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->indexdir_trap);
216 iput(ofs->workdir_trap);
217 iput(ofs->upperdir_trap);
220 if (ofs->workdir_locked)
221 ovl_inuse_unlock(ofs->workbasedir);
222 dput(ofs->workbasedir);
223 if (ofs->upperdir_locked)
224 ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
225 mntput(ofs->upper_mnt);
226 for (i = 0; i < ofs->numlower; i++) {
227 iput(ofs->lower_layers[i].trap);
228 mntput(ofs->lower_layers[i].mnt);
230 for (i = 0; i < ofs->numlowerfs; i++)
231 free_anon_bdev(ofs->lower_fs[i].pseudo_dev);
232 kfree(ofs->lower_layers);
233 kfree(ofs->lower_fs);
235 kfree(ofs->config.lowerdir);
236 kfree(ofs->config.upperdir);
237 kfree(ofs->config.workdir);
238 kfree(ofs->config.redirect_mode);
239 if (ofs->creator_cred)
240 put_cred(ofs->creator_cred);
244 static void ovl_put_super(struct super_block *sb)
246 struct ovl_fs *ofs = sb->s_fs_info;
251 /* Sync real dirty inodes in upper filesystem (if it exists) */
252 static int ovl_sync_fs(struct super_block *sb, int wait)
254 struct ovl_fs *ofs = sb->s_fs_info;
255 struct super_block *upper_sb;
262 * If this is a sync(2) call or an emergency sync, all the super blocks
263 * will be iterated, including upper_sb, so no need to do anything.
265 * If this is a syncfs(2) call, then we do need to call
266 * sync_filesystem() on upper_sb, but enough if we do it when being
267 * called with wait == 1.
272 upper_sb = ofs->upper_mnt->mnt_sb;
274 down_read(&upper_sb->s_umount);
275 ret = sync_filesystem(upper_sb);
276 up_read(&upper_sb->s_umount);
283 * @sb: The overlayfs super block
284 * @buf: The struct kstatfs to fill in with stats
286 * Get the filesystem statistics. As writes always target the upper layer
287 * filesystem pass the statfs to the upper filesystem (if it exists)
289 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
291 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
292 struct dentry *root_dentry = dentry->d_sb->s_root;
296 ovl_path_real(root_dentry, &path);
298 err = vfs_statfs(&path, buf);
300 buf->f_namelen = ofs->namelen;
301 buf->f_type = OVERLAYFS_SUPER_MAGIC;
307 /* Will this overlay be forced to mount/remount ro? */
308 static bool ovl_force_readonly(struct ovl_fs *ofs)
310 return (!ofs->upper_mnt || !ofs->workdir);
313 static const char *ovl_redirect_mode_def(void)
315 return ovl_redirect_dir_def ? "on" : "off";
324 static const char * const ovl_xino_str[] = {
330 static inline int ovl_xino_def(void)
332 return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
338 * Prints the mount options for a given superblock.
339 * Returns zero; does not fail.
