Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszer...
[sfrench/cifs-2.6.git] / fs / overlayfs / super.c
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 "overlayfs.h"
21
22 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
23 MODULE_DESCRIPTION("Overlay filesystem");
24 MODULE_LICENSE("GPL");
25
26
27 struct ovl_dir_cache;
28
29 #define OVL_MAX_STACK 500
30
31 static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
32 module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
33 MODULE_PARM_DESC(ovl_redirect_dir_def,
34                  "Default to on or off for the redirect_dir feature");
35
36 static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
37 module_param_named(index, ovl_index_def, bool, 0644);
38 MODULE_PARM_DESC(ovl_index_def,
39                  "Default to on or off for the inodes index feature");
40
41 static void ovl_entry_stack_free(struct ovl_entry *oe)
42 {
43         unsigned int i;
44
45         for (i = 0; i < oe->numlower; i++)
46                 dput(oe->lowerstack[i].dentry);
47 }
48
49 static void ovl_dentry_release(struct dentry *dentry)
50 {
51         struct ovl_entry *oe = dentry->d_fsdata;
52
53         if (oe) {
54                 ovl_entry_stack_free(oe);
55                 kfree_rcu(oe, rcu);
56         }
57 }
58
59 static int ovl_check_append_only(struct inode *inode, int flag)
60 {
61         /*
62          * This test was moot in vfs may_open() because overlay inode does
63          * not have the S_APPEND flag, so re-check on real upper inode
64          */
65         if (IS_APPEND(inode)) {
66                 if  ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
67                         return -EPERM;
68                 if (flag & O_TRUNC)
69                         return -EPERM;
70         }
71
72         return 0;
73 }
74
75 static struct dentry *ovl_d_real(struct dentry *dentry,
76                                  const struct inode *inode,
77                                  unsigned int open_flags, unsigned int flags)
78 {
79         struct dentry *real;
80         int err;
81
82         if (flags & D_REAL_UPPER)
83                 return ovl_dentry_upper(dentry);
84
85         if (!d_is_reg(dentry)) {
86                 if (!inode || inode == d_inode(dentry))
87                         return dentry;
88                 goto bug;
89         }
90
91         if (open_flags) {
92                 err = ovl_open_maybe_copy_up(dentry, open_flags);
93                 if (err)
94                         return ERR_PTR(err);
95         }
96
97         real = ovl_dentry_upper(dentry);
98         if (real && (!inode || inode == d_inode(real))) {
99                 if (!inode) {
100                         err = ovl_check_append_only(d_inode(real), open_flags);
101                         if (err)
102                                 return ERR_PTR(err);
103                 }
104                 return real;
105         }
106
107         real = ovl_dentry_lower(dentry);
108         if (!real)
109                 goto bug;
110
111         /* Handle recursion */
112         real = d_real(real, inode, open_flags, 0);
113
114         if (!inode || inode == d_inode(real))
115                 return real;
116 bug:
117         WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
118              inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
119         return dentry;
120 }
121
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
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
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         mutex_init(&oi->lock);
191
192         return &oi->vfs_inode;
193 }
194
195 static void ovl_i_callback(struct rcu_head *head)
196 {
197         struct inode *inode = container_of(head, struct inode, i_rcu);
198
199         kmem_cache_free(ovl_inode_cachep, OVL_I(inode));
200 }
201
202 static void ovl_destroy_inode(struct inode *inode)
203 {
204         struct ovl_inode *oi = OVL_I(inode);
205
206         dput(oi->__upperdentry);
207         kfree(oi->redirect);
208         ovl_dir_cache_free(inode);
209         mutex_destroy(&oi->lock);
210
211         call_rcu(&inode->i_rcu, ovl_i_callback);
212 }
213
214 static void ovl_free_fs(struct ovl_fs *ofs)
215 {
216         unsigned i;
217
218         dput(ofs->indexdir);
219         dput(ofs->workdir);
220         if (ofs->workdir_locked)
221                 ovl_inuse_unlock(ofs->workbasedir);
222         dput(ofs->workbasedir);
223         if (ofs->upperdir_locked)
224                 ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
225         mntput(ofs->upper_mnt);
226         for (i = 0; i < ofs->numlower; i++) {
227                 mntput(ofs->lower_layers[i].mnt);
228                 free_anon_bdev(ofs->lower_layers[i].pseudo_dev);
229         }
230         kfree(ofs->lower_layers);
231
232         kfree(ofs->config.lowerdir);
233         kfree(ofs->config.upperdir);
234         kfree(ofs->config.workdir);
235         if (ofs->creator_cred)
236                 put_cred(ofs->creator_cred);
237         kfree(ofs);
