2 * Copyright (C) 2011 Novell Inc.
3 * Copyright (C) 2016 Red Hat, 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/cred.h>
12 #include <linux/namei.h>
13 #include <linux/xattr.h>
14 #include <linux/ratelimit.h>
15 #include <linux/mount.h>
16 #include <linux/exportfs.h>
17 #include "overlayfs.h"
18 #include "ovl_entry.h"
20 struct ovl_lookup_data {
29 static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d,
30 size_t prelen, const char *post)
33 char *s, *next, *buf = NULL;
35 res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, NULL, 0);
37 if (res == -ENODATA || res == -EOPNOTSUPP)
41 buf = kzalloc(prelen + res + strlen(post) + 1, GFP_TEMPORARY);
48 res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, buf, res);
54 for (s = buf; *s++ == '/'; s = next) {
55 next = strchrnul(s, '/');
60 if (strchr(buf, '/') != NULL)
63 memmove(buf + prelen, buf, res);
64 memcpy(buf, d->name.name, prelen);
70 d->name.name = d->redirect;
71 d->name.len = strlen(d->redirect);
79 pr_warn_ratelimited("overlayfs: failed to get redirect (%i)\n", res);
82 pr_warn_ratelimited("overlayfs: invalid redirect (%s)\n", buf);
86 static int ovl_acceptable(void *ctx, struct dentry *dentry)
91 static struct ovl_fh *ovl_get_origin_fh(struct dentry *dentry)
94 struct ovl_fh *fh = NULL;
96 res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);
98 if (res == -ENODATA || res == -EOPNOTSUPP)
102 /* Zero size value means "copied up but origin unknown" */
106 fh = kzalloc(res, GFP_TEMPORARY);
108 return ERR_PTR(-ENOMEM);
110 res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, fh, res);
114 if (res < sizeof(struct ovl_fh) || res < fh->len)
117 if (fh->magic != OVL_FH_MAGIC)
120 /* Treat larger version and unknown flags as "origin unknown" */
121 if (fh->version > OVL_FH_VERSION || fh->flags & ~OVL_FH_FLAG_ALL)
124 /* Treat endianness mismatch as "origin unknown" */
125 if (!(fh->flags & OVL_FH_FLAG_ANY_ENDIAN) &&
126 (fh->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN)
136 pr_warn_ratelimited("overlayfs: failed to get origin (%i)\n", res);
139 pr_warn_ratelimited("overlayfs: invalid origin (%*phN)\n", res, fh);
143 static struct dentry *ovl_get_origin(struct dentry *dentry,
144 struct vfsmount *mnt)
146 struct dentry *origin = NULL;
147 struct ovl_fh *fh = ovl_get_origin_fh(dentry);
150 if (IS_ERR_OR_NULL(fh))
151 return (struct dentry *)fh;
154 * Make sure that the stored uuid matches the uuid of the lower
155 * layer where file handle will be decoded.
157 if (!uuid_equal(&fh->uuid, &mnt->mnt_sb->s_uuid))
160 bytes = (fh->len - offsetof(struct ovl_fh, fid));
161 origin = exportfs_decode_fh(mnt, (struct fid *)fh->fid,
162 bytes >> 2, (int)fh->type,
163 ovl_acceptable, NULL);
164 if (IS_ERR(origin)) {
165 /* Treat stale file handle as "origin unknown" */
166 if (origin == ERR_PTR(-ESTALE))
171 if (ovl_dentry_weird(origin) ||
172 ((d_inode(origin)->i_mode ^ d_inode(dentry)->i_mode) & S_IFMT))
180 pr_warn_ratelimited("overlayfs: invalid origin (%pd2)\n", origin);
186 static bool ovl_is_opaquedir(struct dentry *dentry)
188 return ovl_check_dir_xattr(dentry, OVL_XATTR_OPAQUE);
191 static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
192 const char *name, unsigned int namelen,
193 size_t prelen, const char *post,
199 this = lookup_one_len_unlocked(name, base, namelen);
203 if (err == -ENOENT || err == -ENAMETOOLONG)
210 if (ovl_dentry_weird(this)) {
211 /* Don't support traversing automounts and other weirdness */
215 if (ovl_is_whiteout(this)) {
216 d->stop = d->opaque = true;
219 if (!d_can_lookup(this)) {
226 if (!d->last && ovl_is_opaquedir(this)) {
227 d->stop = d->opaque = true;
230 err = ovl_check_redirect(this, d, prelen, post);
247 static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
250 /* Counting down from the end, since the prefix can change */
251 size_t rem = d->name.len - 1;
252 struct dentry *dentry = NULL;
255 if (d->name.name[0] != '/')
256 return ovl_lookup_single(base, d, d->name.name, d->name.len,
259 while (!IS_ERR_OR_NULL(base) && d_can_lookup(base)) {
260 const char *s = d->name.name + d->name.len - rem;
261 const char *next = strchrnul(s, '/');
262 size_t thislen = next - s;
265 /* Verify we did not go off the rails */
266 if (WARN_ON(s[-1] != '/'))
269 err = ovl_lookup_single(base, d, s, thislen,
270 d->name.len - rem, next, &base);
280 if (WARN_ON(rem >= d->name.len))
288 static int ovl_check_origin(struct dentry *upperdentry,
289 struct path *lowerstack, unsigned int numlower,
290 struct path **stackp, unsigned int *ctrp)
292 struct vfsmount *mnt;
293 struct dentry *origin = NULL;
297 for (i = 0; i < numlower; i++) {
298 mnt = lowerstack[i].mnt;
299 origin = ovl_get_origin(upperdentry, mnt);
301 return PTR_ERR(origin);
312 *stackp = kmalloc(sizeof(struct path), GFP_TEMPORARY);
317 **stackp = (struct path) { .dentry = origin, .mnt = mnt };
324 * Verify that @fh matches the origin file handle stored in OVL_XATTR_ORIGIN.