341 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
343 struct super_block *sb = dentry->d_sb;
344 struct ovl_fs *ofs = sb->s_fs_info;
346 seq_show_option(m, "lowerdir", ofs->config.lowerdir);
347 if (ofs->config.upperdir) {
348 seq_show_option(m, "upperdir", ofs->config.upperdir);
349 seq_show_option(m, "workdir", ofs->config.workdir);
351 if (ofs->config.default_permissions)
352 seq_puts(m, ",default_permissions");
353 if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
354 seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
355 if (ofs->config.index != ovl_index_def)
356 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
357 if (ofs->config.nfs_export != ovl_nfs_export_def)
358 seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
360 if (ofs->config.xino != ovl_xino_def())
361 seq_printf(m, ",xino=%s", ovl_xino_str[ofs->config.xino]);
362 if (ofs->config.metacopy != ovl_metacopy_def)
363 seq_printf(m, ",metacopy=%s",
364 ofs->config.metacopy ? "on" : "off");
368 static int ovl_remount(struct super_block *sb, int *flags, char *data)
370 struct ovl_fs *ofs = sb->s_fs_info;
372 if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
378 static const struct super_operations ovl_super_operations = {
379 .alloc_inode = ovl_alloc_inode,
380 .free_inode = ovl_free_inode,
381 .destroy_inode = ovl_destroy_inode,
382 .drop_inode = generic_delete_inode,
383 .put_super = ovl_put_super,
384 .sync_fs = ovl_sync_fs,
385 .statfs = ovl_statfs,
386 .show_options = ovl_show_options,
387 .remount_fs = ovl_remount,
394 OPT_DEFAULT_PERMISSIONS,
408 static const match_table_t ovl_tokens = {
409 {OPT_LOWERDIR, "lowerdir=%s"},
410 {OPT_UPPERDIR, "upperdir=%s"},
411 {OPT_WORKDIR, "workdir=%s"},
412 {OPT_DEFAULT_PERMISSIONS, "default_permissions"},
413 {OPT_REDIRECT_DIR, "redirect_dir=%s"},
414 {OPT_INDEX_ON, "index=on"},
415 {OPT_INDEX_OFF, "index=off"},
416 {OPT_NFS_EXPORT_ON, "nfs_export=on"},
417 {OPT_NFS_EXPORT_OFF, "nfs_export=off"},
418 {OPT_XINO_ON, "xino=on"},
419 {OPT_XINO_OFF, "xino=off"},
420 {OPT_XINO_AUTO, "xino=auto"},
421 {OPT_METACOPY_ON, "metacopy=on"},
422 {OPT_METACOPY_OFF, "metacopy=off"},
426 static char *ovl_next_opt(char **s)
434 for (p = sbegin; *p; p++) {
439 } else if (*p == ',') {
449 static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
451 if (strcmp(mode, "on") == 0) {
452 config->redirect_dir = true;
454 * Does not make sense to have redirect creation without
455 * redirect following.
457 config->redirect_follow = true;
458 } else if (strcmp(mode, "follow") == 0) {
459 config->redirect_follow = true;
460 } else if (strcmp(mode, "off") == 0) {
461 if (ovl_redirect_always_follow)
462 config->redirect_follow = true;
463 } else if (strcmp(mode, "nofollow") != 0) {
464 pr_err("overlayfs: bad mount option \"redirect_dir=%s\"\n",
472 static int ovl_parse_opt(char *opt, struct ovl_config *config)
476 bool metacopy_opt = false, redirect_opt = false;
478 config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
479 if (!config->redirect_mode)
482 while ((p = ovl_next_opt(&opt)) != NULL) {
484 substring_t args[MAX_OPT_ARGS];
489 token = match_token(p, ovl_tokens, args);
492 kfree(config->upperdir);
493 config->upperdir = match_strdup(&args[0]);
494 if (!config->upperdir)
499 kfree(config->lowerdir);
500 config->lowerdir = match_strdup(&args[0]);
501 if (!config->lowerdir)
506 kfree(config->workdir);
507 config->workdir = match_strdup(&args[0]);
508 if (!config->workdir)
512 case OPT_DEFAULT_PERMISSIONS:
513 config->default_permissions = true;
516 case OPT_REDIRECT_DIR:
517 kfree(config->redirect_mode);
518 config->redirect_mode = match_strdup(&args[0]);
519 if (!config->redirect_mode)
525 config->index = true;
529 config->index = false;
532 case OPT_NFS_EXPORT_ON:
533 config->nfs_export = true;
536 case OPT_NFS_EXPORT_OFF:
537 config->nfs_export = false;
541 config->xino = OVL_XINO_ON;
545 config->xino = OVL_XINO_OFF;
549 config->xino = OVL_XINO_AUTO;
552 case OPT_METACOPY_ON:
553 config->metacopy = true;
557 case OPT_METACOPY_OFF:
558 config->metacopy = false;
562 pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
567 /* Workdir is useless in non-upper mount */
568 if (!config->upperdir && config->workdir) {
569 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
571 kfree(config->workdir);
572 config->workdir = NULL;
575 err = ovl_parse_redirect_mode(config, config->redirect_mode);
580 * This is to make the logic below simpler. It doesn't make any other
581 * difference, since config->redirect_dir is only used for upper.
