3 * Copyright (C) 2011 Novell Inc.
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.
10 #include <uapi/linux/magic.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"
23 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
24 MODULE_DESCRIPTION("Overlay filesystem");
25 MODULE_LICENSE("GPL");
30 #define OVL_MAX_STACK 500
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");
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,
41 MODULE_PARM_DESC(ovl_redirect_always_follow,
42 "Follow redirects even if redirect_dir feature is turned off");
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");
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");
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");
59 static void ovl_entry_stack_free(struct ovl_entry *oe)
63 for (i = 0; i < oe->numlower; i++)
64 dput(oe->lowerstack[i].dentry);
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");
72 static void ovl_dentry_release(struct dentry *dentry)
74 struct ovl_entry *oe = dentry->d_fsdata;
77 ovl_entry_stack_free(oe);
82 static struct dentry *ovl_d_real(struct dentry *dentry,
83 const struct inode *inode)
87 /* It's an overlay file */
88 if (inode && d_inode(dentry) == inode)
91 if (!d_is_reg(dentry)) {
92 if (!inode || inode == d_inode(dentry))
97 real = ovl_dentry_upper(dentry);
98 if (real && (inode == d_inode(real)))
101 if (real && !inode && ovl_has_upperdata(d_inode(dentry)))
104 real = ovl_dentry_lowerdata(dentry);
108 /* Handle recursion */
109 real = d_real(real, inode);
111 if (!inode || inode == d_inode(real))
114 WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
115 inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
119 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
121 struct ovl_entry *oe = dentry->d_fsdata;
125 for (i = 0; i < oe->numlower; i++) {
126 struct dentry *d = oe->lowerstack[i].dentry;
128 if (d->d_flags & DCACHE_OP_REVALIDATE) {
129 ret = d->d_op->d_revalidate(d, flags);
133 if (!(flags & LOOKUP_RCU))
142 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
144 struct ovl_entry *oe = dentry->d_fsdata;
148 for (i = 0; i < oe->numlower; i++) {
149 struct dentry *d = oe->lowerstack[i].dentry;
151 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
152 ret = d->d_op->d_weak_revalidate(d, flags);
160 static const struct dentry_operations ovl_dentry_operations = {
161 .d_release = ovl_dentry_release,
162 .d_real = ovl_d_real,
165 static const struct dentry_operations ovl_reval_dentry_operations = {
166 .d_release = ovl_dentry_release,
167 .d_real = ovl_d_real,
168 .d_revalidate = ovl_dentry_revalidate,
169 .d_weak_revalidate = ovl_dentry_weak_revalidate,
172 static struct kmem_cache *ovl_inode_cachep;
174 static struct inode *ovl_alloc_inode(struct super_block *sb)
176 struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL);
185 oi->__upperdentry = NULL;
187 oi->lowerdata = NULL;
188 mutex_init(&oi->lock);
190 return &oi->vfs_inode;
193 static void ovl_free_inode(struct inode *inode)
195 struct ovl_inode *oi = OVL_I(inode);
198 mutex_destroy(&oi->lock);
199 kmem_cache_free(ovl_inode_cachep, oi);
202 static void ovl_destroy_inode(struct inode *inode)
204 struct ovl_inode *oi = OVL_I(inode);
206 dput(oi->__upperdentry);
208 if (S_ISDIR(inode->i_mode))
209 ovl_dir_cache_free(inode);
214 static void ovl_free_fs(struct ovl_fs *ofs)
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 for (i = 0; i < ofs->numlowerfs; i++)
229 free_anon_bdev(ofs->lower_fs[i].pseudo_dev);
230 kfree(ofs->lower_layers);
231 kfree(ofs->lower_fs);
233 kfree(ofs->config.lowerdir);
234 kfree(ofs->config.upperdir);
235 kfree(ofs->config.workdir);
236 kfree(ofs->config.redirect_mode);
237 if (ofs->creator_cred)
238 put_cred(ofs->creator_cred);
242 static void ovl_put_super(struct super_block *sb)
244 struct ovl_fs *ofs = sb->s_fs_info;
249 /* Sync real dirty inodes in upper filesystem (if it exists) */
250 static int ovl_sync_fs(struct super_block *sb, int wait)
252 struct ovl_fs *ofs = sb->s_fs_info;
253 struct super_block *upper_sb;
260 * If this is a sync(2) call or an emergency sync, all the super blocks
261 * will be iterated, including upper_sb, so no need to do anything.