238 }
239
240 static void ovl_put_super(struct super_block *sb)
241 {
242         struct ovl_fs *ofs = sb->s_fs_info;
243
244         ovl_free_fs(ofs);
245 }
246
247 static int ovl_sync_fs(struct super_block *sb, int wait)
248 {
249         struct ovl_fs *ofs = sb->s_fs_info;
250         struct super_block *upper_sb;
251         int ret;
252
253         if (!ofs->upper_mnt)
254                 return 0;
255         upper_sb = ofs->upper_mnt->mnt_sb;
256         if (!upper_sb->s_op->sync_fs)
257                 return 0;
258
259         /* real inodes have already been synced by sync_filesystem(ovl_sb) */
260         down_read(&upper_sb->s_umount);
261         ret = upper_sb->s_op->sync_fs(upper_sb, wait);
262         up_read(&upper_sb->s_umount);
263         return ret;
264 }
265
266 /**
267  * ovl_statfs
268  * @sb: The overlayfs super block
269  * @buf: The struct kstatfs to fill in with stats
270  *
271  * Get the filesystem statistics.  As writes always target the upper layer
272  * filesystem pass the statfs to the upper filesystem (if it exists)
273  */
274 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
275 {
276         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
277         struct dentry *root_dentry = dentry->d_sb->s_root;
278         struct path path;
279         int err;
280
281         ovl_path_real(root_dentry, &path);
282
283         err = vfs_statfs(&path, buf);
284         if (!err) {
285                 buf->f_namelen = ofs->namelen;
286                 buf->f_type = OVERLAYFS_SUPER_MAGIC;
287         }
288
289         return err;
290 }
291
292 /* Will this overlay be forced to mount/remount ro? */
293 static bool ovl_force_readonly(struct ovl_fs *ofs)
294 {
295         return (!ofs->upper_mnt || !ofs->workdir);
296 }
297
298 /**
299  * ovl_show_options
300  *
301  * Prints the mount options for a given superblock.
302  * Returns zero; does not fail.
303  */
304 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
305 {
306         struct super_block *sb = dentry->d_sb;
307         struct ovl_fs *ofs = sb->s_fs_info;
308
309         seq_show_option(m, "lowerdir", ofs->config.lowerdir);
310         if (ofs->config.upperdir) {
311                 seq_show_option(m, "upperdir", ofs->config.upperdir);
312                 seq_show_option(m, "workdir", ofs->config.workdir);
313         }
314         if (ofs->config.default_permissions)
315                 seq_puts(m, ",default_permissions");
316         if (ofs->config.redirect_dir != ovl_redirect_dir_def)
317                 seq_printf(m, ",redirect_dir=%s",
318                            ofs->config.redirect_dir ? "on" : "off");
319         if (ofs->config.index != ovl_index_def)
320                 seq_printf(m, ",index=%s",
321                            ofs->config.index ? "on" : "off");
322         return 0;
323 }
324
325 static int ovl_remount(struct super_block *sb, int *flags, char *data)
326 {
327         struct ovl_fs *ofs = sb->s_fs_info;
328
329         if (!(*flags & MS_RDONLY) && ovl_force_readonly(ofs))
330                 return -EROFS;
331
332         return 0;
333 }
334
335 static const struct super_operations ovl_super_operations = {
336         .alloc_inode    = ovl_alloc_inode,
337         .destroy_inode  = ovl_destroy_inode,
338         .drop_inode     = generic_delete_inode,
339         .put_super      = ovl_put_super,
340         .sync_fs        = ovl_sync_fs,
341         .statfs         = ovl_statfs,
342         .show_options   = ovl_show_options,
343         .remount_fs     = ovl_remount,
344 };
345
346 enum {
347         OPT_LOWERDIR,
348         OPT_UPPERDIR,
349         OPT_WORKDIR,
350         OPT_DEFAULT_PERMISSIONS,
351         OPT_REDIRECT_DIR_ON,
352         OPT_REDIRECT_DIR_OFF,
353         OPT_INDEX_ON,
354         OPT_INDEX_OFF,
355         OPT_ERR,
356 };
357
358 static const match_table_t ovl_tokens = {
359         {OPT_LOWERDIR,                  "lowerdir=%s"},
360         {OPT_UPPERDIR,                  "upperdir=%s"},
361         {OPT_WORKDIR,                   "workdir=%s"},
362         {OPT_DEFAULT_PERMISSIONS,       "default_permissions"},
363         {OPT_REDIRECT_DIR_ON,           "redirect_dir=on"},
364         {OPT_REDIRECT_DIR_OFF,          "redirect_dir=off"},
365         {OPT_INDEX_ON,                  "index=on"},
366         {OPT_INDEX_OFF,                 "index=off"},
367         {OPT_ERR,                       NULL}
368 };
369
370 static char *ovl_next_opt(char **s)
371 {
372         char *sbegin = *s;
373         char *p;
374
375         if (sbegin == NULL)
376                 return NULL;
377
378         for (p = sbegin; *p; p++) {
379                 if (*p == '\\') {
380                         p++;
381                         if (!*p)
382                                 break;
383                 } else if (*p == ',') {
384                         *p = '\0';
385                         *s = p + 1;
386                         return sbegin;
387                 }
388         }
389         *s = NULL;
390         return sbegin;
