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 #include "ovl_entry.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 void ovl_dentry_release(struct dentry *dentry)
38 {
39         struct ovl_entry *oe = dentry->d_fsdata;
40
41         if (oe) {
42                 unsigned int i;
43
44                 dput(oe->__upperdentry);
45                 kfree(oe->redirect);
46                 for (i = 0; i < oe->numlower; i++)
47                         dput(oe->lowerstack[i].dentry);
48                 kfree_rcu(oe, rcu);
49         }
50 }
51
52 static struct dentry *ovl_d_real(struct dentry *dentry,
53                                  const struct inode *inode,
54                                  unsigned int open_flags)
55 {
56         struct dentry *real;
57
58         if (!d_is_reg(dentry)) {
59                 if (!inode || inode == d_inode(dentry))
60                         return dentry;
61                 goto bug;
62         }
63
64         if (d_is_negative(dentry))
65                 return dentry;
66
67         if (open_flags) {
68                 int err = ovl_open_maybe_copy_up(dentry, open_flags);
69
70                 if (err)
71                         return ERR_PTR(err);
72         }
73
74         real = ovl_dentry_upper(dentry);
75         if (real && (!inode || inode == d_inode(real)))
76                 return real;
77
78         real = ovl_dentry_lower(dentry);
79         if (!real)
80                 goto bug;
81
82         /* Handle recursion */
83         real = d_real(real, inode, open_flags);
84
85         if (!inode || inode == d_inode(real))
86                 return real;
87 bug:
88         WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
89              inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
90         return dentry;
91 }
92
93 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
94 {
95         struct ovl_entry *oe = dentry->d_fsdata;
96         unsigned int i;
97         int ret = 1;
98
99         for (i = 0; i < oe->numlower; i++) {
100                 struct dentry *d = oe->lowerstack[i].dentry;
101
102                 if (d->d_flags & DCACHE_OP_REVALIDATE) {
103                         ret = d->d_op->d_revalidate(d, flags);
104                         if (ret < 0)
105                                 return ret;
106                         if (!ret) {
107                                 if (!(flags & LOOKUP_RCU))
108                                         d_invalidate(d);
109                                 return -ESTALE;
110                         }
111                 }
112         }
113         return 1;
114 }
115
116 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
117 {
118         struct ovl_entry *oe = dentry->d_fsdata;
119         unsigned int i;
120         int ret = 1;
121
122         for (i = 0; i < oe->numlower; i++) {
123                 struct dentry *d = oe->lowerstack[i].dentry;
124
125                 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
126                         ret = d->d_op->d_weak_revalidate(d, flags);
127                         if (ret <= 0)
128                                 break;
129                 }
130         }
131         return ret;
132 }
133
134 static const struct dentry_operations ovl_dentry_operations = {
135         .d_release = ovl_dentry_release,
136         .d_real = ovl_d_real,
137 };
138
139 static const struct dentry_operations ovl_reval_dentry_operations = {
140         .d_release = ovl_dentry_release,
141         .d_real = ovl_d_real,
142         .d_revalidate = ovl_dentry_revalidate,
143         .d_weak_revalidate = ovl_dentry_weak_revalidate,
144 };
145
146 static void ovl_put_super(struct super_block *sb)
147 {
148         struct ovl_fs *ufs = sb->s_fs_info;
149         unsigned i;
150
151         dput(ufs->workdir);
152         mntput(ufs->upper_mnt);
153         for (i = 0; i < ufs->numlower; i++)
154                 mntput(ufs->lower_mnt[i]);
155         kfree(ufs->lower_mnt);
156
157         kfree(ufs->config.lowerdir);
158         kfree(ufs->config.upperdir);
159         kfree(ufs->config.workdir);
160         put_cred(ufs->creator_cred);
161         kfree(ufs);
162 }
163
164 static int ovl_sync_fs(struct super_block *sb, int wait)
165 {
166         struct ovl_fs *ufs = sb->s_fs_info;
167         struct super_block *upper_sb;
168         int ret;
169
170         if (!ufs->upper_mnt)
171                 return 0;
172         upper_sb = ufs->upper_mnt->mnt_sb;
173         if (!upper_sb->s_op->sync_fs)
174                 return 0;
175
176         /* real inodes have already been synced by sync_filesystem(ovl_sb) */
177         down_read(&upper_sb->s_umount);
178         ret = upper_sb->s_op->sync_fs(upper_sb, wait);
179         up_read(&upper_sb->s_umount);
180         return ret;
181 }
182
183 /**
184  * ovl_statfs
185  * @sb: The overlayfs super block
186  * @buf: The struct kstatfs to fill in with stats
187  *
188  * Get the filesystem statistics.  As writes always target the upper layer
189  * filesystem pass the statfs to the upper filesystem (if it exists)
190  */
191 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
192 {
193         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
194         struct dentry *root_dentry = dentry->d_sb->s_root;
195         struct path path;
196         int err;
197
198         ovl_path_real(root_dentry, &path);
199
200         err = vfs_statfs(&path, buf);
201         if (!err) {
202                 buf->f_namelen = ofs->namelen;
203                 buf->f_type = OVERLAYFS_SUPER_MAGIC;
204         }
205
206         return err;
207 }
208
209 /**
210  * ovl_show_options
211  *
212  * Prints the mount options for a given superblock.