263 * If this is a syncfs(2) call, then we do need to call
264 * sync_filesystem() on upper_sb, but enough if we do it when being
265 * called with wait == 1.
270 upper_sb = ofs->upper_mnt->mnt_sb;
272 down_read(&upper_sb->s_umount);
273 ret = sync_filesystem(upper_sb);
274 up_read(&upper_sb->s_umount);
281 * @sb: The overlayfs super block
282 * @buf: The struct kstatfs to fill in with stats
284 * Get the filesystem statistics. As writes always target the upper layer
285 * filesystem pass the statfs to the upper filesystem (if it exists)
287 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
289 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
290 struct dentry *root_dentry = dentry->d_sb->s_root;
294 ovl_path_real(root_dentry, &path);
296 err = vfs_statfs(&path, buf);
298 buf->f_namelen = ofs->namelen;
299 buf->f_type = OVERLAYFS_SUPER_MAGIC;
305 /* Will this overlay be forced to mount/remount ro? */
306 static bool ovl_force_readonly(struct ovl_fs *ofs)
308 return (!ofs->upper_mnt || !ofs->workdir);
311 static const char *ovl_redirect_mode_def(void)
313 return ovl_redirect_dir_def ? "on" : "off";
322 static const char * const ovl_xino_str[] = {
328 static inline int ovl_xino_def(void)
330 return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
336 * Prints the mount options for a given superblock.
337 * Returns zero; does not fail.
339 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
341 struct super_block *sb = dentry->d_sb;
342 struct ovl_fs *ofs = sb->s_fs_info;
344 seq_show_option(m, "lowerdir", ofs->config.lowerdir);
345 if (ofs->config.upperdir) {
346 seq_show_option(m, "upperdir", ofs->config.upperdir);
347 seq_show_option(m, "workdir", ofs->config.workdir);
349 if (ofs->config.default_permissions)
350 seq_puts(m, ",default_permissions");
351 if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
352 seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
353 if (ofs->config.index != ovl_index_def)
354 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
355 if (ofs->config.nfs_export != ovl_nfs_export_def)
356 seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
358 if (ofs->config.xino != ovl_xino_def())
359 seq_printf(m, ",xino=%s", ovl_xino_str[ofs->config.xino]);
360 if (ofs->config.metacopy != ovl_metacopy_def)
361 seq_printf(m, ",metacopy=%s",
362 ofs->config.metacopy ? "on" : "off");
366 static int ovl_remount(struct super_block *sb, int *flags, char *data)
368 struct ovl_fs *ofs = sb->s_fs_info;
370 if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
376 static const struct super_operations ovl_super_operations = {
377 .alloc_inode = ovl_alloc_inode,
378 .free_inode = ovl_free_inode,
379 .destroy_inode = ovl_destroy_inode,
380 .drop_inode = generic_delete_inode,
381 .put_super = ovl_put_super,
382 .sync_fs = ovl_sync_fs,
383 .statfs = ovl_statfs,
384 .show_options = ovl_show_options,
385 .remount_fs = ovl_remount,
392 OPT_DEFAULT_PERMISSIONS,
406 static const match_table_t ovl_tokens = {
407 {OPT_LOWERDIR, "lowerdir=%s"},
408 {OPT_UPPERDIR, "upperdir=%s"},
409 {OPT_WORKDIR, "workdir=%s"},
410 {OPT_DEFAULT_PERMISSIONS, "default_permissions"},
411 {OPT_REDIRECT_DIR, "redirect_dir=%s"},
412 {OPT_INDEX_ON, "index=on"},
413 {OPT_INDEX_OFF, "index=off"},
414 {OPT_NFS_EXPORT_ON, "nfs_export=on"},
415 {OPT_NFS_EXPORT_OFF, "nfs_export=off"},
416 {OPT_XINO_ON, "xino=on"},
417 {OPT_XINO_OFF, "xino=off"},
418 {OPT_XINO_AUTO, "xino=auto"},
419 {OPT_METACOPY_ON, "metacopy=on"},
420 {OPT_METACOPY_OFF, "metacopy=off"},
424 static char *ovl_next_opt(char **s)
432 for (p = sbegin; *p; p++) {
437 } else if (*p == ',') {
447 static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
449 if (strcmp(mode, "on") == 0) {
450 config->redirect_dir = true;
452 * Does not make sense to have redirect creation without
453 * redirect following.
