1 // SPDX-License-Identifier: GPL-2.0-only
4 * Copyright (C) 2011 Novell Inc.
7 #include <uapi/linux/magic.h>
9 #include <linux/namei.h>
10 #include <linux/xattr.h>
11 #include <linux/mount.h>
12 #include <linux/parser.h>
13 #include <linux/module.h>
14 #include <linux/statfs.h>
15 #include <linux/seq_file.h>
16 #include <linux/posix_acl_xattr.h>
17 #include <linux/exportfs.h>
18 #include "overlayfs.h"
20 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
21 MODULE_DESCRIPTION("Overlay filesystem");
22 MODULE_LICENSE("GPL");
27 #define OVL_MAX_STACK 500
29 static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
30 module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
31 MODULE_PARM_DESC(redirect_dir,
32 "Default to on or off for the redirect_dir feature");
34 static bool ovl_redirect_always_follow =
35 IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW);
36 module_param_named(redirect_always_follow, ovl_redirect_always_follow,
38 MODULE_PARM_DESC(redirect_always_follow,
39 "Follow redirects even if redirect_dir feature is turned off");
41 static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
42 module_param_named(index, ovl_index_def, bool, 0644);
43 MODULE_PARM_DESC(index,
44 "Default to on or off for the inodes index feature");
46 static bool ovl_nfs_export_def = IS_ENABLED(CONFIG_OVERLAY_FS_NFS_EXPORT);
47 module_param_named(nfs_export, ovl_nfs_export_def, bool, 0644);
48 MODULE_PARM_DESC(nfs_export,
49 "Default to on or off for the NFS export feature");
51 static bool ovl_xino_auto_def = IS_ENABLED(CONFIG_OVERLAY_FS_XINO_AUTO);
52 module_param_named(xino_auto, ovl_xino_auto_def, bool, 0644);
53 MODULE_PARM_DESC(xino_auto,
54 "Auto enable xino feature");
56 static void ovl_entry_stack_free(struct ovl_entry *oe)
60 for (i = 0; i < oe->numlower; i++)
61 dput(oe->lowerstack[i].dentry);
64 static bool ovl_metacopy_def = IS_ENABLED(CONFIG_OVERLAY_FS_METACOPY);
65 module_param_named(metacopy, ovl_metacopy_def, bool, 0644);
66 MODULE_PARM_DESC(metacopy,
67 "Default to on or off for the metadata only copy up feature");
69 static void ovl_dentry_release(struct dentry *dentry)
71 struct ovl_entry *oe = dentry->d_fsdata;
74 ovl_entry_stack_free(oe);
79 static struct dentry *ovl_d_real(struct dentry *dentry,
80 const struct inode *inode)
84 /* It's an overlay file */
85 if (inode && d_inode(dentry) == inode)
88 if (!d_is_reg(dentry)) {
89 if (!inode || inode == d_inode(dentry))
94 real = ovl_dentry_upper(dentry);
95 if (real && (inode == d_inode(real)))
98 if (real && !inode && ovl_has_upperdata(d_inode(dentry)))
101 real = ovl_dentry_lowerdata(dentry);
105 /* Handle recursion */
106 real = d_real(real, inode);
108 if (!inode || inode == d_inode(real))
111 WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
112 inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
116 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
118 struct ovl_entry *oe = dentry->d_fsdata;
122 for (i = 0; i < oe->numlower; i++) {
123 struct dentry *d = oe->lowerstack[i].dentry;
125 if (d->d_flags & DCACHE_OP_REVALIDATE) {
126 ret = d->d_op->d_revalidate(d, flags);
130 if (!(flags & LOOKUP_RCU))
139 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
141 struct ovl_entry *oe = dentry->d_fsdata;
145 for (i = 0; i < oe->numlower; i++) {
146 struct dentry *d = oe->lowerstack[i].dentry;
148 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
149 ret = d->d_op->d_weak_revalidate(d, flags);
157 static const struct dentry_operations ovl_dentry_operations = {
158 .d_release = ovl_dentry_release,
159 .d_real = ovl_d_real,
162 static const struct dentry_operations ovl_reval_dentry_operations = {
163 .d_release = ovl_dentry_release,
164 .d_real = ovl_d_real,
165 .d_revalidate = ovl_dentry_revalidate,
166 .d_weak_revalidate = ovl_dentry_weak_revalidate,
169 static struct kmem_cache *ovl_inode_cachep;
171 static struct inode *ovl_alloc_inode(struct super_block *sb)
173 struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL);
182 oi->__upperdentry = NULL;
184 oi->lowerdata = NULL;
185 mutex_init(&oi->lock);
187 return &oi->vfs_inode;
190 static void ovl_free_inode(struct inode *inode)
192 struct ovl_inode *oi = OVL_I(inode);
195 mutex_destroy(&oi->lock);
196 kmem_cache_free(ovl_inode_cachep, oi);
199 static void ovl_destroy_inode(struct inode *inode)
201 struct ovl_inode *oi = OVL_I(inode);
203 dput(oi->__upperdentry);
205 if (S_ISDIR(inode->i_mode))
206 ovl_dir_cache_free(inode);
211 static void ovl_free_fs(struct ovl_fs *ofs)
215 iput(ofs->workbasedir_trap);
216 iput(ofs->indexdir_trap);
217 iput(ofs->workdir_trap);
218 iput(ofs->upperdir_trap);
221 if (ofs->workdir_locked)
222 ovl_inuse_unlock(ofs->workbasedir);
223 dput(ofs->workbasedir);
224 if (ofs->upperdir_locked)
225 ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
