linux/statfs.h>
15 #include <linux/seq_file.h>
16 #include <linux/posix_acl_xattr.h>
17 #include <linux/exportfs.h>
18 #include "overlayfs.h"
19
20 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
21 MODULE_DESCRIPTION("Overlay filesystem");
22 MODULE_LICENSE("GPL");
23
24
25 struct ovl_dir_cache;
26
27 #define OVL_MAX_STACK 500
28
29 static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
30 module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
31 MODULE_PARM_DESC(redirect_dir,
32 "Default to on or off for the redirect_dir feature");
33
34 static bool ovl_redirect_always_follow =
35 IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW);
36 module_param_named(redirect_always_follow, ovl_redirect_always_follow,
37 bool, 0644);
38 MODULE_PARM_DESC(redirect_always_follow,
39 "Follow redirects even if redirect_dir feature is turned off");
40
41 static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
42 module_param_named(index, ovl_index_def, bool, 0644);
43 MODULE_PARM_DESC(index,
44 "Default to on or off for the inodes index feature");
45
46 static bool ovl_nfs_export_def = IS_ENABLED(CONFIG_OVERLAY_FS_NFS_EXPORT);
47 module_param_named(nfs_export, ovl_nfs_export_def, bool, 0644);
48 MODULE_PARM_DESC(nfs_export,
49 "Default to on or off for the NFS export feature");
50
51 static bool ovl_xino_auto_def = IS_ENABLED(CONFIG_OVERLAY_FS_XINO_AUTO);
52 module_param_named(xino_auto, ovl_xino_auto_def, bool, 0644);
53 MODULE_PARM_DESC(xino_auto,
54 "Auto enable xino feature");
55
56 static void ovl_entry_stack_free(struct ovl_entry *oe)
57 {
58 unsigned int i;
59
60 for (i = 0; i < oe->numlower; i++)
61 dput(oe->lowerstack[i].dentry);
62 }
63
64 static bool ovl_metacopy_def = IS_ENABLED(CONFIG_OVERLAY_FS_METACOPY);
65 module_param_named(metacopy, ovl_metacopy_def, bool, 0644);
66 MODULE_PARM_DESC(metacopy,
67 "Default to on or off for the metadata only copy up feature");
68
69 static void ovl_dentry_release(struct dentry *dentry)
70 {
71 struct ovl_entry *oe = dentry->d_fsdata;
72
73 if (oe) {
74 ovl_entry_stack_free(oe);
75 kfree_rcu(oe, rcu);
76 }
77 }
78
79 static struct dentry *ovl_d_real(struct dentry *dentry,
80 const struct inode *inode)
81 {
82 struct dentry *real;
83
84 /* It's an overlay file */
85 if (inode && d_inode(dentry) == inode)
86 return dentry;
87
88 if (!d_is_reg(dentry)) {
89 if (!inode || inode == d_inode(dentry))
90 return dentry;
91 goto bug;
92 }
93
94 real = ovl_dentry_upper(dentry);
95 if (real && (inode == d_inode(real)))
96 return real;
97
98 if (real && !inode && ovl_has_upperdata(d_inode(dentry)))
99 return real;
100
101 real = ovl_dentry_lowerdata(dentry);
102 if (!real)
103 goto bug;
104
105 /* Handle recursion */
106 real = d_real(real, inode);
107
108 if (!inode || inode == d_inode(real))
109 return real;
110 bug:
111 WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
112 inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
113 return dentry;
114 }
115
116 static int ovl_revalidate_real(struct dentry *d, unsigned int flags, bool weak)
117 {
118 int ret = 1;
119
120 if (weak) {
121 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE)
122 ret = d->d_op->d_weak_revalidate(d, flags);
123 } else if (d->d_flags & DCACHE_OP_REVALIDATE) {
124 ret = d->d_op->d_revalidate(d, flags);
125 if (!ret) {
126 if (!(flags & LOOKUP_RCU))
127 d_invalidate(d);
128 ret = -ESTALE;
129 }
130 }
131 return ret;
132 }
133
134 static int ovl_dentry_revalidate_common(struct dentry *dentry,
135 unsigned int flags, bool weak)
136 {
137 struct ovl_entry *oe = dentry->d_fsdata;
138 struct dentry *upper;
139 unsigned int i;
140 int ret = 1;
141
142 upper = ovl_dentry_upper(dentry);
143 if (upper)
144 ret = ovl_revalidate_real(upper, flags, weak);
145
146 for (i = 0; ret > 0 && i < oe->numlower; i++) {
147 ret = ovl_revalidate_real(oe->lowerstack[i].dentry, flags,
148 weak);
149 }
150 return ret;
151 }
152
153 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
154 {
155 return ovl_dentry_revalidate_common(dentry, flags, false);
156 }
157
158 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
159 {
160 return ovl_dentry_revalidate_common(dentry, flags, true);
161 }
162
163 static const struct dentry_operations ovl_dentry_operations = {
164 .d_release = ovl_dentry_release,
165 .d_real = ovl_d_real,
166 .d_revalidate = ovl_dentry_revalidate,
167 .d_weak_revalidate = ovl_dentry_weak_revalidate,
168 };
169
170 static struct kmem_cache *ovl_inode_cachep;
171
172 static struct inode *ovl_alloc_inode(struct super_block *sb)
173 {
174 struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL);
175
176 if (!oi)
177 return NULL;
178
179 oi->cache = NULL;
180 oi->redirect = NULL;
181 oi->version = 0;
182 oi->flags = 0;
183 oi->__upperdentry = NULL;
184 oi->lower = NULL;
185 oi->lowerdata = NULL;
186 mutex_init(&oi->lock);
187
188 return &oi->vfs_inode;
189 }
190
191 static void ovl_free_inode(struct inode *inode)
192 {
193 struct ovl_inode *oi = OVL_I(inode);
194
195 kfree(oi->redirect);
196 mutex_destroy(&oi->lock);
197 kmem_cache_free(ovl_inode_cachep, oi);
198 }
199
200 static void ovl_destroy_inode(struct inode *inode)
201 {
202 struct ovl_inode *oi = OVL_I(inode);
203
204 dput(oi->__upperdentry);
205 iput(oi->lower);
206 if (S_ISDIR(inode->i_mode))
207 ovl_dir_cache_free(inode);
208 else
209 iput(oi->lowerdata);
210 }
211
212 static void ovl_free_fs(struct ovl_fs *ofs)
213 {
214 unsigned i;
215
216 iput(ofs->workbasedir_trap);
217 iput(ofs->indexdir_trap);
218 iput(ofs->workdir_trap);
219 iput(ofs->upperdir_trap);
220 dput(ofs->indexdir);
221 dput(ofs->workdir);
222 if (ofs->workdir_locked)
223 ovl_inuse_unlock(ofs->workbasedir);
224 dput(ofs->workbasedir);
225 if (ofs->upperdir_locked)
226 ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
227 mntput(ofs->upper_mnt);
228 for (i = 1; i < ofs->numlayer; i++) {
229 iput(ofs->layers[i].trap);
230 mntput(ofs->layers[i].mnt);
231 }
232 kfree(ofs->layers);
233 for (i = 0; i < ofs->numfs; i++)
234 free_anon_bdev(ofs->fs[i].pseudo_dev);
235 kfree(ofs->fs);
236
237 kfree(ofs->config.lowerdir);
238 kfree(ofs->config.upperdir);
239 kfree(ofs->config.workdir);
240 kfree(ofs->config.redirect_mode);
241 if (ofs->creator_cred)
242 put_cred(ofs->creator_cred);
243 kfree(ofs);
244 }
245
246 static void ovl_put_super(struct super_block *sb)
247 {
248 struct ovl_fs *ofs = sb->s_fs_info;
249
250 ovl_free_fs(ofs);
251 }
252
253 /* Sync real dirty inodes in upper filesystem (if it exists) */
254 static int ovl_sync_fs(struct super_block *sb, int wait)
255 {
256 struct ovl_fs *ofs = sb->s_fs_info;
257 struct super_block *upper_sb;
258 int ret;
259
260 if (!ofs->upper_mnt)
261 return 0;
262
263 /*
264 * If this is a sync(2) call or an emergency sync, all the super blocks
265 * will be iterated, including upper_sb, so no need to do anything.
