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)
82 struct dentry *real = NULL, *lower;
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 lower = ovl_dentry_lowerdata(dentry);
106 /* Handle recursion */
107 real = d_real(real, inode);
109 if (!inode || inode == d_inode(real))
112 WARN(1, "%s(%pd4, %s:%lu): real dentry (%p/%lu) not found\n",
113 __func__, dentry, inode ? inode->i_sb->s_id : "NULL",
114 inode ? inode->i_ino : 0, real,
115 real && d_inode(real) ? d_inode(real)->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)
218 iput(ofs->workbasedir_trap);
219 iput(ofs->indexdir_trap);
220 iput(ofs->workdir_trap);
221 iput(ofs->upperdir_trap);
224 if (ofs->workdir_locked)
225 ovl_inuse_unlock(ofs->workbasedir);
226 dput(ofs->workbasedir);
227 if (ofs->upperdir_locked)
228 ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
229 mntput(ofs->upper_mnt);
230 for (i = 0; i < ofs->numlower; i++) {
231 iput(ofs->lower_layers[i].trap);
232 mntput(ofs->lower_layers[i].mnt);
234 for (i = 0; i < ofs->numlowerfs; i++)
235 free_anon_bdev(ofs->lower_fs[i].pseudo_dev);
236 kfree(ofs->lower_layers);
237 kfree(ofs->lower_fs);
239 kfree(ofs->config.lowerdir);
240 kfree(ofs->config.upperdir);
241 kfree(ofs->config.workdir);
242 kfree(ofs->config.redirect_mode);
243 if (ofs->creator_cred)
244 put_cred(ofs->creator_cred);
248 static void ovl_put_super(struct super_block *sb)
250 struct ovl_fs *ofs = sb->s_fs_info;
255 /* Sync real dirty inodes in upper filesystem (if it exists) */
256 static int ovl_sync_fs(struct super_block *sb, int wait)
258 struct ovl_fs *ofs = sb->s_fs_info;
259 struct super_block *upper_sb;
266 * If this is a sync(2) call or an emergency sync, all the super blocks
267 * will be iterated, including upper_sb, so no need to do anything.
269 * If this is a syncfs(2) call, then we do need to call
270 * sync_filesystem() on upper_sb, but enough if we do it when being
271 * called with wait == 1.
276 upper_sb = ofs->upper_mnt->mnt_sb;
278 down_read(&upper_sb->s_umount);
279 ret = sync_filesystem(upper_sb);
280 up_read(&upper_sb->s_umount);
287 * @sb: The overlayfs super block
288 * @buf: The struct kstatfs to fill in with stats
290 * Get the filesystem statistics. As writes always target the upper layer
291 * filesystem pass the statfs to the upper filesystem (if it exists)
293 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
295 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
296 struct dentry *root_dentry = dentry->d_sb->s_root;
300 ovl_path_real(root_dentry, &path);
302 err = vfs_statfs(&path, buf);
304 buf->f_namelen = ofs->namelen;
305 buf->f_type = OVERLAYFS_SUPER_MAGIC;
311 /* Will this overlay be forced to mount/remount ro? */
312 static bool ovl_force_readonly(struct ovl_fs *ofs)
314 return (!ofs->upper_mnt || !ofs->workdir);
317 static const char *ovl_redirect_mode_def(void)
319 return ovl_redirect_dir_def ? "on" : "off";
328 static const char * const ovl_xino_str[] = {
334 static inline int ovl_xino_def(void)
336 return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
342 * Prints the mount options for a given superblock.
343 * Returns zero; does not fail.
