3 * Copyright (C) 2011 Novell Inc.
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 as published by
7 * the Free Software Foundation.
11 #include <linux/namei.h>
12 #include <linux/xattr.h>
13 #include <linux/security.h>
14 #include <linux/cred.h>
15 #include <linux/module.h>
16 #include <linux/posix_acl.h>
17 #include <linux/posix_acl_xattr.h>
18 #include <linux/atomic.h>
19 #include <linux/ratelimit.h>
20 #include "overlayfs.h"
22 static unsigned short ovl_redirect_max = 256;
23 module_param_named(redirect_max, ovl_redirect_max, ushort, 0644);
24 MODULE_PARM_DESC(ovl_redirect_max,
25 "Maximum length of absolute redirect xattr value");
27 void ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
32 if (d_is_dir(wdentry))
33 err = ovl_do_rmdir(wdir, wdentry);
35 err = ovl_do_unlink(wdir, wdentry);
39 pr_err("overlayfs: cleanup of '%pd2' failed (%i)\n",
44 struct dentry *ovl_lookup_temp(struct dentry *workdir, struct dentry *dentry)
48 static atomic_t temp_id = ATOMIC_INIT(0);
50 /* counter is allowed to wrap, since temp dentries are ephemeral */
51 snprintf(name, sizeof(name), "#%x", atomic_inc_return(&temp_id));
53 temp = lookup_one_len(name, workdir, strlen(name));
54 if (!IS_ERR(temp) && temp->d_inode) {
55 pr_err("overlayfs: workdir/%s already exists\n", name);
63 /* caller holds i_mutex on workdir */
64 static struct dentry *ovl_whiteout(struct dentry *workdir,
65 struct dentry *dentry)
68 struct dentry *whiteout;
69 struct inode *wdir = workdir->d_inode;
71 whiteout = ovl_lookup_temp(workdir, dentry);
75 err = ovl_do_whiteout(wdir, whiteout);
78 whiteout = ERR_PTR(err);
84 int ovl_create_real(struct inode *dir, struct dentry *newdentry,
85 struct cattr *attr, struct dentry *hardlink, bool debug)
89 if (newdentry->d_inode)
93 err = ovl_do_link(hardlink, dir, newdentry, debug);
95 switch (attr->mode & S_IFMT) {
97 err = ovl_do_create(dir, newdentry, attr->mode, debug);
101 err = ovl_do_mkdir(dir, newdentry, attr->mode, debug);
108 err = ovl_do_mknod(dir, newdentry,
109 attr->mode, attr->rdev, debug);
113 err = ovl_do_symlink(dir, newdentry, attr->link, debug);
120 if (!err && WARN_ON(!newdentry->d_inode)) {
122 * Not quite sure if non-instantiated dentry is legal or not.
123 * VFS doesn't seem to care so check and warn here.
130 static int ovl_set_opaque(struct dentry *dentry, struct dentry *upperdentry)
134 err = ovl_do_setxattr(upperdentry, OVL_XATTR_OPAQUE, "y", 1, 0);
136 ovl_dentry_set_opaque(dentry);
141 /* Common operations required to be done after creation of file on upper */
142 static void ovl_instantiate(struct dentry *dentry, struct inode *inode,
143 struct dentry *newdentry, bool hardlink)
145 ovl_dentry_version_inc(dentry->d_parent);
146 ovl_dentry_update(dentry, newdentry);
148 ovl_inode_update(inode, d_inode(newdentry));
149 ovl_copyattr(newdentry->d_inode, inode);
151 WARN_ON(ovl_inode_real(inode, NULL) != d_inode(newdentry));
154 d_instantiate(dentry, inode);
155 /* Force lookup of new upper hardlink to find its lower */
160 static bool ovl_type_merge(struct dentry *dentry)
162 return OVL_TYPE_MERGE(ovl_path_type(dentry));
165 static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
166 struct cattr *attr, struct dentry *hardlink)
168 struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
169 struct inode *udir = upperdir->d_inode;
170 struct dentry *newdentry;
173 if (!hardlink && !IS_POSIXACL(udir))
174 attr->mode &= ~current_umask();
176 inode_lock_nested(udir, I_MUTEX_PARENT);
177 newdentry = lookup_one_len(dentry->d_name.name, upperdir,
179 err = PTR_ERR(newdentry);
180 if (IS_ERR(newdentry))
182 err = ovl_create_real(udir, newdentry, attr, hardlink, false);
186 if (ovl_type_merge(dentry->d_parent) && d_is_dir(newdentry)) {
187 /* Setting opaque here is just an optimization, allow to fail */
