From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:40914 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752975AbeGDF5B (ORCPT ); Wed, 4 Jul 2018 01:57:01 -0400 Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 02F4DAFF7 for ; Wed, 4 Jul 2018 05:57:00 +0000 (UTC) Subject: Re: [PATCH 2/5] btrfs: tree-checker: Detect invalid empty essential tree To: Qu Wenruo , linux-btrfs@vger.kernel.org References: <20180703091009.16399-1-wqu@suse.com> <20180703091009.16399-3-wqu@suse.com> From: Nikolay Borisov Message-ID: <61f1d3f9-5dd5-aa92-f8b4-5d582f1dd99f@suse.com> Date: Wed, 4 Jul 2018 08:56:59 +0300 MIME-Version: 1.0 In-Reply-To: <20180703091009.16399-3-wqu@suse.com> Content-Type: text/plain; charset=utf-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 3.07.2018 12:10, Qu Wenruo wrote: > A crafted image has empty root tree block, which will cause later NULL > pointer dereference. > > The following trees should never be empty: > 1) Tree root > Must contain at least root items for extent tree, device tree and fs > tree > > 2) Chunk tree > Or we can't even bootstrap. > > 3) Fs tree > At least inode item for top level inode (.). > > 4) Device tree > Dev extents for chunks > > 5) Extent tree > Must has corresponding extent for each chunk. > > If any is empty, we are sure the fs is corrupted and no need to mount > it. > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=199847 > Reported-by: Xu Wen > Signed-off-by: Qu Wenruo > --- > fs/btrfs/tree-checker.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c > index 1cd735b099df..3a307efab46b 100644 > --- a/fs/btrfs/tree-checker.c > +++ b/fs/btrfs/tree-checker.c > @@ -497,8 +497,20 @@ static int check_leaf(struct btrfs_fs_info *fs_info, struct extent_buffer *leaf, > * skip this check for relocation trees. > */ > if (nritems == 0 && !btrfs_header_flag(leaf, BTRFS_HEADER_FLAG_RELOC)) { > + u64 owner = btrfs_header_owner(leaf); nit: Since you assign the owner of the leaf to a variable use this variable when initialising key object below. > struct btrfs_root *check_root; > > + /* These trees should never be empty */ > + if (owner == BTRFS_ROOT_TREE_OBJECTID || > + owner == BTRFS_CHUNK_TREE_OBJECTID || > + owner == BTRFS_EXTENT_TREE_OBJECTID || > + owner == BTRFS_DEV_TREE_OBJECTID || > + owner == BTRFS_FS_TREE_OBJECTID) { > + generic_err(fs_info, leaf, 0, > + "invalid root, root %llu should never be empty", > + owner); > + return -EUCLEAN; > + } > key.objectid = btrfs_header_owner(leaf); > key.type = BTRFS_ROOT_ITEM_KEY; > key.offset = (u64)-1; >