213  * Returns zero; does not fail.
214  */
215 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
216 {
217         struct super_block *sb = dentry->d_sb;
218         struct ovl_fs *ufs = sb->s_fs_info;
219
220         seq_show_option(m, "lowerdir", ufs->config.lowerdir);
221         if (ufs->config.upperdir) {
222                 seq_show_option(m, "upperdir", ufs->config.upperdir);
223                 seq_show_option(m, "workdir", ufs->config.workdir);
224         }
225         if (ufs->config.default_permissions)
226                 seq_puts(m, ",default_permissions");
227         if (ufs->config.redirect_dir != ovl_redirect_dir_def)
228                 seq_printf(m, ",redirect_dir=%s",
229                            ufs->config.redirect_dir ? "on" : "off");
230         return 0;
231 }
232
233 static int ovl_remount(struct super_block *sb, int *flags, char *data)
234 {
235         struct ovl_fs *ufs = sb->s_fs_info;
236
237         if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir))
238                 return -EROFS;
239
240         return 0;
241 }
242
243 static const struct super_operations ovl_super_operations = {
244         .put_super      = ovl_put_super,
245         .sync_fs        = ovl_sync_fs,
246         .statfs         = ovl_statfs,
247         .show_options   = ovl_show_options,
248         .remount_fs     = ovl_remount,
249         .drop_inode     = generic_delete_inode,
250 };
251
252 enum {
253         OPT_LOWERDIR,
254         OPT_UPPERDIR,
255         OPT_WORKDIR,
256         OPT_DEFAULT_PERMISSIONS,
257         OPT_REDIRECT_DIR_ON,
258         OPT_REDIRECT_DIR_OFF,
259         OPT_ERR,
260 };
261
262 static const match_table_t ovl_tokens = {
263         {OPT_LOWERDIR,                  "lowerdir=%s"},
264         {OPT_UPPERDIR,                  "upperdir=%s"},
265         {OPT_WORKDIR,                   "workdir=%s"},
266         {OPT_DEFAULT_PERMISSIONS,       "default_permissions"},
267         {OPT_REDIRECT_DIR_ON,           "redirect_dir=on"},
268         {OPT_REDIRECT_DIR_OFF,          "redirect_dir=off"},
269         {OPT_ERR,                       NULL}
270 };
271
272 static char *ovl_next_opt(char **s)
273 {
274         char *sbegin = *s;
275         char *p;
276
277         if (sbegin == NULL)
278                 return NULL;
279
280         for (p = sbegin; *p; p++) {
281                 if (*p == '\\') {
282                         p++;
283                         if (!*p)
284                                 break;
285                 } else if (*p == ',') {
286                         *p = '\0';
287                         *s = p + 1;
288                         return sbegin;
289                 }
290         }
291         *s = NULL;
292         return sbegin;
293 }
294
295 static int ovl_parse_opt(char *opt, struct ovl_config *config)
296 {
297         char *p;
298
299         while ((p = ovl_next_opt(&opt)) != NULL) {
300                 int token;
301                 substring_t args[MAX_OPT_ARGS];
302
303                 if (!*p)
304                         continue;
305
306                 token = match_token(p, ovl_tokens, args);
307                 switch (token) {
308                 case OPT_UPPERDIR:
309                         kfree(config->upperdir);
310                         config->upperdir = match_strdup(&args[0]);
311                         if (!config->upperdir)
312                                 return -ENOMEM;
313                         break;
314
315                 case OPT_LOWERDIR:
316                         kfree(config->lowerdir);
317                         config->lowerdir = match_strdup(&args[0]);
318                         if (!config->lowerdir)