455 config->redirect_follow = true;
456 } else if (strcmp(mode, "follow") == 0) {
457 config->redirect_follow = true;
458 } else if (strcmp(mode, "off") == 0) {
459 if (ovl_redirect_always_follow)
460 config->redirect_follow = true;
461 } else if (strcmp(mode, "nofollow") != 0) {
462 pr_err("overlayfs: bad mount option \"redirect_dir=%s\"\n",
470 static int ovl_parse_opt(char *opt, struct ovl_config *config)
474 bool metacopy_opt = false, redirect_opt = false;
476 config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
477 if (!config->redirect_mode)
480 while ((p = ovl_next_opt(&opt)) != NULL) {
482 substring_t args[MAX_OPT_ARGS];
487 token = match_token(p, ovl_tokens, args);
490 kfree(config->upperdir);
491 config->upperdir = match_strdup(&args[0]);
492 if (!config->upperdir)
497 kfree(config->lowerdir);
498 config->lowerdir = match_strdup(&args[0]);
499 if (!config->lowerdir)
504 kfree(config->workdir);
505 config->workdir = match_strdup(&args[0]);
506 if (!config->workdir)
510 case OPT_DEFAULT_PERMISSIONS:
511 config->default_permissions = true;
514 case OPT_REDIRECT_DIR:
515 kfree(config->redirect_mode);
516 config->redirect_mode = match_strdup(&args[0]);
517 if (!config->redirect_mode)
523 config->index = true;
527 config->index = false;
530 case OPT_NFS_EXPORT_ON:
531 config->nfs_export = true;
534 case OPT_NFS_EXPORT_OFF:
535 config->nfs_export = false;
539 config->xino = OVL_XINO_ON;
543 config->xino = OVL_XINO_OFF;
547 config->xino = OVL_XINO_AUTO;
550 case OPT_METACOPY_ON:
551 config->metacopy = true;
555 case OPT_METACOPY_OFF:
556 config->metacopy = false;
560 pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
565 /* Workdir is useless in non-upper mount */
566 if (!config->upperdir && config->workdir) {
567 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
569 kfree(config->workdir);
570 config->workdir = NULL;
573 err = ovl_parse_redirect_mode(config, config->redirect_mode);
578 * This is to make the logic below simpler. It doesn't make any other
579 * difference, since config->redirect_dir is only used for upper.
581 if (!config->upperdir && config->redirect_follow)
582 config->redirect_dir = true;
584 /* Resolve metacopy -> redirect_dir dependency */
585 if (config->metacopy && !config->redirect_dir) {
586 if (metacopy_opt && redirect_opt) {
587 pr_err("overlayfs: conflicting options: metacopy=on,redirect_dir=%s\n",
588 config->redirect_mode);
593 * There was an explicit redirect_dir=... that resulted
596 pr_info("overlayfs: disabling metacopy due to redirect_dir=%s\n",
597 config->redirect_mode);
598 config->metacopy = false;
600 /* Automatically enable redirect otherwise. */
601 config->redirect_follow = config->redirect_dir = true;
608 #define OVL_WORKDIR_NAME "work"
609 #define OVL_INDEXDIR_NAME "index"
611 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
612 const char *name, bool persist)
614 struct inode *dir = ofs->workbasedir->d_inode;
615 struct vfsmount *mnt = ofs->upper_mnt;
618 bool retried = false;
621 inode_lock_nested(dir, I_MUTEX_PARENT);
625 work = lookup_one_len(name, ofs->workbasedir, strlen(name));
628 struct iattr attr = {
629 .ia_valid = ATTR_MODE,
630 .ia_mode = S_IFDIR | 0,
642 ovl_workdir_cleanup(dir, mnt, work, 0);
647 work = ovl_create_real(dir, work, OVL_CATTR(attr.ia_mode));
653 * Try to remove POSIX ACL xattrs from workdir. We are good if:
655 * a) success (there was a POSIX ACL xattr and was removed)
656 * b) -ENODATA (there was no POSIX ACL xattr)
657 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
659 * There are various other error values that could effectively
660 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
661 * if the xattr name is too long), but the set of filesystems
662 * allowed as upper are limited to "normal" ones, where checking
663 * for the above two errors is sufficient.