188 ovl_set_opaque(dentry, newdentry);
191 ovl_instantiate(dentry, inode, newdentry, !!hardlink);
200 static int ovl_lock_rename_workdir(struct dentry *workdir,
201 struct dentry *upperdir)
203 /* Workdir should not be the same as upperdir */
204 if (workdir == upperdir)
207 /* Workdir should not be subdir of upperdir and vice versa */
208 if (lock_rename(workdir, upperdir) != NULL)
214 unlock_rename(workdir, upperdir);
216 pr_err("overlayfs: failed to lock workdir+upperdir\n");
220 static struct dentry *ovl_clear_empty(struct dentry *dentry,
221 struct list_head *list)
223 struct dentry *workdir = ovl_workdir(dentry);
224 struct inode *wdir = workdir->d_inode;
225 struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
226 struct inode *udir = upperdir->d_inode;
227 struct path upperpath;
228 struct dentry *upper;
229 struct dentry *opaquedir;
233 if (WARN_ON(!workdir))
234 return ERR_PTR(-EROFS);
236 err = ovl_lock_rename_workdir(workdir, upperdir);
240 ovl_path_upper(dentry, &upperpath);
241 err = vfs_getattr(&upperpath, &stat,
242 STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
247 if (!S_ISDIR(stat.mode))
249 upper = upperpath.dentry;
250 if (upper->d_parent->d_inode != udir)
253 opaquedir = ovl_lookup_temp(workdir, dentry);
254 err = PTR_ERR(opaquedir);
255 if (IS_ERR(opaquedir))
258 err = ovl_create_real(wdir, opaquedir,
259 &(struct cattr){.mode = stat.mode}, NULL, true);
263 err = ovl_copy_xattr(upper, opaquedir);
267 err = ovl_set_opaque(dentry, opaquedir);
271 inode_lock(opaquedir->d_inode);
272 err = ovl_set_attr(opaquedir, &stat);
273 inode_unlock(opaquedir->d_inode);
277 err = ovl_do_rename(wdir, opaquedir, udir, upper, RENAME_EXCHANGE);
281 ovl_cleanup_whiteouts(upper, list);
282 ovl_cleanup(wdir, upper);
283 unlock_rename(workdir, upperdir);
285 /* dentry's upper doesn't match now, get rid of it */
291 ovl_cleanup(wdir, opaquedir);
295 unlock_rename(workdir, upperdir);
300 static struct dentry *ovl_check_empty_and_clear(struct dentry *dentry)
303 struct dentry *ret = NULL;
304 enum ovl_path_type type = ovl_path_type(dentry);
307 err = ovl_check_empty_dir(dentry, &list);
314 * When removing an empty opaque directory, then it makes no sense to
315 * replace it with an exact replica of itself.
317 * If no upperdentry then skip clearing whiteouts.
319 * Can race with copy-up, since we don't hold the upperdir mutex.
320 * Doesn't matter, since copy-up can't create a non-empty directory
323 if (OVL_TYPE_UPPER(type) && OVL_TYPE_MERGE(type))
324 ret = ovl_clear_empty(dentry, &list);
327 ovl_cache_free(&list);
332 static int ovl_set_upper_acl(struct dentry *upperdentry, const char *name,
333 const struct posix_acl *acl)
339 if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !acl)
342 size = posix_acl_to_xattr(NULL, acl, NULL, 0);
343 buffer = kmalloc(size, GFP_KERNEL);
347 size = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
352 err = vfs_setxattr(upperdentry, name, buffer, size, XATTR_CREATE);
358 static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
360 struct dentry *hardlink)
362 struct dentry *workdir = ovl_workdir(dentry);
363 struct inode *wdir = workdir->d_inode;
364 struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
365 struct inode *udir = upperdir->d_inode;
366 struct dentry *upper;
367 struct dentry *newdentry;
369 struct posix_acl *acl, *default_acl;
371 if (WARN_ON(!workdir))
375 err = posix_acl_create(dentry->d_parent->d_inode,
376 &cattr->mode, &default_acl, &acl);
381 err = ovl_lock_rename_workdir(workdir, upperdir);
385 newdentry = ovl_lookup_temp(workdir, dentry);
386 err = PTR_ERR(newdentry);
387 if (IS_ERR(newdentry))
390 upper = lookup_one_len(dentry->d_name.name, upperdir,
392 err = PTR_ERR(upper);