391 }
392
393 static int ovl_parse_opt(char *opt, struct ovl_config *config)
394 {
395         char *p;
396
397         while ((p = ovl_next_opt(&opt)) != NULL) {
398                 int token;
399                 substring_t args[MAX_OPT_ARGS];
400
401                 if (!*p)
402                         continue;
403
404                 token = match_token(p, ovl_tokens, args);
405                 switch (token) {
406                 case OPT_UPPERDIR:
407                         kfree(config->upperdir);
408                         config->upperdir = match_strdup(&args[0]);
409                         if (!config->upperdir)
410                                 return -ENOMEM;
411                         break;
412
413                 case OPT_LOWERDIR:
414                         kfree(config->lowerdir);
415                         config->lowerdir = match_strdup(&args[0]);
416                         if (!config->lowerdir)
417                                 return -ENOMEM;
418                         break;
419
420                 case OPT_WORKDIR:
421                         kfree(config->workdir);
422                         config->workdir = match_strdup(&args[0]);
423                         if (!config->workdir)
424                                 return -ENOMEM;
425                         break;
426
427                 case OPT_DEFAULT_PERMISSIONS:
428                         config->default_permissions = true;
429                         break;
430
431                 case OPT_REDIRECT_DIR_ON:
432                         config->redirect_dir = true;
433                         break;
434
435                 case OPT_REDIRECT_DIR_OFF:
436                         config->redirect_dir = false;
437                         break;
438
439                 case OPT_INDEX_ON:
440                         config->index = true;
441                         break;
442
443                 case OPT_INDEX_OFF:
444                         config->index = false;
445                         break;
446
447                 default:
448                         pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
449                         return -EINVAL;
450                 }
451         }
452
453         /* Workdir is useless in non-upper mount */
454         if (!config->upperdir && config->workdir) {
455                 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
456                         config->workdir);
457                 kfree(config->workdir);
458                 config->workdir = NULL;
459         }
460
461         return 0;
462 }
463
464 #define OVL_WORKDIR_NAME "work"
465 #define OVL_INDEXDIR_NAME "index"
466
467 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
468                                          const char *name, bool persist)
469 {
470         struct inode *dir =  ofs->workbasedir->d_inode;
471         struct vfsmount *mnt = ofs->upper_mnt;
472         struct dentry *work;
473         int err;
474         bool retried = false;
475         bool locked = false;
476
477         err = mnt_want_write(mnt);
478         if (err)
479                 goto out_err;
480
481         inode_lock_nested(dir, I_MUTEX_PARENT);
482         locked = true;
483
484 retry:
485         work = lookup_one_len(name, ofs->workbasedir, strlen(name));
486
487         if (!IS_ERR(work)) {
488                 struct iattr attr = {
489                         .ia_valid = ATTR_MODE,
490                         .ia_mode = S_IFDIR | 0,
491                 };
492
493                 if (work->d_inode) {
494                         err = -EEXIST;
495                         if (retried)
496                                 goto out_dput;
497
498                         if (persist)
499                                 goto out_unlock;
500
501                         retried = true;
502                         ovl_workdir_cleanup(dir, mnt, work, 0);
503                         dput(work);
504                         goto retry;
505                 }
506
507                 err = ovl_create_real(dir, work,
508                                       &(struct cattr){.mode = S_IFDIR | 0},
509                                       NULL, true);
510                 if (err)
511                         goto out_dput;
512
513                 /*
514                  * Try to remove POSIX ACL xattrs from workdir.  We are good if:
515                  *
516                  * a) success (there was a POSIX ACL xattr and was removed)
517                  * b) -ENODATA (there was no POSIX ACL xattr)
518                  * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
519                  *
520                  * There are various other error values that could effectively
521                  * mean that the xattr doesn't exist (e.g. -ERANGE is returned
522                  * if the xattr name is too long), but the set of filesystems
523                  * allowed as upper are limited to "normal" ones, where checking
524                  * for the above two errors is sufficient.