345 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
347 struct super_block *sb = dentry->d_sb;
348 struct ovl_fs *ofs = sb->s_fs_info;
350 seq_show_option(m, "lowerdir", ofs->config.lowerdir);
351 if (ofs->config.upperdir) {
352 seq_show_option(m, "upperdir", ofs->config.upperdir);
353 seq_show_option(m, "workdir", ofs->config.workdir);
355 if (ofs->config.default_permissions)
356 seq_puts(m, ",default_permissions");
357 if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
358 seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
359 if (ofs->config.index != ovl_index_def)
360 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
361 if (ofs->config.nfs_export != ovl_nfs_export_def)
362 seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
364 if (ofs->config.xino != ovl_xino_def())
365 seq_printf(m, ",xino=%s", ovl_xino_str[ofs->config.xino]);
366 if (ofs->config.metacopy != ovl_metacopy_def)
367 seq_printf(m, ",metacopy=%s",
368 ofs->config.metacopy ? "on" : "off");
372 static int ovl_remount(struct super_block *sb, int *flags, char *data)
374 struct ovl_fs *ofs = sb->s_fs_info;
376 if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
382 static const struct super_operations ovl_super_operations = {
383 .alloc_inode = ovl_alloc_inode,
384 .free_inode = ovl_free_inode,
385 .destroy_inode = ovl_destroy_inode,
386 .drop_inode = generic_delete_inode,
387 .put_super = ovl_put_super,
388 .sync_fs = ovl_sync_fs,
389 .statfs = ovl_statfs,
390 .show_options = ovl_show_options,
391 .remount_fs = ovl_remount,
398 OPT_DEFAULT_PERMISSIONS,
412 static const match_table_t ovl_tokens = {
413 {OPT_LOWERDIR, "lowerdir=%s"},
414 {OPT_UPPERDIR, "upperdir=%s"},
415 {OPT_WORKDIR, "workdir=%s"},
416 {OPT_DEFAULT_PERMISSIONS, "default_permissions"},
417 {OPT_REDIRECT_DIR, "redirect_dir=%s"},
418 {OPT_INDEX_ON, "index=on"},
419 {OPT_INDEX_OFF, "index=off"},
420 {OPT_NFS_EXPORT_ON, "nfs_export=on"},
421 {OPT_NFS_EXPORT_OFF, "nfs_export=off"},
422 {OPT_XINO_ON, "xino=on"},
423 {OPT_XINO_OFF, "xino=off"},
424 {OPT_XINO_AUTO, "xino=auto"},
425 {OPT_METACOPY_ON, "metacopy=on"},
426 {OPT_METACOPY_OFF, "metacopy=off"},
430 static char *ovl_next_opt(char **s)
438 for (p = sbegin; *p; p++) {
443 } else if (*p == ',') {
453 static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
455 if (strcmp(mode, "on") == 0) {
456 config->redirect_dir = true;
458 * Does not make sense to have redirect creation without
459 * redirect following.
461 config->redirect_follow = true;
462 } else if (strcmp(mode, "follow") == 0) {
463 config->redirect_follow = true;
464 } else if (strcmp(mode, "off") == 0) {
465 if (ovl_redirect_always_follow)
466 config->redirect_follow = true;
467 } else if (strcmp(mode, "nofollow") != 0) {
468 pr_err("overlayfs: bad mount option \"redirect_dir=%s\"\n",
476 static int ovl_parse_opt(char *opt, struct ovl_config *config)
480 bool metacopy_opt = false, redirect_opt = false;
482 config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
483 if (!config->redirect_mode)
486 while ((p = ovl_next_opt(&opt)) != NULL) {
488 substring_t args[MAX_OPT_ARGS];
493 token = match_token(p, ovl_tokens, args);
496 kfree(config->upperdir);
497 config->upperdir = match_strdup(&args[0]);
498 if (!config->upperdir)
503 kfree(config->lowerdir);
504 config->lowerdir = match_strdup(&args[0]);
505 if (!config->lowerdir)
510 kfree(config->workdir);
511 config->workdir = match_strdup(&args[0]);
512 if (!config->workdir)
516 case OPT_DEFAULT_PERMISSIONS:
517 config->default_permissions = true;
520 case OPT_REDIRECT_DIR:
521 kfree(config->redirect_mode);
522 config->redirect_mode = match_strdup(&args[0]);
523 if (!config->redirect_mode)
529 config->index = true;
533 config->index = false;
536 case OPT_NFS_EXPORT_ON:
537 config->nfs_export = true;
540 case OPT_NFS_EXPORT_OFF:
541 config->nfs_export = false;
545 config->xino = OVL_XINO_ON;
549 config->xino = OVL_XINO_OFF;
553 config->xino = OVL_XINO_AUTO;
556 case OPT_METACOPY_ON:
557 config->metacopy = true;
561 case OPT_METACOPY_OFF:
562 config->metacopy = false;
566 pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
571 /* Workdir is useless in non-upper mount */
572 if (!config->upperdir && config->workdir) {
573 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
575 kfree(config->workdir);
576 config->workdir = NULL;
579 err = ovl_parse_redirect_mode(config, config->redirect_mode);
584 * This is to make the logic below simpler. It doesn't make any other
585 * difference, since config->redirect_dir is only used for upper.