226 mntput(ofs->upper_mnt);
227 for (i = 0; i < ofs->numlower; i++) {
228 iput(ofs->lower_layers[i].trap);
229 mntput(ofs->lower_layers[i].mnt);
231 for (i = 0; i < ofs->numlowerfs; i++)
232 free_anon_bdev(ofs->lower_fs[i].pseudo_dev);
233 kfree(ofs->lower_layers);
234 kfree(ofs->lower_fs);
236 kfree(ofs->config.lowerdir);
237 kfree(ofs->config.upperdir);
238 kfree(ofs->config.workdir);
239 kfree(ofs->config.redirect_mode);
240 if (ofs->creator_cred)
241 put_cred(ofs->creator_cred);
245 static void ovl_put_super(struct super_block *sb)
247 struct ovl_fs *ofs = sb->s_fs_info;
252 /* Sync real dirty inodes in upper filesystem (if it exists) */
253 static int ovl_sync_fs(struct super_block *sb, int wait)
255 struct ovl_fs *ofs = sb->s_fs_info;
256 struct super_block *upper_sb;
263 * If this is a sync(2) call or an emergency sync, all the super blocks
264 * will be iterated, including upper_sb, so no need to do anything.
266 * If this is a syncfs(2) call, then we do need to call
267 * sync_filesystem() on upper_sb, but enough if we do it when being
268 * called with wait == 1.
273 upper_sb = ofs->upper_mnt->mnt_sb;
275 down_read(&upper_sb->s_umount);
276 ret = sync_filesystem(upper_sb);
277 up_read(&upper_sb->s_umount);
284 * @sb: The overlayfs super block
285 * @buf: The struct kstatfs to fill in with stats
287 * Get the filesystem statistics. As writes always target the upper layer
288 * filesystem pass the statfs to the upper filesystem (if it exists)
290 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
292 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
293 struct dentry *root_dentry = dentry->d_sb->s_root;
297 ovl_path_real(root_dentry, &path);
299 err = vfs_statfs(&path, buf);
301 buf->f_namelen = ofs->namelen;
302 buf->f_type = OVERLAYFS_SUPER_MAGIC;
308 /* Will this overlay be forced to mount/remount ro? */
309 static bool ovl_force_readonly(struct ovl_fs *ofs)
311 return (!ofs->upper_mnt || !ofs->workdir);
314 static const char *ovl_redirect_mode_def(void)
316 return ovl_redirect_dir_def ? "on" : "off";
325 static const char * const ovl_xino_str[] = {
331 static inline int ovl_xino_def(void)
333 return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
339 * Prints the mount options for a given superblock.
340 * Returns zero; does not fail.
342 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
344 struct super_block *sb = dentry->d_sb;
345 struct ovl_fs *ofs = sb->s_fs_info;
347 seq_show_option(m, "lowerdir", ofs->config.lowerdir);
348 if (ofs->config.upperdir) {
349 seq_show_option(m, "upperdir", ofs->config.upperdir);
350 seq_show_option(m, "workdir", ofs->config.workdir);
352 if (ofs->config.default_permissions)
353 seq_puts(m, ",default_permissions");
354 if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
355 seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
356 if (ofs->config.index != ovl_index_def)
357 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
358 if (ofs->config.nfs_export != ovl_nfs_export_def)
359 seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
361 if (ofs->config.xino != ovl_xino_def())
362 seq_printf(m, ",xino=%s", ovl_xino_str[ofs->config.xino]);
363 if (ofs->config.metacopy != ovl_metacopy_def)
364 seq_printf(m, ",metacopy=%s",
365 ofs->config.metacopy ? "on" : "off");
369 static int ovl_remount(struct super_block *sb, int *flags, char *data)
371 struct ovl_fs *ofs = sb->s_fs_info;
373 if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
379 static const struct super_operations ovl_super_operations = {
380 .alloc_inode = ovl_alloc_inode,
381 .free_inode = ovl_free_inode,
382 .destroy_inode = ovl_destroy_inode,
383 .drop_inode = generic_delete_inode,
384 .put_super = ovl_put_super,
385 .sync_fs = ovl_sync_fs,
386 .statfs = ovl_statfs,
387 .show_options = ovl_show_options,
388 .remount_fs = ovl_remount,
395 OPT_DEFAULT_PERMISSIONS,
409 static const match_table_t ovl_tokens = {
410 {OPT_LOWERDIR, "lowerdir=%s"},
411 {OPT_UPPERDIR, "upperdir=%s"},
412 {OPT_WORKDIR, "workdir=%s"},
413 {OPT_DEFAULT_PERMISSIONS, "default_permissions"},
414 {OPT_REDIRECT_DIR, "redirect_dir=%s"},
415 {OPT_INDEX_ON, "index=on"},
416 {OPT_INDEX_OFF, "index=off"},
417 {OPT_NFS_EXPORT_ON, "nfs_export=on"},
418 {OPT_NFS_EXPORT_OFF, "nfs_export=off"},
419 {OPT_XINO_ON, "xino=on"},
420 {OPT_XINO_OFF, "xino=off"},
421 {OPT_XINO_AUTO, "xino=auto"},
422 {OPT_METACOPY_ON, "metacopy=on"},
423 {OPT_METACOPY_OFF, "metacopy=off"},
427 static char *ovl_next_opt(char **s)
435 for (p = sbegin; *p; p++) {
440 } else if (*p == ',') {
450 static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
452 if (strcmp(mode, "on") == 0) {
453 config->redirect_dir = true;
455 * Does not make sense to have redirect creation without
456 * redirect following.
