fix-inode-checksum-calculation-if-i_extra_size-is-too-small

   1 ext4: fix inode checksum calculation problem if i_extra_size is small
   2
   3 From: Daeho Jeong <daeho.jeong@samsung.com>
   4
   5 We've fixed the race condition problem in calculating ext4 checksum
   6 value in commit b47820edd163 ("ext4: avoid modifying checksum fields
   7 directly during checksum veficationon"). However, by this change,
   8 when calculating the checksum value of inode whose i_extra_size is
   9 less than 4, we couldn't calculate the checksum value in a proper way.
  10 This problem was found and reported by Nix, Thank you.
  11
  12 Reported-by: Nix <nix@esperi.org.uk>
  13 Signed-off-by: Daeho Jeong <daeho.jeong@samsung.com>
  14 Signed-off-by: Youngjin Gil <youngjin.gil@samsung.com>
  15 Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
  16 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  17 ---
  18  fs/ext4/inode.c |    5 ++---
  19  1 file changed, 2 insertions(+), 3 deletions(-)
  20
  21 diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
  22 index 9c06472..eaab3c3 100644
  23 --- a/fs/ext4/inode.c
  24 +++ b/fs/ext4/inode.c
  25 @@ -71,10 +71,9 @@ static __u32 ext4_inode_csum(struct inode *inode, struct ext4_inode *raw,
  26                         csum = ext4_chksum(sbi, csum, (__u8 *)&dummy_csum,
  27                                            csum_size);
  28                         offset += csum_size;
  29 -                       csum = ext4_chksum(sbi, csum, (__u8 *)raw + offset,
  30 -                                          EXT4_INODE_SIZE(inode->i_sb) -
  31 -                                          offset);
  32                 }
  33 +               csum = ext4_chksum(sbi, csum, (__u8 *)raw + offset,
  34 +                                  EXT4_INODE_SIZE(inode->i_sb) - offset);
  35         }
  36
  37         return csum;
  38 --
  39 1.7.9.5
  40
  41