583 if (!config->upperdir && config->redirect_follow)
584 config->redirect_dir = true;
586 /* Resolve metacopy -> redirect_dir dependency */
587 if (config->metacopy && !config->redirect_dir) {
588 if (metacopy_opt && redirect_opt) {
589 pr_err("overlayfs: conflicting options: metacopy=on,redirect_dir=%s\n",
590 config->redirect_mode);
595 * There was an explicit redirect_dir=... that resulted
598 pr_info("overlayfs: disabling metacopy due to redirect_dir=%s\n",
599 config->redirect_mode);
600 config->metacopy = false;
602 /* Automatically enable redirect otherwise. */
603 config->redirect_follow = config->redirect_dir = true;
610 #define OVL_WORKDIR_NAME "work"
611 #define OVL_INDEXDIR_NAME "index"
613 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
614 const char *name, bool persist)
616 struct inode *dir = ofs->workbasedir->d_inode;
617 struct vfsmount *mnt = ofs->upper_mnt;
620 bool retried = false;
623 inode_lock_nested(dir, I_MUTEX_PARENT);
627 work = lookup_one_len(name, ofs->workbasedir, strlen(name));
630 struct iattr attr = {
631 .ia_valid = ATTR_MODE,
632 .ia_mode = S_IFDIR | 0,
644 ovl_workdir_cleanup(dir, mnt, work, 0);
649 work = ovl_create_real(dir, work, OVL_CATTR(attr.ia_mode));
655 * Try to remove POSIX ACL xattrs from workdir. We are good if:
657 * a) success (there was a POSIX ACL xattr and was removed)
658 * b) -ENODATA (there was no POSIX ACL xattr)
659 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
661 * There are various other error values that could effectively
662 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
663 * if the xattr name is too long), but the set of filesystems
664 * allowed as upper are limited to "normal" ones, where checking
665 * for the above two errors is sufficient.
667 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
668 if (err && err != -ENODATA && err != -EOPNOTSUPP)
671 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
672 if (err && err != -ENODATA && err != -EOPNOTSUPP)
675 /* Clear any inherited mode bits */
676 inode_lock(work->d_inode);
677 err = notify_change(work, &attr, NULL);
678 inode_unlock(work->d_inode);
694 pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
695 ofs->config.workdir, name, -err);
700 static void ovl_unescape(char *s)
713 static int ovl_mount_dir_noesc(const char *name, struct path *path)
718 pr_err("overlayfs: empty lowerdir\n");
721 err = kern_path(name, LOOKUP_FOLLOW, path);
723 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
727 if (ovl_dentry_weird(path->dentry)) {
728 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
731 if (!d_is_dir(path->dentry)) {
732 pr_err("overlayfs: '%s' not a directory\n", name);
743 static int ovl_mount_dir(const char *name, struct path *path)
746 char *tmp = kstrdup(name, GFP_KERNEL);
750 err = ovl_mount_dir_noesc(tmp, path);
753 if (ovl_dentry_remote(path->dentry)) {
754 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
764 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
767 struct kstatfs statfs;
768 int err = vfs_statfs(path, &statfs);
771 pr_err("overlayfs: statfs failed on '%s'\n", name);
773 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
778 static int ovl_lower_dir(const char *name, struct path *path,
779 struct ovl_fs *ofs, int *stack_depth, bool *remote)
784 err = ovl_mount_dir_noesc(name, path);
788 err = ovl_check_namelen(path, ofs, name);
792 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
794 if (ovl_dentry_remote(path->dentry))
798 * The inodes index feature and NFS export need to encode and decode
799 * file handles, so they require that all layers support them.