458 config->redirect_follow = true;
459 } else if (strcmp(mode, "follow") == 0) {
460 config->redirect_follow = true;
461 } else if (strcmp(mode, "off") == 0) {
462 if (ovl_redirect_always_follow)
463 config->redirect_follow = true;
464 } else if (strcmp(mode, "nofollow") != 0) {
465 pr_err("overlayfs: bad mount option \"redirect_dir=%s\"\n",
473 static int ovl_parse_opt(char *opt, struct ovl_config *config)
477 bool metacopy_opt = false, redirect_opt = false;
479 config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
480 if (!config->redirect_mode)
483 while ((p = ovl_next_opt(&opt)) != NULL) {
485 substring_t args[MAX_OPT_ARGS];
490 token = match_token(p, ovl_tokens, args);
493 kfree(config->upperdir);
494 config->upperdir = match_strdup(&args[0]);
495 if (!config->upperdir)
500 kfree(config->lowerdir);
501 config->lowerdir = match_strdup(&args[0]);
502 if (!config->lowerdir)
507 kfree(config->workdir);
508 config->workdir = match_strdup(&args[0]);
509 if (!config->workdir)
513 case OPT_DEFAULT_PERMISSIONS:
514 config->default_permissions = true;
517 case OPT_REDIRECT_DIR:
518 kfree(config->redirect_mode);
519 config->redirect_mode = match_strdup(&args[0]);
520 if (!config->redirect_mode)
526 config->index = true;
530 config->index = false;
533 case OPT_NFS_EXPORT_ON:
534 config->nfs_export = true;
537 case OPT_NFS_EXPORT_OFF:
538 config->nfs_export = false;
542 config->xino = OVL_XINO_ON;
546 config->xino = OVL_XINO_OFF;
550 config->xino = OVL_XINO_AUTO;
553 case OPT_METACOPY_ON:
554 config->metacopy = true;
558 case OPT_METACOPY_OFF:
559 config->metacopy = false;
563 pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
568 /* Workdir is useless in non-upper mount */
569 if (!config->upperdir && config->workdir) {
570 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
572 kfree(config->workdir);
573 config->workdir = NULL;
576 err = ovl_parse_redirect_mode(config, config->redirect_mode);
581 * This is to make the logic below simpler. It doesn't make any other
582 * difference, since config->redirect_dir is only used for upper.
584 if (!config->upperdir && config->redirect_follow)
585 config->redirect_dir = true;
587 /* Resolve metacopy -> redirect_dir dependency */
588 if (config->metacopy && !config->redirect_dir) {
589 if (metacopy_opt && redirect_opt) {
590 pr_err("overlayfs: conflicting options: metacopy=on,redirect_dir=%s\n",
591 config->redirect_mode);
596 * There was an explicit redirect_dir=... that resulted
599 pr_info("overlayfs: disabling metacopy due to redirect_dir=%s\n",
600 config->redirect_mode);
601 config->metacopy = false;
603 /* Automatically enable redirect otherwise. */
604 config->redirect_follow = config->redirect_dir = true;
611 #define OVL_WORKDIR_NAME "work"
612 #define OVL_INDEXDIR_NAME "index"
614 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
615 const char *name, bool persist)
617 struct inode *dir = ofs->workbasedir->d_inode;
618 struct vfsmount *mnt = ofs->upper_mnt;
621 bool retried = false;
624 inode_lock_nested(dir, I_MUTEX_PARENT);
628 work = lookup_one_len(name, ofs->workbasedir, strlen(name));
631 struct iattr attr = {
632 .ia_valid = ATTR_MODE,
633 .ia_mode = S_IFDIR | 0,
645 ovl_workdir_cleanup(dir, mnt, work, 0);
650 work = ovl_create_real(dir, work, OVL_CATTR(attr.ia_mode));
656 * Try to remove POSIX ACL xattrs from workdir. We are good if:
658 * a) success (there was a POSIX ACL xattr and was removed)
659 * b) -ENODATA (there was no POSIX ACL xattr)
660 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
662 * There are various other error values that could effectively
663 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
664 * if the xattr name is too long), but the set of filesystems
665 * allowed as upper are limited to "normal" ones, where checking
666 * for the above two errors is sufficient.
