fix-block-tag-checksum-verification-brokenness

   1 jbd2: fix block tag checksum verification brokenness
   2
   3 From: "Darrick J. Wong" <darrick.wong@oracle.com>
   4
   5 Al Viro complained of a ton of bogosity with regards to the jbd2 block
   6 tag header checksum.  This one checksum is 16 bits, so cut off the
   7 upper 16 bits and treat it as a 16-bit value and don't mess around
   8 with be32* conversions.  Fortunately metadata checksumming is still
   9 "experimental" and not in a shipping e2fsprogs, so there should be few
  10 users affected by this.
  11
  12 Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
  13 Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
  14 ---
  15  fs/jbd2/commit.c   |   13 +++++++------
  16  fs/jbd2/recovery.c |   11 +++++------
  17  2 files changed, 12 insertions(+), 12 deletions(-)
  18
  19 diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
  20 index 0f53946..e61d722 100644
  21 --- a/fs/jbd2/commit.c
  22 +++ b/fs/jbd2/commit.c
  23 @@ -343,20 +343,21 @@ static void jbd2_block_tag_csum_set(journal_t *j, journal_block_tag_t *tag,
  24  {
  25         struct page *page = bh->b_page;
  26         __u8 *addr;
  27 -       __u32 csum;
  28 +       __u32 csum32;
  29
  30         if (!JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V2))
  31                 return;
  32
  33         sequence = cpu_to_be32(sequence);
  34         addr = kmap_atomic(page);
  35 -       csum = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&sequence,
  36 -                         sizeof(sequence));
  37 -       csum = jbd2_chksum(j, csum, addr + offset_in_page(bh->b_data),
  38 -                         bh->b_size);
  39 +       csum32 = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&sequence,
  40 +                            sizeof(sequence));
  41 +       csum32 = jbd2_chksum(j, csum32, addr + offset_in_page(bh->b_data),
  42 +                            bh->b_size);
  43         kunmap_atomic(addr);
  44
  45 -       tag->t_checksum = cpu_to_be32(csum);
  46 +       /* We only have space to store the lower 16 bits of the crc32c. */
  47 +       tag->t_checksum = cpu_to_be16(csum32);
  48  }
  49  /*
  50   * jbd2_journal_commit_transaction
  51 diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c
  52 index 626846b..d4851464 100644
  53 --- a/fs/jbd2/recovery.c
  54 +++ b/fs/jbd2/recovery.c
  55 @@ -399,18 +399,17 @@ static int jbd2_commit_block_csum_verify(journal_t *j, void *buf)
  56  static int jbd2_block_tag_csum_verify(journal_t *j, journal_block_tag_t *tag,
  57                                       void *buf, __u32 sequence)
  58  {
  59 -       __u32 provided, calculated;
  60 +       __u32 csum32;
  61
  62         if (!JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V2))
  63                 return 1;
  64
  65         sequence = cpu_to_be32(sequence);
  66 -       calculated = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&sequence,
  67 -                                sizeof(sequence));
  68 -       calculated = jbd2_chksum(j, calculated, buf, j->j_blocksize);
  69 -       provided = be32_to_cpu(tag->t_checksum);
  70 +       csum32 = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&sequence,
  71 +                            sizeof(sequence));
  72 +       csum32 = jbd2_chksum(j, csum32, buf, j->j_blocksize);
  73
  74 -       return provided == cpu_to_be32(calculated);
  75 +       return tag->t_checksum == cpu_to_be16(csum32);
  76  }
  77
  78  static int do_one_pass(journal_t *journal,
  79