5 files changed, 130 insertions, 10 deletions

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index d0d6292e069a..a072c27e03bc 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -24,7 +24,7 @@ module_param_named(redirect_max, ovl_redirect_max, ushort, 0644);
 MODULE_PARM_DESC(ovl_redirect_max,
 		 "Maximum length of absolute redirect xattr value");
 
-void ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
+int ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
 {
 	int err;
 
@@ -39,6 +39,8 @@ void ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
 		pr_err("overlayfs: cleanup of '%pd2' failed (%i)\n",
 		       wdentry, err);
 	}
+
+	return err;
 }
 
 struct dentry *ovl_lookup_temp(struct dentry *workdir)
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 3bec4cb39967..4df37e805eb7 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -285,17 +285,17 @@ static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
 }
 
 
-static int ovl_check_origin(struct dentry *dentry, struct dentry *upperdentry,
+static int ovl_check_origin(struct dentry *upperdentry,
+			    struct path *lowerstack, unsigned int numlower,
 			    struct path **stackp, unsigned int *ctrp)
 {
-	struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata;
 	struct vfsmount *mnt;
 	struct dentry *origin = NULL;
 	int i;
 
 
-	for (i = 0; i < roe->numlower; i++) {
-		mnt = roe->lowerstack[i].mnt;
+	for (i = 0; i < numlower; i++) {
+		mnt = lowerstack[i].mnt;
 		origin = ovl_get_origin(upperdentry, mnt);
 		if (IS_ERR(origin))
 			return PTR_ERR(origin);
@@ -307,8 +307,9 @@ static int ovl_check_origin(struct dentry *dentry, struct dentry *upperdentry,
 	if (!origin)
 		return 0;
 
-	BUG_ON(*stackp || *ctrp);
-	*stackp = kmalloc(sizeof(struct path), GFP_TEMPORARY);
+	BUG_ON(*ctrp);
+	if (!*stackp)
+		*stackp = kmalloc(sizeof(struct path), GFP_TEMPORARY);
 	if (!*stackp) {
 		dput(origin);
 		return -ENOMEM;
@@ -379,6 +380,63 @@ fail:
 }
 
 /*
+ * Verify that an index entry name matches the origin file handle stored in
+ * OVL_XATTR_ORIGIN and that origin file handle can be decoded to lower path.
+ * Return 0 on match, -ESTALE on mismatch or stale origin, < 0 on error.
+ */
+int ovl_verify_index(struct dentry *index, struct path *lowerstack,
+		     unsigned int numlower)
+{
+	struct ovl_fh *fh = NULL;
+	size_t len;
+	struct path origin = { };
+	struct path *stack = &origin;
+	unsigned int ctr = 0;
+	int err;
+
+	if (!d_inode(index))
+		return 0;
+
+	err = -EISDIR;
+	if (d_is_dir(index))
+		goto fail;
+
+	err = -EINVAL;
+	if (index->d_name.len < sizeof(struct ovl_fh)*2)
+		goto fail;
+
+	err = -ENOMEM;
+	len = index->d_name.len / 2;
+	fh = kzalloc(len, GFP_TEMPORARY);
+	if (!fh)
+		goto fail;
+
+	err = -EINVAL;
+	if (hex2bin((u8 *)fh, index->d_name.name, len) || len != fh->len)
+		goto fail;
+
+	err = ovl_verify_origin_fh(index, fh);
+	if (err)
+		goto fail;
+
+	err = ovl_check_origin(index, lowerstack, numlower, &stack, &ctr);
+	if (!err && !ctr)
+		err = -ESTALE;
+	if (err)
+		goto fail;
+
+	dput(origin.dentry);
+out:
+	kfree(fh);
+	return err;
+
+fail:
+	pr_warn_ratelimited("overlayfs: failed to verify index (%pd2, err=%i)\n",
+			    index, err);
+	goto out;
+}
+
+/*
  * Lookup in indexdir for the index entry of a lower real inode or a copy up
  * origin inode. The index entry name is the hex representation of the lower
  * inode file handle.
@@ -541,8 +599,8 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 			 * number - it's the same as if we held a reference
 			 * to a dentry in lower layer that was moved under us.
 			 */
-			err = ovl_check_origin(dentry, upperdentry,
-					       &stack, &ctr);
+			err = ovl_check_origin(upperdentry, roe->lowerstack,
+					       roe->numlower, &stack, &ctr);
 			if (err)
 				goto out;
 		}
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 437a0301e1b6..f3e49cf34517 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -237,6 +237,8 @@ static inline bool ovl_is_impuredir(struct dentry *dentry)
 /* namei.c */
 int ovl_verify_origin(struct dentry *dentry, struct vfsmount *mnt,
 		      struct dentry *origin, bool is_upper, bool set);
+int ovl_verify_index(struct dentry *index, struct path *lowerstack,
+		     unsigned int numlower);
 int ovl_get_index_name(struct dentry *origin, struct qstr *name);
 int ovl_path_next(int idx, struct dentry *dentry, struct path *path);
 struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags);
@@ -250,6 +252,8 @@ void ovl_cache_free(struct list_head *list);
 int ovl_check_d_type_supported(struct path *realpath);
 void ovl_workdir_cleanup(struct inode *dir, struct vfsmount *mnt,
 			 struct dentry *dentry, int level);
+int ovl_indexdir_cleanup(struct dentry *dentry, struct vfsmount *mnt,
+			 struct path *lowerstack, unsigned int numlower);
 