668 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
669 if (err && err != -ENODATA && err != -EOPNOTSUPP)
672 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
673 if (err && err != -ENODATA && err != -EOPNOTSUPP)
676 /* Clear any inherited mode bits */
677 inode_lock(work->d_inode);
678 err = notify_change(work, &attr, NULL);
679 inode_unlock(work->d_inode);
695 pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
696 ofs->config.workdir, name, -err);
701 static void ovl_unescape(char *s)
714 static int ovl_mount_dir_noesc(const char *name, struct path *path)
719 pr_err("overlayfs: empty lowerdir\n");
722 err = kern_path(name, LOOKUP_FOLLOW, path);
724 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
728 if (ovl_dentry_weird(path->dentry)) {
729 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
732 if (!d_is_dir(path->dentry)) {
733 pr_err("overlayfs: '%s' not a directory\n", name);
744 static int ovl_mount_dir(const char *name, struct path *path)
747 char *tmp = kstrdup(name, GFP_KERNEL);
751 err = ovl_mount_dir_noesc(tmp, path);
754 if (ovl_dentry_remote(path->dentry)) {
755 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
765 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
768 struct kstatfs statfs;
769 int err = vfs_statfs(path, &statfs);
772 pr_err("overlayfs: statfs failed on '%s'\n", name);
774 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
779 static int ovl_lower_dir(const char *name, struct path *path,
780 struct ovl_fs *ofs, int *stack_depth, bool *remote)
785 err = ovl_mount_dir_noesc(name, path);
789 err = ovl_check_namelen(path, ofs, name);
793 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
795 if (ovl_dentry_remote(path->dentry))
799 * The inodes index feature and NFS export need to encode and decode
800 * file handles, so they require that all layers support them.
802 fh_type = ovl_can_decode_fh(path->dentry->d_sb);
803 if ((ofs->config.nfs_export ||
804 (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
805 ofs->config.index = false;
806 ofs->config.nfs_export = false;
807 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
811 /* Check if lower fs has 32bit inode numbers */
812 if (fh_type != FILEID_INO32_GEN)
823 /* Workdir should not be subdir of upperdir and vice versa */
824 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
828 if (workdir != upperdir) {
829 ok = (lock_rename(workdir, upperdir) == NULL);
830 unlock_rename(workdir, upperdir);
835 static unsigned int ovl_split_lowerdirs(char *str)
837 unsigned int ctr = 1;
840 for (s = d = str;; s++, d++) {
843 } else if (*s == ':') {
855 static int __maybe_unused
856 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
857 struct dentry *dentry, struct inode *inode,
858 const char *name, void *buffer, size_t size)
860 return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
863 static int __maybe_unused
864 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
865 struct dentry *dentry, struct inode *inode,
866 const char *name, const void *value,
867 size_t size, int flags)
869 struct dentry *workdir = ovl_workdir(dentry);
870 struct inode *realinode = ovl_inode_real(inode);
871 struct posix_acl *acl = NULL;
874 /* Check that everything is OK before copy-up */
876 acl = posix_acl_from_xattr(&init_user_ns, value, size);
881 if (!IS_POSIXACL(d_inode(workdir)))
882 goto out_acl_release;
883 if (!realinode->i_op->set_acl)
884 goto out_acl_release;
885 if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
886 err = acl ? -EACCES : 0;
887 goto out_acl_release;
890 if (!inode_owner_or_capable(inode))
891 goto out_acl_release;
893 posix_acl_release(acl);
896 * Check if sgid bit needs to be cleared (actual setacl operation will
897 * be done with mounter's capabilities and so that won't do it for us).