587 if (!config->upperdir && config->redirect_follow)
588 config->redirect_dir = true;
590 /* Resolve metacopy -> redirect_dir dependency */
591 if (config->metacopy && !config->redirect_dir) {
592 if (metacopy_opt && redirect_opt) {
593 pr_err("overlayfs: conflicting options: metacopy=on,redirect_dir=%s\n",
594 config->redirect_mode);
599 * There was an explicit redirect_dir=... that resulted
602 pr_info("overlayfs: disabling metacopy due to redirect_dir=%s\n",
603 config->redirect_mode);
604 config->metacopy = false;
606 /* Automatically enable redirect otherwise. */
607 config->redirect_follow = config->redirect_dir = true;
614 #define OVL_WORKDIR_NAME "work"
615 #define OVL_INDEXDIR_NAME "index"
617 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
618 const char *name, bool persist)
620 struct inode *dir = ofs->workbasedir->d_inode;
621 struct vfsmount *mnt = ofs->upper_mnt;
624 bool retried = false;
627 inode_lock_nested(dir, I_MUTEX_PARENT);
631 work = lookup_one_len(name, ofs->workbasedir, strlen(name));
634 struct iattr attr = {
635 .ia_valid = ATTR_MODE,
636 .ia_mode = S_IFDIR | 0,
648 ovl_workdir_cleanup(dir, mnt, work, 0);
653 err = ovl_mkdir_real(dir, &work, attr.ia_mode);
657 /* Weird filesystem returning with hashed negative (kernfs)? */
659 if (d_really_is_negative(work))
663 * Try to remove POSIX ACL xattrs from workdir. We are good if:
665 * a) success (there was a POSIX ACL xattr and was removed)
666 * b) -ENODATA (there was no POSIX ACL xattr)
667 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
669 * There are various other error values that could effectively
670 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
671 * if the xattr name is too long), but the set of filesystems
672 * allowed as upper are limited to "normal" ones, where checking
673 * for the above two errors is sufficient.
675 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
676 if (err && err != -ENODATA && err != -EOPNOTSUPP)
679 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
680 if (err && err != -ENODATA && err != -EOPNOTSUPP)
683 /* Clear any inherited mode bits */
684 inode_lock(work->d_inode);
685 err = notify_change(work, &attr, NULL);
686 inode_unlock(work->d_inode);
702 pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
703 ofs->config.workdir, name, -err);
708 static void ovl_unescape(char *s)
721 static int ovl_mount_dir_noesc(const char *name, struct path *path)
726 pr_err("overlayfs: empty lowerdir\n");
729 err = kern_path(name, LOOKUP_FOLLOW, path);
731 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
735 if (ovl_dentry_weird(path->dentry)) {
736 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
739 if (!d_is_dir(path->dentry)) {
740 pr_err("overlayfs: '%s' not a directory\n", name);
751 static int ovl_mount_dir(const char *name, struct path *path)
754 char *tmp = kstrdup(name, GFP_KERNEL);
758 err = ovl_mount_dir_noesc(tmp, path);
761 if (ovl_dentry_remote(path->dentry)) {
762 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
772 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
775 struct kstatfs statfs;
776 int err = vfs_statfs(path, &statfs);
779 pr_err("overlayfs: statfs failed on '%s'\n", name);
781 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
786 static int ovl_lower_dir(const char *name, struct path *path,
787 struct ovl_fs *ofs, int *stack_depth, bool *remote)
792 err = ovl_mount_dir_noesc(name, path);
796 err = ovl_check_namelen(path, ofs, name);
800 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
802 if (ovl_dentry_remote(path->dentry))
806 * The inodes index feature and NFS export need to encode and decode
807 * file handles, so they require that all layers support them.
809 fh_type = ovl_can_decode_fh(path->dentry->d_sb);
810 if ((ofs->config.nfs_export ||
811 (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
812 ofs->config.index = false;
813 ofs->config.nfs_export = false;
814 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
818 /* Check if lower fs has 32bit inode numbers */
819 if (fh_type != FILEID_INO32_GEN)
830 /* Workdir should not be subdir of upperdir and vice versa */
831 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
835 if (workdir != upperdir) {
836 ok = (lock_rename(workdir, upperdir) == NULL);
837 unlock_rename(workdir, upperdir);
842 static unsigned int ovl_split_lowerdirs(char *str)
844 unsigned int ctr = 1;
847 for (s = d = str;; s++, d++) {
850 } else if (*s == ':') {
862 static int __maybe_unused
863 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
864 struct dentry *dentry, struct inode *inode,
865 const char *name, void *buffer, size_t size)
867 return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
870 static int __maybe_unused
871 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
872 struct dentry *dentry, struct inode *inode,
873 const char *name, const void *value,
874 size_t size, int flags)
876 struct dentry *workdir = ovl_workdir(dentry);
877 struct inode *realinode = ovl_inode_real(inode);
878 struct posix_acl *acl = NULL;
881 /* Check that everything is OK before copy-up */
883 acl = posix_acl_from_xattr(&init_user_ns, value, size);
888 if (!IS_POSIXACL(d_inode(workdir)))
889 goto out_acl_release;
890 if (!realinode->i_op->set_acl)
891 goto out_acl_release;
892 if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
893 err = acl ? -EACCES : 0;
894 goto out_acl_release;
897 if (!inode_owner_or_capable(inode))
898 goto out_acl_release;
900 posix_acl_release(acl);
903 * Check if sgid bit needs to be cleared (actual setacl operation will
904 * be done with mounter's capabilities and so that won't do it for us).