665 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
666 if (err && err != -ENODATA && err != -EOPNOTSUPP)
669 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
670 if (err && err != -ENODATA && err != -EOPNOTSUPP)
673 /* Clear any inherited mode bits */
674 inode_lock(work->d_inode);
675 err = notify_change(work, &attr, NULL);
676 inode_unlock(work->d_inode);
692 pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
693 ofs->config.workdir, name, -err);
698 static void ovl_unescape(char *s)
711 static int ovl_mount_dir_noesc(const char *name, struct path *path)
716 pr_err("overlayfs: empty lowerdir\n");
719 err = kern_path(name, LOOKUP_FOLLOW, path);
721 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
725 if (ovl_dentry_weird(path->dentry)) {
726 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
729 if (!d_is_dir(path->dentry)) {
730 pr_err("overlayfs: '%s' not a directory\n", name);
741 static int ovl_mount_dir(const char *name, struct path *path)
744 char *tmp = kstrdup(name, GFP_KERNEL);
748 err = ovl_mount_dir_noesc(tmp, path);
751 if (ovl_dentry_remote(path->dentry)) {
752 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
762 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
765 struct kstatfs statfs;
766 int err = vfs_statfs(path, &statfs);
769 pr_err("overlayfs: statfs failed on '%s'\n", name);
771 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
776 static int ovl_lower_dir(const char *name, struct path *path,
777 struct ovl_fs *ofs, int *stack_depth, bool *remote)
782 err = ovl_mount_dir_noesc(name, path);
786 err = ovl_check_namelen(path, ofs, name);
790 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
792 if (ovl_dentry_remote(path->dentry))
796 * The inodes index feature and NFS export need to encode and decode
797 * file handles, so they require that all layers support them.
799 fh_type = ovl_can_decode_fh(path->dentry->d_sb);
800 if ((ofs->config.nfs_export ||
801 (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
802 ofs->config.index = false;
803 ofs->config.nfs_export = false;
804 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
808 /* Check if lower fs has 32bit inode numbers */
809 if (fh_type != FILEID_INO32_GEN)
820 /* Workdir should not be subdir of upperdir and vice versa */
821 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
825 if (workdir != upperdir) {
826 ok = (lock_rename(workdir, upperdir) == NULL);
827 unlock_rename(workdir, upperdir);
832 static unsigned int ovl_split_lowerdirs(char *str)
834 unsigned int ctr = 1;
837 for (s = d = str;; s++, d++) {
840 } else if (*s == ':') {
852 static int __maybe_unused
853 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
854 struct dentry *dentry, struct inode *inode,
855 const char *name, void *buffer, size_t size)
857 return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
860 static int __maybe_unused
861 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
862 struct dentry *dentry, struct inode *inode,
863 const char *name, const void *value,
864 size_t size, int flags)
866 struct dentry *workdir = ovl_workdir(dentry);
867 struct inode *realinode = ovl_inode_real(inode);
868 struct posix_acl *acl = NULL;
871 /* Check that everything is OK before copy-up */
873 acl = posix_acl_from_xattr(&init_user_ns, value, size);
878 if (!IS_POSIXACL(d_inode(workdir)))
879 goto out_acl_release;
880 if (!realinode->i_op->set_acl)
881 goto out_acl_release;
882 if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
883 err = acl ? -EACCES : 0;
884 goto out_acl_release;
887 if (!inode_owner_or_capable(inode))
888 goto out_acl_release;
890 posix_acl_release(acl);
893 * Check if sgid bit needs to be cleared (actual setacl operation will
894 * be done with mounter's capabilities and so that won't do it for us).