319                                 return -ENOMEM;
320                         break;
321
322                 case OPT_WORKDIR:
323                         kfree(config->workdir);
324                         config->workdir = match_strdup(&args[0]);
325                         if (!config->workdir)
326                                 return -ENOMEM;
327                         break;
328
329                 case OPT_DEFAULT_PERMISSIONS:
330                         config->default_permissions = true;
331                         break;
332
333                 case OPT_REDIRECT_DIR_ON:
334                         config->redirect_dir = true;
335                         break;
336
337                 case OPT_REDIRECT_DIR_OFF:
338                         config->redirect_dir = false;
339                         break;
340
341                 default:
342                         pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
343                         return -EINVAL;
344                 }
345         }
346
347         /* Workdir is useless in non-upper mount */
348         if (!config->upperdir && config->workdir) {
349                 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
350                         config->workdir);
351                 kfree(config->workdir);
352                 config->workdir = NULL;
353         }
354
355         return 0;
356 }
357
358 #define OVL_WORKDIR_NAME "work"
359
360 static struct dentry *ovl_workdir_create(struct vfsmount *mnt,
361                                          struct dentry *dentry)
362 {
363         struct inode *dir = dentry->d_inode;
364         struct dentry *work;
365         int err;
366         bool retried = false;
367
368         err = mnt_want_write(mnt);
369         if (err)
370                 return ERR_PTR(err);
371
372         inode_lock_nested(dir, I_MUTEX_PARENT);
373 retry:
374         work = lookup_one_len(OVL_WORKDIR_NAME, dentry,
375                               strlen(OVL_WORKDIR_NAME));
376
377         if (!IS_ERR(work)) {
378                 struct iattr attr = {
379                         .ia_valid = ATTR_MODE,
380                         .ia_mode = S_IFDIR | 0,
381                 };
382
383                 if (work->d_inode) {
384                         err = -EEXIST;
385                         if (retried)
386                                 goto out_dput;
387
388                         retried = true;
389                         ovl_workdir_cleanup(dir, mnt, work, 0);
390                         dput(work);
391                         goto retry;
392                 }
393
394                 err = ovl_create_real(dir, work,
395                                       &(struct cattr){.mode = S_IFDIR | 0},
396                                       NULL, true);
397                 if (err)
398                         goto out_dput;
399
400                 /*
401                  * Try to remove POSIX ACL xattrs from workdir.  We are good if:
402                  *
403                  * a) success (there was a POSIX ACL xattr and was removed)
404                  * b) -ENODATA (there was no POSIX ACL xattr)
405                  * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
406                  *
407                  * There are various other error values that could effectively
408                  * mean that the xattr doesn't exist (e.g. -ERANGE is returned
409                  * if the xattr name is too long), but the set of filesystems
410                  * allowed as upper are limited to "normal" ones, where checking
411                  * for the above two errors is sufficient.