906 if (unlikely(inode->i_mode & S_ISGID) &&
907 handler->flags == ACL_TYPE_ACCESS &&
908 !in_group_p(inode->i_gid) &&
909 !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
910 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
912 err = ovl_setattr(dentry, &iattr);
917 err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
919 ovl_copyattr(ovl_inode_real(inode), inode);
924 posix_acl_release(acl);
928 static int ovl_own_xattr_get(const struct xattr_handler *handler,
929 struct dentry *dentry, struct inode *inode,
930 const char *name, void *buffer, size_t size)
935 static int ovl_own_xattr_set(const struct xattr_handler *handler,
936 struct dentry *dentry, struct inode *inode,
937 const char *name, const void *value,
938 size_t size, int flags)
943 static int ovl_other_xattr_get(const struct xattr_handler *handler,
944 struct dentry *dentry, struct inode *inode,
945 const char *name, void *buffer, size_t size)
947 return ovl_xattr_get(dentry, inode, name, buffer, size);
950 static int ovl_other_xattr_set(const struct xattr_handler *handler,
951 struct dentry *dentry, struct inode *inode,
952 const char *name, const void *value,
953 size_t size, int flags)
955 return ovl_xattr_set(dentry, inode, name, value, size, flags);
958 static const struct xattr_handler __maybe_unused
959 ovl_posix_acl_access_xattr_handler = {
960 .name = XATTR_NAME_POSIX_ACL_ACCESS,
961 .flags = ACL_TYPE_ACCESS,
962 .get = ovl_posix_acl_xattr_get,
963 .set = ovl_posix_acl_xattr_set,
966 static const struct xattr_handler __maybe_unused
967 ovl_posix_acl_default_xattr_handler = {
968 .name = XATTR_NAME_POSIX_ACL_DEFAULT,
969 .flags = ACL_TYPE_DEFAULT,
970 .get = ovl_posix_acl_xattr_get,
971 .set = ovl_posix_acl_xattr_set,
974 static const struct xattr_handler ovl_own_xattr_handler = {
975 .prefix = OVL_XATTR_PREFIX,
976 .get = ovl_own_xattr_get,
977 .set = ovl_own_xattr_set,
980 static const struct xattr_handler ovl_other_xattr_handler = {
981 .prefix = "", /* catch all */
982 .get = ovl_other_xattr_get,
983 .set = ovl_other_xattr_set,
986 static const struct xattr_handler *ovl_xattr_handlers[] = {
987 #ifdef CONFIG_FS_POSIX_ACL
988 &ovl_posix_acl_access_xattr_handler,
989 &ovl_posix_acl_default_xattr_handler,
991 &ovl_own_xattr_handler,
992 &ovl_other_xattr_handler,
996 static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
997 struct inode **ptrap, const char *name)
1002 trap = ovl_get_trap_inode(sb, dir);
1003 err = PTR_ERR_OR_ZERO(trap);
1006 pr_err("overlayfs: conflicting %s path\n", name);
1015 * Determine how we treat concurrent use of upperdir/workdir based on the
1016 * index feature. This is papering over mount leaks of container runtimes,
1017 * for example, an old overlay mount is leaked and now its upperdir is
1018 * attempted to be used as a lower layer in a new overlay mount.