525                  */
526                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
527                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
528                         goto out_dput;
529
530                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
531                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
532                         goto out_dput;
533
534                 /* Clear any inherited mode bits */
535                 inode_lock(work->d_inode);
536                 err = notify_change(work, &attr, NULL);
537                 inode_unlock(work->d_inode);
538                 if (err)
539                         goto out_dput;
540         } else {
541                 err = PTR_ERR(work);
542                 goto out_err;
543         }
544 out_unlock:
545         mnt_drop_write(mnt);
546         if (locked)
547                 inode_unlock(dir);
548
549         return work;
550
551 out_dput:
552         dput(work);
553 out_err:
554         pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
555                 ofs->config.workdir, name, -err);
556         work = NULL;
557         goto out_unlock;
558 }
559
560 static void ovl_unescape(char *s)
561 {
562         char *d = s;
563
564         for (;; s++, d++) {
565                 if (*s == '\\')
566                         s++;
567                 *d = *s;
568                 if (!*s)
569                         break;
570         }
571 }
572
573 static int ovl_mount_dir_noesc(const char *name, struct path *path)
574 {
575         int err = -EINVAL;
576
577         if (!*name) {
578                 pr_err("overlayfs: empty lowerdir\n");
579                 goto out;
580         }
581         err = kern_path(name, LOOKUP_FOLLOW, path);
582         if (err) {
583                 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
584                 goto out;
585         }
586         err = -EINVAL;
587         if (ovl_dentry_weird(path->dentry)) {
588                 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
589                 goto out_put;
590         }
591         if (!d_is_dir(path->dentry)) {
592                 pr_err("overlayfs: '%s' not a directory\n", name);
593                 goto out_put;
594         }
595         return 0;
596
597 out_put:
598         path_put_init(path);
599 out:
600         return err;
601 }
602
603 static int ovl_mount_dir(const char *name, struct path *path)
604 {
605         int err = -ENOMEM;
606         char *tmp = kstrdup(name, GFP_KERNEL);
607
608         if (tmp) {
609                 ovl_unescape(tmp);
610                 err = ovl_mount_dir_noesc(tmp, path);
611
612                 if (!err)
613                         if (ovl_dentry_remote(path->dentry)) {
614                                 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
615                                        tmp);
616                                 path_put_init(path);
617                                 err = -EINVAL;
618                         }
619                 kfree(tmp);
620         }
621         return err;
622 }
623
624 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
625                              const char *name)
626 {
627         struct kstatfs statfs;
628         int err = vfs_statfs(path, &statfs);
629
630         if (err)
631                 pr_err("overlayfs: statfs failed on '%s'\n", name);
632         else
633                 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
634
635         return err;
636 }
637
638 static int ovl_lower_dir(const char *name, struct path *path,
639                          struct ovl_fs *ofs, int *stack_depth, bool *remote)
640 {
641         int err;
642
643         err = ovl_mount_dir_noesc(name, path);
644         if (err)
645                 goto out;
646
647         err = ovl_check_namelen(path, ofs, name);
648         if (err)
649                 goto out_put;
650
651         *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
652
653         if (ovl_dentry_remote(path->dentry))
654                 *remote = true;
655
656         /*
657          * The inodes index feature needs to encode and decode file
658          * handles, so it requires that all layers support them.
659          */
660         if (ofs->config.index && !ovl_can_decode_fh(path->dentry->d_sb)) {
661                 ofs->config.index = false;
662                 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off.\n", name);
663         }
664
665         return 0;
666
667 out_put:
668         path_put_init(path);
669 out:
670         return err;
671 }
672
673 /* Workdir should not be subdir of upperdir and vice versa */
674 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
675 {
676         bool ok = false;
677
678         if (workdir != upperdir) {
679                 ok = (lock_rename(workdir, upperdir) == NULL);
680                 unlock_rename(workdir, upperdir);
681         }
682         return ok;
683 }
684
685 static unsigned int ovl_split_lowerdirs(char *str)
686 {
687         unsigned int ctr = 1;
688         char *s, *d;
689
690         for (s = d = str;; s++, d++) {
691                 if (*s == '\\') {
692                         s++;
693                 } else if (*s == ':') {
694                         *d = '\0';
695                         ctr++;
696                         continue;
697                 }
698                 *d = *s;
699                 if (!*s)
700                         break;
701         }
702         return ctr;
703 }
704
705 static int __maybe_unused
706 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
707                         struct dentry *dentry, struct inode *inode,
708                         const char *name, void *buffer, size_t size)
709 {
710         return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
711 }
712
713 static int __maybe_unused
714 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
715                         struct dentry *dentry, struct inode *inode,
716                         const char *name, const void *value,
717                         size_t size, int flags)
718 {
719         struct dentry *workdir = ovl_workdir(dentry);
720         struct inode *realinode = ovl_inode_real(inode);
721         struct posix_acl *acl = NULL;
722         int err;
723
724         /* Check that everything is OK before copy-up */
725         if (value) {
726                 acl = posix_acl_from_xattr(&init_user_ns, value, size);
727                 if (IS_ERR(acl))
728                         return PTR_ERR(acl);
729         }
730         err = -EOPNOTSUPP;
731         if (!IS_POSIXACL(d_inode(workdir)))
732                 goto out_acl_release;
733         if (!realinode->i_op->set_acl)
734                 goto out_acl_release;
735         if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
736                 err = acl ? -EACCES : 0;
737                 goto out_acl_release;
738         }
739         err = -EPERM;
740         if (!inode_owner_or_capable(inode))
741                 goto out_acl_release;
742
743         posix_acl_release(acl);
744
745         /*
746          * Check if sgid bit needs to be cleared (actual setacl operation will
747          * be done with mounter's capabilities and so that won't do it for us).