412                  */
413                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
414                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
415                         goto out_dput;
416
417                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
418                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
419                         goto out_dput;
420
421                 /* Clear any inherited mode bits */
422                 inode_lock(work->d_inode);
423                 err = notify_change(work, &attr, NULL);
424                 inode_unlock(work->d_inode);
425                 if (err)
426                         goto out_dput;
427         }
428 out_unlock:
429         inode_unlock(dir);
430         mnt_drop_write(mnt);
431
432         return work;
433
434 out_dput:
435         dput(work);
436         work = ERR_PTR(err);
437         goto out_unlock;
438 }
439
440 static void ovl_unescape(char *s)
441 {
442         char *d = s;
443
444         for (;; s++, d++) {
445                 if (*s == '\\')
446                         s++;
447                 *d = *s;
448                 if (!*s)
449                         break;
450         }
451 }
452
453 static int ovl_mount_dir_noesc(const char *name, struct path *path)
454 {
455         int err = -EINVAL;
456
457         if (!*name) {
458                 pr_err("overlayfs: empty lowerdir\n");
459                 goto out;
460         }
461         err = kern_path(name, LOOKUP_FOLLOW, path);
462         if (err) {
463                 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
464                 goto out;
465         }
466         err = -EINVAL;
467         if (ovl_dentry_weird(path->dentry)) {
468                 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
469                 goto out_put;
470         }
471         if (!d_is_dir(path->dentry)) {
472                 pr_err("overlayfs: '%s' not a directory\n", name);
473                 goto out_put;
474         }
475         return 0;
476
477 out_put:
478         path_put(path);
479 out:
480         return err;
481 }
482
483 static int ovl_mount_dir(const char *name, struct path *path)
484 {
485         int err = -ENOMEM;
486         char *tmp = kstrdup(name, GFP_KERNEL);
487
488         if (tmp) {
489                 ovl_unescape(tmp);
490                 err = ovl_mount_dir_noesc(tmp, path);
491
492                 if (!err)
493                         if (ovl_dentry_remote(path->dentry)) {
494                                 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
495                                        tmp);
496                                 path_put(path);
497                                 err = -EINVAL;
498                         }
499                 kfree(tmp);
500         }
501         return err;
502 }
503
504 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
505                              const char *name)
506 {
507         struct kstatfs statfs;
508         int err = vfs_statfs(path, &statfs);
509
510         if (err)
511                 pr_err("overlayfs: statfs failed on '%s'\n", name);
512         else
513                 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
514
515         return err;
516 }
517
518 static int ovl_lower_dir(const char *name, struct path *path,
519                          struct ovl_fs *ofs, int *stack_depth, bool *remote)
520 {
521         int err;
522
523         err = ovl_mount_dir_noesc(name, path);
524         if (err)
525                 goto out;
526
527         err = ovl_check_namelen(path, ofs, name);
528         if (err)
529                 goto out_put;
530
531         *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
532
533         if (ovl_dentry_remote(path->dentry))
534                 *remote = true;
535
536         return 0;
537
538 out_put:
539         path_put(path);
540 out:
541         return err;
542 }
543
544 /* Workdir should not be subdir of upperdir and vice versa */
545 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
546 {
547         bool ok = false;
548
549         if (workdir != upperdir) {
550                 ok = (lock_rename(workdir, upperdir) == NULL);
551                 unlock_rename(workdir, upperdir);
552         }
553         return ok;
554 }
555
556 static unsigned int ovl_split_lowerdirs(char *str)
557 {
558         unsigned int ctr = 1;
559         char *s, *d;
560
561         for (s = d = str;; s++, d++) {
562                 if (*s == '\\') {
563                         s++;
564                 } else if (*s == ':') {
565                         *d = '\0';
566                         ctr++;
567                         continue;
568                 }
569                 *d = *s;
570                 if (!*s)
571                         break;
572         }
573         return ctr;
574 }
575
576 static int __maybe_unused
577 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
578                         struct dentry *dentry, struct inode *inode,
579                         const char *name, void *buffer, size_t size)
580 {
581         return ovl_xattr_get(dentry, handler->name, buffer, size);
582 }
583
584 static int __maybe_unused
585 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
586                         struct dentry *dentry, struct inode *inode,
587                         const char *name, const void *value,
588                         size_t size, int flags)
589 {
590         struct dentry *workdir = ovl_workdir(dentry);
591         struct inode *realinode = ovl_inode_real(inode, NULL);
592         struct posix_acl *acl = NULL;
593         int err;
594
595         /* Check that everything is OK before copy-up */
596         if (value) {
597                 acl = posix_acl_from_xattr(&init_user_ns, value, size);
598                 if (IS_ERR(acl))
599                         return PTR_ERR(acl);
600         }
601         err = -EOPNOTSUPP;
602         if (!IS_POSIXACL(d_inode(workdir)))
603                 goto out_acl_release;
604         if (!realinode->i_op->set_acl)
605                 goto out_acl_release;
606         if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
607                 err = acl ? -EACCES : 0;
608                 goto out_acl_release;
609         }
610         err = -EPERM;
611         if (!inode_owner_or_capable(inode))
612                 goto out_acl_release;
613
614         posix_acl_release(acl);
615
616         /*
617          * Check if sgid bit needs to be cleared (actual setacl operation will
618          * be done with mounter's capabilities and so that won't do it for us).
