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)
85 struct dentry *real = NULL, *lower;
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 lower = ovl_dentry_lowerdata(dentry);
109 /* Handle recursion */
110 real = d_real(real, inode);
112 if (!inode || inode == d_inode(real))
115 WARN(1, "%s(%pd4, %s:%lu): real dentry (%p/%lu) not found\n",
116 __func__, dentry, inode ? inode->i_sb->s_id : "NULL",
117 inode ? inode->i_ino : 0, real,
118 real && d_inode(real) ? d_inode(real)->i_ino : 0);
122 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
124 struct ovl_entry *oe = dentry->d_fsdata;
128 for (i = 0; i < oe->numlower; i++) {
129 struct dentry *d = oe->lowerstack[i].dentry;
131 if (d->d_flags & DCACHE_OP_REVALIDATE) {
132 ret = d->d_op->d_revalidate(d, flags);
136 if (!(flags & LOOKUP_RCU))
145 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
147 struct ovl_entry *oe = dentry->d_fsdata;
151 for (i = 0; i < oe->numlower; i++) {
152 struct dentry *d = oe->lowerstack[i].dentry;
154 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
155 ret = d->d_op->d_weak_revalidate(d, flags);
163 static const struct dentry_operations ovl_dentry_operations = {
164 .d_release = ovl_dentry_release,
165 .d_real = ovl_d_real,
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,
175 static struct kmem_cache *ovl_inode_cachep;
177 static struct inode *ovl_alloc_inode(struct super_block *sb)
179 struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL);
188 oi->__upperdentry = NULL;
190 oi->lowerdata = NULL;
191 mutex_init(&oi->lock);
193 return &oi->vfs_inode;
196 static void ovl_i_callback(struct rcu_head *head)
198 struct inode *inode = container_of(head, struct inode, i_rcu);
200 kmem_cache_free(ovl_inode_cachep, OVL_I(inode));
203 static void ovl_destroy_inode(struct inode *inode)
205 struct ovl_inode *oi = OVL_I(inode);
207 dput(oi->__upperdentry);
209 if (S_ISDIR(inode->i_mode))
210 ovl_dir_cache_free(inode);
214 mutex_destroy(&oi->lock);
216 call_rcu(&inode->i_rcu, ovl_i_callback);
219 static void ovl_free_fs(struct ovl_fs *ofs)
223 iput(ofs->workbasedir_trap);
224 iput(ofs->indexdir_trap);
225 iput(ofs->workdir_trap);
226 iput(ofs->upperdir_trap);
229 if (ofs->workdir_locked)
230 ovl_inuse_unlock(ofs->workbasedir);
231 dput(ofs->workbasedir);
232 if (ofs->upperdir_locked)
233 ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
234 mntput(ofs->upper_mnt);
235 for (i = 0; i < ofs->numlower; i++) {
236 iput(ofs->lower_layers[i].trap);
237 mntput(ofs->lower_layers[i].mnt);
239 for (i = 0; i < ofs->numlowerfs; i++)
240 free_anon_bdev(ofs->lower_fs[i].pseudo_dev);
241 kfree(ofs->lower_layers);
242 kfree(ofs->lower_fs);
244 kfree(ofs->config.lowerdir);
245 kfree(ofs->config.upperdir);
246 kfree(ofs->config.workdir);
247 kfree(ofs->config.redirect_mode);
248 if (ofs->creator_cred)
249 put_cred(ofs->creator_cred);
253 static void ovl_put_super(struct super_block *sb)
255 struct ovl_fs *ofs = sb->s_fs_info;
260 /* Sync real dirty inodes in upper filesystem (if it exists) */
261 static int ovl_sync_fs(struct super_block *sb, int wait)
263 struct ovl_fs *ofs = sb->s_fs_info;
264 struct super_block *upper_sb;
271 * If this is a sync(2) call or an emergency sync, all the super blocks
272 * will be iterated, including upper_sb, so no need to do anything.
274 * If this is a syncfs(2) call, then we do need to call
275 * sync_filesystem() on upper_sb, but enough if we do it when being
276 * called with wait == 1.