266 *
267 * If this is a syncfs(2) call, then we do need to call
268 * sync_filesystem() on upper_sb, but enough if we do it when being
269 * called with wait == 1.
270 */
271 if (!wait)
272 return 0;
273
274 upper_sb = ofs->upper_mnt->mnt_sb;
275
276 down_read(&upper_sb->s_umount);
277 ret = sync_filesystem(upper_sb);
278 up_read(&upper_sb->s_umount);
279
280 return ret;
281 }
282
283 /**
284 * ovl_statfs
285 * @sb: The overlayfs super block
286 * @buf: The struct kstatfs to fill in with stats
287 *
288 * Get the filesystem statistics. As writes always target the upper layer
289 * filesystem pass the statfs to the upper filesystem (if it exists)
290 */
291 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
292 {
293 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
294 struct dentry *root_dentry = dentry->d_sb->s_root;
295 struct path path;
296 int err;
297
298 ovl_path_real(root_dentry, &path);
299
300 err = vfs_statfs(&path, buf);
301 if (!err) {
302 buf->f_namelen = ofs->namelen;
303 buf->f_type = OVERLAYFS_SUPER_MAGIC;
304 }
305
306 return err;
307 }
308
309 /* Will this overlay be forced to mount/remount ro? */
310 static bool ovl_force_readonly(struct ovl_fs *ofs)
311 {
312 return (!ofs->upper_mnt || !ofs->workdir);
313 }
314
315 static const char *ovl_redirect_mode_def(void)
316 {
317 return ovl_redirect_dir_def ? "on" : "off";
318 }
319
320 static const char * const ovl_xino_str[] = {
321 "off",
322 "auto",
323 "on",
324 };
325
326 static inline int ovl_xino_def(void)
327 {
328 return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
329 }
330
331 /**
332 * ovl_show_options
333 *
334 * Prints the mount options for a given superblock.
335 * Returns zero; does not fail.
336 */
337 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
338 {
339 struct super_block *sb = dentry->d_sb;
340 struct ovl_fs *ofs = sb->s_fs_info;
341
342 seq_show_option(m, "lowerdir", ofs->config.lowerdir);
343 if (ofs->config.upperdir) {
344 seq_show_option(m, "upperdir", ofs->config.upperdir);
345 seq_show_option(m, "workdir", ofs->config.workdir);
346 }
347 if (ofs->config.default_permissions)
348 seq_puts(m, ",default_permissions");
349 if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
350 seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
351 if (ofs->config.index != ovl_index_def)
352 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
353 if (ofs->config.nfs_export != ovl_nfs_export_def)
354 seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
355 "on" : "off");
356 if (ofs->config.xino != ovl_xino_def() && !ovl_same_fs(sb))
357 seq_printf(m, ",xino=%s", ovl_xino_str[ofs->config.xino]);
358 if (ofs->config.metacopy != ovl_metacopy_def)
359 seq_printf(m, ",metacopy=%s",
360 ofs->config.metacopy ? "on" : "off");
361 return 0;
362 }
363
364 static int ovl_remount(struct super_block *sb, int *flags, char *data)
365 {
366 struct ovl_fs *ofs = sb->s_fs_info;
367
368 if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
369 return -EROFS;
370
371 return 0;
372 }
373
374 static const struct super_operations ovl_super_operations = {
375 .alloc_inode = ovl_alloc_inode,
376 .free_inode = ovl_free_inode,
377 .destroy_inode = ovl_destroy_inode,
378 .drop_inode = generic_delete_inode,
379 .put_super = ovl_put_super,
380 .sync_fs = ovl_sync_fs,
381 .statfs = ovl_statfs,
382 .show_options = ovl_show_options,
383 .remount_fs = ovl_remount,
384 };
385
386 enum {
387 OPT_LOWERDIR,
388 OPT_UPPERDIR,
389 OPT_WORKDIR,
390 OPT_DEFAULT_PERMISSIONS,
391 OPT_REDIRECT_DIR,
392 OPT_INDEX_ON,
393 OPT_INDEX_OFF,
394 OPT_NFS_EXPORT_ON,
395 OPT_NFS_EXPORT_OFF,
396 OPT_XINO_ON,
397 OPT_XINO_OFF,
398 OPT_XINO_AUTO,
399 OPT_METACOPY_ON,
400 OPT_METACOPY_OFF,
401 OPT_ERR,
402 };
403
404 static const match_table_t ovl_tokens = {
405 {OPT_LOWERDIR, "lowerdir=%s"},
406 {OPT_UPPERDIR, "upperdir=%s"},
407 {OPT_WORKDIR, "workdir=%s"},
408 {OPT_DEFAULT_PERMISSIONS, "default_permissions"},
409 {OPT_REDIRECT_DIR, "redirect_dir=%s"},
410 {OPT_INDEX_ON, "index=on"},
411 {OPT_INDEX_OFF, "index=off"},
412 {OPT_NFS_EXPORT_ON, "nfs_export=on"},
413 {OPT_NFS_EXPORT_OFF, "nfs_export=off"},
414 {OPT_XINO_ON, "xino=on"},
415 {OPT_XINO_OFF, "xino=off"},
416 {OPT_XINO_AUTO, "xino=auto"},
417 {OPT_METACOPY_ON, "metacopy=on"},
418 {OPT_METACOPY_OFF, "metacopy=off"},
419 {OPT_ERR, NULL}
420 };
421
422 static char *ovl_next_opt(char **s)
423 {
424 char *sbegin = *s;
425 char *p;
426
427 if (sbegin == NULL)
428 return NULL;
429
430 for (p = sbegin; *p; p++) {
431 if (*p == '\\') {
432 p++;
433 if (!*p)
434 break;
435 } else if (*p == ',') {
436 *p = '\0';
437 *s = p + 1;
438 return sbegin;
439 }
440 }
441 *s = NULL;
442 return sbegin;
443 }
444
445 static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
446 {
447 if (strcmp(mode, "on") == 0) {
448 config->redirect_dir = true;
449 /*
450 * Does not make sense to have redirect creation without
451 * redirect following.