325 * Return 0 on match, -ESTALE on mismatch, < 0 on error.
327 static int ovl_verify_origin_fh(struct dentry *dentry, const struct ovl_fh *fh)
329 struct ovl_fh *ofh = ovl_get_origin_fh(dentry);
338 if (fh->len != ofh->len || memcmp(fh, ofh, fh->len))
346 * Verify that an inode matches the origin file handle stored in upper inode.
348 * If @set is true and there is no stored file handle, encode and store origin
349 * file handle in OVL_XATTR_ORIGIN.
351 * Return 0 on match, -ESTALE on mismatch, < 0 on error.
353 int ovl_verify_origin(struct dentry *dentry, struct vfsmount *mnt,
354 struct dentry *origin, bool is_upper, bool set)
360 fh = ovl_encode_fh(origin, is_upper);
365 err = ovl_verify_origin_fh(dentry, fh);
366 if (set && err == -ENODATA)
367 err = ovl_do_setxattr(dentry, OVL_XATTR_ORIGIN, fh, fh->len, 0);
376 inode = d_inode(origin);
377 pr_warn_ratelimited("overlayfs: failed to verify origin (%pd2, ino=%lu, err=%i)\n",
378 origin, inode ? inode->i_ino : 0, err);
383 * Verify that an index entry name matches the origin file handle stored in
384 * OVL_XATTR_ORIGIN and that origin file handle can be decoded to lower path.
385 * Return 0 on match, -ESTALE on mismatch or stale origin, < 0 on error.
387 int ovl_verify_index(struct dentry *index, struct path *lowerstack,
388 unsigned int numlower)
390 struct ovl_fh *fh = NULL;
392 struct path origin = { };
393 struct path *stack = &origin;
394 unsigned int ctr = 0;
405 if (index->d_name.len < sizeof(struct ovl_fh)*2)
409 len = index->d_name.len / 2;
410 fh = kzalloc(len, GFP_TEMPORARY);
415 if (hex2bin((u8 *)fh, index->d_name.name, len) || len != fh->len)
418 err = ovl_verify_origin_fh(index, fh);
422 err = ovl_check_origin(index, lowerstack, numlower, &stack, &ctr);
428 /* Check if index is orphan and don't warn before cleaning it */
429 if (d_inode(index)->i_nlink == 1 &&
430 ovl_get_nlink(index, origin.dentry, 0) == 0)
439 pr_warn_ratelimited("overlayfs: failed to verify index (%pd2, err=%i)\n",
445 * Lookup in indexdir for the index entry of a lower real inode or a copy up
446 * origin inode. The index entry name is the hex representation of the lower
449 * If the index dentry in negative, then either no lower aliases have been
450 * copied up yet, or aliases have been copied up in older kernels and are
453 * If the index dentry for a copy up origin inode is positive, but points
454 * to an inode different than the upper inode, then either the upper inode
455 * has been copied up and not indexed or it was indexed, but since then
456 * index dir was cleared. Either way, that index cannot be used to indentify
459 int ovl_get_index_name(struct dentry *origin, struct qstr *name)
465 fh = ovl_encode_fh(origin, false);
470 n = kzalloc(fh->len * 2, GFP_TEMPORARY);
472 s = bin2hex(n, fh, fh->len);
473 *name = (struct qstr) QSTR_INIT(n, s - n);
482 static struct dentry *ovl_lookup_index(struct dentry *dentry,
483 struct dentry *upper,
484 struct dentry *origin)
486 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
487 struct dentry *index;
492 err = ovl_get_index_name(origin, &name);
496 index = lookup_one_len_unlocked(name.name, ofs->indexdir, name.len);
498 pr_warn_ratelimited("overlayfs: failed inode index lookup (ino=%lu, key=%*s, err=%i);\n"
499 "overlayfs: mount with '-o index=off' to disable inodes index.\n",
500 d_inode(origin)->i_ino, name.len, name.name,
505 if (d_is_negative(index)) {
506 if (upper && d_inode(origin)->i_nlink > 1) {
507 pr_warn_ratelimited("overlayfs: hard link with origin but no index (ino=%lu).\n",
508 d_inode(origin)->i_ino);
514 } else if (upper && d_inode(index) != d_inode(upper)) {
515 inode = d_inode(index);
516 pr_warn_ratelimited("overlayfs: wrong index found (index ino: %lu, upper ino: %lu).\n",
517 d_inode(index)->i_ino,
518 d_inode(upper)->i_ino);
528 index = ERR_PTR(-EIO);
533 * Returns next layer in stack starting from top.