899 if (unlikely(inode->i_mode & S_ISGID) &&
900 handler->flags == ACL_TYPE_ACCESS &&
901 !in_group_p(inode->i_gid) &&
902 !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
903 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
905 err = ovl_setattr(dentry, &iattr);
910 err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
912 ovl_copyattr(ovl_inode_real(inode), inode);
917 posix_acl_release(acl);
921 static int ovl_own_xattr_get(const struct xattr_handler *handler,
922 struct dentry *dentry, struct inode *inode,
923 const char *name, void *buffer, size_t size)
928 static int ovl_own_xattr_set(const struct xattr_handler *handler,
929 struct dentry *dentry, struct inode *inode,
930 const char *name, const void *value,
931 size_t size, int flags)
936 static int ovl_other_xattr_get(const struct xattr_handler *handler,
937 struct dentry *dentry, struct inode *inode,
938 const char *name, void *buffer, size_t size)
940 return ovl_xattr_get(dentry, inode, name, buffer, size);
943 static int ovl_other_xattr_set(const struct xattr_handler *handler,
944 struct dentry *dentry, struct inode *inode,
945 const char *name, const void *value,
946 size_t size, int flags)
948 return ovl_xattr_set(dentry, inode, name, value, size, flags);
951 static const struct xattr_handler __maybe_unused
952 ovl_posix_acl_access_xattr_handler = {
953 .name = XATTR_NAME_POSIX_ACL_ACCESS,
954 .flags = ACL_TYPE_ACCESS,
955 .get = ovl_posix_acl_xattr_get,
956 .set = ovl_posix_acl_xattr_set,
959 static const struct xattr_handler __maybe_unused
960 ovl_posix_acl_default_xattr_handler = {
961 .name = XATTR_NAME_POSIX_ACL_DEFAULT,
962 .flags = ACL_TYPE_DEFAULT,
963 .get = ovl_posix_acl_xattr_get,
964 .set = ovl_posix_acl_xattr_set,
967 static const struct xattr_handler ovl_own_xattr_handler = {
968 .prefix = OVL_XATTR_PREFIX,
969 .get = ovl_own_xattr_get,
970 .set = ovl_own_xattr_set,
973 static const struct xattr_handler ovl_other_xattr_handler = {
974 .prefix = "", /* catch all */
975 .get = ovl_other_xattr_get,
976 .set = ovl_other_xattr_set,
979 static const struct xattr_handler *ovl_xattr_handlers[] = {
980 #ifdef CONFIG_FS_POSIX_ACL
981 &ovl_posix_acl_access_xattr_handler,
982 &ovl_posix_acl_default_xattr_handler,
984 &ovl_own_xattr_handler,
985 &ovl_other_xattr_handler,
989 static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
990 struct inode **ptrap, const char *name)
995 trap = ovl_get_trap_inode(sb, dir);
996 err = PTR_ERR_OR_ZERO(trap);
999 pr_err("overlayfs: conflicting %s path\n", name);
1008 * Determine how we treat concurrent use of upperdir/workdir based on the
1009 * index feature. This is papering over mount leaks of container runtimes,
1010 * for example, an old overlay mount is leaked and now its upperdir is
1011 * attempted to be used as a lower layer in a new overlay mount.
1013 static int ovl_report_in_use(struct ovl_fs *ofs, const char *name)
1015 if (ofs->config.index) {
1016 pr_err("overlayfs: %s is in-use as upperdir/workdir of another mount, mount with '-o index=off' to override exclusive upperdir protection.\n",
1020 pr_warn("overlayfs: %s is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.\n",
1026 static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
1027 struct path *upperpath)
1029 struct vfsmount *upper_mnt;
1032 err = ovl_mount_dir(ofs->config.upperdir, upperpath);
1036 /* Upper fs should not be r/o */
1037 if (sb_rdonly(upperpath->mnt->mnt_sb)) {
1038 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
1043 err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
1047 err = ovl_setup_trap(sb, upperpath->dentry, &ofs->upperdir_trap,
1052 upper_mnt = clone_private_mount(upperpath);
1053 err = PTR_ERR(upper_mnt);
1054 if (IS_ERR(upper_mnt)) {
1055 pr_err("overlayfs: failed to clone upperpath\n");
1059 /* Don't inherit atime flags */
1060 upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
1061 ofs->upper_mnt = upper_mnt;
1063 if (ovl_inuse_trylock(ofs->upper_mnt->mnt_root)) {
1064 ofs->upperdir_locked = true;
1066 err = ovl_report_in_use(ofs, "upperdir");
1076 static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
1077 struct path *workpath)
1079 struct vfsmount *mnt = ofs->upper_mnt;
1080 struct dentry *temp;
1084 err = mnt_want_write(mnt);
1088 ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
1092 err = ovl_setup_trap(sb, ofs->workdir, &ofs->workdir_trap, "workdir");
1097 * Upper should support d_type, else whiteouts are visible. Given
1098 * workdir and upper are on same fs, we can do iterate_dir() on
1099 * workdir. This check requires successful creation of workdir in
1102 err = ovl_check_d_type_supported(workpath);
1107 * We allowed this configuration and don't want to break users over
1108 * kernel upgrade. So warn instead of erroring out.