396 err = ovl_create_real(wdir, newdentry, cattr, hardlink, true);
401 * mode could have been mutilated due to umask (e.g. sgid directory)
404 !S_ISLNK(cattr->mode) &&
405 newdentry->d_inode->i_mode != cattr->mode) {
406 struct iattr attr = {
407 .ia_valid = ATTR_MODE,
408 .ia_mode = cattr->mode,
410 inode_lock(newdentry->d_inode);
411 err = notify_change(newdentry, &attr, NULL);
412 inode_unlock(newdentry->d_inode);
417 err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_ACCESS,
422 err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_DEFAULT,
428 if (!hardlink && S_ISDIR(cattr->mode)) {
429 err = ovl_set_opaque(dentry, newdentry);
433 err = ovl_do_rename(wdir, newdentry, udir, upper,
438 ovl_cleanup(wdir, upper);
440 err = ovl_do_rename(wdir, newdentry, udir, upper, 0);
444 ovl_instantiate(dentry, inode, newdentry, !!hardlink);
451 unlock_rename(workdir, upperdir);
454 posix_acl_release(acl);
455 posix_acl_release(default_acl);
460 ovl_cleanup(wdir, newdentry);
464 static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
465 struct cattr *attr, struct dentry *hardlink)
468 const struct cred *old_cred;
469 struct cred *override_cred;
471 err = ovl_copy_up(dentry->d_parent);
475 old_cred = ovl_override_creds(dentry->d_sb);
477 override_cred = prepare_creds();
479 override_cred->fsuid = inode->i_uid;
480 override_cred->fsgid = inode->i_gid;
482 err = security_dentry_create_files_as(dentry,
483 attr->mode, &dentry->d_name, old_cred,
486 put_cred(override_cred);
487 goto out_revert_creds;
490 put_cred(override_creds(override_cred));
491 put_cred(override_cred);
493 if (!ovl_dentry_is_whiteout(dentry))
494 err = ovl_create_upper(dentry, inode, attr,
497 err = ovl_create_over_whiteout(dentry, inode, attr,
501 revert_creds(old_cred);
503 struct inode *realinode = d_inode(ovl_dentry_upper(dentry));
505 WARN_ON(inode->i_mode != realinode->i_mode);
506 WARN_ON(!uid_eq(inode->i_uid, realinode->i_uid));
507 WARN_ON(!gid_eq(inode->i_gid, realinode->i_gid));
512 static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
517 struct cattr attr = {
522 err = ovl_want_write(dentry);
527 inode = ovl_new_inode(dentry->d_sb, mode, rdev);
531 inode_init_owner(inode, dentry->d_parent->d_inode, mode);
532 attr.mode = inode->i_mode;
534 err = ovl_create_or_link(dentry, inode, &attr, NULL);
539 ovl_drop_write(dentry);
544 static int ovl_create(struct inode *dir, struct dentry *dentry, umode_t mode,
547 return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
550 static int ovl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
552 return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
555 static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
558 /* Don't allow creation of "whiteout" on overlay */
559 if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
562 return ovl_create_object(dentry, mode, rdev, NULL);
565 static int ovl_symlink(struct inode *dir, struct dentry *dentry,
568 return ovl_create_object(dentry, S_IFLNK, 0, link);
571 static int ovl_link(struct dentry *old, struct inode *newdir,
577 err = ovl_want_write(old);
581 err = ovl_copy_up(old);
585 inode = d_inode(old);
588 err = ovl_create_or_link(new, inode, NULL, ovl_dentry_upper(old));
598 static int ovl_remove_and_whiteout(struct dentry *dentry, bool is_dir)
600 struct dentry *workdir = ovl_workdir(dentry);
601 struct inode *wdir = workdir->d_inode;
602 struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
603 struct inode *udir = upperdir->d_inode;
604 struct dentry *whiteout;
605 struct dentry *upper;
606 struct dentry *opaquedir = NULL;
610 if (WARN_ON(!workdir))
614 opaquedir = ovl_check_empty_and_clear(dentry);
615 err = PTR_ERR(opaquedir);
616 if (IS_ERR(opaquedir))
620 err = ovl_lock_rename_workdir(workdir, upperdir);
