validate-external-journal-superblock-checksum

   1 ext4: validate external journal superblock checksum
   2
   3 From: "Darrick J. Wong" <darrick.wong@oracle.com>
   4
   5 If the external journal device has metadata_csum enabled, verify
   6 that the superblock checksum matches the block before we try to
   7 mount.
   8
   9 Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
  10 Reviewed-by: Jan Kara <jack@suse.cz>
  11 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  12 ---
  13  fs/ext4/super.c | 9 +++++++++
  14  1 file changed, 9 insertions(+)
  15
  16 diff --git a/fs/ext4/super.c b/fs/ext4/super.c
  17 index fb219b9..2632017 100644
  18 --- a/fs/ext4/super.c
  19 +++ b/fs/ext4/super.c
  20 @@ -4414,6 +4414,15 @@ static journal_t *ext4_get_dev_journal(struct super_block *sb,
  21                 goto out_bdev;
  22         }
  23
  24 +       if ((le32_to_cpu(es->s_feature_ro_compat) &
  25 +            EXT4_FEATURE_RO_COMPAT_METADATA_CSUM) &&
  26 +           es->s_checksum != ext4_superblock_csum(sb, es)) {
  27 +               ext4_msg(sb, KERN_ERR, "external journal has "
  28 +                                      "corrupt superblock");
  29 +               brelse(bh);
  30 +               goto out_bdev;
  31 +       }
  32 +
  33         if (memcmp(EXT4_SB(sb)->s_es->s_journal_uuid, es->s_uuid, 16)) {
  34                 ext4_msg(sb, KERN_ERR, "journal UUID does not match");
  35                 brelse(bh);