801 fh_type = ovl_can_decode_fh(path->dentry->d_sb);
802 if ((ofs->config.nfs_export ||
803 (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
804 ofs->config.index = false;
805 ofs->config.nfs_export = false;
806 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
810 /* Check if lower fs has 32bit inode numbers */
811 if (fh_type != FILEID_INO32_GEN)
822 /* Workdir should not be subdir of upperdir and vice versa */
823 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
827 if (workdir != upperdir) {
828 ok = (lock_rename(workdir, upperdir) == NULL);
829 unlock_rename(workdir, upperdir);
834 static unsigned int ovl_split_lowerdirs(char *str)
836 unsigned int ctr = 1;
839 for (s = d = str;; s++, d++) {
842 } else if (*s == ':') {
854 static int __maybe_unused
855 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
856 struct dentry *dentry, struct inode *inode,
857 const char *name, void *buffer, size_t size)
859 return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
862 static int __maybe_unused
863 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
864 struct dentry *dentry, struct inode *inode,
865 const char *name, const void *value,
866 size_t size, int flags)
868 struct dentry *workdir = ovl_workdir(dentry);
869 struct inode *realinode = ovl_inode_real(inode);
870 struct posix_acl *acl = NULL;
873 /* Check that everything is OK before copy-up */
875 acl = posix_acl_from_xattr(&init_user_ns, value, size);
880 if (!IS_POSIXACL(d_inode(workdir)))
881 goto out_acl_release;
882 if (!realinode->i_op->set_acl)
883 goto out_acl_release;
884 if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
885 err = acl ? -EACCES : 0;
886 goto out_acl_release;
889 if (!inode_owner_or_capable(inode))
890 goto out_acl_release;
892 posix_acl_release(acl);
895 * Check if sgid bit needs to be cleared (actual setacl operation will
896 * be done with mounter's capabilities and so that won't do it for us).
898 if (unlikely(inode->i_mode & S_ISGID) &&
899 handler->flags == ACL_TYPE_ACCESS &&
900 !in_group_p(inode->i_gid) &&
901 !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
902 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
904 err = ovl_setattr(dentry, &iattr);
909 err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
911 ovl_copyattr(ovl_inode_real(inode), inode);
916 posix_acl_release(acl);
920 static int ovl_own_xattr_get(const struct xattr_handler *handler,
921 struct dentry *dentry, struct inode *inode,
922 const char *name, void *buffer, size_t size)
927 static int ovl_own_xattr_set(const struct xattr_handler *handler,
928 struct dentry *dentry, struct inode *inode,
929 const char *name, const void *value,
930 size_t size, int flags)
935 static int ovl_other_xattr_get(const struct xattr_handler *handler,
936 struct dentry *dentry, struct inode *inode,
937 const char *name, void *buffer, size_t size)
939 return ovl_xattr_get(dentry, inode, name, buffer, size);
942 static int ovl_other_xattr_set(const struct xattr_handler *handler,
943 struct dentry *dentry, struct inode *inode,
944 const char *name, const void *value,
945 size_t size, int flags)
947 return ovl_xattr_set(dentry, inode, name, value, size, flags);
950 static const struct xattr_handler __maybe_unused
951 ovl_posix_acl_access_xattr_handler = {
952 .name = XATTR_NAME_POSIX_ACL_ACCESS,
953 .flags = ACL_TYPE_ACCESS,
954 .get = ovl_posix_acl_xattr_get,
955 .set = ovl_posix_acl_xattr_set,
958 static const struct xattr_handler __maybe_unused
959 ovl_posix_acl_default_xattr_handler = {
960 .name = XATTR_NAME_POSIX_ACL_DEFAULT,
961 .flags = ACL_TYPE_DEFAULT,
962 .get = ovl_posix_acl_xattr_get,
963 .set = ovl_posix_acl_xattr_set,
966 static const struct xattr_handler ovl_own_xattr_handler = {
967 .prefix = OVL_XATTR_PREFIX,
968 .get = ovl_own_xattr_get,
969 .set = ovl_own_xattr_set,
972 static const struct xattr_handler ovl_other_xattr_handler = {
973 .prefix = "", /* catch all */
974 .get = ovl_other_xattr_get,
975 .set = ovl_other_xattr_set,
978 static const struct xattr_handler *ovl_xattr_handlers[] = {
979 #ifdef CONFIG_FS_POSIX_ACL
980 &ovl_posix_acl_access_xattr_handler,
981 &ovl_posix_acl_default_xattr_handler,
983 &ovl_own_xattr_handler,
984 &ovl_other_xattr_handler,
988 static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
989 struct inode **ptrap, const char *name)
994 trap = ovl_get_trap_inode(sb, dir);
995 err = PTR_ERR_OR_ZERO(trap);
998 pr_err("overlayfs: conflicting %s path\n", name);
1006 static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