281 upper_sb = ofs->upper_mnt->mnt_sb;
283 down_read(&upper_sb->s_umount);
284 ret = sync_filesystem(upper_sb);
285 up_read(&upper_sb->s_umount);
292 * @sb: The overlayfs super block
293 * @buf: The struct kstatfs to fill in with stats
295 * Get the filesystem statistics. As writes always target the upper layer
296 * filesystem pass the statfs to the upper filesystem (if it exists)
298 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
300 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
301 struct dentry *root_dentry = dentry->d_sb->s_root;
305 ovl_path_real(root_dentry, &path);
307 err = vfs_statfs(&path, buf);
309 buf->f_namelen = ofs->namelen;
310 buf->f_type = OVERLAYFS_SUPER_MAGIC;
316 /* Will this overlay be forced to mount/remount ro? */
317 static bool ovl_force_readonly(struct ovl_fs *ofs)
319 return (!ofs->upper_mnt || !ofs->workdir);
322 static const char *ovl_redirect_mode_def(void)
324 return ovl_redirect_dir_def ? "on" : "off";
333 static const char * const ovl_xino_str[] = {
339 static inline int ovl_xino_def(void)
341 return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
347 * Prints the mount options for a given superblock.
348 * Returns zero; does not fail.
350 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
352 struct super_block *sb = dentry->d_sb;
353 struct ovl_fs *ofs = sb->s_fs_info;
355 seq_show_option(m, "lowerdir", ofs->config.lowerdir);
356 if (ofs->config.upperdir) {
357 seq_show_option(m, "upperdir", ofs->config.upperdir);
358 seq_show_option(m, "workdir", ofs->config.workdir);
360 if (ofs->config.default_permissions)
361 seq_puts(m, ",default_permissions");
362 if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
363 seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
364 if (ofs->config.index != ovl_index_def)
365 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
366 if (ofs->config.nfs_export != ovl_nfs_export_def)
367 seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
369 if (ofs->config.xino != ovl_xino_def())
370 seq_printf(m, ",xino=%s", ovl_xino_str[ofs->config.xino]);
371 if (ofs->config.metacopy != ovl_metacopy_def)
372 seq_printf(m, ",metacopy=%s",
373 ofs->config.metacopy ? "on" : "off");
377 static int ovl_remount(struct super_block *sb, int *flags, char *data)
379 struct ovl_fs *ofs = sb->s_fs_info;
381 if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
387 static const struct super_operations ovl_super_operations = {
388 .alloc_inode = ovl_alloc_inode,
389 .destroy_inode = ovl_destroy_inode,
390 .drop_inode = generic_delete_inode,
391 .put_super = ovl_put_super,
392 .sync_fs = ovl_sync_fs,
393 .statfs = ovl_statfs,
394 .show_options = ovl_show_options,
395 .remount_fs = ovl_remount,
402 OPT_DEFAULT_PERMISSIONS,
416 static const match_table_t ovl_tokens = {
417 {OPT_LOWERDIR, "lowerdir=%s"},
418 {OPT_UPPERDIR, "upperdir=%s"},
419 {OPT_WORKDIR, "workdir=%s"},
420 {OPT_DEFAULT_PERMISSIONS, "default_permissions"},
421 {OPT_REDIRECT_DIR, "redirect_dir=%s"},
422 {OPT_INDEX_ON, "index=on"},
423 {OPT_INDEX_OFF, "index=off"},
424 {OPT_NFS_EXPORT_ON, "nfs_export=on"},
425 {OPT_NFS_EXPORT_OFF, "nfs_export=off"},
426 {OPT_XINO_ON, "xino=on"},
427 {OPT_XINO_OFF, "xino=off"},
428 {OPT_XINO_AUTO, "xino=auto"},
429 {OPT_METACOPY_ON, "metacopy=on"},
430 {OPT_METACOPY_OFF, "metacopy=off"},
434 static char *ovl_next_opt(char **s)
442 for (p = sbegin; *p; p++) {
447 } else if (*p == ',') {
457 static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
459 if (strcmp(mode, "on") == 0) {
460 config->redirect_dir = true;
462 * Does not make sense to have redirect creation without
463 * redirect following.