452 */
453 config->redirect_follow = true;
454 } else if (strcmp(mode, "follow") == 0) {
455 config->redirect_follow = true;
456 } else if (strcmp(mode, "off") == 0) {
457 if (ovl_redirect_always_follow)
458 config->redirect_follow = true;
459 } else if (strcmp(mode, "nofollow") != 0) {
460 pr_err("bad mount option \"redirect_dir=%s\"\n",
461 mode);
462 return -EINVAL;
463 }
464
465 return 0;
466 }
467
468 static int ovl_parse_opt(char *opt, struct ovl_config *config)
469 {
470 char *p;
471 int err;
472 bool metacopy_opt = false, redirect_opt = false;
473
474 config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
475 if (!config->redirect_mode)
476 return -ENOMEM;
477
478 while ((p = ovl_next_opt(&opt)) != NULL) {
479 int token;
480 substring_t args[MAX_OPT_ARGS];
481
482 if (!*p)
483 continue;
484
485 token = match_token(p, ovl_tokens, args);
486 switch (token) {
487 case OPT_UPPERDIR:
488 kfree(config->upperdir);
489 config->upperdir = match_strdup(&args[0]);
490 if (!config->upperdir)
491 return -ENOMEM;
492 break;
493
494 case OPT_LOWERDIR:
495 kfree(config->lowerdir);
496 config->lowerdir = match_strdup(&args[0]);
497 if (!config->lowerdir)
498 return -ENOMEM;
499 break;
500
501 case OPT_WORKDIR:
502 kfree(config->workdir);
503 config->workdir = match_strdup(&args[0]);
504 if (!config->workdir)
505 return -ENOMEM;
506 break;
507
508 case OPT_DEFAULT_PERMISSIONS:
509 config->default_permissions = true;
510 break;
511
512 case OPT_REDIRECT_DIR:
513 kfree(config->redirect_mode);
514 config->redirect_mode = match_strdup(&args[0]);
515 if (!config->redirect_mode)
516 return -ENOMEM;
517 redirect_opt = true;
518 break;
519
520 case OPT_INDEX_ON:
521 config->index = true;
522 break;
523
524 case OPT_INDEX_OFF:
525 config->index = false;
526 break;
527
528 case OPT_NFS_EXPORT_ON:
529 config->nfs_export = true;
530 break;
531
532 case OPT_NFS_EXPORT_OFF:
533 config->nfs_export = false;
534 break;
535
536 case OPT_XINO_ON:
537 config->xino = OVL_XINO_ON;
538 break;
539
540 case OPT_XINO_OFF:
541 config->xino = OVL_XINO_OFF;
542 break;
543
544 case OPT_XINO_AUTO:
545 config->xino = OVL_XINO_AUTO;
546 break;
547
548 case OPT_METACOPY_ON:
549 config->metacopy = true;
550 metacopy_opt = true;
551 break;
552
553 case OPT_METACOPY_OFF:
554 config->metacopy = false;
555 break;
556
557 default:
558 pr_err("unrecognized mount option \"%s\" or missing value\n",
559 p);
560 return -EINVAL;
561 }
562 }
563
564 /* Workdir is useless in non-upper mount */
565 if (!config->upperdir && config->workdir) {
566 pr_info("option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
567 config->workdir);
568 kfree(config->workdir);
569 config->workdir = NULL;
570 }
571
572 err = ovl_parse_redirect_mode(config, config->redirect_mode);
573 if (err)
574 return err;
575
576 /*
577 * This is to make the logic below simpler. It doesn't make any other
578 * difference, since config->redirect_dir is only used for upper.
579 */
580 if (!config->upperdir && config->redirect_follow)
581 config->redirect_dir = true;
582
583 /* Resolve metacopy -> redirect_dir dependency */
584 if (config->metacopy && !config->redirect_dir) {
585 if (metacopy_opt && redirect_opt) {
586 pr_err("conflicting options: metacopy=on,redirect_dir=%s\n",
587 config->redirect_mode);
588 return -EINVAL;
589 }
590 if (redirect_opt) {
591 /*
592 * There was an explicit redirect_dir=... that resulted
593 * in this conflict.
594 */
595 pr_info("disabling metacopy due to redirect_dir=%s\n",
596 config->redirect_mode);
597 config->metacopy = false;
598 } else {
599 /* Automatically enable redirect otherwise. */
600 config->redirect_follow = config->redirect_dir = true;
601 }
602 }
603
604 return 0;
605 }
606
607 #define OVL_WORKDIR_NAME "work"
608 #define OVL_INDEXDIR_NAME "index"
609
610 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
611 const char *name, bool persist)
612 {
613 struct inode *dir = ofs->workbasedir->d_inode;
614 struct vfsmount *mnt = ofs->upper_mnt;
615 struct dentry *work;
616 int err;
617 bool retried = false;
618 bool locked = false;
619
620 inode_lock_nested(dir, I_MUTEX_PARENT);
621 locked = true;
622
623 retry:
624 work = lookup_one_len(name, ofs->workbasedir, strlen(name));
625
626 if (!IS_ERR(work)) {
627 struct iattr attr = {
628 .ia_valid = ATTR_MODE,
629 .ia_mode = S_IFDIR | 0,
630 };
631
632 if (work->d_inode) {
633 err = -EEXIST;
634 if (retried)
635 goto out_dput;
636
637 if (persist)
638 goto out_unlock;
639
640 retried = true;
641 ovl_workdir_cleanup(dir, mnt, work, 0);
642 dput(work);
643 goto retry;
644 }
645
646 work = ovl_create_real(dir, work, OVL_CATTR(attr.ia_mode));
647 err = PTR_ERR(work);
648 if (IS_ERR(work))
649 goto out_err;
650
651 /*
652 * Try to remove POSIX ACL xattrs from workdir. We are good if:
653 *
654 * a) success (there was a POSIX ACL xattr and was removed)
655 * b) -ENODATA (there was no POSIX ACL xattr)
656 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
657 *
658 * There are various other error values that could effectively
659 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
660 * if the xattr name is too long), but the set of filesystems
661 * allowed as upper are limited to "normal" ones, where checking
662 * for the above two errors is sufficient.
663 */
664 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
665 if (err && err != -ENODATA && err != -EOPNOTSUPP)
666 goto out_dput;
667
668 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
669 if (err && err != -ENODATA && err != -EOPNOTSUPP)
670 goto out_dput;
671
672 /* Clear any inherited mode bits */
673 inode_lock(work->d_inode);
674 err = notify_change(work, &attr, NULL);
675 inode_unlock(work->d_inode);
676 if (err)
677 goto out_dput;
678 } else {
679 err = PTR_ERR(work);
680 goto out_err;
681 }
682 out_unlock:
683 if (locked)
684 inode_unlock(dir);
685
686 return work;
687
688 out_dput:
689 dput(work);
690 out_err:
691 pr_warn("failed to create directory %s/%s (errno: %i); mounting read-only\n",
692 ofs->config.workdir, name, -err);
693 work = NULL;
694 goto out_unlock;
695 }
696
697 static void ovl_unescape(char *s)
698 {
699 char *d = s;
700
701 for (;; s++, d++) {
702 if (*s == '\\')
703 s++;
704 *d = *s;
705 if (!*s)
706 break;
707 }
708 }
709
710 static int ovl_mount_dir_noesc(const char *name, struct path *path)
711 {
712 int err = -EINVAL;
713
714 if (!*name) {
715 pr_err("empty lowerdir\n");
716 goto out;
717 }
718 err = kern_path(name, LOOKUP_FOLLOW, path);
719 if (err) {
720 pr_err("failed to resolve '%s': %i\n", name, err);
721 goto out;
722 }
723 err = -EINVAL;
724 if (ovl_dentry_weird(path->dentry)) {
725 pr_err("filesystem on '%s' not supported\n", name);
726 goto out_put;
727 }
728 if (!d_is_dir(path->dentry)) {
729 pr_err("'%s' not a directory\n", name);
730 goto out_put;
731 }
732 return 0;
733
734 out_put:
735 path_put_init(path);
736 out:
737 return err;
738 }
739
740 static int ovl_mount_dir(const char *name, struct path *path)
741 {
742 int err = -ENOMEM;
743 char *tmp = kstrdup(name, GFP_KERNEL);
744
745 if (tmp) {
746 ovl_unescape(tmp);
747 err = ovl_mount_dir_noesc(tmp, path);
748
749 if (!err && path->dentry->d_flags & DCACHE_OP_REAL) {
750 pr_err("filesystem on '%s' not supported as upperdir\n",
751 tmp);
752 path_put_init(path);
753 err = -EINVAL;
754 }
755 kfree(tmp);
756 }
757 return err;
758 }
759
760 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
761 const char *name)
762 {
763 struct kstatfs statfs;
764 int err = vfs_statfs(path, &statfs);
765
766 if (err)
767 pr_err("statfs failed on '%s'\n", name);
768 else
769 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
770
771 return err;
772 }
773
774 static int ovl_lower_dir(const char *name, struct path *path,
775 struct ovl_fs *ofs, int *stack_depth)
776 {
777 int fh_type;
778 int err;
779
780 err = ovl_mount_dir_noesc(name, path);
781 if (err)
782 goto out;
783
784 err = ovl_check_namelen(path, ofs, name);
785 if (err)
786 goto out_put;
787
788 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
789
790 /*
791 * The inodes index feature and NFS export need to encode and decode
792 * file handles, so they require that all layers support them.