1007 struct path *upperpath)
1009 struct vfsmount *upper_mnt;
1012 err = ovl_mount_dir(ofs->config.upperdir, upperpath);
1016 /* Upper fs should not be r/o */
1017 if (sb_rdonly(upperpath->mnt->mnt_sb)) {
1018 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
1023 err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
1027 err = ovl_setup_trap(sb, upperpath->dentry, &ofs->upperdir_trap,
1032 upper_mnt = clone_private_mount(upperpath);
1033 err = PTR_ERR(upper_mnt);
1034 if (IS_ERR(upper_mnt)) {
1035 pr_err("overlayfs: failed to clone upperpath\n");
1039 /* Don't inherit atime flags */
1040 upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
1041 ofs->upper_mnt = upper_mnt;
1044 if (ovl_inuse_trylock(ofs->upper_mnt->mnt_root)) {
1045 ofs->upperdir_locked = true;
1046 } else if (ofs->config.index) {
1047 pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
1050 pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
1058 static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
1059 struct path *workpath)
1061 struct vfsmount *mnt = ofs->upper_mnt;
1062 struct dentry *temp;
1066 err = mnt_want_write(mnt);
1070 ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
1074 err = ovl_setup_trap(sb, ofs->workdir, &ofs->workdir_trap, "workdir");
1079 * Upper should support d_type, else whiteouts are visible. Given
1080 * workdir and upper are on same fs, we can do iterate_dir() on
1081 * workdir. This check requires successful creation of workdir in
1084 err = ovl_check_d_type_supported(workpath);
1089 * We allowed this configuration and don't want to break users over
1090 * kernel upgrade. So warn instead of erroring out.
1093 pr_warn("overlayfs: upper fs needs to support d_type.\n");
1095 /* Check if upper/work fs supports O_TMPFILE */
1096 temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
1097 ofs->tmpfile = !IS_ERR(temp);
1101 pr_warn("overlayfs: upper fs does not support tmpfile.\n");
1104 * Check if upper/work fs supports trusted.overlay.* xattr
1106 err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
1108 ofs->noxattr = true;
1109 ofs->config.index = false;
1110 ofs->config.metacopy = false;
1111 pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off and metacopy=off.\n");
1114 vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
1117 /* Check if upper/work fs supports file handles */
1118 fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
1119 if (ofs->config.index && !fh_type) {
1120 ofs->config.index = false;
1121 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
1124 /* Check if upper fs has 32bit inode numbers */
1125 if (fh_type != FILEID_INO32_GEN)
1128 /* NFS export of r/w mount depends on index */
1129 if (ofs->config.nfs_export && !ofs->config.index) {
1130 pr_warn("overlayfs: NFS export requires \"index=on\", falling back to nfs_export=off.\n");
1131 ofs->config.nfs_export = false;
1134 mnt_drop_write(mnt);
1138 static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
1139 struct path *upperpath)
1142 struct path workpath = { };
1144 err = ovl_mount_dir(ofs->config.workdir, &workpath);
1149 if (upperpath->mnt != workpath.mnt) {
1150 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
1153 if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
1154 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
1158 ofs->workbasedir = dget(workpath.dentry);
1161 if (ovl_inuse_trylock(ofs->workbasedir)) {
1162 ofs->workdir_locked = true;
1163 } else if (ofs->config.index) {
1164 pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
1167 pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
1170 err = ovl_make_workdir(sb, ofs, &workpath);
1173 path_put(&workpath);
1178 static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
1179 struct ovl_entry *oe, struct path *upperpath)
1181 struct vfsmount *mnt = ofs->upper_mnt;
1184 err = mnt_want_write(mnt);
1188 /* Verify lower root is upper root origin */
1189 err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
1192 pr_err("overlayfs: failed to verify upper root origin\n");
1196 ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
1197 if (ofs->indexdir) {
1198 err = ovl_setup_trap(sb, ofs->indexdir, &ofs->indexdir_trap,
1204 * Verify upper root is exclusively associated with index dir.
1205 * Older kernels stored upper fh in "trusted.overlay.origin"
1206 * xattr. If that xattr exists, verify that it is a match to
1207 * upper dir file handle. In any case, verify or set xattr
1208 * "trusted.overlay.upper" to indicate that index may have
1209 * directory entries.