624 upper = lookup_one_len(dentry->d_name.name, upperdir,
626 err = PTR_ERR(upper);
631 if ((opaquedir && upper != opaquedir) ||
632 (!opaquedir && ovl_dentry_upper(dentry) &&
633 upper != ovl_dentry_upper(dentry))) {
637 whiteout = ovl_whiteout(workdir, dentry);
638 err = PTR_ERR(whiteout);
639 if (IS_ERR(whiteout))
643 flags = RENAME_EXCHANGE;
645 err = ovl_do_rename(wdir, whiteout, udir, upper, flags);
649 ovl_cleanup(wdir, upper);
651 ovl_dentry_version_inc(dentry->d_parent);
658 unlock_rename(workdir, upperdir);
665 ovl_cleanup(wdir, whiteout);
669 static int ovl_remove_upper(struct dentry *dentry, bool is_dir)
671 struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
672 struct inode *dir = upperdir->d_inode;
673 struct dentry *upper;
674 struct dentry *opaquedir = NULL;
677 /* Redirect dir can be !ovl_lower_positive && OVL_TYPE_MERGE */
678 if (is_dir && ovl_dentry_get_redirect(dentry)) {
679 opaquedir = ovl_check_empty_and_clear(dentry);
680 err = PTR_ERR(opaquedir);
681 if (IS_ERR(opaquedir))
685 inode_lock_nested(dir, I_MUTEX_PARENT);
686 upper = lookup_one_len(dentry->d_name.name, upperdir,
688 err = PTR_ERR(upper);
693 if ((opaquedir && upper != opaquedir) ||
694 (!opaquedir && upper != ovl_dentry_upper(dentry)))
698 err = vfs_rmdir(dir, upper);
700 err = vfs_unlink(dir, upper, NULL);
701 ovl_dentry_version_inc(dentry->d_parent);
704 * Keeping this dentry hashed would mean having to release
705 * upperpath/lowerpath, which could only be done if we are the
706 * sole user of this dentry. Too tricky... Just unhash for
720 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
722 enum ovl_path_type type;
724 const struct cred *old_cred;
726 err = ovl_want_write(dentry);
730 err = ovl_copy_up(dentry->d_parent);
734 type = ovl_path_type(dentry);
736 old_cred = ovl_override_creds(dentry->d_sb);
737 if (!ovl_lower_positive(dentry))
738 err = ovl_remove_upper(dentry, is_dir);
740 err = ovl_remove_and_whiteout(dentry, is_dir);
741 revert_creds(old_cred);
744 clear_nlink(dentry->d_inode);
746 drop_nlink(dentry->d_inode);
749 ovl_drop_write(dentry);
754 static int ovl_unlink(struct inode *dir, struct dentry *dentry)
756 return ovl_do_remove(dentry, false);
759 static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
761 return ovl_do_remove(dentry, true);
764 static bool ovl_type_merge_or_lower(struct dentry *dentry)
766 enum ovl_path_type type = ovl_path_type(dentry);
768 return OVL_TYPE_MERGE(type) || !OVL_TYPE_UPPER(type);
771 static bool ovl_can_move(struct dentry *dentry)
773 return ovl_redirect_dir(dentry->d_sb) ||
774 !d_is_dir(dentry) || !ovl_type_merge_or_lower(dentry);
777 static char *ovl_get_redirect(struct dentry *dentry, bool samedir)
780 struct dentry *d, *tmp;
781 int buflen = ovl_redirect_max + 1;
784 ret = kstrndup(dentry->d_name.name, dentry->d_name.len,
789 buf = ret = kmalloc(buflen, GFP_TEMPORARY);
795 for (d = dget(dentry); !IS_ROOT(d);) {
799 spin_lock(&d->d_lock);
800 name = ovl_dentry_get_redirect(d);
802 thislen = strlen(name);
804 name = d->d_name.name;
805 thislen = d->d_name.len;
808 /* If path is too long, fall back to userspace move */
809 if (thislen + (name[0] != '/') > buflen) {
810 ret = ERR_PTR(-EXDEV);
811 spin_unlock(&d->d_lock);
816 memcpy(&buf[buflen], name, thislen);
817 tmp = dget_dlock(d->d_parent);
818 spin_unlock(&d->d_lock);
823 /* Absolute redirect: finished */
824 if (buf[buflen] == '/')
829 ret = kstrdup(&buf[buflen], GFP_KERNEL);
834 return ret ? ret : ERR_PTR(-ENOMEM);
837 static int ovl_set_redirect(struct dentry *dentry, bool samedir)
840 const char *redirect = ovl_dentry_get_redirect(dentry);
842 if (redirect && (samedir || redirect[0] == '/'))
845 redirect = ovl_get_redirect(dentry, samedir);
846 if (IS_ERR(redirect))
847 return PTR_ERR(redirect);