1020 static int ovl_report_in_use(struct ovl_fs *ofs, const char *name)
1022 if (ofs->config.index) {
1023 pr_err("overlayfs: %s is in-use as upperdir/workdir of another mount, mount with '-o index=off' to override exclusive upperdir protection.\n",
1027 pr_warn("overlayfs: %s is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.\n",
1033 static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
1034 struct path *upperpath)
1036 struct vfsmount *upper_mnt;
1039 err = ovl_mount_dir(ofs->config.upperdir, upperpath);
1043 /* Upper fs should not be r/o */
1044 if (sb_rdonly(upperpath->mnt->mnt_sb)) {
1045 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
1050 err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
1054 err = ovl_setup_trap(sb, upperpath->dentry, &ofs->upperdir_trap,
1059 upper_mnt = clone_private_mount(upperpath);
1060 err = PTR_ERR(upper_mnt);
1061 if (IS_ERR(upper_mnt)) {
1062 pr_err("overlayfs: failed to clone upperpath\n");
1066 /* Don't inherit atime flags */
1067 upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
1068 ofs->upper_mnt = upper_mnt;
1070 if (ovl_inuse_trylock(ofs->upper_mnt->mnt_root)) {
1071 ofs->upperdir_locked = true;
1073 err = ovl_report_in_use(ofs, "upperdir");
1083 static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
1084 struct path *workpath)
1086 struct vfsmount *mnt = ofs->upper_mnt;
1087 struct dentry *temp;
1091 err = mnt_want_write(mnt);
1095 ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
1099 err = ovl_setup_trap(sb, ofs->workdir, &ofs->workdir_trap, "workdir");
1104 * Upper should support d_type, else whiteouts are visible. Given
1105 * workdir and upper are on same fs, we can do iterate_dir() on
1106 * workdir. This check requires successful creation of workdir in
1109 err = ovl_check_d_type_supported(workpath);
1114 * We allowed this configuration and don't want to break users over
1115 * kernel upgrade. So warn instead of erroring out.
1118 pr_warn("overlayfs: upper fs needs to support d_type.\n");
1120 /* Check if upper/work fs supports O_TMPFILE */
1121 temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
1122 ofs->tmpfile = !IS_ERR(temp);
1126 pr_warn("overlayfs: upper fs does not support tmpfile.\n");
1129 * Check if upper/work fs supports trusted.overlay.* xattr
1131 err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
1133 ofs->noxattr = true;
1134 ofs->config.index = false;
1135 ofs->config.metacopy = false;
1136 pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off and metacopy=off.\n");
1139 vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
1142 /* Check if upper/work fs supports file handles */
1143 fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
1144 if (ofs->config.index && !fh_type) {
1145 ofs->config.index = false;
1146 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
1149 /* Check if upper fs has 32bit inode numbers */
1150 if (fh_type != FILEID_INO32_GEN)
1153 /* NFS export of r/w mount depends on index */
1154 if (ofs->config.nfs_export && !ofs->config.index) {
1155 pr_warn("overlayfs: NFS export requires \"index=on\", falling back to nfs_export=off.\n");
1156 ofs->config.nfs_export = false;
1159 mnt_drop_write(mnt);
1163 static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
1164 struct path *upperpath)
1167 struct path workpath = { };
1169 err = ovl_mount_dir(ofs->config.workdir, &workpath);
1174 if (upperpath->mnt != workpath.mnt) {
1175 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
1178 if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
1179 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
1183 ofs->workbasedir = dget(workpath.dentry);
1185 if (ovl_inuse_trylock(ofs->workbasedir)) {
1186 ofs->workdir_locked = true;
1188 err = ovl_report_in_use(ofs, "workdir");
1193 err = ovl_setup_trap(sb, ofs->workbasedir, &ofs->workbasedir_trap,
1198 err = ovl_make_workdir(sb, ofs, &workpath);
1201 path_put(&workpath);
1206 static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
1207 struct ovl_entry *oe, struct path *upperpath)
1209 struct vfsmount *mnt = ofs->upper_mnt;
1212 err = mnt_want_write(mnt);
1216 /* Verify lower root is upper root origin */
1217 err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
1220 pr_err("overlayfs: failed to verify upper root origin\n");
1224 ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
1225 if (ofs->indexdir) {
1226 err = ovl_setup_trap(sb, ofs->indexdir, &ofs->indexdir_trap,
1232 * Verify upper root is exclusively associated with index dir.
1233 * Older kernels stored upper fh in "trusted.overlay.origin"
1234 * xattr. If that xattr exists, verify that it is a match to
1235 * upper dir file handle. In any case, verify or set xattr
1236 * "trusted.overlay.upper" to indicate that index may have
1237 * directory entries.