619          */
620         if (unlikely(inode->i_mode & S_ISGID) &&
621             handler->flags == ACL_TYPE_ACCESS &&
622             !in_group_p(inode->i_gid) &&
623             !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
624                 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
625
626                 err = ovl_setattr(dentry, &iattr);
627                 if (err)
628                         return err;
629         }
630
631         err = ovl_xattr_set(dentry, handler->name, value, size, flags);
632         if (!err)
633                 ovl_copyattr(ovl_inode_real(inode, NULL), inode);
634
635         return err;
636
637 out_acl_release:
638         posix_acl_release(acl);
639         return err;
640 }
641
642 static int ovl_own_xattr_get(const struct xattr_handler *handler,
643                              struct dentry *dentry, struct inode *inode,
644                              const char *name, void *buffer, size_t size)
645 {
646         return -EOPNOTSUPP;
647 }
648
649 static int ovl_own_xattr_set(const struct xattr_handler *handler,
650                              struct dentry *dentry, struct inode *inode,
651                              const char *name, const void *value,
652                              size_t size, int flags)
653 {
654         return -EOPNOTSUPP;
655 }
656
657 static int ovl_other_xattr_get(const struct xattr_handler *handler,
658                                struct dentry *dentry, struct inode *inode,
659                                const char *name, void *buffer, size_t size)
660 {
661         return ovl_xattr_get(dentry, name, buffer, size);
662 }
663
664 static int ovl_other_xattr_set(const struct xattr_handler *handler,
665                                struct dentry *dentry, struct inode *inode,
666                                const char *name, const void *value,
667                                size_t size, int flags)
668 {
669         return ovl_xattr_set(dentry, name, value, size, flags);
670 }
671
672 static const struct xattr_handler __maybe_unused
673 ovl_posix_acl_access_xattr_handler = {
674         .name = XATTR_NAME_POSIX_ACL_ACCESS,
675         .flags = ACL_TYPE_ACCESS,
676         .get = ovl_posix_acl_xattr_get,
677         .set = ovl_posix_acl_xattr_set,
678 };
679
680 static const struct xattr_handler __maybe_unused
681 ovl_posix_acl_default_xattr_handler = {
682         .name = XATTR_NAME_POSIX_ACL_DEFAULT,
683         .flags = ACL_TYPE_DEFAULT,
684         .get = ovl_posix_acl_xattr_get,
685         .set = ovl_posix_acl_xattr_set,
686 };
687
688 static const struct xattr_handler ovl_own_xattr_handler = {
689         .prefix = OVL_XATTR_PREFIX,
690         .get = ovl_own_xattr_get,
691         .set = ovl_own_xattr_set,
692 };
693
694 static const struct xattr_handler ovl_other_xattr_handler = {
695         .prefix = "", /* catch all */
696         .get = ovl_other_xattr_get,
697         .set = ovl_other_xattr_set,
698 };
699
700 static const struct xattr_handler *ovl_xattr_handlers[] = {
701 #ifdef CONFIG_FS_POSIX_ACL
702         &ovl_posix_acl_access_xattr_handler,
703         &ovl_posix_acl_default_xattr_handler,
704 #endif
705         &ovl_own_xattr_handler,
706         &ovl_other_xattr_handler,
707         NULL
708 };
709
710 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
711 {
712         struct path upperpath = { NULL, NULL };
713         struct path workpath = { NULL, NULL };
714         struct dentry *root_dentry;
715         struct inode *realinode;
716         struct ovl_entry *oe;
717         struct ovl_fs *ufs;
718         struct path *stack = NULL;
719         char *lowertmp;
720         char *lower;
721         unsigned int numlower;
722         unsigned int stacklen = 0;
723         unsigned int i;
724         bool remote = false;
725         struct cred *cred;
726         int err;
727
728         err = -ENOMEM;
729         ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
730         if (!ufs)
731                 goto out;
732
733         init_waitqueue_head(&ufs->copyup_wq);
734         ufs->config.redirect_dir = ovl_redirect_dir_def;
735         err = ovl_parse_opt((char *) data, &ufs->config);
736         if (err)
737                 goto out_free_config;
738
739         err = -EINVAL;
740         if (!ufs->config.lowerdir) {
741                 if (!silent)
742                         pr_err("overlayfs: missing 'lowerdir'\n");
743                 goto out_free_config;
744         }
745
746         sb->s_stack_depth = 0;
747         sb->s_maxbytes = MAX_LFS_FILESIZE;
748         if (ufs->config.upperdir) {
749                 if (!ufs->config.workdir) {
750                         pr_err("overlayfs: missing 'workdir'\n");
751                         goto out_free_config;
752                 }
753
754                 err = ovl_mount_dir(ufs->config.upperdir, &upperpath);
755                 if (err)
756                         goto out_free_config;
757
758                 /* Upper fs should not be r/o */
759                 if (upperpath.mnt->mnt_sb->s_flags & MS_RDONLY) {
760                         pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
761                         err = -EINVAL;
762                         goto out_put_upperpath;
763                 }
764
765                 err = ovl_check_namelen(&upperpath, ufs, ufs->config.upperdir);
766                 if (err)
767                         goto out_put_upperpath;
768