1111 pr_warn("overlayfs: upper fs needs to support d_type.\n");
1113 /* Check if upper/work fs supports O_TMPFILE */
1114 temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
1115 ofs->tmpfile = !IS_ERR(temp);
1119 pr_warn("overlayfs: upper fs does not support tmpfile.\n");
1122 * Check if upper/work fs supports trusted.overlay.* xattr
1124 err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
1126 ofs->noxattr = true;
1127 ofs->config.index = false;
1128 ofs->config.metacopy = false;
1129 pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off and metacopy=off.\n");
1132 vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
1135 /* Check if upper/work fs supports file handles */
1136 fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
1137 if (ofs->config.index && !fh_type) {
1138 ofs->config.index = false;
1139 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
1142 /* Check if upper fs has 32bit inode numbers */
1143 if (fh_type != FILEID_INO32_GEN)
1146 /* NFS export of r/w mount depends on index */
1147 if (ofs->config.nfs_export && !ofs->config.index) {
1148 pr_warn("overlayfs: NFS export requires \"index=on\", falling back to nfs_export=off.\n");
1149 ofs->config.nfs_export = false;
1152 mnt_drop_write(mnt);
1156 static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
1157 struct path *upperpath)
1160 struct path workpath = { };
1162 err = ovl_mount_dir(ofs->config.workdir, &workpath);
1167 if (upperpath->mnt != workpath.mnt) {
1168 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
1171 if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
1172 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
1176 ofs->workbasedir = dget(workpath.dentry);
1178 if (ovl_inuse_trylock(ofs->workbasedir)) {
1179 ofs->workdir_locked = true;
1181 err = ovl_report_in_use(ofs, "workdir");
1186 err = ovl_setup_trap(sb, ofs->workbasedir, &ofs->workbasedir_trap,
1191 err = ovl_make_workdir(sb, ofs, &workpath);
1194 path_put(&workpath);
1199 static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
1200 struct ovl_entry *oe, struct path *upperpath)
1202 struct vfsmount *mnt = ofs->upper_mnt;
1205 err = mnt_want_write(mnt);
1209 /* Verify lower root is upper root origin */
1210 err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
1213 pr_err("overlayfs: failed to verify upper root origin\n");
1217 ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
1218 if (ofs->indexdir) {
1219 err = ovl_setup_trap(sb, ofs->indexdir, &ofs->indexdir_trap,
1225 * Verify upper root is exclusively associated with index dir.
1226 * Older kernels stored upper fh in "trusted.overlay.origin"
1227 * xattr. If that xattr exists, verify that it is a match to
1228 * upper dir file handle. In any case, verify or set xattr
1229 * "trusted.overlay.upper" to indicate that index may have
1230 * directory entries.
1232 if (ovl_check_origin_xattr(ofs->indexdir)) {
1233 err = ovl_verify_set_fh(ofs->indexdir, OVL_XATTR_ORIGIN,
1234 upperpath->dentry, true, false);
1236 pr_err("overlayfs: failed to verify index dir 'origin' xattr\n");
1238 err = ovl_verify_upper(ofs->indexdir, upperpath->dentry, true);
1240 pr_err("overlayfs: failed to verify index dir 'upper' xattr\n");
1242 /* Cleanup bad/stale/orphan index entries */
1244 err = ovl_indexdir_cleanup(ofs);
1246 if (err || !ofs->indexdir)
1247 pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1250 mnt_drop_write(mnt);
1254 static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
1258 if (!ofs->config.nfs_export && !(ofs->config.index && ofs->upper_mnt))
1261 for (i = 0; i < ofs->numlowerfs; i++) {
1263 * We use uuid to associate an overlay lower file handle with a
1264 * lower layer, so we can accept lower fs with null uuid as long
1265 * as all lower layers with null uuid are on the same fs.
1267 if (uuid_equal(&ofs->lower_fs[i].sb->s_uuid, uuid))
1273 /* Get a unique fsid for the layer */
1274 static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
1276 struct super_block *sb = path->mnt->mnt_sb;
1281 /* fsid 0 is reserved for upper fs even with non upper overlay */
1282 if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb)
1285 for (i = 0; i < ofs->numlowerfs; i++) {
1286 if (ofs->lower_fs[i].sb == sb)
1290 if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) {
1291 ofs->config.index = false;
1292 ofs->config.nfs_export = false;
1293 pr_warn("overlayfs: %s uuid detected in lower fs '%pd2', falling back to index=off,nfs_export=off.\n",
1294 uuid_is_null(&sb->s_uuid) ? "null" : "conflicting",
1298 err = get_anon_bdev(&dev);
1300 pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
1304 ofs->lower_fs[ofs->numlowerfs].sb = sb;
1305 ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev;
1308 return ofs->numlowerfs;
1311 static int ovl_get_lower_layers(struct super_block *sb, struct ovl_fs *ofs,
1312 struct path *stack, unsigned int numlower)
1318 ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
1320 if (ofs->lower_layers == NULL)
1323 ofs->lower_fs = kcalloc(numlower, sizeof(struct ovl_sb),
1325 if (ofs->lower_fs == NULL)
1328 for (i = 0; i < numlower; i++) {
1329 struct vfsmount *mnt;
1333 err = fsid = ovl_get_fsid(ofs, &stack[i]);
1337 err = ovl_setup_trap(sb, stack[i].dentry, &trap, "lowerdir");
1341 if (ovl_is_inuse(stack[i].dentry)) {
1342 err = ovl_report_in_use(ofs, "lowerdir");
1347 mnt = clone_private_mount(&stack[i]);
1350 pr_err("overlayfs: failed to clone lowerpath\n");
1356 * Make lower layers R/O. That way fchmod/fchown on lower file
1357 * will fail instead of modifying lower fs.