1239 if (ovl_check_origin_xattr(ofs->indexdir)) {
1240 err = ovl_verify_set_fh(ofs->indexdir, OVL_XATTR_ORIGIN,
1241 upperpath->dentry, true, false);
1243 pr_err("overlayfs: failed to verify index dir 'origin' xattr\n");
1245 err = ovl_verify_upper(ofs->indexdir, upperpath->dentry, true);
1247 pr_err("overlayfs: failed to verify index dir 'upper' xattr\n");
1249 /* Cleanup bad/stale/orphan index entries */
1251 err = ovl_indexdir_cleanup(ofs);
1253 if (err || !ofs->indexdir)
1254 pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1257 mnt_drop_write(mnt);
1261 static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
1265 if (!ofs->config.nfs_export && !ofs->upper_mnt)
1269 * We allow using single lower with null uuid for index and nfs_export
1270 * for example to support those features with single lower squashfs.
1271 * To avoid regressions in setups of overlay with re-formatted lower
1272 * squashfs, do not allow decoding origin with lower null uuid unless
1273 * user opted-in to one of the new features that require following the
1274 * lower inode of non-dir upper.
1276 if (!ofs->config.index && !ofs->config.metacopy && !ofs->config.xino &&
1280 for (i = 0; i < ofs->numlowerfs; i++) {
1282 * We use uuid to associate an overlay lower file handle with a
1283 * lower layer, so we can accept lower fs with null uuid as long
1284 * as all lower layers with null uuid are on the same fs.
1285 * if we detect multiple lower fs with the same uuid, we
1286 * disable lower file handle decoding on all of them.
1288 if (uuid_equal(&ofs->lower_fs[i].sb->s_uuid, uuid)) {
1289 ofs->lower_fs[i].bad_uuid = true;
1296 /* Get a unique fsid for the layer */
1297 static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
1299 struct super_block *sb = path->mnt->mnt_sb;
1303 bool bad_uuid = false;
1305 /* fsid 0 is reserved for upper fs even with non upper overlay */
1306 if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb)
1309 for (i = 0; i < ofs->numlowerfs; i++) {
1310 if (ofs->lower_fs[i].sb == sb)
1314 if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) {
1316 if (ofs->config.index || ofs->config.nfs_export) {
1317 ofs->config.index = false;
1318 ofs->config.nfs_export = false;
1319 pr_warn("overlayfs: %s uuid detected in lower fs '%pd2', falling back to index=off,nfs_export=off.\n",
1320 uuid_is_null(&sb->s_uuid) ? "null" :
1326 err = get_anon_bdev(&dev);
1328 pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
1332 ofs->lower_fs[ofs->numlowerfs].sb = sb;
1333 ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev;
1334 ofs->lower_fs[ofs->numlowerfs].bad_uuid = bad_uuid;
1337 return ofs->numlowerfs;
1340 static int ovl_get_lower_layers(struct super_block *sb, struct ovl_fs *ofs,
1341 struct path *stack, unsigned int numlower)
1347 ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
1349 if (ofs->lower_layers == NULL)
1352 ofs->lower_fs = kcalloc(numlower, sizeof(struct ovl_sb),
1354 if (ofs->lower_fs == NULL)
1357 for (i = 0; i < numlower; i++) {
1358 struct vfsmount *mnt;
1362 err = fsid = ovl_get_fsid(ofs, &stack[i]);
1367 * Check if lower root conflicts with this overlay layers before
1368 * checking if it is in-use as upperdir/workdir of "another"
1369 * mount, because we do not bother to check in ovl_is_inuse() if
1370 * the upperdir/workdir is in fact in-use by our
1373 err = ovl_setup_trap(sb, stack[i].dentry, &trap, "lowerdir");
1377 if (ovl_is_inuse(stack[i].dentry)) {
1378 err = ovl_report_in_use(ofs, "lowerdir");
1385 mnt = clone_private_mount(&stack[i]);
1388 pr_err("overlayfs: failed to clone lowerpath\n");
1394 * Make lower layers R/O. That way fchmod/fchown on lower file
1395 * will fail instead of modifying lower fs.
1397 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1399 ofs->lower_layers[ofs->numlower].trap = trap;
1400 ofs->lower_layers[ofs->numlower].mnt = mnt;
1401 ofs->lower_layers[ofs->numlower].idx = i + 1;
1402 ofs->lower_layers[ofs->numlower].fsid = fsid;
1404 ofs->lower_layers[ofs->numlower].fs =
1405 &ofs->lower_fs[fsid - 1];
1411 * When all layers on same fs, overlay can use real inode numbers.
1412 * With mount option "xino=on", mounter declares that there are enough
1413 * free high bits in underlying fs to hold the unique fsid.