896 if (unlikely(inode->i_mode & S_ISGID) &&
897 handler->flags == ACL_TYPE_ACCESS &&
898 !in_group_p(inode->i_gid) &&
899 !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
900 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
902 err = ovl_setattr(dentry, &iattr);
907 err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
909 ovl_copyattr(ovl_inode_real(inode), inode);
914 posix_acl_release(acl);
918 static int ovl_own_xattr_get(const struct xattr_handler *handler,
919 struct dentry *dentry, struct inode *inode,
920 const char *name, void *buffer, size_t size)
925 static int ovl_own_xattr_set(const struct xattr_handler *handler,
926 struct dentry *dentry, struct inode *inode,
927 const char *name, const void *value,
928 size_t size, int flags)
933 static int ovl_other_xattr_get(const struct xattr_handler *handler,
934 struct dentry *dentry, struct inode *inode,
935 const char *name, void *buffer, size_t size)
937 return ovl_xattr_get(dentry, inode, name, buffer, size);
940 static int ovl_other_xattr_set(const struct xattr_handler *handler,
941 struct dentry *dentry, struct inode *inode,
942 const char *name, const void *value,
943 size_t size, int flags)
945 return ovl_xattr_set(dentry, inode, name, value, size, flags);
948 static const struct xattr_handler __maybe_unused
949 ovl_posix_acl_access_xattr_handler = {
950 .name = XATTR_NAME_POSIX_ACL_ACCESS,
951 .flags = ACL_TYPE_ACCESS,
952 .get = ovl_posix_acl_xattr_get,
953 .set = ovl_posix_acl_xattr_set,
956 static const struct xattr_handler __maybe_unused
957 ovl_posix_acl_default_xattr_handler = {
958 .name = XATTR_NAME_POSIX_ACL_DEFAULT,
959 .flags = ACL_TYPE_DEFAULT,
960 .get = ovl_posix_acl_xattr_get,
961 .set = ovl_posix_acl_xattr_set,
964 static const struct xattr_handler ovl_own_xattr_handler = {
965 .prefix = OVL_XATTR_PREFIX,
966 .get = ovl_own_xattr_get,
967 .set = ovl_own_xattr_set,
970 static const struct xattr_handler ovl_other_xattr_handler = {
971 .prefix = "", /* catch all */
972 .get = ovl_other_xattr_get,
973 .set = ovl_other_xattr_set,
976 static const struct xattr_handler *ovl_xattr_handlers[] = {
977 #ifdef CONFIG_FS_POSIX_ACL
978 &ovl_posix_acl_access_xattr_handler,
979 &ovl_posix_acl_default_xattr_handler,
981 &ovl_own_xattr_handler,
982 &ovl_other_xattr_handler,
986 static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath)
988 struct vfsmount *upper_mnt;
991 err = ovl_mount_dir(ofs->config.upperdir, upperpath);
995 /* Upper fs should not be r/o */
996 if (sb_rdonly(upperpath->mnt->mnt_sb)) {
997 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
1002 err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
1006 upper_mnt = clone_private_mount(upperpath);
1007 err = PTR_ERR(upper_mnt);
1008 if (IS_ERR(upper_mnt)) {
1009 pr_err("overlayfs: failed to clone upperpath\n");
1013 /* Don't inherit atime flags */
1014 upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
1015 ofs->upper_mnt = upper_mnt;
1018 if (ovl_inuse_trylock(ofs->upper_mnt->mnt_root)) {
1019 ofs->upperdir_locked = true;
1020 } else if (ofs->config.index) {
1021 pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
1024 pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
1032 static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
1034 struct vfsmount *mnt = ofs->upper_mnt;
1035 struct dentry *temp;
1039 err = mnt_want_write(mnt);
1043 ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
1048 * Upper should support d_type, else whiteouts are visible. Given
1049 * workdir and upper are on same fs, we can do iterate_dir() on
1050 * workdir. This check requires successful creation of workdir in
1053 err = ovl_check_d_type_supported(workpath);
1058 * We allowed this configuration and don't want to break users over
1059 * kernel upgrade. So warn instead of erroring out.