1359 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1361 ofs->lower_layers[ofs->numlower].trap = trap;
1362 ofs->lower_layers[ofs->numlower].mnt = mnt;
1363 ofs->lower_layers[ofs->numlower].idx = i + 1;
1364 ofs->lower_layers[ofs->numlower].fsid = fsid;
1366 ofs->lower_layers[ofs->numlower].fs =
1367 &ofs->lower_fs[fsid - 1];
1373 * When all layers on same fs, overlay can use real inode numbers.
1374 * With mount option "xino=on", mounter declares that there are enough
1375 * free high bits in underlying fs to hold the unique fsid.
1376 * If overlayfs does encounter underlying inodes using the high xino
1377 * bits reserved for fsid, it emits a warning and uses the original
1380 if (!ofs->numlowerfs || (ofs->numlowerfs == 1 && !ofs->upper_mnt)) {
1382 ofs->config.xino = OVL_XINO_OFF;
1383 } else if (ofs->config.xino == OVL_XINO_ON && !ofs->xino_bits) {
1385 * This is a roundup of number of bits needed for numlowerfs+1
1386 * (i.e. ilog2(numlowerfs+1 - 1) + 1). fsid 0 is reserved for
1387 * upper fs even with non upper overlay.
1389 BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 31);
1390 ofs->xino_bits = ilog2(ofs->numlowerfs) + 1;
1393 if (ofs->xino_bits) {
1394 pr_info("overlayfs: \"xino\" feature enabled using %d upper inode bits.\n",
1403 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1407 char *lowertmp, *lower;
1408 struct path *stack = NULL;
1409 unsigned int stacklen, numlower = 0, i;
1410 bool remote = false;
1411 struct ovl_entry *oe;
1414 lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
1419 stacklen = ovl_split_lowerdirs(lowertmp);
1420 if (stacklen > OVL_MAX_STACK) {
1421 pr_err("overlayfs: too many lower directories, limit is %d\n",
1424 } else if (!ofs->config.upperdir && stacklen == 1) {
1425 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
1427 } else if (!ofs->config.upperdir && ofs->config.nfs_export &&
1428 ofs->config.redirect_follow) {
1429 pr_warn("overlayfs: NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
1430 ofs->config.nfs_export = false;
1434 stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
1440 for (numlower = 0; numlower < stacklen; numlower++) {
1441 err = ovl_lower_dir(lower, &stack[numlower], ofs,
1442 &sb->s_stack_depth, &remote);
1446 lower = strchr(lower, '\0') + 1;
1450 sb->s_stack_depth++;
1451 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1452 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1456 err = ovl_get_lower_layers(sb, ofs, stack, numlower);
1461 oe = ovl_alloc_entry(numlower);
1465 for (i = 0; i < numlower; i++) {
1466 oe->lowerstack[i].dentry = dget(stack[i].dentry);
1467 oe->lowerstack[i].layer = &ofs->lower_layers[i];
1471 sb->s_d_op = &ovl_reval_dentry_operations;
1473 sb->s_d_op = &ovl_dentry_operations;
1476 for (i = 0; i < numlower; i++)
1477 path_put(&stack[i]);
1489 * Check if this layer root is a descendant of:
1490 * - another layer of this overlayfs instance
1491 * - upper/work dir of any overlayfs instance
1493 static int ovl_check_layer(struct super_block *sb, struct ovl_fs *ofs,
1494 struct dentry *dentry, const char *name)
1496 struct dentry *next = dentry, *parent;
1502 parent = dget_parent(next);
1504 /* Walk back ancestors to root (inclusive) looking for traps */
1505 while (!err && parent != next) {
1506 if (ovl_lookup_trap_inode(sb, parent)) {
1508 pr_err("overlayfs: overlapping %s path\n", name);
1509 } else if (ovl_is_inuse(parent)) {
1510 err = ovl_report_in_use(ofs, name);
1513 parent = dget_parent(next);
1523 * Check if any of the layers or work dirs overlap.
1525 static int ovl_check_overlapping_layers(struct super_block *sb,
1530 if (ofs->upper_mnt) {
1531 err = ovl_check_layer(sb, ofs, ofs->upper_mnt->mnt_root,
1537 * Checking workbasedir avoids hitting ovl_is_inuse(parent) of
1538 * this instance and covers overlapping work and index dirs,
1539 * unless work or index dir have been moved since created inside
1540 * workbasedir. In that case, we already have their traps in
1541 * inode cache and we will catch that case on lookup.