793 */
794 fh_type = ovl_can_decode_fh(path->dentry->d_sb);
795 if ((ofs->config.nfs_export ||
796 (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
797 ofs->config.index = false;
798 ofs->config.nfs_export = false;
799 pr_warn("fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
800 name);
801 }
802
803 /* Check if lower fs has 32bit inode numbers */
804 if (fh_type != FILEID_INO32_GEN)
805 ofs->xino_mode = -1;
806
807 return 0;
808
809 out_put:
810 path_put_init(path);
811 out:
812 return err;
813 }
814
815 /* Workdir should not be subdir of upperdir and vice versa */
816 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
817 {
818 bool ok = false;
819
820 if (workdir != upperdir) {
821 ok = (lock_rename(workdir, upperdir) == NULL);
822 unlock_rename(workdir, upperdir);
823 }
824 return ok;
825 }
826
827 static unsigned int ovl_split_lowerdirs(char *str)
828 {
829 unsigned int ctr = 1;
830 char *s, *d;
831
832 for (s = d = str;; s++, d++) {
833 if (*s == '\\') {
834 s++;
835 } else if (*s == ':') {
836 *d = '\0';
837 ctr++;
838 continue;
839 }
840 *d = *s;
841 if (!*s)
842 break;
843 }
844 return ctr;
845 }
846
847 static int __maybe_unused
848 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
849 struct dentry *dentry, struct inode *inode,
850 const char *name, void *buffer, size_t size)
851 {
852 return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
853 }
854
855 static int __maybe_unused
856 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
857 struct dentry *dentry, struct inode *inode,
858 const char *name, const void *value,
859 size_t size, int flags)
860 {
861 struct dentry *workdir = ovl_workdir(dentry);
862 struct inode *realinode = ovl_inode_real(inode);
863 struct posix_acl *acl = NULL;
864 int err;
865
866 /* Check that everything is OK before copy-up */
867 if (value) {
868 acl = posix_acl_from_xattr(&init_user_ns, value, size);
869 if (IS_ERR(acl))
870 return PTR_ERR(acl);
871 }
872 err = -EOPNOTSUPP;
873 if (!IS_POSIXACL(d_inode(workdir)))
874 goto out_acl_release;
875 if (!realinode->i_op->set_acl)
876 goto out_acl_release;
877 if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
878 err = acl ? -EACCES : 0;
879 goto out_acl_release;
880 }
881 err = -EPERM;
882 if (!inode_owner_or_capable(inode))
883 goto out_acl_release;
884
885 posix_acl_release(acl);
886
887 /*
888 * Check if sgid bit needs to be cleared (actual setacl operation will
889 * be done with mounter's capabilities and so that won't do it for us).
890 */
891 if (unlikely(inode->i_mode & S_ISGID) &&
892 handler->flags == ACL_TYPE_ACCESS &&
893 !in_group_p(inode->i_gid) &&
894 !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
895 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
896
897 err = ovl_setattr(dentry, &iattr);
898 if (err)
899 return err;
900 }
901
902 err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
903 if (!err)
904 ovl_copyattr(ovl_inode_real(inode), inode);
905
906 return err;
907
908 out_acl_release:
909 posix_acl_release(acl);
910 return err;
911 }
912
913 static int ovl_own_xattr_get(const struct xattr_handler *handler,
914 struct dentry *dentry, struct inode *inode,
915 const char *name, void *buffer, size_t size)
916 {
917 return -EOPNOTSUPP;
918 }
919
920 static int ovl_own_xattr_set(const struct xattr_handler *handler,
921 struct dentry *dentry, struct inode *inode,
922 const char *name, const void *value,
923 size_t size, int flags)
924 {
925 return -EOPNOTSUPP;
926 }
927
928 static int ovl_other_xattr_get(const struct xattr_handler *handler,
929 struct dentry *dentry, struct inode *inode,
930 const char *name, void *buffer, size_t size)
931 {
932 return ovl_xattr_get(dentry, inode, name, buffer, size);
933 }
934
935 static int ovl_other_xattr_set(const struct xattr_handler *handler,
936 struct dentry *dentry, struct inode *inode,
937 const char *name, const void *value,
938 size_t size, int flags)
939 {
940 return ovl_xattr_set(dentry, inode, name, value, size, flags);
941 }
942
943 static const struct xattr_handler __maybe_unused
944 ovl_posix_acl_access_xattr_handler = {
945 .name = XATTR_NAME_POSIX_ACL_ACCESS,
946 .flags = ACL_TYPE_ACCESS,
947 .get = ovl_posix_acl_xattr_get,
948 .set = ovl_posix_acl_xattr_set,
949 };
950
951 static const struct xattr_handler __maybe_unused
952 ovl_posix_acl_default_xattr_handler = {
953 .name = XATTR_NAME_POSIX_ACL_DEFAULT,
954 .flags = ACL_TYPE_DEFAULT,
955 .get = ovl_posix_acl_xattr_get,
956 .set = ovl_posix_acl_xattr_set,
957 };
958
959 static const struct xattr_handler ovl_own_xattr_handler = {
960 .prefix = OVL_XATTR_PREFIX,
961 .get = ovl_own_xattr_get,
962 .set = ovl_own_xattr_set,
963 };
964
965 static const struct xattr_handler ovl_other_xattr_handler = {
966 .prefix = "", /* catch all */
967 .get = ovl_other_xattr_get,
968 .set = ovl_other_xattr_set,
969 };
970
971 static const struct xattr_handler *ovl_xattr_handlers[] = {
972 #ifdef CONFIG_FS_POSIX_ACL
973 &ovl_posix_acl_access_xattr_handler,
974 &ovl_posix_acl_default_xattr_handler,
975 #endif
976 &ovl_own_xattr_handler,
977 &ovl_other_xattr_handler,
978 NULL
979 };
980
981 static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
982 struct inode **ptrap, const char *name)
983 {
984 struct inode *trap;
985 int err;
986
987 trap = ovl_get_trap_inode(sb, dir);
988 err = PTR_ERR_OR_ZERO(trap);
989 if (err) {
990 if (err == -ELOOP)
991 pr_err("conflicting %s path\n", name);
992 return err;
993 }
994
995 *ptrap = trap;
996 return 0;
997 }
998
999 /*
1000 * Determine how we treat concurrent use of upperdir/workdir based on the
1001 * index feature. This is papering over mount leaks of container runtimes,
1002 * for example, an old overlay mount is leaked and now its upperdir is
1003 * attempted to be used as a lower layer in a new overlay mount.