 /* inode.c */
 int ovl_setattr(struct dentry *dentry, struct iattr *attr);
@@ -289,7 +293,7 @@ struct cattr {
 int ovl_create_real(struct inode *dir, struct dentry *newdentry,
 		    struct cattr *attr,
 		    struct dentry *hardlink, bool debug);
-void ovl_cleanup(struct inode *dir, struct dentry *dentry);
+int ovl_cleanup(struct inode *dir, struct dentry *dentry);
 
 /* copy_up.c */
 int ovl_copy_up(struct dentry *dentry);
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index f241b4ee3d8a..0298463cf9c3 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -667,3 +667,53 @@ void ovl_workdir_cleanup(struct inode *dir, struct vfsmount *mnt,
 		ovl_cleanup(dir, dentry);
 	}
 }
+
+int ovl_indexdir_cleanup(struct dentry *dentry, struct vfsmount *mnt,
+			 struct path *lowerstack, unsigned int numlower)
+{
+	int err;
+	struct inode *dir = dentry->d_inode;
+	struct path path = { .mnt = mnt, .dentry = dentry };
+	LIST_HEAD(list);
+	struct ovl_cache_entry *p;
+	struct ovl_readdir_data rdd = {
+		.ctx.actor = ovl_fill_merge,
+		.dentry = NULL,
+		.list = &list,
+		.root = RB_ROOT,
+		.is_lowest = false,
+	};
+
+	err = ovl_dir_read(&path, &rdd);
+	if (err)
+		goto out;
+
+	inode_lock_nested(dir, I_MUTEX_PARENT);
+	list_for_each_entry(p, &list, l_node) {
+		struct dentry *index;
+
+		if (p->name[0] == '.') {
+			if (p->len == 1)
+				continue;
+			if (p->len == 2 && p->name[1] == '.')
+				continue;
+		}
+		index = lookup_one_len(p->name, dentry, p->len);
+		if (IS_ERR(index)) {
+			err = PTR_ERR(index);
+			break;
+		}
+		if (ovl_verify_index(index, lowerstack, numlower)) {
+			err = ovl_cleanup(dir, index);
+			if (err)
+				break;
+		}
+		dput(index);
+	}
+	inode_unlock(dir);
+out:
+	ovl_cache_free(&list);
+	if (err)
+		pr_err("overlayfs: failed index dir cleanup (%i)\n", err);
+	return err;
+}
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index a313af25dac2..791581c370f5 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1068,6 +1068,12 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 						upperpath.dentry, true, true);
 			if (err)
 				pr_err("overlayfs: failed to verify index dir origin\n");
+
+			/* Cleanup bad/stale index entries */
+			if (!err)
+				err = ovl_indexdir_cleanup(ufs->indexdir,
+							   ufs->upper_mnt,
+							   stack, numlower);
 		}
 		if (err || !ufs->indexdir)
 			pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");