748          */
749         if (unlikely(inode->i_mode & S_ISGID) &&
750             handler->flags == ACL_TYPE_ACCESS &&
751             !in_group_p(inode->i_gid) &&
752             !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
753                 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
754
755                 err = ovl_setattr(dentry, &iattr);
756                 if (err)
757                         return err;
758         }
759
760         err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
761         if (!err)
762                 ovl_copyattr(ovl_inode_real(inode), inode);
763
764         return err;
765
766 out_acl_release:
767         posix_acl_release(acl);
768         return err;
769 }
770
771 static int ovl_own_xattr_get(const struct xattr_handler *handler,
772                              struct dentry *dentry, struct inode *inode,
773                              const char *name, void *buffer, size_t size)
774 {
775         return -EOPNOTSUPP;
776 }
777
778 static int ovl_own_xattr_set(const struct xattr_handler *handler,
779                              struct dentry *dentry, struct inode *inode,
780                              const char *name, const void *value,
781                              size_t size, int flags)
782 {
783         return -EOPNOTSUPP;
784 }
785
786 static int ovl_other_xattr_get(const struct xattr_handler *handler,
787                                struct dentry *dentry, struct inode *inode,
788                                const char *name, void *buffer, size_t size)
789 {
790         return ovl_xattr_get(dentry, inode, name, buffer, size);
791 }
792
793 static int ovl_other_xattr_set(const struct xattr_handler *handler,
794                                struct dentry *dentry, struct inode *inode,
795                                const char *name, const void *value,
796                                size_t size, int flags)
797 {
798         return ovl_xattr_set(dentry, inode, name, value, size, flags);
799 }
800
801 static const struct xattr_handler __maybe_unused
802 ovl_posix_acl_access_xattr_handler = {
803         .name = XATTR_NAME_POSIX_ACL_ACCESS,
804         .flags = ACL_TYPE_ACCESS,
805         .get = ovl_posix_acl_xattr_get,
806         .set = ovl_posix_acl_xattr_set,
807 };
808
809 static const struct xattr_handler __maybe_unused
810 ovl_posix_acl_default_xattr_handler = {
811         .name = XATTR_NAME_POSIX_ACL_DEFAULT,
812         .flags = ACL_TYPE_DEFAULT,
813         .get = ovl_posix_acl_xattr_get,
814         .set = ovl_posix_acl_xattr_set,
815 };
816
817 static const struct xattr_handler ovl_own_xattr_handler = {
818         .prefix = OVL_XATTR_PREFIX,
819         .get = ovl_own_xattr_get,
820         .set = ovl_own_xattr_set,
821 };
822
823 static const struct xattr_handler ovl_other_xattr_handler = {
824         .prefix = "", /* catch all */
825         .get = ovl_other_xattr_get,
826         .set = ovl_other_xattr_set,
827 };
828
829 static const struct xattr_handler *ovl_xattr_handlers[] = {
830 #ifdef CONFIG_FS_POSIX_ACL
831         &ovl_posix_acl_access_xattr_handler,
832         &ovl_posix_acl_default_xattr_handler,
833 #endif
834         &ovl_own_xattr_handler,
835         &ovl_other_xattr_handler,
836         NULL
837 };
838
839 static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath)
840 {
841         struct vfsmount *upper_mnt;
842         int err;
843
844         err = ovl_mount_dir(ofs->config.upperdir, upperpath);
845         if (err)
846                 goto out;
847
848         /* Upper fs should not be r/o */
849         if (sb_rdonly(upperpath->mnt->mnt_sb)) {
850                 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
851                 err = -EINVAL;
852                 goto out;
853         }
854
855         err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
856         if (err)
857                 goto out;
858
859         err = -EBUSY;
860         if (ovl_inuse_trylock(upperpath->dentry)) {
861                 ofs->upperdir_locked = true;
862         } else if (ofs->config.index) {
863                 pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
864                 goto out;
865         } else {
866                 pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
867         }
868
869         upper_mnt = clone_private_mount(upperpath);
870         err = PTR_ERR(upper_mnt);
871         if (IS_ERR(upper_mnt)) {
872                 pr_err("overlayfs: failed to clone upperpath\n");
873                 goto out;
874         }
875
876         /* Don't inherit atime flags */
877         upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
878         ofs->upper_mnt = upper_mnt;
879         err = 0;
880 out:
881         return err;
882 }
883
884 static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
885 {
886         struct dentry *temp;
887         int err;
888
889         ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
890         if (!ofs->workdir)
891                 return 0;
892
893         /*
894          * Upper should support d_type, else whiteouts are visible.  Given
895          * workdir and upper are on same fs, we can do iterate_dir() on
896          * workdir. This check requires successful creation of workdir in
897          * previous step.