1414 * If overlayfs does encounter underlying inodes using the high xino
1415 * bits reserved for fsid, it emits a warning and uses the original
1418 if (!ofs->numlowerfs || (ofs->numlowerfs == 1 && !ofs->upper_mnt)) {
1420 ofs->config.xino = OVL_XINO_OFF;
1421 } else if (ofs->config.xino == OVL_XINO_ON && !ofs->xino_bits) {
1423 * This is a roundup of number of bits needed for numlowerfs+1
1424 * (i.e. ilog2(numlowerfs+1 - 1) + 1). fsid 0 is reserved for
1425 * upper fs even with non upper overlay.
1427 BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 31);
1428 ofs->xino_bits = ilog2(ofs->numlowerfs) + 1;
1431 if (ofs->xino_bits) {
1432 pr_info("overlayfs: \"xino\" feature enabled using %d upper inode bits.\n",
1441 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1445 char *lowertmp, *lower;
1446 struct path *stack = NULL;
1447 unsigned int stacklen, numlower = 0, i;
1448 bool remote = false;
1449 struct ovl_entry *oe;
1452 lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
1457 stacklen = ovl_split_lowerdirs(lowertmp);
1458 if (stacklen > OVL_MAX_STACK) {
1459 pr_err("overlayfs: too many lower directories, limit is %d\n",
1462 } else if (!ofs->config.upperdir && stacklen == 1) {
1463 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
1465 } else if (!ofs->config.upperdir && ofs->config.nfs_export &&
1466 ofs->config.redirect_follow) {
1467 pr_warn("overlayfs: NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
1468 ofs->config.nfs_export = false;
1472 stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
1478 for (numlower = 0; numlower < stacklen; numlower++) {
1479 err = ovl_lower_dir(lower, &stack[numlower], ofs,
1480 &sb->s_stack_depth, &remote);
1484 lower = strchr(lower, '\0') + 1;
1488 sb->s_stack_depth++;
1489 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1490 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1494 err = ovl_get_lower_layers(sb, ofs, stack, numlower);
1499 oe = ovl_alloc_entry(numlower);
1503 for (i = 0; i < numlower; i++) {
1504 oe->lowerstack[i].dentry = dget(stack[i].dentry);
1505 oe->lowerstack[i].layer = &ofs->lower_layers[i];
1509 sb->s_d_op = &ovl_reval_dentry_operations;
1511 sb->s_d_op = &ovl_dentry_operations;
1514 for (i = 0; i < numlower; i++)
1515 path_put(&stack[i]);
1527 * Check if this layer root is a descendant of:
1528 * - another layer of this overlayfs instance
1529 * - upper/work dir of any overlayfs instance
1531 static int ovl_check_layer(struct super_block *sb, struct ovl_fs *ofs,
1532 struct dentry *dentry, const char *name,
1535 struct dentry *next = dentry, *parent;
1541 parent = dget_parent(next);
1543 /* Walk back ancestors to root (inclusive) looking for traps */
1544 while (!err && parent != next) {
1545 if (is_lower && ovl_lookup_trap_inode(sb, parent)) {
1547 pr_err("overlayfs: overlapping %s path\n", name);
1548 } else if (ovl_is_inuse(parent)) {
1549 err = ovl_report_in_use(ofs, name);
1552 parent = dget_parent(next);
1562 * Check if any of the layers or work dirs overlap.
1564 static int ovl_check_overlapping_layers(struct super_block *sb,
1569 if (ofs->upper_mnt) {
1570 err = ovl_check_layer(sb, ofs, ofs->upper_mnt->mnt_root,
1576 * Checking workbasedir avoids hitting ovl_is_inuse(parent) of
1577 * this instance and covers overlapping work and index dirs,
1578 * unless work or index dir have been moved since created inside
1579 * workbasedir. In that case, we already have their traps in
1580 * inode cache and we will catch that case on lookup.