1062 pr_warn("overlayfs: upper fs needs to support d_type.\n");
1064 /* Check if upper/work fs supports O_TMPFILE */
1065 temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
1066 ofs->tmpfile = !IS_ERR(temp);
1070 pr_warn("overlayfs: upper fs does not support tmpfile.\n");
1073 * Check if upper/work fs supports trusted.overlay.* xattr
1075 err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
1077 ofs->noxattr = true;
1078 ofs->config.index = false;
1079 ofs->config.metacopy = false;
1080 pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off and metacopy=off.\n");
1083 vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
1086 /* Check if upper/work fs supports file handles */
1087 fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
1088 if (ofs->config.index && !fh_type) {
1089 ofs->config.index = false;
1090 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
1093 /* Check if upper fs has 32bit inode numbers */
1094 if (fh_type != FILEID_INO32_GEN)
1097 /* NFS export of r/w mount depends on index */
1098 if (ofs->config.nfs_export && !ofs->config.index) {
1099 pr_warn("overlayfs: NFS export requires \"index=on\", falling back to nfs_export=off.\n");
1100 ofs->config.nfs_export = false;
1103 mnt_drop_write(mnt);
1107 static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath)
1110 struct path workpath = { };
1112 err = ovl_mount_dir(ofs->config.workdir, &workpath);
1117 if (upperpath->mnt != workpath.mnt) {
1118 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
1121 if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
1122 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
1126 ofs->workbasedir = dget(workpath.dentry);
1129 if (ovl_inuse_trylock(ofs->workbasedir)) {
1130 ofs->workdir_locked = true;
1131 } else if (ofs->config.index) {
1132 pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
1135 pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
1138 err = ovl_make_workdir(ofs, &workpath);
1144 path_put(&workpath);
1149 static int ovl_get_indexdir(struct ovl_fs *ofs, struct ovl_entry *oe,
1150 struct path *upperpath)
1152 struct vfsmount *mnt = ofs->upper_mnt;
1155 err = mnt_want_write(mnt);
1159 /* Verify lower root is upper root origin */
1160 err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
1163 pr_err("overlayfs: failed to verify upper root origin\n");
1167 ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
1168 if (ofs->indexdir) {
1170 * Verify upper root is exclusively associated with index dir.
1171 * Older kernels stored upper fh in "trusted.overlay.origin"
1172 * xattr. If that xattr exists, verify that it is a match to
1173 * upper dir file handle. In any case, verify or set xattr
1174 * "trusted.overlay.upper" to indicate that index may have
1175 * directory entries.
1177 if (ovl_check_origin_xattr(ofs->indexdir)) {
1178 err = ovl_verify_set_fh(ofs->indexdir, OVL_XATTR_ORIGIN,
1179 upperpath->dentry, true, false);
1181 pr_err("overlayfs: failed to verify index dir 'origin' xattr\n");
1183 err = ovl_verify_upper(ofs->indexdir, upperpath->dentry, true);
1185 pr_err("overlayfs: failed to verify index dir 'upper' xattr\n");
1187 /* Cleanup bad/stale/orphan index entries */
1189 err = ovl_indexdir_cleanup(ofs);
1191 if (err || !ofs->indexdir)
1192 pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1195 mnt_drop_write(mnt);
1199 static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
1203 if (!ofs->config.nfs_export && !(ofs->config.index && ofs->upper_mnt))
1206 for (i = 0; i < ofs->numlowerfs; i++) {
1208 * We use uuid to associate an overlay lower file handle with a
1209 * lower layer, so we can accept lower fs with null uuid as long
1210 * as all lower layers with null uuid are on the same fs.
1212 if (uuid_equal(&ofs->lower_fs[i].sb->s_uuid, uuid))
1218 /* Get a unique fsid for the layer */
1219 static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
1221 struct super_block *sb = path->mnt->mnt_sb;
1226 /* fsid 0 is reserved for upper fs even with non upper overlay */
1227 if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb)
1230 for (i = 0; i < ofs->numlowerfs; i++) {
1231 if (ofs->lower_fs[i].sb == sb)
1235 if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) {
1236 ofs->config.index = false;
1237 ofs->config.nfs_export = false;
1238 pr_warn("overlayfs: %s uuid detected in lower fs '%pd2', falling back to index=off,nfs_export=off.\n",
1239 uuid_is_null(&sb->s_uuid) ? "null" : "conflicting",
1243 err = get_anon_bdev(&dev);
1245 pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
1249 ofs->lower_fs[ofs->numlowerfs].sb = sb;
1250 ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev;
1253 return ofs->numlowerfs;
1256 static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
1257 unsigned int numlower)
1263 ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
1265 if (ofs->lower_layers == NULL)
1268 ofs->lower_fs = kcalloc(numlower, sizeof(struct ovl_sb),
1270 if (ofs->lower_fs == NULL)
1273 for (i = 0; i < numlower; i++) {
1274 struct vfsmount *mnt;
1277 err = fsid = ovl_get_fsid(ofs, &stack[i]);
1281 mnt = clone_private_mount(&stack[i]);
1284 pr_err("overlayfs: failed to clone lowerpath\n");
1289 * Make lower layers R/O. That way fchmod/fchown on lower file
1290 * will fail instead of modifying lower fs.