1543 err = ovl_check_layer(sb, ofs, ofs->workbasedir, "workdir");
1548 for (i = 0; i < ofs->numlower; i++) {
1549 err = ovl_check_layer(sb, ofs,
1550 ofs->lower_layers[i].mnt->mnt_root,
1559 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
1561 struct path upperpath = { };
1562 struct dentry *root_dentry;
1563 struct ovl_entry *oe;
1569 ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
1573 ofs->creator_cred = cred = prepare_creds();
1577 ofs->config.index = ovl_index_def;
1578 ofs->config.nfs_export = ovl_nfs_export_def;
1579 ofs->config.xino = ovl_xino_def();
1580 ofs->config.metacopy = ovl_metacopy_def;
1581 err = ovl_parse_opt((char *) data, &ofs->config);
1586 if (!ofs->config.lowerdir) {
1588 pr_err("overlayfs: missing 'lowerdir'\n");
1592 sb->s_stack_depth = 0;
1593 sb->s_maxbytes = MAX_LFS_FILESIZE;
1594 /* Assume underlaying fs uses 32bit inodes unless proven otherwise */
1595 if (ofs->config.xino != OVL_XINO_OFF)
1596 ofs->xino_bits = BITS_PER_LONG - 32;
1598 /* alloc/destroy_inode needed for setting up traps in inode cache */
1599 sb->s_op = &ovl_super_operations;
1601 if (ofs->config.upperdir) {
1602 if (!ofs->config.workdir) {
1603 pr_err("overlayfs: missing 'workdir'\n");
1607 err = ovl_get_upper(sb, ofs, &upperpath);
1611 err = ovl_get_workdir(sb, ofs, &upperpath);
1616 sb->s_flags |= SB_RDONLY;
1618 sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
1619 sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
1622 oe = ovl_get_lowerstack(sb, ofs);
1627 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1628 if (!ofs->upper_mnt)
1629 sb->s_flags |= SB_RDONLY;
1631 if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
1632 err = ovl_get_indexdir(sb, ofs, oe, &upperpath);
1636 /* Force r/o mount with no index dir */
1637 if (!ofs->indexdir) {
1639 ofs->workdir = NULL;
1640 sb->s_flags |= SB_RDONLY;
1645 err = ovl_check_overlapping_layers(sb, ofs);
1649 /* Show index=off in /proc/mounts for forced r/o mount */
1650 if (!ofs->indexdir) {
1651 ofs->config.index = false;
1652 if (ofs->upper_mnt && ofs->config.nfs_export) {
1653 pr_warn("overlayfs: NFS export requires an index dir, falling back to nfs_export=off.\n");
1654 ofs->config.nfs_export = false;
1658 if (ofs->config.metacopy && ofs->config.nfs_export) {
1659 pr_warn("overlayfs: NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
1660 ofs->config.nfs_export = false;
1663 if (ofs->config.nfs_export)
1664 sb->s_export_op = &ovl_export_operations;
1666 /* Never override disk quota limits or use reserved space */
1667 cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1669 sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1670 sb->s_xattr = ovl_xattr_handlers;
1671 sb->s_fs_info = ofs;
1672 sb->s_flags |= SB_POSIXACL;
1675 root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1679 root_dentry->d_fsdata = oe;
1681 mntput(upperpath.mnt);
1682 if (upperpath.dentry) {
1683 ovl_dentry_set_upper_alias(root_dentry);
1684 if (ovl_is_impuredir(upperpath.dentry))
1685 ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
1688 /* Root is always merge -> can have whiteouts */
1689 ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
1690 ovl_dentry_set_flag(OVL_E_CONNECTED, root_dentry);
1691 ovl_set_upperdata(d_inode(root_dentry));
1692 ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
1693 ovl_dentry_lower(root_dentry), NULL);
1695 sb->s_root = root_dentry;
1700 ovl_entry_stack_free(oe);
1703 path_put(&upperpath);
1709 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1710 const char *dev_name, void *raw_data)
1712 return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1715 static struct file_system_type ovl_fs_type = {
1716 .owner = THIS_MODULE,
1719 .kill_sb = kill_anon_super,
1721 MODULE_ALIAS_FS("overlay");
1723 static void ovl_inode_init_once(void *foo)
1725 struct ovl_inode *oi = foo;
1727 inode_init_once(&oi->vfs_inode);
1730 static int __init ovl_init(void)
1734 ovl_inode_cachep = kmem_cache_create("ovl_inode",
1735 sizeof(struct ovl_inode), 0,
1736 (SLAB_RECLAIM_ACCOUNT|
1737 SLAB_MEM_SPREAD|SLAB_ACCOUNT),
1738 ovl_inode_init_once);
1739 if (ovl_inode_cachep == NULL)
1742 err = register_filesystem(&ovl_fs_type);
1744 kmem_cache_destroy(ovl_inode_cachep);
1749 static void __exit ovl_exit(void)
1751 unregister_filesystem(&ovl_fs_type);
1754 * Make sure all delayed rcu free inodes are flushed before we
1758 kmem_cache_destroy(ovl_inode_cachep);
1762 module_init(ovl_init);
1763 module_exit(ovl_exit);