465 config->redirect_follow = true;
466 } else if (strcmp(mode, "follow") == 0) {
467 config->redirect_follow = true;
468 } else if (strcmp(mode, "off") == 0) {
469 if (ovl_redirect_always_follow)
470 config->redirect_follow = true;
471 } else if (strcmp(mode, "nofollow") != 0) {
472 pr_err("overlayfs: bad mount option \"redirect_dir=%s\"\n",
480 static int ovl_parse_opt(char *opt, struct ovl_config *config)
484 bool metacopy_opt = false, redirect_opt = false;
486 config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
487 if (!config->redirect_mode)
490 while ((p = ovl_next_opt(&opt)) != NULL) {
492 substring_t args[MAX_OPT_ARGS];
497 token = match_token(p, ovl_tokens, args);
500 kfree(config->upperdir);
501 config->upperdir = match_strdup(&args[0]);
502 if (!config->upperdir)
507 kfree(config->lowerdir);
508 config->lowerdir = match_strdup(&args[0]);
509 if (!config->lowerdir)
514 kfree(config->workdir);
515 config->workdir = match_strdup(&args[0]);
516 if (!config->workdir)
520 case OPT_DEFAULT_PERMISSIONS:
521 config->default_permissions = true;
524 case OPT_REDIRECT_DIR:
525 kfree(config->redirect_mode);
526 config->redirect_mode = match_strdup(&args[0]);
527 if (!config->redirect_mode)
533 config->index = true;
537 config->index = false;
540 case OPT_NFS_EXPORT_ON:
541 config->nfs_export = true;
544 case OPT_NFS_EXPORT_OFF:
545 config->nfs_export = false;
549 config->xino = OVL_XINO_ON;
553 config->xino = OVL_XINO_OFF;
557 config->xino = OVL_XINO_AUTO;
560 case OPT_METACOPY_ON:
561 config->metacopy = true;
565 case OPT_METACOPY_OFF:
566 config->metacopy = false;
570 pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
575 /* Workdir is useless in non-upper mount */
576 if (!config->upperdir && config->workdir) {
577 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
579 kfree(config->workdir);
580 config->workdir = NULL;
583 err = ovl_parse_redirect_mode(config, config->redirect_mode);
588 * This is to make the logic below simpler. It doesn't make any other
589 * difference, since config->redirect_dir is only used for upper.
591 if (!config->upperdir && config->redirect_follow)
592 config->redirect_dir = true;
594 /* Resolve metacopy -> redirect_dir dependency */
595 if (config->metacopy && !config->redirect_dir) {
596 if (metacopy_opt && redirect_opt) {
597 pr_err("overlayfs: conflicting options: metacopy=on,redirect_dir=%s\n",
598 config->redirect_mode);
603 * There was an explicit redirect_dir=... that resulted
606 pr_info("overlayfs: disabling metacopy due to redirect_dir=%s\n",
607 config->redirect_mode);
608 config->metacopy = false;
610 /* Automatically enable redirect otherwise. */
611 config->redirect_follow = config->redirect_dir = true;
618 #define OVL_WORKDIR_NAME "work"
619 #define OVL_INDEXDIR_NAME "index"
621 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
622 const char *name, bool persist)
624 struct inode *dir = ofs->workbasedir->d_inode;
625 struct vfsmount *mnt = ofs->upper_mnt;
628 bool retried = false;
631 inode_lock_nested(dir, I_MUTEX_PARENT);
635 work = lookup_one_len(name, ofs->workbasedir, strlen(name));
638 struct iattr attr = {
639 .ia_valid = ATTR_MODE,
640 .ia_mode = S_IFDIR | 0,
652 ovl_workdir_cleanup(dir, mnt, work, 0);
657 err = ovl_mkdir_real(dir, &work, attr.ia_mode);
661 /* Weird filesystem returning with hashed negative (kernfs)? */
663 if (d_really_is_negative(work))
667 * Try to remove POSIX ACL xattrs from workdir. We are good if:
669 * a) success (there was a POSIX ACL xattr and was removed)
670 * b) -ENODATA (there was no POSIX ACL xattr)
671 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
673 * There are various other error values that could effectively
674 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
675 * if the xattr name is too long), but the set of filesystems
676 * allowed as upper are limited to "normal" ones, where checking
677 * for the above two errors is sufficient.
679 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
680 if (err && err != -ENODATA && err != -EOPNOTSUPP)
683 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
684 if (err && err != -ENODATA && err != -EOPNOTSUPP)
687 /* Clear any inherited mode bits */
688 inode_lock(work->d_inode);
689 err = notify_change(work, &attr, NULL);
690 inode_unlock(work->d_inode);
706 pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
707 ofs->config.workdir, name, -err);
712 static void ovl_unescape(char *s)
725 static int ovl_mount_dir_noesc(const char *name, struct path *path)
730 pr_err("overlayfs: empty lowerdir\n");
733 err = kern_path(name, LOOKUP_FOLLOW, path);
735 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
739 if (ovl_dentry_weird(path->dentry)) {
740 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
743 if (!d_is_dir(path->dentry)) {
744 pr_err("overlayfs: '%s' not a directory\n", name);
755 static int ovl_mount_dir(const char *name, struct path *path)
758 char *tmp = kstrdup(name, GFP_KERNEL);
762 err = ovl_mount_dir_noesc(tmp, path);
765 if (ovl_dentry_remote(path->dentry)) {
766 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
776 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
779 struct kstatfs statfs;
780 int err = vfs_statfs(path, &statfs);
783 pr_err("overlayfs: statfs failed on '%s'\n", name);
785 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
790 static int ovl_lower_dir(const char *name, struct path *path,
791 struct ovl_fs *ofs, int *stack_depth, bool *remote)
796 err = ovl_mount_dir_noesc(name, path);
800 err = ovl_check_namelen(path, ofs, name);
804 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
806 if (ovl_dentry_remote(path->dentry))
810 * The inodes index feature and NFS export need to encode and decode
811 * file handles, so they require that all layers support them.