1292 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1294 ofs->lower_layers[ofs->numlower].mnt = mnt;
1295 ofs->lower_layers[ofs->numlower].idx = i + 1;
1296 ofs->lower_layers[ofs->numlower].fsid = fsid;
1298 ofs->lower_layers[ofs->numlower].fs =
1299 &ofs->lower_fs[fsid - 1];
1305 * When all layers on same fs, overlay can use real inode numbers.
1306 * With mount option "xino=on", mounter declares that there are enough
1307 * free high bits in underlying fs to hold the unique fsid.
1308 * If overlayfs does encounter underlying inodes using the high xino
1309 * bits reserved for fsid, it emits a warning and uses the original
1312 if (!ofs->numlowerfs || (ofs->numlowerfs == 1 && !ofs->upper_mnt)) {
1314 ofs->config.xino = OVL_XINO_OFF;
1315 } else if (ofs->config.xino == OVL_XINO_ON && !ofs->xino_bits) {
1317 * This is a roundup of number of bits needed for numlowerfs+1
1318 * (i.e. ilog2(numlowerfs+1 - 1) + 1). fsid 0 is reserved for
1319 * upper fs even with non upper overlay.
1321 BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 31);
1322 ofs->xino_bits = ilog2(ofs->numlowerfs) + 1;
1325 if (ofs->xino_bits) {
1326 pr_info("overlayfs: \"xino\" feature enabled using %d upper inode bits.\n",
1335 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1339 char *lowertmp, *lower;
1340 struct path *stack = NULL;
1341 unsigned int stacklen, numlower = 0, i;
1342 bool remote = false;
1343 struct ovl_entry *oe;
1346 lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
1351 stacklen = ovl_split_lowerdirs(lowertmp);
1352 if (stacklen > OVL_MAX_STACK) {
1353 pr_err("overlayfs: too many lower directories, limit is %d\n",
1356 } else if (!ofs->config.upperdir && stacklen == 1) {
1357 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
1359 } else if (!ofs->config.upperdir && ofs->config.nfs_export &&
1360 ofs->config.redirect_follow) {
1361 pr_warn("overlayfs: NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
1362 ofs->config.nfs_export = false;
1366 stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
1372 for (numlower = 0; numlower < stacklen; numlower++) {
1373 err = ovl_lower_dir(lower, &stack[numlower], ofs,
1374 &sb->s_stack_depth, &remote);
1378 lower = strchr(lower, '\0') + 1;
1382 sb->s_stack_depth++;
1383 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1384 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1388 err = ovl_get_lower_layers(ofs, stack, numlower);
1393 oe = ovl_alloc_entry(numlower);
1397 for (i = 0; i < numlower; i++) {
1398 oe->lowerstack[i].dentry = dget(stack[i].dentry);
1399 oe->lowerstack[i].layer = &ofs->lower_layers[i];
1403 sb->s_d_op = &ovl_reval_dentry_operations;
1405 sb->s_d_op = &ovl_dentry_operations;
1408 for (i = 0; i < numlower; i++)
1409 path_put(&stack[i]);
1420 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
1422 struct path upperpath = { };
1423 struct dentry *root_dentry;
1424 struct ovl_entry *oe;
1430 ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
1434 ofs->creator_cred = cred = prepare_creds();
1438 ofs->config.index = ovl_index_def;
1439 ofs->config.nfs_export = ovl_nfs_export_def;
1440 ofs->config.xino = ovl_xino_def();
1441 ofs->config.metacopy = ovl_metacopy_def;
1442 err = ovl_parse_opt((char *) data, &ofs->config);
1447 if (!ofs->config.lowerdir) {
1449 pr_err("overlayfs: missing 'lowerdir'\n");
1453 sb->s_stack_depth = 0;
1454 sb->s_maxbytes = MAX_LFS_FILESIZE;
1455 /* Assume underlaying fs uses 32bit inodes unless proven otherwise */
