From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eryu Guan Subject: [PATCH 1/2] jbd/jbd2: validate sb->s_first in journal_get_superblock() Date: Tue, 1 Nov 2011 10:05:03 +0800 Message-ID: <1320113103-27406-1-git-send-email-guaneryu@gmail.com> Cc: Eryu Guan , Jan Kara , "Theodore Ts'o" To: linux-ext4@vger.kernel.org Return-path: Received: from mail-vw0-f46.google.com ([209.85.212.46]:54420 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751682Ab1KACFp (ORCPT ); Mon, 31 Oct 2011 22:05:45 -0400 Received: by vws1 with SMTP id 1so5422570vws.19 for ; Mon, 31 Oct 2011 19:05:44 -0700 (PDT) Sender: linux-ext4-owner@vger.kernel.org List-ID: I hit a J_ASSERT(blocknr != 0) failure in cleanup_journal_tail() when mounting a fsfuzzed ext3 image. It turns out that the corrupted ext3 image has s_first = 0 in journal superblock, and the 0 is passed to journal->j_head in journal_reset(), then to blocknr in cleanup_journal_tail(), in the end the J_ASSERT failed. So validate s_first after reading journal superblock from disk in journal_get_superblock() to ensure s_first is valid. The following script could reproduce it: fstype=ext3 blocksize=1024 img=$fstype.img offset=0 found=0 magic="c0 3b 39 98" dd if=/dev/zero of=$img bs=1M count=8 mkfs -t $fstype -b $blocksize -F $img filesize=`stat -c %s $img` while [ $offset -lt $filesize ] do if od -j $offset -N 4 -t x1 $img | grep -i "$magic";then echo "Found journal: $offset" found=1 break fi offset=`echo "$offset+$blocksize" | bc` done if [ $found -ne 1 ];then echo "Magic \"$magic\" not found" exit 1 fi dd if=/dev/zero of=$img seek=$(($offset+23)) conv=notrunc bs=1 count=1 mkdir -p ./mnt mount -o loop $img ./mnt Cc: Jan Kara Cc: "Theodore Ts'o" Signed-off-by: Eryu Guan --- fs/jbd/journal.c | 8 ++++++++ fs/jbd2/journal.c | 8 ++++++++ 2 files changed, 16 insertions(+), 0 deletions(-) diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c index 9fe061f..0c401de 100644 --- a/fs/jbd/journal.c +++ b/fs/jbd/journal.c @@ -1135,6 +1135,14 @@ static int journal_get_superblock(journal_t *journal) goto out; } + if (be32_to_cpu(sb->s_first) == 0 || + be32_to_cpu(sb->s_first) >= journal->j_maxlen) { + printk(KERN_WARNING + "JBD: Invalid start block of journal: %u\n", + be32_to_cpu(sb->s_first)); + goto out; + } + return 0; out: diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index f24df13..e2d0e13 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -1251,6 +1251,14 @@ static int journal_get_superblock(journal_t *journal) goto out; } + if (be32_to_cpu(sb->s_first) == 0 || + be32_to_cpu(sb->s_first) >= journal->j_maxlen) { + printk(KERN_WARNING + "JBD2: Invalid start block of journal: %u\n", + be32_to_cpu(sb->s_first)); + goto out; + } + return 0; out: -- 1.7.7.1