1211 if (ovl_check_origin_xattr(ofs->indexdir)) {
1212 err = ovl_verify_set_fh(ofs->indexdir, OVL_XATTR_ORIGIN,
1213 upperpath->dentry, true, false);
1215 pr_err("overlayfs: failed to verify index dir 'origin' xattr\n");
1217 err = ovl_verify_upper(ofs->indexdir, upperpath->dentry, true);
1219 pr_err("overlayfs: failed to verify index dir 'upper' xattr\n");
1221 /* Cleanup bad/stale/orphan index entries */
1223 err = ovl_indexdir_cleanup(ofs);
1225 if (err || !ofs->indexdir)
1226 pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1229 mnt_drop_write(mnt);
1233 static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
1237 if (!ofs->config.nfs_export && !(ofs->config.index && ofs->upper_mnt))
1240 for (i = 0; i < ofs->numlowerfs; i++) {
1242 * We use uuid to associate an overlay lower file handle with a
1243 * lower layer, so we can accept lower fs with null uuid as long
1244 * as all lower layers with null uuid are on the same fs.
1246 if (uuid_equal(&ofs->lower_fs[i].sb->s_uuid, uuid))
1252 /* Get a unique fsid for the layer */
1253 static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
1255 struct super_block *sb = path->mnt->mnt_sb;
1260 /* fsid 0 is reserved for upper fs even with non upper overlay */
1261 if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb)
1264 for (i = 0; i < ofs->numlowerfs; i++) {
1265 if (ofs->lower_fs[i].sb == sb)
1269 if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) {
1270 ofs->config.index = false;
1271 ofs->config.nfs_export = false;
1272 pr_warn("overlayfs: %s uuid detected in lower fs '%pd2', falling back to index=off,nfs_export=off.\n",
1273 uuid_is_null(&sb->s_uuid) ? "null" : "conflicting",
1277 err = get_anon_bdev(&dev);
1279 pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
1283 ofs->lower_fs[ofs->numlowerfs].sb = sb;
1284 ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev;
1287 return ofs->numlowerfs;
1290 static int ovl_get_lower_layers(struct super_block *sb, struct ovl_fs *ofs,
1291 struct path *stack, unsigned int numlower)
1297 ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
1299 if (ofs->lower_layers == NULL)
1302 ofs->lower_fs = kcalloc(numlower, sizeof(struct ovl_sb),
1304 if (ofs->lower_fs == NULL)
1307 for (i = 0; i < numlower; i++) {
1308 struct vfsmount *mnt;
1312 err = fsid = ovl_get_fsid(ofs, &stack[i]);
1317 if (ovl_is_inuse(stack[i].dentry)) {
1318 pr_err("overlayfs: lowerdir is in-use as upperdir/workdir\n");
1322 err = ovl_setup_trap(sb, stack[i].dentry, &trap, "lowerdir");
1326 mnt = clone_private_mount(&stack[i]);
1329 pr_err("overlayfs: failed to clone lowerpath\n");
1335 * Make lower layers R/O. That way fchmod/fchown on lower file
1336 * will fail instead of modifying lower fs.
1338 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1340 ofs->lower_layers[ofs->numlower].trap = trap;
1341 ofs->lower_layers[ofs->numlower].mnt = mnt;
1342 ofs->lower_layers[ofs->numlower].idx = i + 1;
1343 ofs->lower_layers[ofs->numlower].fsid = fsid;
1345 ofs->lower_layers[ofs->numlower].fs =
1346 &ofs->lower_fs[fsid - 1];
1352 * When all layers on same fs, overlay can use real inode numbers.
1353 * With mount option "xino=on", mounter declares that there are enough
1354 * free high bits in underlying fs to hold the unique fsid.
1355 * If overlayfs does encounter underlying inodes using the high xino
1356 * bits reserved for fsid, it emits a warning and uses the original
1359 if (!ofs->numlowerfs || (ofs->numlowerfs == 1 && !ofs->upper_mnt)) {
1361 ofs->config.xino = OVL_XINO_OFF;
1362 } else if (ofs->config.xino == OVL_XINO_ON && !ofs->xino_bits) {
1364 * This is a roundup of number of bits needed for numlowerfs+1
1365 * (i.e. ilog2(numlowerfs+1 - 1) + 1). fsid 0 is reserved for
1366 * upper fs even with non upper overlay.
