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