898          */
899         err = ovl_check_d_type_supported(workpath);
900         if (err < 0)
901                 return err;
902
903         /*
904          * We allowed this configuration and don't want to break users over
905          * kernel upgrade. So warn instead of erroring out.
906          */
907         if (!err)
908                 pr_warn("overlayfs: upper fs needs to support d_type.\n");
909
910         /* Check if upper/work fs supports O_TMPFILE */
911         temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
912         ofs->tmpfile = !IS_ERR(temp);
913         if (ofs->tmpfile)
914                 dput(temp);
915         else
916                 pr_warn("overlayfs: upper fs does not support tmpfile.\n");
917
918         /*
919          * Check if upper/work fs supports trusted.overlay.* xattr
920          */
921         err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
922         if (err) {
923                 ofs->noxattr = true;
924                 pr_warn("overlayfs: upper fs does not support xattr.\n");
925         } else {
926                 vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
927         }
928
929         /* Check if upper/work fs supports file handles */
930         if (ofs->config.index &&
931             !ovl_can_decode_fh(ofs->workdir->d_sb)) {
932                 ofs->config.index = false;
933                 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
934         }
935
936         return 0;
937 }
938
939 static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath)
940 {
941         int err;
942         struct path workpath = { };
943
944         err = ovl_mount_dir(ofs->config.workdir, &workpath);
945         if (err)
946                 goto out;
947
948         err = -EINVAL;
949         if (upperpath->mnt != workpath.mnt) {
950                 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
951                 goto out;
952         }
953         if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
954                 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
955                 goto out;
956         }
957
958         err = -EBUSY;
959         if (ovl_inuse_trylock(workpath.dentry)) {
960                 ofs->workdir_locked = true;
961         } else if (ofs->config.index) {
962                 pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
963                 goto out;
964         } else {
965                 pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
966         }
967
968         ofs->workbasedir = dget(workpath.dentry);
969         err = ovl_make_workdir(ofs, &workpath);
970         if (err)
971                 goto out;
972
973         err = 0;
974 out:
975         path_put(&workpath);
976
977         return err;
978 }
979
980 static int ovl_get_indexdir(struct ovl_fs *ofs, struct ovl_entry *oe,
981                             struct path *upperpath)
982 {
983         int err;
984
985         /* Verify lower root is upper root origin */
986         err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
987                                 false, true);
988         if (err) {
989                 pr_err("overlayfs: failed to verify upper root origin\n");
990                 goto out;
991         }
992
993         ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
994         if (ofs->indexdir) {
995                 /* Verify upper root is index dir origin */
996                 err = ovl_verify_origin(ofs->indexdir, upperpath->dentry,
997                                         true, true);
998                 if (err)
999                         pr_err("overlayfs: failed to verify index dir origin\n");
1000
1001                 /* Cleanup bad/stale/orphan index entries */
1002                 if (!err)
1003                         err = ovl_indexdir_cleanup(ofs->indexdir,
1004                                                    ofs->upper_mnt,
1005                                                    oe->lowerstack,
1006                                                    oe->numlower);
1007         }
1008         if (err || !ofs->indexdir)
1009                 pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1010
1011 out:
1012         return err;
1013 }
1014
1015 static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
1016                                 unsigned int numlower)
1017 {
1018         int err;
1019         unsigned int i;
1020
1021         err = -ENOMEM;
1022         ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
1023                                     GFP_KERNEL);
1024         if (ofs->lower_layers == NULL)
1025                 goto out;
1026         for (i = 0; i < numlower; i++) {
1027                 struct vfsmount *mnt;
1028                 dev_t dev;
1029
1030                 err = get_anon_bdev(&dev);
1031                 if (err) {
1032                         pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
1033                         goto out;
1034                 }
1035
1036                 mnt = clone_private_mount(&stack[i]);
1037                 err = PTR_ERR(mnt);
1038                 if (IS_ERR(mnt)) {
1039                         pr_err("overlayfs: failed to clone lowerpath\n");
1040                         free_anon_bdev(dev);
1041                         goto out;
1042                 }
1043                 /*
1044                  * Make lower layers R/O.  That way fchmod/fchown on lower file
1045                  * will fail instead of modifying lower fs.