1004 */
1005 static int ovl_report_in_use(struct ovl_fs *ofs, const char *name)
1006 {
1007 if (ofs->config.index) {
1008 pr_err("%s is in-use as upperdir/workdir of another mount, mount with '-o index=off' to override exclusive upperdir protection.\n",
1009 name);
1010 return -EBUSY;
1011 } else {
1012 pr_warn("%s is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.\n",
1013 name);
1014 return 0;
1015 }
1016 }
1017
1018 static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
1019 struct path *upperpath)
1020 {
1021 struct vfsmount *upper_mnt;
1022 int err;
1023
1024 err = ovl_mount_dir(ofs->config.upperdir, upperpath);
1025 if (err)
1026 goto out;
1027
1028 /* Upper fs should not be r/o */
1029 if (sb_rdonly(upperpath->mnt->mnt_sb)) {
1030 pr_err("upper fs is r/o, try multi-lower layers mount\n");
1031 err = -EINVAL;
1032 goto out;
1033 }
1034
1035 err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
1036 if (err)
1037 goto out;
1038
1039 err = ovl_setup_trap(sb, upperpath->dentry, &ofs->upperdir_trap,
1040 "upperdir");
1041 if (err)
1042 goto out;
1043
1044 upper_mnt = clone_private_mount(upperpath);
1045 err = PTR_ERR(upper_mnt);
1046 if (IS_ERR(upper_mnt)) {
1047 pr_err("failed to clone upperpath\n");
1048 goto out;
1049 }
1050
1051 /* Don't inherit atime flags */
1052 upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
1053 ofs->upper_mnt = upper_mnt;
1054
1055 if (ovl_inuse_trylock(ofs->upper_mnt->mnt_root)) {
1056 ofs->upperdir_locked = true;
1057 } else {
1058 err = ovl_report_in_use(ofs, "upperdir");
1059 if (err)
1060 goto out;
1061 }
1062
1063 err = 0;
1064 out:
1065 return err;
1066 }
1067
1068 /*
1069 * Returns 1 if RENAME_WHITEOUT is supported, 0 if not supported and
1070 * negative values if error is encountered.
1071 */
1072 static int ovl_check_rename_whiteout(struct dentry *workdir)
1073 {
1074 struct inode *dir = d_inode(workdir);
1075 struct dentry *temp;
1076 struct dentry *dest;
1077 struct dentry *whiteout;
1078 struct name_snapshot name;
1079 int err;
1080
1081 inode_lock_nested(dir, I_MUTEX_PARENT);
1082
1083 temp = ovl_create_temp(workdir, OVL_CATTR(S_IFREG | 0));
1084 err = PTR_ERR(temp);
1085 if (IS_ERR(temp))
1086 goto out_unlock;
1087
1088 dest = ovl_lookup_temp(workdir);
1089 err = PTR_ERR(dest);
1090 if (IS_ERR(dest)) {
1091 dput(temp);
1092 goto out_unlock;
1093 }
1094
1095 /* Name is inline and stable - using snapshot as a copy helper */
1096 take_dentry_name_snapshot(&name, temp);
1097 err = ovl_do_rename(dir, temp, dir, dest, RENAME_WHITEOUT);
1098 if (err) {
1099 if (err == -EINVAL)
1100 err = 0;
1101 goto cleanup_temp;
1102 }
1103
1104 whiteout = lookup_one_len(name.name.name, workdir, name.name.len);
1105 err = PTR_ERR(whiteout);
1106 if (IS_ERR(whiteout))
1107 goto cleanup_temp;
1108
1109 err = ovl_is_whiteout(whiteout);
1110
1111 /* Best effort cleanup of whiteout and temp file */
1112 if (err)
1113 ovl_cleanup(dir, whiteout);
1114 dput(whiteout);
1115
1116 cleanup_temp:
1117 ovl_cleanup(dir, temp);
1118 release_dentry_name_snapshot(&name);
1119 dput(temp);
1120 dput(dest);
1121
1122 out_unlock:
1123 inode_unlock(dir);
1124
1125 return err;
1126 }
1127
1128 static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
1129 struct path *workpath)
1130 {
1131 struct vfsmount *mnt = ofs->upper_mnt;
1132 struct dentry *temp;
1133 bool rename_whiteout;
1134 bool d_type;
1135 int fh_type;
1136 int err;
1137
1138 err = mnt_want_write(mnt);
1139 if (err)
1140 return err;
1141
1142 ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
1143 if (!ofs->workdir)
1144 goto out;
1145
1146 err = ovl_setup_trap(sb, ofs->workdir, &ofs->workdir_trap, "workdir");
1147 if (err)
1148 goto out;
1149
1150 /*
1151 * Upper should support d_type, else whiteouts are visible. Given
1152 * workdir and upper are on same fs, we can do iterate_dir() on
1153 * workdir. This check requires successful creation of workdir in
1154 * previous step.
1155 */
1156 err = ovl_check_d_type_supported(workpath);
1157 if (err < 0)
1158 goto out;
1159
1160 d_type = err;
1161 if (!d_type)
1162 pr_warn("upper fs needs to support d_type.\n");
1163
1164 /* Check if upper/work fs supports O_TMPFILE */
1165 temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
1166 ofs->tmpfile = !IS_ERR(temp);
1167 if (ofs->tmpfile)
1168 dput(temp);
1169 else
1170 pr_warn("upper fs does not support tmpfile.\n");
1171
1172
1173 /* Check if upper/work fs supports RENAME_WHITEOUT */
1174 err = ovl_check_rename_whiteout(ofs->workdir);
1175 if (err < 0)
1176 goto out;
1177
1178 rename_whiteout = err;
1179 if (!rename_whiteout)
1180 pr_warn("upper fs does not support RENAME_WHITEOUT.\n");
1181
1182 /*
1183 * Check if upper/work fs supports trusted.overlay.* xattr
1184 */
1185 err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
1186 if (err) {
1187 ofs->noxattr = true;
1188 ofs->config.index = false;
1189 ofs->config.metacopy = false;
1190 pr_warn("upper fs does not support xattr, falling back to index=off and metacopy=off.\n");
1191 err = 0;
1192 } else {
1193 vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
1194 }
1195
1196 /*
1197 * We allowed sub-optimal upper fs configuration and don't want to break
1198 * users over kernel upgrade, but we never allowed remote upper fs, so
1199 * we can enforce strict requirements for remote upper fs.