534 * Returns -1 if this is the last layer.
536 int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
538 struct ovl_entry *oe = dentry->d_fsdata;
542 ovl_path_upper(dentry, path);
544 return oe->numlower ? 1 : -1;
547 BUG_ON(idx > oe->numlower);
548 *path = oe->lowerstack[idx - 1];
550 return (idx < oe->numlower) ? idx + 1 : -1;
553 struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
556 struct ovl_entry *oe;
557 const struct cred *old_cred;
558 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
559 struct ovl_entry *poe = dentry->d_parent->d_fsdata;
560 struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata;
561 struct path *stack = NULL;
562 struct dentry *upperdir, *upperdentry = NULL;
563 struct dentry *index = NULL;
564 unsigned int ctr = 0;
565 struct inode *inode = NULL;
566 bool upperopaque = false;
567 char *upperredirect = NULL;
571 struct ovl_lookup_data d = {
572 .name = dentry->d_name,
576 .last = !poe->numlower,
580 if (dentry->d_name.len > ofs->namelen)
581 return ERR_PTR(-ENAMETOOLONG);
583 old_cred = ovl_override_creds(dentry->d_sb);
584 upperdir = ovl_dentry_upper(dentry->d_parent);
586 err = ovl_lookup_layer(upperdir, &d, &upperdentry);
590 if (upperdentry && unlikely(ovl_dentry_remote(upperdentry))) {
595 if (upperdentry && !d.is_dir) {
596 BUG_ON(!d.stop || d.redirect);
598 * Lookup copy up origin by decoding origin file handle.
599 * We may get a disconnected dentry, which is fine,
600 * because we only need to hold the origin inode in
601 * cache and use its inode number. We may even get a
602 * connected dentry, that is not under any of the lower
603 * layers root. That is also fine for using it's inode
604 * number - it's the same as if we held a reference
605 * to a dentry in lower layer that was moved under us.
607 err = ovl_check_origin(upperdentry, roe->lowerstack,
608 roe->numlower, &stack, &ctr);
614 upperredirect = kstrdup(d.redirect, GFP_KERNEL);
617 if (d.redirect[0] == '/')
620 upperopaque = d.opaque;
623 if (!d.stop && poe->numlower) {
625 stack = kcalloc(ofs->numlower, sizeof(struct path),
631 for (i = 0; !d.stop && i < poe->numlower; i++) {
632 struct path lowerpath = poe->lowerstack[i];
634 d.last = i == poe->numlower - 1;
635 err = ovl_lookup_layer(lowerpath.dentry, &d, &this);
642 stack[ctr].dentry = this;
643 stack[ctr].mnt = lowerpath.mnt;
649 if (d.redirect && d.redirect[0] == '/' && poe != roe) {
652 /* Find the current layer on the root dentry */
653 for (i = 0; i < poe->numlower; i++)
654 if (poe->lowerstack[i].mnt == lowerpath.mnt)
656 if (WARN_ON(i == poe->numlower))
661 /* Lookup index by lower inode and verify it matches upper inode */
662 if (ctr && !d.is_dir && ovl_indexdir(dentry->d_sb)) {
663 struct dentry *origin = stack[0].dentry;
665 index = ovl_lookup_index(dentry, upperdentry, origin);
667 err = PTR_ERR(index);
673 oe = ovl_alloc_entry(ctr);
678 oe->opaque = upperopaque;
679 memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
680 dentry->d_fsdata = oe;
683 ovl_dentry_set_upper_alias(dentry);
685 upperdentry = dget(index);
687 if (upperdentry || ctr) {
688 inode = ovl_get_inode(dentry, upperdentry);
689 err = PTR_ERR(inode);
693 OVL_I(inode)->redirect = upperredirect;
695 ovl_set_flag(OVL_INDEX, inode);
698 revert_creds(old_cred);
702 d_add(dentry, inode);
707 dentry->d_fsdata = NULL;
711 for (i = 0; i < ctr; i++)
712 dput(stack[i].dentry);
716 kfree(upperredirect);
719 revert_creds(old_cred);
723 bool ovl_lower_positive(struct dentry *dentry)
725 struct ovl_entry *oe = dentry->d_fsdata;
726 struct ovl_entry *poe = dentry->d_parent->d_fsdata;
727 const struct qstr *name = &dentry->d_name;
729 bool positive = false;
733 * If dentry is negative, then lower is positive iff this is a
736 if (!dentry->d_inode)
739 /* Negative upper -> positive lower */
740 if (!ovl_dentry_upper(dentry))
743 /* Positive upper -> have to look up lower to see whether it exists */
744 for (i = 0; !done && !positive && i < poe->numlower; i++) {
746 struct dentry *lowerdir = poe->lowerstack[i].dentry;
748 this = lookup_one_len_unlocked(name->name, lowerdir,
751 switch (PTR_ERR(this)) {
758 * Assume something is there, we just couldn't
766 positive = !ovl_is_whiteout(this);