769                 err = ovl_mount_dir(ufs->config.workdir, &workpath);
770                 if (err)
771                         goto out_put_upperpath;
772
773                 err = -EINVAL;
774                 if (upperpath.mnt != workpath.mnt) {
775                         pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
776                         goto out_put_workpath;
777                 }
778                 if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry)) {
779                         pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
780                         goto out_put_workpath;
781                 }
782                 sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
783         }
784         err = -ENOMEM;
785         lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL);
786         if (!lowertmp)
787                 goto out_put_workpath;
788
789         err = -EINVAL;
790         stacklen = ovl_split_lowerdirs(lowertmp);
791         if (stacklen > OVL_MAX_STACK) {
792                 pr_err("overlayfs: too many lower directories, limit is %d\n",
793                        OVL_MAX_STACK);
794                 goto out_free_lowertmp;
795         } else if (!ufs->config.upperdir && stacklen == 1) {
796                 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
797                 goto out_free_lowertmp;
798         }
799
800         err = -ENOMEM;
801         stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
802         if (!stack)
803                 goto out_free_lowertmp;
804
805         err = -EINVAL;
806         lower = lowertmp;
807         for (numlower = 0; numlower < stacklen; numlower++) {
808                 err = ovl_lower_dir(lower, &stack[numlower], ufs,
809                                     &sb->s_stack_depth, &remote);
810                 if (err)
811                         goto out_put_lowerpath;
812
813                 lower = strchr(lower, '\0') + 1;
814         }
815
816         err = -EINVAL;
817         sb->s_stack_depth++;
818         if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
819                 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
820                 goto out_put_lowerpath;
821         }
822
823         if (ufs->config.upperdir) {
824                 ufs->upper_mnt = clone_private_mount(&upperpath);
825                 err = PTR_ERR(ufs->upper_mnt);
826                 if (IS_ERR(ufs->upper_mnt)) {
827                         pr_err("overlayfs: failed to clone upperpath\n");
828                         goto out_put_lowerpath;
829                 }
830                 /* Don't inherit atime flags */
831                 ufs->upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
832
833                 sb->s_time_gran = ufs->upper_mnt->mnt_sb->s_time_gran;
834
835                 ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
836                 err = PTR_ERR(ufs->workdir);
837                 if (IS_ERR(ufs->workdir)) {
838                         pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
839                                 ufs->config.workdir, OVL_WORKDIR_NAME, -err);
840                         sb->s_flags |= MS_RDONLY;
841                         ufs->workdir = NULL;
842                 }
843
844                 /*
845                  * Upper should support d_type, else whiteouts are visible.
846                  * Given workdir and upper are on same fs, we can do
847                  * iterate_dir() on workdir. This check requires successful
848                  * creation of workdir in previous step.
849                  */
850                 if (ufs->workdir) {
851                         struct dentry *temp;
852
853                         err = ovl_check_d_type_supported(&workpath);
854                         if (err < 0)
855                                 goto out_put_workdir;
856
857                         /*
858                          * We allowed this configuration and don't want to
859                          * break users over kernel upgrade. So warn instead
860                          * of erroring out.
861                          */
862                         if (!err)
863                                 pr_warn("overlayfs: upper fs needs to support d_type.\n");
864
865                         /* Check if upper/work fs supports O_TMPFILE */
866                         temp = ovl_do_tmpfile(ufs->workdir, S_IFREG | 0);
867                         ufs->tmpfile = !IS_ERR(temp);
868                         if (ufs->tmpfile)
869                                 dput(temp);
870                         else
871                                 pr_warn("overlayfs: upper fs does not support tmpfile.\n");
872                 }
873         }
874
875         err = -ENOMEM;
876         ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL);
877         if (ufs->lower_mnt == NULL)
878                 goto out_put_workdir;
879         for (i = 0; i < numlower; i++) {
880                 struct vfsmount *mnt = clone_private_mount(&stack[i]);
881
882                 err = PTR_ERR(mnt);
883                 if (IS_ERR(mnt)) {
884                         pr_err("overlayfs: failed to clone lowerpath\n");
885                         goto out_put_lower_mnt;
886                 }
887                 /*
888                  * Make lower_mnt R/O.  That way fchmod/fchown on lower file
889                  * will fail instead of modifying lower fs.