1046                  */
1047                 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1048
1049                 ofs->lower_layers[ofs->numlower].mnt = mnt;
1050                 ofs->lower_layers[ofs->numlower].pseudo_dev = dev;
1051                 ofs->numlower++;
1052
1053                 /* Check if all lower layers are on same sb */
1054                 if (i == 0)
1055                         ofs->same_sb = mnt->mnt_sb;
1056                 else if (ofs->same_sb != mnt->mnt_sb)
1057                         ofs->same_sb = NULL;
1058         }
1059         err = 0;
1060 out:
1061         return err;
1062 }
1063
1064 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1065                                             struct ovl_fs *ofs)
1066 {
1067         int err;
1068         char *lowertmp, *lower;
1069         struct path *stack = NULL;
1070         unsigned int stacklen, numlower = 0, i;
1071         bool remote = false;
1072         struct ovl_entry *oe;
1073
1074         err = -ENOMEM;
1075         lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
1076         if (!lowertmp)
1077                 goto out_err;
1078
1079         err = -EINVAL;
1080         stacklen = ovl_split_lowerdirs(lowertmp);
1081         if (stacklen > OVL_MAX_STACK) {
1082                 pr_err("overlayfs: too many lower directories, limit is %d\n",
1083                        OVL_MAX_STACK);
1084                 goto out_err;
1085         } else if (!ofs->config.upperdir && stacklen == 1) {
1086                 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
1087                 goto out_err;
1088         }
1089
1090         err = -ENOMEM;
1091         stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
1092         if (!stack)
1093                 goto out_err;
1094
1095         err = -EINVAL;
1096         lower = lowertmp;
1097         for (numlower = 0; numlower < stacklen; numlower++) {
1098                 err = ovl_lower_dir(lower, &stack[numlower], ofs,
1099                                     &sb->s_stack_depth, &remote);
1100                 if (err)
1101                         goto out_err;
1102
1103                 lower = strchr(lower, '\0') + 1;
1104         }
1105
1106         err = -EINVAL;
1107         sb->s_stack_depth++;
1108         if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1109                 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1110                 goto out_err;
1111         }
1112
1113         err = ovl_get_lower_layers(ofs, stack, numlower);
1114         if (err)
1115                 goto out_err;
1116
1117         err = -ENOMEM;
1118         oe = ovl_alloc_entry(numlower);
1119         if (!oe)
1120                 goto out_err;
1121
1122         for (i = 0; i < numlower; i++) {
1123                 oe->lowerstack[i].dentry = dget(stack[i].dentry);
1124                 oe->lowerstack[i].layer = &ofs->lower_layers[i];
1125         }
1126
1127         if (remote)
1128                 sb->s_d_op = &ovl_reval_dentry_operations;
1129         else
1130                 sb->s_d_op = &ovl_dentry_operations;
1131
1132 out:
1133         for (i = 0; i < numlower; i++)
1134                 path_put(&stack[i]);
1135         kfree(stack);
1136         kfree(lowertmp);
1137
1138         return oe;
1139
1140 out_err:
1141         oe = ERR_PTR(err);
1142         goto out;
1143 }
1144
1145 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
1146 {
1147         struct path upperpath = { };
1148         struct dentry *root_dentry;
1149         struct ovl_entry *oe;
1150         struct ovl_fs *ofs;
1151         struct cred *cred;
1152         int err;
1153
1154         err = -ENOMEM;
1155         ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
1156         if (!ofs)
1157                 goto out;
1158
1159         ofs->creator_cred = cred = prepare_creds();
1160         if (!cred)
1161                 goto out_err;
1162
1163         ofs->config.redirect_dir = ovl_redirect_dir_def;
1164         ofs->config.index = ovl_index_def;
1165         err = ovl_parse_opt((char *) data, &ofs->config);
1166         if (err)
1167                 goto out_err;
1168
1169         err = -EINVAL;
1170         if (!ofs->config.lowerdir) {
1171                 if (!silent)
1172                         pr_err("overlayfs: missing 'lowerdir'\n");
1173                 goto out_err;
1174         }
1175
1176         sb->s_stack_depth = 0;
1177         sb->s_maxbytes = MAX_LFS_FILESIZE;
1178         if (ofs->config.upperdir) {
1179                 if (!ofs->config.workdir) {
1180                         pr_err("overlayfs: missing 'workdir'\n");
1181                         goto out_err;
