From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eryu Guan Subject: [PATCH] ext4: don't cache out of order extents Date: Thu, 17 Oct 2013 17:27:53 +0800 Message-ID: <1382002073-27862-1-git-send-email-guaneryu@gmail.com> Cc: Eryu Guan , "Theodore Ts'o" To: linux-ext4@vger.kernel.org Return-path: Received: from mail-pb0-f54.google.com ([209.85.160.54]:49221 "EHLO mail-pb0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753118Ab3JQJ3D (ORCPT ); Thu, 17 Oct 2013 05:29:03 -0400 Received: by mail-pb0-f54.google.com with SMTP id ro12so2057142pbb.13 for ; Thu, 17 Oct 2013 02:28:59 -0700 (PDT) Sender: linux-ext4-owner@vger.kernel.org List-ID: A corrupted ext4 may have out of order leaf extents, i.e. extent: lblk 0--1023, len 1024, pblk 9217, flags: LEAF UNINIT extent: lblk 1000--2047, len 1024, pblk 10241, flags: LEAF UNINIT ^^^^ overlap with previous extent Reading such extent could hit BUG_ON() in ext4_es_cache_extent(). BUG_ON(end < lblk); The problem is that __read_extent_tree_block() tries to cache holes as well but assumes 'lblk' is greater than 'prev' and passes underflowed length to ext4_es_cache_extent(). I hit this when fuzz testing ext4, and am able to reproduce it by modifying the on-disk extent by hand. Ran xfstests on patched ext4 and no regression. Cc: "Theodore Ts'o" Signed-off-by: Eryu Guan --- fs/ext4/extents.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 54d52af..c9ebcb9 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -503,7 +503,7 @@ __read_extent_tree_block(const char *function, unsigned int line, ext4_lblk_t lblk = le32_to_cpu(ex->ee_block); int len = ext4_ext_get_actual_len(ex); - if (prev && (prev != lblk)) + if (prev && (prev < lblk)) ext4_es_cache_extent(inode, prev, lblk - prev, ~0, EXTENT_STATUS_HOLE); -- 1.8.3.1