Messages in this thread Patch in this message |  | | From | Paul Gortmaker <> | Subject | [v2.6.34-stable 52/77] jbd/jbd2: validate sb->s_first in journal_get_superblock() | Date | Tue, 8 Jan 2013 18:35:31 -0500 |
| |
From: Eryu Guan <guaneryu@gmail.com>
------------------- This is a commit scheduled for the next v2.6.34 longterm release. http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git If you see a problem with using this for longterm, please comment. -------------------
commit 8762202dd0d6e46854f786bdb6fb3780a1625efe upstream.
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> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> --- fs/jbd/journal.c | 8 ++++++++ fs/jbd2/journal.c | 8 ++++++++ 2 files changed, 16 insertions(+)
diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c index 45905ff..70713d5 100644 --- a/fs/jbd/journal.c +++ b/fs/jbd/journal.c @@ -1070,6 +1070,14 @@ 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 c03d4dc..7f16fea 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -1186,6 +1186,14 @@ 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: -- 1.7.12.1
|  |