813 fh_type = ovl_can_decode_fh(path->dentry->d_sb);
814 if ((ofs->config.nfs_export ||
815 (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
816 ofs->config.index = false;
817 ofs->config.nfs_export = false;
818 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
822 /* Check if lower fs has 32bit inode numbers */
823 if (fh_type != FILEID_INO32_GEN)
834 /* Workdir should not be subdir of upperdir and vice versa */
835 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
839 if (workdir != upperdir) {
840 ok = (lock_rename(workdir, upperdir) == NULL);
841 unlock_rename(workdir, upperdir);
846 static unsigned int ovl_split_lowerdirs(char *str)
848 unsigned int ctr = 1;
851 for (s = d = str;; s++, d++) {
854 } else if (*s == ':') {
866 static int __maybe_unused
867 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
868 struct dentry *dentry, struct inode *inode,
869 const char *name, void *buffer, size_t size)
871 return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
874 static int __maybe_unused
875 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
876 struct dentry *dentry, struct inode *inode,
877 const char *name, const void *value,
878 size_t size, int flags)
880 struct dentry *workdir = ovl_workdir(dentry);
881 struct inode *realinode = ovl_inode_real(inode);
882 struct posix_acl *acl = NULL;
885 /* Check that everything is OK before copy-up */
887 acl = posix_acl_from_xattr(&init_user_ns, value, size);
892 if (!IS_POSIXACL(d_inode(workdir)))
893 goto out_acl_release;
894 if (!realinode->i_op->set_acl)
895 goto out_acl_release;
896 if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
897 err = acl ? -EACCES : 0;
898 goto out_acl_release;
901 if (!inode_owner_or_capable(inode))
902 goto out_acl_release;
904 posix_acl_release(acl);
907 * Check if sgid bit needs to be cleared (actual setacl operation will
908 * be done with mounter's capabilities and so that won't do it for us).
910 if (unlikely(inode->i_mode & S_ISGID) &&
911 handler->flags == ACL_TYPE_ACCESS &&
912 !in_group_p(inode->i_gid) &&
913 !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
914 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
916 err = ovl_setattr(dentry, &iattr);
921 err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
923 ovl_copyattr(ovl_inode_real(inode), inode);
928 posix_acl_release(acl);
932 static int ovl_own_xattr_get(const struct xattr_handler *handler,
933 struct dentry *dentry, struct inode *inode,
934 const char *name, void *buffer, size_t size)
939 static int ovl_own_xattr_set(const struct xattr_handler *handler,
940 struct dentry *dentry, struct inode *inode,
941 const char *name, const void *value,
942 size_t size, int flags)
947 static int ovl_other_xattr_get(const struct xattr_handler *handler,
948 struct dentry *dentry, struct inode *inode,
949 const char *name, void *buffer, size_t size)
951 return ovl_xattr_get(dentry, inode, name, buffer, size);
954 static int ovl_other_xattr_set(const struct xattr_handler *handler,
955 struct dentry *dentry, struct inode *inode,
956 const char *name, const void *value,
957 size_t size, int flags)
959 return ovl_xattr_set(dentry, inode, name, value, size, flags);
962 static const struct xattr_handler __maybe_unused
963 ovl_posix_acl_access_xattr_handler = {
964 .name = XATTR_NAME_POSIX_ACL_ACCESS,
965 .flags = ACL_TYPE_ACCESS,
966 .get = ovl_posix_acl_xattr_get,
967 .set = ovl_posix_acl_xattr_set,
970 static const struct xattr_handler __maybe_unused
971 ovl_posix_acl_default_xattr_handler = {
972 .name = XATTR_NAME_POSIX_ACL_DEFAULT,
973 .flags = ACL_TYPE_DEFAULT,
974 .get = ovl_posix_acl_xattr_get,
975 .set = ovl_posix_acl_xattr_set,
978 static const struct xattr_handler ovl_own_xattr_handler = {
979 .prefix = OVL_XATTR_PREFIX,
980 .get = ovl_own_xattr_get,
981 .set = ovl_own_xattr_set,
984 static const struct xattr_handler ovl_other_xattr_handler = {
985 .prefix = "", /* catch all */
986 .get = ovl_other_xattr_get,
987 .set = ovl_other_xattr_set,
990 static const struct xattr_handler *ovl_xattr_handlers[] = {
991 #ifdef CONFIG_FS_POSIX_ACL
992 &ovl_posix_acl_access_xattr_handler,
993 &ovl_posix_acl_default_xattr_handler,
995 &ovl_own_xattr_handler,
996 &ovl_other_xattr_handler,
1000 static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
1001 struct inode **ptrap, const char *name)
1006 trap = ovl_get_trap_inode(sb, dir);
1007 err = PTR_ERR_OR_ZERO(trap);
1010 pr_err("overlayfs: conflicting %s path\n", name);
1019 * Determine how we treat concurrent use of upperdir/workdir based on the
1020 * index feature. This is papering over mount leaks of container runtimes,
1021 * for example, an old overlay mount is leaked and now its upperdir is
1022 * attempted to be used as a lower layer in a new overlay mount.