1182                 }
1183
1184                 err = ovl_get_upper(ofs, &upperpath);
1185                 if (err)
1186                         goto out_err;
1187
1188                 err = ovl_get_workdir(ofs, &upperpath);
1189                 if (err)
1190                         goto out_err;
1191
1192                 if (!ofs->workdir)
1193                         sb->s_flags |= MS_RDONLY;
1194
1195                 sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
1196                 sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
1197
1198         }
1199         oe = ovl_get_lowerstack(sb, ofs);
1200         err = PTR_ERR(oe);
1201         if (IS_ERR(oe))
1202                 goto out_err;
1203
1204         /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1205         if (!ofs->upper_mnt)
1206                 sb->s_flags |= MS_RDONLY;
1207         else if (ofs->upper_mnt->mnt_sb != ofs->same_sb)
1208                 ofs->same_sb = NULL;
1209
1210         if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
1211                 err = ovl_get_indexdir(ofs, oe, &upperpath);
1212                 if (err)
1213                         goto out_free_oe;
1214
1215                 if (!ofs->indexdir)
1216                         sb->s_flags |= MS_RDONLY;
1217         }
1218
1219         /* Show index=off/on in /proc/mounts for any of the reasons above */
1220         if (!ofs->indexdir)
1221                 ofs->config.index = false;
1222
1223         /* Never override disk quota limits or use reserved space */
1224         cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1225
1226         sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1227         sb->s_op = &ovl_super_operations;
1228         sb->s_xattr = ovl_xattr_handlers;
1229         sb->s_fs_info = ofs;
1230         sb->s_flags |= MS_POSIXACL | MS_NOREMOTELOCK;
1231
1232         err = -ENOMEM;
1233         root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1234         if (!root_dentry)
1235                 goto out_free_oe;
1236
1237         mntput(upperpath.mnt);
1238         if (upperpath.dentry) {
1239                 oe->has_upper = true;
1240                 if (ovl_is_impuredir(upperpath.dentry))
1241                         ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
1242         }
1243
1244         root_dentry->d_fsdata = oe;
1245
1246         /* Root is always merge -> can have whiteouts */
1247         ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
1248         ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
1249                        ovl_dentry_lower(root_dentry));
1250
1251         sb->s_root = root_dentry;
1252
1253         return 0;
1254
1255 out_free_oe:
1256         ovl_entry_stack_free(oe);
1257         kfree(oe);
1258 out_err:
1259         path_put(&upperpath);
1260         ovl_free_fs(ofs);
1261 out:
1262         return err;
1263 }
1264
1265 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1266                                 const char *dev_name, void *raw_data)
1267 {
1268         return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1269 }
1270
1271 static struct file_system_type ovl_fs_type = {
1272         .owner          = THIS_MODULE,
1273         .name           = "overlay",
1274         .mount          = ovl_mount,
1275         .kill_sb        = kill_anon_super,
1276 };
1277 MODULE_ALIAS_FS("overlay");
1278
1279 static void ovl_inode_init_once(void *foo)
1280 {
1281         struct ovl_inode *oi = foo;
1282
1283         inode_init_once(&oi->vfs_inode);
1284 }
1285
1286 static int __init ovl_init(void)
1287 {
1288         int err;
1289
1290         ovl_inode_cachep = kmem_cache_create("ovl_inode",
1291                                              sizeof(struct ovl_inode), 0,
1292                                              (SLAB_RECLAIM_ACCOUNT|
1293                                               SLAB_MEM_SPREAD|SLAB_ACCOUNT),
1294                                              ovl_inode_init_once);
1295         if (ovl_inode_cachep == NULL)
1296                 return -ENOMEM;
1297
1298         err = register_filesystem(&ovl_fs_type);
1299         if (err)
1300                 kmem_cache_destroy(ovl_inode_cachep);
1301
1302         return err;
1303 }
1304
1305 static void __exit ovl_exit(void)
1306 {
1307         unregister_filesystem(&ovl_fs_type);
1308
1309         /*
1310          * Make sure all delayed rcu free inodes are flushed before we
1311          * destroy cache.
1312          */
1313         rcu_barrier();
1314         kmem_cache_destroy(ovl_inode_cachep);
1315
1316 }
1317
1318 module_init(ovl_init);
1319 module_exit(ovl_exit);