890                  */
891                 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
892
893                 ufs->lower_mnt[ufs->numlower] = mnt;
894                 ufs->numlower++;
895         }
896
897         /* If the upper fs is nonexistent, we mark overlayfs r/o too */
898         if (!ufs->upper_mnt)
899                 sb->s_flags |= MS_RDONLY;
900
901         if (remote)
902                 sb->s_d_op = &ovl_reval_dentry_operations;
903         else
904                 sb->s_d_op = &ovl_dentry_operations;
905
906         ufs->creator_cred = cred = prepare_creds();
907         if (!cred)
908                 goto out_put_lower_mnt;
909
910         /* Never override disk quota limits or use reserved space */
911         cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
912
913         err = -ENOMEM;
914         oe = ovl_alloc_entry(numlower);
915         if (!oe)
916                 goto out_put_cred;
917
918         sb->s_magic = OVERLAYFS_SUPER_MAGIC;
919         sb->s_op = &ovl_super_operations;
920         sb->s_xattr = ovl_xattr_handlers;
921         sb->s_fs_info = ufs;
922         sb->s_flags |= MS_POSIXACL | MS_NOREMOTELOCK;
923
924         root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
925         if (!root_dentry)
926                 goto out_free_oe;
927
928         mntput(upperpath.mnt);
929         for (i = 0; i < numlower; i++)
930                 mntput(stack[i].mnt);
931         path_put(&workpath);
932         kfree(lowertmp);
933
934         oe->__upperdentry = upperpath.dentry;
935         for (i = 0; i < numlower; i++) {
936                 oe->lowerstack[i].dentry = stack[i].dentry;
937                 oe->lowerstack[i].mnt = ufs->lower_mnt[i];
938         }
939         kfree(stack);
940
941         root_dentry->d_fsdata = oe;
942
943         realinode = d_inode(ovl_dentry_real(root_dentry));
944         ovl_inode_init(d_inode(root_dentry), realinode, !!upperpath.dentry);
945         ovl_copyattr(realinode, d_inode(root_dentry));
946
947         sb->s_root = root_dentry;
948
949         return 0;
950
951 out_free_oe:
952         kfree(oe);
953 out_put_cred:
954         put_cred(ufs->creator_cred);
955 out_put_lower_mnt:
956         for (i = 0; i < ufs->numlower; i++)
957                 mntput(ufs->lower_mnt[i]);
958         kfree(ufs->lower_mnt);
959 out_put_workdir:
960         dput(ufs->workdir);
961         mntput(ufs->upper_mnt);
962 out_put_lowerpath:
963         for (i = 0; i < numlower; i++)
964                 path_put(&stack[i]);
965         kfree(stack);
966 out_free_lowertmp:
967         kfree(lowertmp);
968 out_put_workpath:
969         path_put(&workpath);
970 out_put_upperpath:
971         path_put(&upperpath);
972 out_free_config:
973         kfree(ufs->config.lowerdir);
974         kfree(ufs->config.upperdir);
975         kfree(ufs->config.workdir);
976         kfree(ufs);
977 out:
978         return err;
979 }
980
981 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
982                                 const char *dev_name, void *raw_data)
983 {
984         return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
985 }
986
987 static struct file_system_type ovl_fs_type = {
988         .owner          = THIS_MODULE,
989         .name           = "overlay",
990         .mount          = ovl_mount,
991         .kill_sb        = kill_anon_super,
992 };
993 MODULE_ALIAS_FS("overlay");
994
995 static int __init ovl_init(void)
996 {
997         return register_filesystem(&ovl_fs_type);
998 }
999
1000 static void __exit ovl_exit(void)
1001 {
1002         unregister_filesystem(&ovl_fs_type);
1003 }
1004
1005 module_init(ovl_init);
1006 module_exit(ovl_exit);