1024 static int ovl_report_in_use(struct ovl_fs *ofs, const char *name)
1026 if (ofs->config.index) {
1027 pr_err("overlayfs: %s is in-use as upperdir/workdir of another mount, mount with '-o index=off' to override exclusive upperdir protection.\n",
1031 pr_warn("overlayfs: %s is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.\n",
1037 static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
1038 struct path *upperpath)
1040 struct vfsmount *upper_mnt;
1043 err = ovl_mount_dir(ofs->config.upperdir, upperpath);
1047 /* Upper fs should not be r/o */
1048 if (sb_rdonly(upperpath->mnt->mnt_sb)) {
1049 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
1054 err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
1058 err = ovl_setup_trap(sb, upperpath->dentry, &ofs->upperdir_trap,
1063 upper_mnt = clone_private_mount(upperpath);
1064 err = PTR_ERR(upper_mnt);
1065 if (IS_ERR(upper_mnt)) {
1066 pr_err("overlayfs: failed to clone upperpath\n");
1070 /* Don't inherit atime flags */
1071 upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
1072 ofs->upper_mnt = upper_mnt;
1074 if (ovl_inuse_trylock(ofs->upper_mnt->mnt_root)) {
1075 ofs->upperdir_locked = true;
1077 err = ovl_report_in_use(ofs, "upperdir");
1087 static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
1088 struct path *workpath)
1090 struct vfsmount *mnt = ofs->upper_mnt;
1091 struct dentry *temp;
1095 err = mnt_want_write(mnt);
1099 ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
1103 err = ovl_setup_trap(sb, ofs->workdir, &ofs->workdir_trap, "workdir");
1108 * Upper should support d_type, else whiteouts are visible. Given
1109 * workdir and upper are on same fs, we can do iterate_dir() on
1110 * workdir. This check requires successful creation of workdir in
1113 err = ovl_check_d_type_supported(workpath);
1118 * We allowed this configuration and don't want to break users over
1119 * kernel upgrade. So warn instead of erroring out.
1122 pr_warn("overlayfs: upper fs needs to support d_type.\n");
1124 /* Check if upper/work fs supports O_TMPFILE */
1125 temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
1126 ofs->tmpfile = !IS_ERR(temp);
1130 pr_warn("overlayfs: upper fs does not support tmpfile.\n");
1133 * Check if upper/work fs supports trusted.overlay.* xattr
1135 err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
1137 ofs->noxattr = true;
1138 ofs->config.index = false;
1139 ofs->config.metacopy = false;
1140 pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off and metacopy=off.\n");
1143 vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
1146 /* Check if upper/work fs supports file handles */
1147 fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
1148 if (ofs->config.index && !fh_type) {
1149 ofs->config.index = false;
1150 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
1153 /* Check if upper fs has 32bit inode numbers */
1154 if (fh_type != FILEID_INO32_GEN)
1157 /* NFS export of r/w mount depends on index */
1158 if (ofs->config.nfs_export && !ofs->config.index) {
1159 pr_warn("overlayfs: NFS export requires \"index=on\", falling back to nfs_export=off.\n");
1160 ofs->config.nfs_export = false;
1163 mnt_drop_write(mnt);
1167 static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
1168 struct path *upperpath)
1171 struct path workpath = { };
1173 err = ovl_mount_dir(ofs->config.workdir, &workpath);
1178 if (upperpath->mnt != workpath.mnt) {
1179 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
1182 if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
1183 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
1187 ofs->workbasedir = dget(workpath.dentry);
1189 if (ovl_inuse_trylock(ofs->workbasedir)) {
1190 ofs->workdir_locked = true;
1192 err = ovl_report_in_use(ofs, "workdir");
1197 err = ovl_setup_trap(sb, ofs->workbasedir, &ofs->workbasedir_trap,
1202 err = ovl_make_workdir(sb, ofs, &workpath);
1205 path_put(&workpath);
1210 static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
1211 struct ovl_entry *oe, struct path *upperpath)
1213 struct vfsmount *mnt = ofs->upper_mnt;
1216 err = mnt_want_write(mnt);
1220 /* Verify lower root is upper root origin */
1221 err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
1224 pr_err("overlayfs: failed to verify upper root origin\n");
1228 ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
1229 if (ofs->indexdir) {
1230 err = ovl_setup_trap(sb, ofs->indexdir, &ofs->indexdir_trap,
1236 * Verify upper root is exclusively associated with index dir.