1456 if (ofs->config.xino != OVL_XINO_OFF)
1457 ofs->xino_bits = BITS_PER_LONG - 32;
1459 if (ofs->config.upperdir) {
1460 if (!ofs->config.workdir) {
1461 pr_err("overlayfs: missing 'workdir'\n");
1465 err = ovl_get_upper(ofs, &upperpath);
1469 err = ovl_get_workdir(ofs, &upperpath);
1474 sb->s_flags |= SB_RDONLY;
1476 sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
1477 sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
1480 oe = ovl_get_lowerstack(sb, ofs);
1485 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1486 if (!ofs->upper_mnt)
1487 sb->s_flags |= SB_RDONLY;
1489 if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
1490 err = ovl_get_indexdir(ofs, oe, &upperpath);
1494 /* Force r/o mount with no index dir */
1495 if (!ofs->indexdir) {
1497 ofs->workdir = NULL;
1498 sb->s_flags |= SB_RDONLY;
1503 /* Show index=off in /proc/mounts for forced r/o mount */
1504 if (!ofs->indexdir) {
1505 ofs->config.index = false;
1506 if (ofs->upper_mnt && ofs->config.nfs_export) {
1507 pr_warn("overlayfs: NFS export requires an index dir, falling back to nfs_export=off.\n");
1508 ofs->config.nfs_export = false;
1512 if (ofs->config.metacopy && ofs->config.nfs_export) {
1513 pr_warn("overlayfs: NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
1514 ofs->config.nfs_export = false;
1517 if (ofs->config.nfs_export)
1518 sb->s_export_op = &ovl_export_operations;
1520 /* Never override disk quota limits or use reserved space */
1521 cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1523 sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1524 sb->s_op = &ovl_super_operations;
1525 sb->s_xattr = ovl_xattr_handlers;
1526 sb->s_fs_info = ofs;
1527 sb->s_flags |= SB_POSIXACL;
1530 root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1534 root_dentry->d_fsdata = oe;
1536 mntput(upperpath.mnt);
1537 if (upperpath.dentry) {
1538 ovl_dentry_set_upper_alias(root_dentry);
1539 if (ovl_is_impuredir(upperpath.dentry))
1540 ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
1543 /* Root is always merge -> can have whiteouts */
1544 ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
1545 ovl_dentry_set_flag(OVL_E_CONNECTED, root_dentry);
1546 ovl_set_upperdata(d_inode(root_dentry));
1547 ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
1548 ovl_dentry_lower(root_dentry), NULL);
1550 sb->s_root = root_dentry;
1555 ovl_entry_stack_free(oe);
1558 path_put(&upperpath);
1564 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1565 const char *dev_name, void *raw_data)
1567 return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1570 static struct file_system_type ovl_fs_type = {
1571 .owner = THIS_MODULE,
1574 .kill_sb = kill_anon_super,
1576 MODULE_ALIAS_FS("overlay");
1578 static void ovl_inode_init_once(void *foo)
1580 struct ovl_inode *oi = foo;
1582 inode_init_once(&oi->vfs_inode);
1585 static int __init ovl_init(void)
1589 ovl_inode_cachep = kmem_cache_create("ovl_inode",
1590 sizeof(struct ovl_inode), 0,
1591 (SLAB_RECLAIM_ACCOUNT|
1592 SLAB_MEM_SPREAD|SLAB_ACCOUNT),
1593 ovl_inode_init_once);
1594 if (ovl_inode_cachep == NULL)
1597 err = register_filesystem(&ovl_fs_type);
1599 kmem_cache_destroy(ovl_inode_cachep);
1604 static void __exit ovl_exit(void)
1606 unregister_filesystem(&ovl_fs_type);
1609 * Make sure all delayed rcu free inodes are flushed before we
1613 kmem_cache_destroy(ovl_inode_cachep);
1617 module_init(ovl_init);
1618 module_exit(ovl_exit);