1368 BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 31);
1369 ofs->xino_bits = ilog2(ofs->numlowerfs) + 1;
1372 if (ofs->xino_bits) {
1373 pr_info("overlayfs: \"xino\" feature enabled using %d upper inode bits.\n",
1382 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1386 char *lowertmp, *lower;
1387 struct path *stack = NULL;
1388 unsigned int stacklen, numlower = 0, i;
1389 bool remote = false;
1390 struct ovl_entry *oe;
1393 lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
1398 stacklen = ovl_split_lowerdirs(lowertmp);
1399 if (stacklen > OVL_MAX_STACK) {
1400 pr_err("overlayfs: too many lower directories, limit is %d\n",
1403 } else if (!ofs->config.upperdir && stacklen == 1) {
1404 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
1406 } else if (!ofs->config.upperdir && ofs->config.nfs_export &&
1407 ofs->config.redirect_follow) {
1408 pr_warn("overlayfs: NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
1409 ofs->config.nfs_export = false;
1413 stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
1419 for (numlower = 0; numlower < stacklen; numlower++) {
1420 err = ovl_lower_dir(lower, &stack[numlower], ofs,
1421 &sb->s_stack_depth, &remote);
1425 lower = strchr(lower, '\0') + 1;
1429 sb->s_stack_depth++;
1430 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1431 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1435 err = ovl_get_lower_layers(sb, ofs, stack, numlower);
1440 oe = ovl_alloc_entry(numlower);
1444 for (i = 0; i < numlower; i++) {
1445 oe->lowerstack[i].dentry = dget(stack[i].dentry);
1446 oe->lowerstack[i].layer = &ofs->lower_layers[i];
1450 sb->s_d_op = &ovl_reval_dentry_operations;
1452 sb->s_d_op = &ovl_dentry_operations;
1455 for (i = 0; i < numlower; i++)
1456 path_put(&stack[i]);
1468 * Check if this layer root is a descendant of:
1469 * - another layer of this overlayfs instance
1470 * - upper/work dir of any overlayfs instance
1472 static int ovl_check_layer(struct super_block *sb, struct dentry *dentry,
1475 struct dentry *next = dentry, *parent;
1481 parent = dget_parent(next);
1483 /* Walk back ancestors to root (inclusive) looking for traps */
1484 while (!err && parent != next) {
1485 if (ovl_is_inuse(parent)) {
1487 pr_err("overlayfs: %s path overlapping in-use upperdir/workdir\n",
1489 } else if (ovl_lookup_trap_inode(sb, parent)) {
1491 pr_err("overlayfs: overlapping %s path\n", name);
1494 parent = dget_parent(next);
1504 * Check if any of the layers or work dirs overlap.
1506 static int ovl_check_overlapping_layers(struct super_block *sb,
1511 if (ofs->upper_mnt) {
1512 err = ovl_check_layer(sb, ofs->upper_mnt->mnt_root, "upperdir");
1517 * Checking workbasedir avoids hitting ovl_is_inuse(parent) of
1518 * this instance and covers overlapping work and index dirs,
1519 * unless work or index dir have been moved since created inside
1520 * workbasedir. In that case, we already have their traps in
1521 * inode cache and we will catch that case on lookup.
