linux/fs/jbd
Eryu Guan 8762202dd0 jbd/jbd2: validate sb->s_first in journal_get_superblock()
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 <jack@suse.cz>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-11-01 19:04:59 -04:00
..
checkpoint.c jbd: Use WRITE_SYNC in journal checkpoint. 2011-06-28 00:06:41 +02:00
commit.c jbd: Fix oops in journal_remove_journal_head() 2011-06-27 11:44:37 +02:00
journal.c jbd/jbd2: validate sb->s_first in journal_get_superblock() 2011-11-01 19:04:59 -04:00
Kconfig Revert "task_struct: make journal_info conditional" 2009-12-17 13:23:24 -08:00
Makefile Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
recovery.c jbd: Move debug message into #ifdef area 2010-10-28 01:30:01 +02:00
revoke.c Fix common misspellings 2011-03-31 11:26:23 -03:00
transaction.c jbd: Fix oops in journal_remove_journal_head() 2011-06-27 11:44:37 +02:00