1237 * Older kernels stored upper fh in "trusted.overlay.origin"
1238 * xattr. If that xattr exists, verify that it is a match to
1239 * upper dir file handle. In any case, verify or set xattr
1240 * "trusted.overlay.upper" to indicate that index may have
1241 * directory entries.
1243 if (ovl_check_origin_xattr(ofs->indexdir)) {
1244 err = ovl_verify_set_fh(ofs->indexdir, OVL_XATTR_ORIGIN,
1245 upperpath->dentry, true, false);
1247 pr_err("overlayfs: failed to verify index dir 'origin' xattr\n");
1249 err = ovl_verify_upper(ofs->indexdir, upperpath->dentry, true);
1251 pr_err("overlayfs: failed to verify index dir 'upper' xattr\n");
1253 /* Cleanup bad/stale/orphan index entries */
1255 err = ovl_indexdir_cleanup(ofs);
1257 if (err || !ofs->indexdir)
1258 pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1261 mnt_drop_write(mnt);
1265 /* Get a unique fsid for the layer */
1266 static int ovl_get_fsid(struct ovl_fs *ofs, struct super_block *sb)
1272 /* fsid 0 is reserved for upper fs even with non upper overlay */
1273 if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb)
1276 for (i = 0; i < ofs->numlowerfs; i++) {
1277 if (ofs->lower_fs[i].sb == sb)
1281 err = get_anon_bdev(&dev);
1283 pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
1287 ofs->lower_fs[ofs->numlowerfs].sb = sb;
1288 ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev;
1291 return ofs->numlowerfs;
1294 static int ovl_get_lower_layers(struct super_block *sb, struct ovl_fs *ofs,
1295 struct path *stack, unsigned int numlower)
1301 ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
1303 if (ofs->lower_layers == NULL)
1306 ofs->lower_fs = kcalloc(numlower, sizeof(struct ovl_sb),
1308 if (ofs->lower_fs == NULL)
1311 for (i = 0; i < numlower; i++) {
1312 struct vfsmount *mnt;
1316 err = fsid = ovl_get_fsid(ofs, stack[i].mnt->mnt_sb);
1321 * Check if lower root conflicts with this overlay layers before
1322 * checking if it is in-use as upperdir/workdir of "another"
1323 * mount, because we do not bother to check in ovl_is_inuse() if
1324 * the upperdir/workdir is in fact in-use by our
1327 err = ovl_setup_trap(sb, stack[i].dentry, &trap, "lowerdir");
1331 if (ovl_is_inuse(stack[i].dentry)) {
1332 err = ovl_report_in_use(ofs, "lowerdir");
1339 mnt = clone_private_mount(&stack[i]);
1342 pr_err("overlayfs: failed to clone lowerpath\n");
1348 * Make lower layers R/O. That way fchmod/fchown on lower file
1349 * will fail instead of modifying lower fs.
1351 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1353 ofs->lower_layers[ofs->numlower].trap = trap;
1354 ofs->lower_layers[ofs->numlower].mnt = mnt;
1355 ofs->lower_layers[ofs->numlower].idx = i + 1;
1356 ofs->lower_layers[ofs->numlower].fsid = fsid;
1358 ofs->lower_layers[ofs->numlower].fs =
1359 &ofs->lower_fs[fsid - 1];
1365 * When all layers on same fs, overlay can use real inode numbers.
1366 * With mount option "xino=on", mounter declares that there are enough
1367 * free high bits in underlying fs to hold the unique fsid.