1523 err = ovl_check_layer(sb, ofs->workbasedir, "workdir");
1528 for (i = 0; i < ofs->numlower; i++) {
1529 err = ovl_check_layer(sb, ofs->lower_layers[i].mnt->mnt_root,
1538 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
1540 struct path upperpath = { };
1541 struct dentry *root_dentry;
1542 struct ovl_entry *oe;
1548 ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
1552 ofs->creator_cred = cred = prepare_creds();
1556 ofs->config.index = ovl_index_def;
1557 ofs->config.nfs_export = ovl_nfs_export_def;
1558 ofs->config.xino = ovl_xino_def();
1559 ofs->config.metacopy = ovl_metacopy_def;
1560 err = ovl_parse_opt((char *) data, &ofs->config);
1565 if (!ofs->config.lowerdir) {
1567 pr_err("overlayfs: missing 'lowerdir'\n");
1571 sb->s_stack_depth = 0;
1572 sb->s_maxbytes = MAX_LFS_FILESIZE;
1573 /* Assume underlaying fs uses 32bit inodes unless proven otherwise */
1574 if (ofs->config.xino != OVL_XINO_OFF)
1575 ofs->xino_bits = BITS_PER_LONG - 32;
1577 /* alloc/destroy_inode needed for setting up traps in inode cache */
1578 sb->s_op = &ovl_super_operations;
1580 if (ofs->config.upperdir) {
1581 if (!ofs->config.workdir) {
1582 pr_err("overlayfs: missing 'workdir'\n");
1586 err = ovl_get_upper(sb, ofs, &upperpath);
1590 err = ovl_get_workdir(sb, ofs, &upperpath);
1595 sb->s_flags |= SB_RDONLY;
1597 sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
1598 sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
1601 oe = ovl_get_lowerstack(sb, ofs);
1606 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1607 if (!ofs->upper_mnt)
1608 sb->s_flags |= SB_RDONLY;
1610 if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
1611 err = ovl_get_indexdir(sb, ofs, oe, &upperpath);
1615 /* Force r/o mount with no index dir */
1616 if (!ofs->indexdir) {
1618 ofs->workdir = NULL;
1619 sb->s_flags |= SB_RDONLY;
1624 err = ovl_check_overlapping_layers(sb, ofs);
1628 /* Show index=off in /proc/mounts for forced r/o mount */
1629 if (!ofs->indexdir) {
1630 ofs->config.index = false;
1631 if (ofs->upper_mnt && ofs->config.nfs_export) {
1632 pr_warn("overlayfs: NFS export requires an index dir, falling back to nfs_export=off.\n");
1633 ofs->config.nfs_export = false;
1637 if (ofs->config.metacopy && ofs->config.nfs_export) {
1638 pr_warn("overlayfs: NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
1639 ofs->config.nfs_export = false;
1642 if (ofs->config.nfs_export)
1643 sb->s_export_op = &ovl_export_operations;
1645 /* Never override disk quota limits or use reserved space */
1646 cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1648 sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1649 sb->s_xattr = ovl_xattr_handlers;
1650 sb->s_fs_info = ofs;
1651 sb->s_flags |= SB_POSIXACL;
1654 root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1658 root_dentry->d_fsdata = oe;
1660 mntput(upperpath.mnt);
1661 if (upperpath.dentry) {
1662 ovl_dentry_set_upper_alias(root_dentry);
1663 if (ovl_is_impuredir(upperpath.dentry))
1664 ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
1667 /* Root is always merge -> can have whiteouts */
1668 ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
1669 ovl_dentry_set_flag(OVL_E_CONNECTED, root_dentry);
1670 ovl_set_upperdata(d_inode(root_dentry));
1671 ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
1672 ovl_dentry_lower(root_dentry), NULL);
1674 sb->s_root = root_dentry;
1679 ovl_entry_stack_free(oe);
1682 path_put(&upperpath);
1688 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1689 const char *dev_name, void *raw_data)
1691 return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1694 static struct file_system_type ovl_fs_type = {
1695 .owner = THIS_MODULE,
1698 .kill_sb = kill_anon_super,
1700 MODULE_ALIAS_FS("overlay");
1702 static void ovl_inode_init_once(void *foo)
1704 struct ovl_inode *oi = foo;
1706 inode_init_once(&oi->vfs_inode);
1709 static int __init ovl_init(void)
1713 ovl_inode_cachep = kmem_cache_create("ovl_inode",
1714 sizeof(struct ovl_inode), 0,
1715 (SLAB_RECLAIM_ACCOUNT|
1716 SLAB_MEM_SPREAD|SLAB_ACCOUNT),
1717 ovl_inode_init_once);
1718 if (ovl_inode_cachep == NULL)
1721 err = register_filesystem(&ovl_fs_type);
1723 kmem_cache_destroy(ovl_inode_cachep);
1728 static void __exit ovl_exit(void)
1730 unregister_filesystem(&ovl_fs_type);
1733 * Make sure all delayed rcu free inodes are flushed before we
1737 kmem_cache_destroy(ovl_inode_cachep);
1741 module_init(ovl_init);
1742 module_exit(ovl_exit);