849 err = ovl_do_setxattr(ovl_dentry_upper(dentry), OVL_XATTR_REDIRECT,
850 redirect, strlen(redirect), 0);
852 spin_lock(&dentry->d_lock);
853 ovl_dentry_set_redirect(dentry, redirect);
854 spin_unlock(&dentry->d_lock);
857 if (err == -EOPNOTSUPP)
858 ovl_clear_redirect_dir(dentry->d_sb);
860 pr_warn_ratelimited("overlay: failed to set redirect (%i)\n", err);
861 /* Fall back to userspace copy-up */
867 static int ovl_rename(struct inode *olddir, struct dentry *old,
868 struct inode *newdir, struct dentry *new,
872 struct dentry *old_upperdir;
873 struct dentry *new_upperdir;
874 struct dentry *olddentry;
875 struct dentry *newdentry;
879 bool cleanup_whiteout = false;
880 bool overwrite = !(flags & RENAME_EXCHANGE);
881 bool is_dir = d_is_dir(old);
882 bool new_is_dir = d_is_dir(new);
883 bool samedir = olddir == newdir;
884 struct dentry *opaquedir = NULL;
885 const struct cred *old_cred = NULL;
888 if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
891 flags &= ~RENAME_NOREPLACE;
893 /* Don't copy up directory trees */
895 if (!ovl_can_move(old))
897 if (!overwrite && !ovl_can_move(new))
900 err = ovl_want_write(old);
904 err = ovl_copy_up(old);
908 err = ovl_copy_up(new->d_parent);
912 err = ovl_copy_up(new);
917 old_cred = ovl_override_creds(old->d_sb);
919 if (overwrite && new_is_dir && ovl_type_merge_or_lower(new)) {
920 opaquedir = ovl_check_empty_and_clear(new);
921 err = PTR_ERR(opaquedir);
922 if (IS_ERR(opaquedir)) {
924 goto out_revert_creds;
929 if (ovl_lower_positive(old)) {
930 if (!ovl_dentry_is_whiteout(new)) {
931 /* Whiteout source */
932 flags |= RENAME_WHITEOUT;
934 /* Switch whiteouts */
935 flags |= RENAME_EXCHANGE;
937 } else if (is_dir && ovl_dentry_is_whiteout(new)) {
938 flags |= RENAME_EXCHANGE;
939 cleanup_whiteout = true;
943 old_upperdir = ovl_dentry_upper(old->d_parent);
944 new_upperdir = ovl_dentry_upper(new->d_parent);
946 trap = lock_rename(new_upperdir, old_upperdir);
948 olddentry = lookup_one_len(old->d_name.name, old_upperdir,
950 err = PTR_ERR(olddentry);
951 if (IS_ERR(olddentry))
955 if (olddentry != ovl_dentry_upper(old))
958 newdentry = lookup_one_len(new->d_name.name, new_upperdir,
960 err = PTR_ERR(newdentry);
961 if (IS_ERR(newdentry))
964 old_opaque = ovl_dentry_is_opaque(old);
965 new_opaque = ovl_dentry_is_opaque(new);
968 if (ovl_dentry_upper(new)) {
970 if (newdentry != opaquedir)
973 if (newdentry != ovl_dentry_upper(new))
977 if (!d_is_negative(newdentry) &&
978 (!new_opaque || !ovl_is_whiteout(newdentry)))
982 if (olddentry == trap)
984 if (newdentry == trap)
987 if (WARN_ON(olddentry->d_inode == newdentry->d_inode))
992 if (ovl_type_merge_or_lower(old))
993 err = ovl_set_redirect(old, samedir);
994 else if (!old_opaque && ovl_type_merge(new->d_parent))
995 err = ovl_set_opaque(old, olddentry);
999 if (!overwrite && new_is_dir) {
1000 if (ovl_type_merge_or_lower(new))
1001 err = ovl_set_redirect(new, samedir);
1002 else if (!new_opaque && ovl_type_merge(old->d_parent))
1003 err = ovl_set_opaque(new, newdentry);
1008 err = ovl_do_rename(old_upperdir->d_inode, olddentry,
1009 new_upperdir->d_inode, newdentry, flags);
1013 if (cleanup_whiteout)
1014 ovl_cleanup(old_upperdir->d_inode, newdentry);
1016 ovl_dentry_version_inc(old->d_parent);
1017 ovl_dentry_version_inc(new->d_parent);
1024 unlock_rename(new_upperdir, old_upperdir);
1026 revert_creds(old_cred);
1028 ovl_drop_write(old);
1034 const struct inode_operations ovl_dir_inode_operations = {
1035 .lookup = ovl_lookup,
1037 .symlink = ovl_symlink,
1038 .unlink = ovl_unlink,
1040 .rename = ovl_rename,
1042 .setattr = ovl_setattr,
1043 .create = ovl_create,
1045 .permission = ovl_permission,
1046 .getattr = ovl_getattr,
1047 .listxattr = ovl_listxattr,
1048 .get_acl = ovl_get_acl,
1049 .update_time = ovl_update_time,