1200 */
1201 if (ovl_dentry_remote(ofs->workdir) &&
1202 (!d_type || !rename_whiteout || ofs->noxattr)) {
1203 pr_err("upper fs missing required features.\n");
1204 err = -EINVAL;
1205 goto out;
1206 }
1207
1208 /* Check if upper/work fs supports file handles */
1209 fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
1210 if (ofs->config.index && !fh_type) {
1211 ofs->config.index = false;
1212 pr_warn("upper fs does not support file handles, falling back to index=off.\n");
1213 }
1214
1215 /* Check if upper fs has 32bit inode numbers */
1216 if (fh_type != FILEID_INO32_GEN)
1217 ofs->xino_mode = -1;
1218
1219 /* NFS export of r/w mount depends on index */
1220 if (ofs->config.nfs_export && !ofs->config.index) {
1221 pr_warn("NFS export requires \"index=on\", falling back to nfs_export=off.\n");
1222 ofs->config.nfs_export = false;
1223 }
1224 out:
1225 mnt_drop_write(mnt);
1226 return err;
1227 }
1228
1229 static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
1230 struct path *upperpath)
1231 {
1232 int err;
1233 struct path workpath = { };
1234
1235 err = ovl_mount_dir(ofs->config.workdir, &workpath);
1236 if (err)
1237 goto out;
1238
1239 err = -EINVAL;
1240 if (upperpath->mnt != workpath.mnt) {
1241 pr_err("workdir and upperdir must reside under the same mount\n");
1242 goto out;
1243 }
1244 if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
1245 pr_err("workdir and upperdir must be separate subtrees\n");
1246 goto out;
1247 }
1248
1249 ofs->workbasedir = dget(workpath.dentry);
1250
1251 if (ovl_inuse_trylock(ofs->workbasedir)) {
1252 ofs->workdir_locked = true;
1253 } else {
1254 err = ovl_report_in_use(ofs, "workdir");
1255 if (err)
1256 goto out;
1257 }
1258
1259 err = ovl_setup_trap(sb, ofs->workbasedir, &ofs->workbasedir_trap,
1260 "workdir");
1261 if (err)
1262 goto out;
1263
1264 err = ovl_make_workdir(sb, ofs, &workpath);
1265
1266 out:
1267 path_put(&workpath);
1268
1269 return err;
1270 }
1271
1272 static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
1273 struct ovl_entry *oe, struct path *upperpath)
1274 {
1275 struct vfsmount *mnt = ofs->upper_mnt;
1276 int err;
1277
1278 err = mnt_want_write(mnt);
1279 if (err)
1280 return err;
1281
1282 /* Verify lower root is upper root origin */
1283 err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
1284 true);
1285 if (err) {
1286 pr_err("failed to verify upper root origin\n");
1287 goto out;
1288 }
1289
1290 ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
1291 if (ofs->indexdir) {
1292 err = ovl_setup_trap(sb, ofs->indexdir, &ofs->indexdir_trap,
1293 "indexdir");
1294 if (err)
1295 goto out;
1296
1297 /*
1298 * Verify upper root is exclusively associated with index dir.
1299 * Older kernels stored upper fh in "trusted.overlay.origin"
1300 * xattr. If that xattr exists, verify that it is a match to
1301 * upper dir file handle. In any case, verify or set xattr
1302 * "trusted.overlay.upper" to indicate that index may have
1303 * directory entries.
1304 */
1305 if (ovl_check_origin_xattr(ofs->indexdir)) {
1306 err = ovl_verify_set_fh(ofs->indexdir, OVL_XATTR_ORIGIN,
1307 upperpath->dentry, true, false);
1308 if (err)
1309 pr_err("failed to verify index dir 'origin' xattr\n");
1310 }
1311 err = ovl_verify_upper(ofs->indexdir, upperpath->dentry, true);
1312 if (err)
1313 pr_err("failed to verify index dir 'upper' xattr\n");
1314
1315 /* Cleanup bad/stale/orphan index entries */
1316 if (!err)
1317 err = ovl_indexdir_cleanup(ofs);
1318 }
1319 if (err || !ofs->indexdir)
1320 pr_warn("try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1321
1322 out:
1323 mnt_drop_write(mnt);
1324 return err;
1325 }
1326
1327 static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
1328 {
1329 unsigned int i;
1330
1331 if (!ofs->config.nfs_export && !ofs->upper_mnt)
1332 return true;
1333
1334 for (i = 0; i < ofs->numfs; i++) {
1335 /*
1336 * We use uuid to associate an overlay lower file handle with a
1337 * lower layer, so we can accept lower fs with null uuid as long
1338 * as all lower layers with null uuid are on the same fs.
1339 * if we detect multiple lower fs with the same uuid, we
1340 * disable lower file handle decoding on all of them.
1341 */
1342 if (ofs->fs[i].is_lower &&
1343 uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) {
1344 ofs->fs[i].bad_uuid = true;
1345 return false;
1346 }
1347 }
1348 return true;
1349 }
1350
1351 /* Get a unique fsid for the layer */
1352 static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
1353 {
1354 struct super_block *sb = path->mnt->mnt_sb;
1355 unsigned int i;
1356 dev_t dev;
1357 int err;
1358 bool bad_uuid = false;
1359
1360 for (i = 0; i < ofs->numfs; i++) {
1361 if (ofs->fs[i].sb == sb)
1362 return i;
1363 }
1364
1365 if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) {
1366 bad_uuid = true;
1367 if (ofs->config.index || ofs->config.nfs_export) {
1368 ofs->config.index = false;
1369 ofs->config.nfs_export = false;
1370 pr_warn("%s uuid detected in lower fs '%pd2', falling back to index=off,nfs_export=off.\n",
1371 uuid_is_null(&sb->s_uuid) ? "null" :
1372 "conflicting",
1373 path->dentry);
1374 }
1375 }
1376
1377 err = get_anon_bdev(&dev);
1378 if (err) {
1379 pr_err("failed to get anonymous bdev for lowerpath\n");
1380 return err;
1381 }
1382
1383 ofs->fs[ofs->numfs].sb = sb;
1384 ofs->fs[ofs->numfs].pseudo_dev = dev;
1385 ofs->fs[ofs->numfs].bad_uuid = bad_uuid;
1386
1387 return ofs->numfs++;
1388 }
1389
1390 static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
1391 struct path *stack, unsigned int numlower)
1392 {
1393 int err;
1394 unsigned int i;
1395 struct ovl_layer *layers;
1396
1397 err = -ENOMEM;
1398 layers = kcalloc(numlower + 1, sizeof(struct ovl_layer), GFP_KERNEL);
1399 if (!layers)
1400 goto out;
1401 ofs->layers = layers;
1402
1403 ofs->fs = kcalloc(numlower + 1, sizeof(struct ovl_sb), GFP_KERNEL);
1404 if (ofs->fs == NULL)
1405 goto out;
1406
1407 /* idx/fsid 0 are reserved for upper fs even with lower only overlay */
1408 ofs->numfs++;
1409
1410 layers[0].mnt = ofs->upper_mnt;
1411 layers[0].idx = 0;
1412 layers[0].fsid = 0;
1413 ofs->numlayer = 1;
1414
1415 /*
1416 * All lower layers that share the same fs as upper layer, use the same
1417 * pseudo_dev as upper layer. Allocate fs[0].pseudo_dev even for lower
1418 * only overlay to simplify ovl_fs_free().
1419 * is_lower will be set if upper fs is shared with a lower layer.
1420 */
1421 err = get_anon_bdev(&ofs->fs[0].pseudo_dev);
1422 if (err) {
1423 pr_err("failed to get anonymous bdev for upper fs\n");
1424 goto out;
1425 }
1426
1427 if (ofs->upper_mnt) {
1428 ofs->fs[0].sb = ofs->upper_mnt->mnt_sb;
1429 ofs->fs[0].is_lower = false;
1430 }
1431
1432 for (i = 0; i < numlower; i++) {
1433 struct vfsmount *mnt;
1434 struct inode *trap;
1435 int fsid;
1436
1437 err = fsid = ovl_get_fsid(ofs, &stack[i]);
1438 if (err < 0)
1439 goto out;
1440
1441 err = ovl_setup_trap(sb, stack[i].dentry, &trap, "lowerdir");
1442 if (err)
1443 goto out;
1444
1445 if (ovl_is_inuse(stack[i].dentry)) {
1446 err = ovl_report_in_use(ofs, "lowerdir");
1447 if (err)
1448 goto out;
1449 }
1450
1451 mnt = clone_private_mount(&stack[i]);
1452 err = PTR_ERR(mnt);
1453 if (IS_ERR(mnt)) {
1454 pr_err("failed to clone lowerpath\n");
1455 iput(trap);
1456 goto out;
1457 }
1458
1459 /*
1460 * Make lower layers R/O. That way fchmod/fchown on lower file
1461 * will fail instead of modifying lower fs.