1368 * If overlayfs does encounter underlying inodes using the high xino
1369 * bits reserved for fsid, it emits a warning and uses the original
1372 if (!ofs->numlowerfs || (ofs->numlowerfs == 1 && !ofs->upper_mnt)) {
1374 ofs->config.xino = OVL_XINO_OFF;
1375 } else if (ofs->config.xino == OVL_XINO_ON && !ofs->xino_bits) {
1377 * This is a roundup of number of bits needed for numlowerfs+1
1378 * (i.e. ilog2(numlowerfs+1 - 1) + 1). fsid 0 is reserved for
1379 * upper fs even with non upper overlay.
1381 BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 31);
1382 ofs->xino_bits = ilog2(ofs->numlowerfs) + 1;
1385 if (ofs->xino_bits) {
1386 pr_info("overlayfs: \"xino\" feature enabled using %d upper inode bits.\n",
1395 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1399 char *lowertmp, *lower;
1400 struct path *stack = NULL;
1401 unsigned int stacklen, numlower = 0, i;
1402 bool remote = false;
1403 struct ovl_entry *oe;
1406 lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
1411 stacklen = ovl_split_lowerdirs(lowertmp);
1412 if (stacklen > OVL_MAX_STACK) {
1413 pr_err("overlayfs: too many lower directories, limit is %d\n",
1416 } else if (!ofs->config.upperdir && stacklen == 1) {
1417 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
1419 } else if (!ofs->config.upperdir && ofs->config.nfs_export &&
1420 ofs->config.redirect_follow) {
1421 pr_warn("overlayfs: NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
1422 ofs->config.nfs_export = false;
1426 stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
1432 for (numlower = 0; numlower < stacklen; numlower++) {
1433 err = ovl_lower_dir(lower, &stack[numlower], ofs,
1434 &sb->s_stack_depth, &remote);
1438 lower = strchr(lower, '\0') + 1;
1442 sb->s_stack_depth++;
1443 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1444 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1448 err = ovl_get_lower_layers(sb, ofs, stack, numlower);
1453 oe = ovl_alloc_entry(numlower);
1457 for (i = 0; i < numlower; i++) {
1458 oe->lowerstack[i].dentry = dget(stack[i].dentry);
1459 oe->lowerstack[i].layer = &ofs->lower_layers[i];
1463 sb->s_d_op = &ovl_reval_dentry_operations;
1465 sb->s_d_op = &ovl_dentry_operations;
1468 for (i = 0; i < numlower; i++)
1469 path_put(&stack[i]);
1481 * Check if this layer root is a descendant of:
1482 * - another layer of this overlayfs instance
1483 * - upper/work dir of any overlayfs instance
1485 static int ovl_check_layer(struct super_block *sb, struct ovl_fs *ofs,
1486 struct dentry *dentry, const char *name,
1489 struct dentry *next = dentry, *parent;
1495 parent = dget_parent(next);
1497 /* Walk back ancestors to root (inclusive) looking for traps */
1498 while (!err && parent != next) {
1499 if (is_lower && ovl_lookup_trap_inode(sb, parent)) {
1501 pr_err("overlayfs: overlapping %s path\n", name);
1502 } else if (ovl_is_inuse(parent)) {
1503 err = ovl_report_in_use(ofs, name);
1506 parent = dget_parent(next);
1516 * Check if any of the layers or work dirs overlap.
1518 static int ovl_check_overlapping_layers(struct super_block *sb,
1523 if (ofs->upper_mnt) {
1524 err = ovl_check_layer(sb, ofs, ofs->upper_mnt->mnt_root,
1530 * Checking workbasedir avoids hitting ovl_is_inuse(parent) of
1531 * this instance and covers overlapping work and index dirs,
1532 * unless work or index dir have been moved since created inside
1533 * workbasedir. In that case, we already have their traps in
1534 * inode cache and we will catch that case on lookup.
