path: root/fs/jbd
diff options
authorEryu Guan <guaneryu@gmail.com>2011-11-01 19:04:59 -0400
committerTheodore Ts'o <tytso@mit.edu>2011-11-01 19:04:59 -0400
commit8762202dd0d6e46854f786bdb6fb3780a1625efe (patch)
tree0fe3a7e102bfefa0bbb5810f934fbf93840459dd /fs/jbd
parentext4: let ext4_ext_rm_leaf work with EXT_DEBUG defined (diff)
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>
Diffstat (limited to 'fs/jbd')
1 files changed, 8 insertions, 0 deletions
diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
index 9fe061fb8779..fea8dd661d2b 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) {
+ "JBD: Invalid start block of journal: %u\n",
+ be32_to_cpu(sb->s_first));
+ goto out;
+ }
return 0;