1462 */
1463 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1464
1465 layers[ofs->numlayer].trap = trap;
1466 layers[ofs->numlayer].mnt = mnt;
1467 layers[ofs->numlayer].idx = ofs->numlayer;
1468 layers[ofs->numlayer].fsid = fsid;
1469 layers[ofs->numlayer].fs = &ofs->fs[fsid];
1470 ofs->numlayer++;
1471 ofs->fs[fsid].is_lower = true;
1472 }
1473
1474 /*
1475 * When all layers on same fs, overlay can use real inode numbers.
1476 * With mount option "xino=<on|auto>", mounter declares that there are
1477 * enough free high bits in underlying fs to hold the unique fsid.
1478 * If overlayfs does encounter underlying inodes using the high xino
1479 * bits reserved for fsid, it emits a warning and uses the original
1480 * inode number or a non persistent inode number allocated from a
1481 * dedicated range.
1482 */
1483 if (ofs->numfs - !ofs->upper_mnt == 1) {
1484 if (ofs->config.xino == OVL_XINO_ON)
1485 pr_info("\"xino=on\" is useless with all layers on same fs, ignore.\n");
1486 ofs->xino_mode = 0;
1487 } else if (ofs->config.xino == OVL_XINO_OFF) {
1488 ofs->xino_mode = -1;
1489 } else if (ofs->xino_mode < 0) {
1490 /*
1491 * This is a roundup of number of bits needed for encoding
1492 * fsid, where fsid 0 is reserved for upper fs (even with
1493 * lower only overlay) +1 extra bit is reserved for the non
1494 * persistent inode number range that is used for resolving
1495 * xino lower bits overflow.
1496 */
1497 BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 30);
1498 ofs->xino_mode = ilog2(ofs->numfs - 1) + 2;
1499 }
1500
1501 if (ofs->xino_mode > 0) {
1502 pr_info("\"xino\" feature enabled using %d upper inode bits.\n",
1503 ofs->xino_mode);
1504 }
1505
1506 err = 0;
1507 out:
1508 return err;
1509 }
1510
1511 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1512 struct ovl_fs *ofs)
1513 {
1514 int err;
1515 char *lowertmp, *lower;
1516 struct path *stack = NULL;
1517 unsigned int stacklen, numlower = 0, i;
1518 struct ovl_entry *oe;
1519
1520 err = -ENOMEM;
1521 lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
1522 if (!lowertmp)
1523 goto out_err;
1524
1525 err = -EINVAL;
1526 stacklen = ovl_split_lowerdirs(lowertmp);
1527 if (stacklen > OVL_MAX_STACK) {
1528 pr_err("too many lower directories, limit is %d\n",
1529 OVL_MAX_STACK);
1530 goto out_err;
1531 } else if (!ofs->config.upperdir && stacklen == 1) {
1532 pr_err("at least 2 lowerdir are needed while upperdir nonexistent\n");
1533 goto out_err;
1534 } else if (!ofs->config.upperdir && ofs->config.nfs_export &&
1535 ofs->config.redirect_follow) {
1536 pr_warn("NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
1537 ofs->config.nfs_export = false;
1538 }
1539
1540 err = -ENOMEM;
1541 stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
1542 if (!stack)
1543 goto out_err;
1544
1545 err = -EINVAL;
1546 lower = lowertmp;
1547 for (numlower = 0; numlower < stacklen; numlower++) {
1548 err = ovl_lower_dir(lower, &stack[numlower], ofs,
1549 &sb->s_stack_depth);
1550 if (err)
1551 goto out_err;
1552
1553 lower = strchr(lower, '\0') + 1;
1554 }
1555
1556 err = -EINVAL;
1557 sb->s_stack_depth++;
1558 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1559 pr_err("maximum fs stacking depth exceeded\n");
1560 goto out_err;
1561 }
1562
1563 err = ovl_get_layers(sb, ofs, stack, numlower);
1564 if (err)
1565 goto out_err;
1566
1567 err = -ENOMEM;
1568 oe = ovl_alloc_entry(numlower);
1569 if (!oe)
1570 goto out_err;
1571
1572 for (i = 0; i < numlower; i++) {
1573 oe->lowerstack[i].dentry = dget(stack[i].dentry);
1574 oe->lowerstack[i].layer = &ofs->layers[i+1];
1575 }
1576
1577 out:
1578 for (i = 0; i < numlower; i++)
1579 path_put(&stack[i]);
1580 kfree(stack);
1581 kfree(lowertmp);
1582
1583 return oe;
1584
1585 out_err:
1586 oe = ERR_PTR(err);
1587 goto out;
1588 }
1589
1590 /*
1591 * Check if this layer root is a descendant of:
1592 * - another layer of this overlayfs instance
1593 * - upper/work dir of any overlayfs instance
1594 */
1595 static int ovl_check_layer(struct super_block *sb, struct ovl_fs *ofs,
1596 struct dentry *dentry, const char *name)
1597 {
1598 struct dentry *next = dentry, *parent;
1599 int err = 0;
1600
1601 if (!dentry)
1602 return 0;
1603
1604 parent = dget_parent(next);
1605
1606 /* Walk back ancestors to root (inclusive) looking for traps */
1607 while (!err && parent != next) {
1608 if (ovl_lookup_trap_inode(sb, parent)) {
1609 err = -ELOOP;
1610 pr_err("overlapping %s path\n", name);
1611 } else if (ovl_is_inuse(parent)) {
1612 err = ovl_report_in_use(ofs, name);
1613 }
1614 next = parent;
1615 parent = dget_parent(next);
1616 dput(next);
1617 }
1618
1619 dput(parent);
1620
1621 return err;
1622 }
1623
1624 /*
1625 * Check if any of the layers or work dirs overlap.
1626 */
1627 static int ovl_check_overlapping_layers(struct super_block *sb,
1628 struct ovl_fs *ofs)
1629 {
1630 int i, err;
1631
1632 if (ofs->upper_mnt) {
1633 err = ovl_check_layer(sb, ofs, ofs->upper_mnt->mnt_root,
1634 "upperdir");
1635 if (err)
1636 return err;
1637
1638 /*
1639 * Checking workbasedir avoids hitting ovl_is_inuse(parent) of
1640 * this instance and covers overlapping work and index dirs,
1641 * unless work or index dir have been moved since created inside
1642 * workbasedir. In that case, we already have their traps in
1643 * inode cache and we will catch that case on lookup.
