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| author | Eryu Guan <guaneryu@gmail.com> | 2011-11-01 19:04:59 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-12-21 12:57:40 -0800 |
| commit | b98eb43012d8679aa6c9e5527a7cc5706ee192f6 (patch) | |
| tree | 8bda82a1966d0765095a78f0d87c948469f281b6 | |
| parent | f4347eb6d2aae437d9552a26704bcb07f4626d6c (diff) | |
| download | lwn-b98eb43012d8679aa6c9e5527a7cc5706ee192f6.tar.gz lwn-b98eb43012d8679aa6c9e5527a7cc5706ee192f6.zip | |
jbd/jbd2: validate sb->s_first in journal_get_superblock()
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>
Cc: Moritz Mühlenhoff <jmm@inutil.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | fs/jbd/journal.c | 8 | ||||
| -rw-r--r-- | 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 e2d4285fbe90..9f36384e2e87 100644 --- a/fs/jbd/journal.c +++ b/fs/jbd/journal.c @@ -1131,6 +1131,14 @@ 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 0dfa5b598e68..40c5fb73e9c6 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: |