1536 err = ovl_check_layer(sb, ofs, ofs->workbasedir, "workdir",
1542 for (i = 0; i < ofs->numlower; i++) {
1543 err = ovl_check_layer(sb, ofs,
1544 ofs->lower_layers[i].mnt->mnt_root,
1553 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
1555 struct path upperpath = { };
1556 struct dentry *root_dentry;
1557 struct ovl_entry *oe;
1563 ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
1567 ofs->creator_cred = cred = prepare_creds();
1571 ofs->config.index = ovl_index_def;
1572 ofs->config.nfs_export = ovl_nfs_export_def;
1573 ofs->config.xino = ovl_xino_def();
1574 ofs->config.metacopy = ovl_metacopy_def;
1575 err = ovl_parse_opt((char *) data, &ofs->config);
1580 if (!ofs->config.lowerdir) {
1582 pr_err("overlayfs: missing 'lowerdir'\n");
1586 sb->s_stack_depth = 0;
1587 sb->s_maxbytes = MAX_LFS_FILESIZE;
1588 /* Assume underlaying fs uses 32bit inodes unless proven otherwise */
1589 if (ofs->config.xino != OVL_XINO_OFF)
1590 ofs->xino_bits = BITS_PER_LONG - 32;
1592 /* alloc/destroy_inode needed for setting up traps in inode cache */
1593 sb->s_op = &ovl_super_operations;
1595 if (ofs->config.upperdir) {
1596 if (!ofs->config.workdir) {
1597 pr_err("overlayfs: missing 'workdir'\n");
1601 err = ovl_get_upper(sb, ofs, &upperpath);
1605 err = ovl_get_workdir(sb, ofs, &upperpath);
1610 sb->s_flags |= SB_RDONLY;
1612 sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
1613 sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
1616 oe = ovl_get_lowerstack(sb, ofs);
1621 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1622 if (!ofs->upper_mnt)
1623 sb->s_flags |= SB_RDONLY;
1625 if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
1626 err = ovl_get_indexdir(sb, ofs, oe, &upperpath);
1630 /* Force r/o mount with no index dir */
1631 if (!ofs->indexdir) {
1633 ofs->workdir = NULL;
1634 sb->s_flags |= SB_RDONLY;
1639 err = ovl_check_overlapping_layers(sb, ofs);
1643 /* Show index=off in /proc/mounts for forced r/o mount */
1644 if (!ofs->indexdir) {
1645 ofs->config.index = false;
1646 if (ofs->upper_mnt && ofs->config.nfs_export) {
1647 pr_warn("overlayfs: NFS export requires an index dir, falling back to nfs_export=off.\n");
1648 ofs->config.nfs_export = false;
1652 if (ofs->config.metacopy && ofs->config.nfs_export) {
1653 pr_warn("overlayfs: NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
1654 ofs->config.nfs_export = false;
1657 if (ofs->config.nfs_export)
1658 sb->s_export_op = &ovl_export_operations;
1660 /* Never override disk quota limits or use reserved space */
1661 cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1663 sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1664 sb->s_xattr = ovl_xattr_handlers;
1665 sb->s_fs_info = ofs;
1666 sb->s_flags |= SB_POSIXACL;
1669 root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1673 root_dentry->d_fsdata = oe;
1675 mntput(upperpath.mnt);
1676 if (upperpath.dentry) {
1677 ovl_dentry_set_upper_alias(root_dentry);
1678 if (ovl_is_impuredir(upperpath.dentry))
1679 ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
1682 /* Root is always merge -> can have whiteouts */
1683 ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
1684 ovl_dentry_set_flag(OVL_E_CONNECTED, root_dentry);
1685 ovl_set_upperdata(d_inode(root_dentry));
1686 ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
1687 ovl_dentry_lower(root_dentry), NULL);
1689 sb->s_root = root_dentry;
1694 ovl_entry_stack_free(oe);
1697 path_put(&upperpath);
1703 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1704 const char *dev_name, void *raw_data)
1706 return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1709 static struct file_system_type ovl_fs_type = {
1710 .owner = THIS_MODULE,
1713 .kill_sb = kill_anon_super,
1715 MODULE_ALIAS_FS("overlay");
1717 static void ovl_inode_init_once(void *foo)
1719 struct ovl_inode *oi = foo;
1721 inode_init_once(&oi->vfs_inode);
1724 static int __init ovl_init(void)
1728 ovl_inode_cachep = kmem_cache_create("ovl_inode",
1729 sizeof(struct ovl_inode), 0,
1730 (SLAB_RECLAIM_ACCOUNT|
1731 SLAB_MEM_SPREAD|SLAB_ACCOUNT),
1732 ovl_inode_init_once);
1733 if (ovl_inode_cachep == NULL)
1736 err = register_filesystem(&ovl_fs_type);
1738 kmem_cache_destroy(ovl_inode_cachep);
1743 static void __exit ovl_exit(void)
1745 unregister_filesystem(&ovl_fs_type);
1748 * Make sure all delayed rcu free inodes are flushed before we
1752 kmem_cache_destroy(ovl_inode_cachep);
1756 module_init(ovl_init);
1757 module_exit(ovl_exit);