1644 */
1645 err = ovl_check_layer(sb, ofs, ofs->workbasedir, "workdir");
1646 if (err)
1647 return err;
1648 }
1649
1650 for (i = 1; i < ofs->numlayer; i++) {
1651 err = ovl_check_layer(sb, ofs,
1652 ofs->layers[i].mnt->mnt_root,
1653 "lowerdir");
1654 if (err)
1655 return err;
1656 }
1657
1658 return 0;
1659 }
1660
1661 static struct dentry *ovl_get_root(struct super_block *sb,
1662 struct dentry *upperdentry,
1663 struct ovl_entry *oe)
1664 {
1665 struct dentry *root;
1666 struct ovl_path *lowerpath = &oe->lowerstack[0];
1667 unsigned long ino = d_inode(lowerpath->dentry)->i_ino;
1668 int fsid = lowerpath->layer->fsid;
1669 struct ovl_inode_params oip = {
1670 .upperdentry = upperdentry,
1671 .lowerpath = lowerpath,
1672 };
1673
1674 root = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1675 if (!root)
1676 return NULL;
1677
1678 root->d_fsdata = oe;
1679
1680 if (upperdentry) {
1681 /* Root inode uses upper st_ino/i_ino */
1682 ino = d_inode(upperdentry)->i_ino;
1683 fsid = 0;
1684 ovl_dentry_set_upper_alias(root);
1685 if (ovl_is_impuredir(upperdentry))
1686 ovl_set_flag(OVL_IMPURE, d_inode(root));
1687 }
1688
1689 /* Root is always merge -> can have whiteouts */
1690 ovl_set_flag(OVL_WHITEOUTS, d_inode(root));
1691 ovl_dentry_set_flag(OVL_E_CONNECTED, root);
1692 ovl_set_upperdata(d_inode(root));
1693 ovl_inode_init(d_inode(root), &oip, ino, fsid);
1694 ovl_dentry_update_reval(root, upperdentry, DCACHE_OP_WEAK_REVALIDATE);
1695
1696 return root;
1697 }
1698
1699 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
1700 {
1701 struct path upperpath = { };
1702 struct dentry *root_dentry;
1703 struct ovl_entry *oe;
1704 struct ovl_fs *ofs;
1705 struct cred *cred;
1706 int err;
1707
1708 sb->s_d_op = &ovl_dentry_operations;
1709
1710 err = -ENOMEM;
1711 ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
1712 if (!ofs)
1713 goto out;
1714
1715 ofs->creator_cred = cred = prepare_creds();
1716 if (!cred)
1717 goto out_err;
1718
1719 ofs->config.index = ovl_index_def;
1720 ofs->config.nfs_export = ovl_nfs_export_def;
1721 ofs->config.xino = ovl_xino_def();
1722 ofs->config.metacopy = ovl_metacopy_def;
1723 err = ovl_parse_opt((char *) data, &ofs->config);
1724 if (err)
1725 goto out_err;
1726
1727 err = -EINVAL;
1728 if (!ofs->config.lowerdir) {
1729 if (!silent)
1730 pr_err("missing 'lowerdir'\n");
1731 goto out_err;
1732 }
1733
1734 sb->s_stack_depth = 0;
1735 sb->s_maxbytes = MAX_LFS_FILESIZE;
1736 atomic_long_set(&ofs->last_ino, 1);
1737 /* Assume underlaying fs uses 32bit inodes unless proven otherwise */
1738 if (ofs->config.xino != OVL_XINO_OFF) {
1739 ofs->xino_mode = BITS_PER_LONG - 32;
1740 if (!ofs->xino_mode) {
1741 pr_warn("xino not supported on 32bit kernel, falling back to xino=off.\n");
1742 ofs->config.xino = OVL_XINO_OFF;
1743 }
1744 }
1745
1746 /* alloc/destroy_inode needed for setting up traps in inode cache */
1747 sb->s_op = &ovl_super_operations;
1748
1749 if (ofs->config.upperdir) {
1750 if (!ofs->config.workdir) {
1751 pr_err("missing 'workdir'\n");
1752 goto out_err;
1753 }
1754
1755 err = ovl_get_upper(sb, ofs, &upperpath);
1756 if (err)
1757 goto out_err;
1758
1759 err = ovl_get_workdir(sb, ofs, &upperpath);
1760 if (err)
1761 goto out_err;
1762
1763 if (!ofs->workdir)
1764 sb->s_flags |= SB_RDONLY;
1765
1766 sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
1767 sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
1768
1769 }
1770 oe = ovl_get_lowerstack(sb, ofs);
1771 err = PTR_ERR(oe);
1772 if (IS_ERR(oe))
1773 goto out_err;
1774
1775 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1776 if (!ofs->upper_mnt)
1777 sb->s_flags |= SB_RDONLY;
1778
1779 if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
1780 err = ovl_get_indexdir(sb, ofs, oe, &upperpath);
1781 if (err)
1782 goto out_free_oe;
1783
1784 /* Force r/o mount with no index dir */
1785 if (!ofs->indexdir) {
1786 dput(ofs->workdir);
1787 ofs->workdir = NULL;
1788 sb->s_flags |= SB_RDONLY;
1789 }
1790
1791 }
1792
1793 err = ovl_check_overlapping_layers(sb, ofs);
1794 if (err)
1795 goto out_free_oe;
1796
1797 /* Show index=off in /proc/mounts for forced r/o mount */
1798 if (!ofs->indexdir) {
1799 ofs->config.index = false;
1800 if (ofs->upper_mnt && ofs->config.nfs_export) {
1801 pr_warn("NFS export requires an index dir, falling back to nfs_export=off.\n");
1802 ofs->config.nfs_export = false;
1803 }
1804 }
1805
1806 if (ofs->config.metacopy && ofs->config.nfs_export) {
1807 pr_warn("NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
1808 ofs->config.nfs_export = false;
1809 }
1810
1811 if (ofs->config.nfs_export)
1812 sb->s_export_op = &ovl_export_operations;
1813
1814 /* Never override disk quota limits or use reserved space */
1815 cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1816
1817 sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1818 sb->s_xattr = ovl_xattr_handlers;
1819 sb->s_fs_info = ofs;
1820 sb->s_flags |= SB_POSIXACL;
1821
1822 err = -ENOMEM;
1823 root_dentry = ovl_get_root(sb, upperpath.dentry, oe);
1824 if (!root_dentry)
1825 goto out_free_oe;
1826
1827 mntput(upperpath.mnt);
1828
1829 sb->s_root = root_dentry;
1830
1831 return 0;
1832
1833 out_free_oe:
1834 ovl_entry_stack_free(oe);
1835 kfree(oe);
1836 out_err:
1837 path_put(&upperpath);
1838 ovl_free_fs(ofs);
1839 out:
1840 return err;
1841 }
1842
1843 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1844 const char *dev_name, void *raw_data)
1845 {
1846 return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1847 }
1848
1849 static struct file_system_type ovl_fs_type = {
1850 .owner = THIS_MODULE,
1851 .name = "overlay",
1852 .mount = ovl_mount,
1853 .kill_sb = kill_anon_super,
1854 };
1855 MODULE_ALIAS_FS("overlay");
1856
1857 static void ovl_inode_init_once(void *foo)
1858 {
1859 struct ovl_inode *oi = foo;
1860
1861 inode_init_once(&oi->vfs_inode);
1862 }
1863
1864 static int __init ovl_init(void)
1865 {
1866 int err;
1867
1868 ovl_inode_cachep = kmem_cache_create("ovl_inode",
1869 sizeof(struct ovl_inode), 0,
1870 (SLAB_RECLAIM_ACCOUNT|
1871 SLAB_MEM_SPREAD|SLAB_ACCOUNT),
1872 ovl_inode_init_once);
1873 if (ovl_inode_cachep == NULL)
1874 return -ENOMEM;
1875
1876 err = ovl_aio_request_cache_init();
1877 if (!err) {
1878 err = register_filesystem(&ovl_fs_type);
1879 if (!err)
1880 return 0;
1881
1882 ovl_aio_request_cache_destroy();
1883 }
1884 kmem_cache_destroy(ovl_inode_cachep);
1885
1886 return err;
1887 }
1888
1889 static void __exit ovl_exit(void)
1890 {
1891 unregister_filesystem(&ovl_fs_type);
1892
1893 /*
1894 * Make sure all delayed rcu free inodes are flushed before we
1895 * destroy cache.
1896 */
1897 rcu_barrier();
1898 kmem_cache_destroy(ovl_inode_cachep);
1899 ovl_aio_request_cache_destroy();
1900 }
1901
1902 module_init(ovl_init);
1903 module_exit(ovl_exit);
Linux with added FPC-III support