1582 err = ovl_check_layer(sb, ofs, ofs->workbasedir, "workdir",
1588 for (i = 0; i < ofs->numlower; i++) {
1589 err = ovl_check_layer(sb, ofs,
1590 ofs->lower_layers[i].mnt->mnt_root,
1599 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
1601 struct path upperpath = { };
1602 struct dentry *root_dentry;
1603 struct ovl_entry *oe;
1609 ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
1613 ofs->creator_cred = cred = prepare_creds();
1617 ofs->config.index = ovl_index_def;
1618 ofs->config.nfs_export = ovl_nfs_export_def;
1619 ofs->config.xino = ovl_xino_def();
1620 ofs->config.metacopy = ovl_metacopy_def;
1621 err = ovl_parse_opt((char *) data, &ofs->config);
1626 if (!ofs->config.lowerdir) {
1628 pr_err("overlayfs: missing 'lowerdir'\n");
1632 sb->s_stack_depth = 0;
1633 sb->s_maxbytes = MAX_LFS_FILESIZE;
1634 /* Assume underlaying fs uses 32bit inodes unless proven otherwise */
1635 if (ofs->config.xino != OVL_XINO_OFF)
1636 ofs->xino_bits = BITS_PER_LONG - 32;
1638 /* alloc/destroy_inode needed for setting up traps in inode cache */
1639 sb->s_op = &ovl_super_operations;
1641 if (ofs->config.upperdir) {
1642 if (!ofs->config.workdir) {
1643 pr_err("overlayfs: missing 'workdir'\n");
1647 err = ovl_get_upper(sb, ofs, &upperpath);
1651 err = ovl_get_workdir(sb, ofs, &upperpath);
1656 sb->s_flags |= SB_RDONLY;
1658 sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
1659 sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
1662 oe = ovl_get_lowerstack(sb, ofs);
1667 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1668 if (!ofs->upper_mnt)
1669 sb->s_flags |= SB_RDONLY;
1671 if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
1672 err = ovl_get_indexdir(sb, ofs, oe, &upperpath);
1676 /* Force r/o mount with no index dir */
1677 if (!ofs->indexdir) {
1679 ofs->workdir = NULL;
1680 sb->s_flags |= SB_RDONLY;
1685 err = ovl_check_overlapping_layers(sb, ofs);
1689 /* Show index=off in /proc/mounts for forced r/o mount */
1690 if (!ofs->indexdir) {
1691 ofs->config.index = false;
1692 if (ofs->upper_mnt && ofs->config.nfs_export) {
1693 pr_warn("overlayfs: NFS export requires an index dir, falling back to nfs_export=off.\n");
1694 ofs->config.nfs_export = false;
1698 if (ofs->config.metacopy && ofs->config.nfs_export) {
1699 pr_warn("overlayfs: NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
1700 ofs->config.nfs_export = false;
1703 if (ofs->config.nfs_export)
1704 sb->s_export_op = &ovl_export_operations;
1706 /* Never override disk quota limits or use reserved space */
1707 cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1709 sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1710 sb->s_xattr = ovl_xattr_handlers;
1711 sb->s_fs_info = ofs;
1712 sb->s_flags |= SB_POSIXACL;
1715 root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1719 root_dentry->d_fsdata = oe;
1721 mntput(upperpath.mnt);
1722 if (upperpath.dentry) {
1723 ovl_dentry_set_upper_alias(root_dentry);
1724 if (ovl_is_impuredir(upperpath.dentry))
1725 ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
1728 /* Root is always merge -> can have whiteouts */
1729 ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
1730 ovl_dentry_set_flag(OVL_E_CONNECTED, root_dentry);
1731 ovl_set_upperdata(d_inode(root_dentry));
1732 ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
1733 ovl_dentry_lower(root_dentry), NULL);
1735 sb->s_root = root_dentry;
1740 ovl_entry_stack_free(oe);
1743 path_put(&upperpath);
1749 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1750 const char *dev_name, void *raw_data)
1752 return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1755 static struct file_system_type ovl_fs_type = {
1756 .owner = THIS_MODULE,
1759 .kill_sb = kill_anon_super,
1761 MODULE_ALIAS_FS("overlay");
1763 static void ovl_inode_init_once(void *foo)
1765 struct ovl_inode *oi = foo;
1767 inode_init_once(&oi->vfs_inode);
1770 static int __init ovl_init(void)
1774 ovl_inode_cachep = kmem_cache_create("ovl_inode",
1775 sizeof(struct ovl_inode), 0,
1776 (SLAB_RECLAIM_ACCOUNT|
1777 SLAB_MEM_SPREAD|SLAB_ACCOUNT),
1778 ovl_inode_init_once);
1779 if (ovl_inode_cachep == NULL)
1782 err = register_filesystem(&ovl_fs_type);
1784 kmem_cache_destroy(ovl_inode_cachep);
1789 static void __exit ovl_exit(void)
1791 unregister_filesystem(&ovl_fs_type);
1794 * Make sure all delayed rcu free inodes are flushed before we
1798 kmem_cache_destroy(ovl_inode_cachep);
1802 module_init(ovl_init);
1803 module_exit(ovl_exit);