ext4: fix inode checksum calculation problem if i_extra_size is small

commit 05ac5aa18abd7db341e54df4ae2b4c98ea0e43b7 upstream.

We've fixed the race condition problem in calculating ext4 checksum
value in commit b47820edd163 ("ext4: avoid modifying checksum fields
directly during checksum veficationon"). However, by this change,
when calculating the checksum value of inode whose i_extra_size is
less than 4, we couldn't calculate the checksum value in a proper way.
This problem was found and reported by Nix, Thank you.

Reported-by: Nix <nix@esperi.org.uk>
Signed-off-by: Daeho Jeong <daeho.jeong@samsung.com>
Signed-off-by: Youngjin Gil <youngjin.gil@samsung.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 2 insertions, 3 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index dc9d64ac5969..c78fce404654 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -71,10 +71,9 @@ static __u32 ext4_inode_csum(struct inode *inode, struct ext4_inode *raw,
                         csum = ext4_chksum(sbi, csum, (__u8 *)&dummy_csum,
                                            csum_size);
                         offset += csum_size;
-                        csum = ext4_chksum(sbi, csum, (__u8 *)raw + offset,
-                                           EXT4_INODE_SIZE(inode->i_sb) -
-                                           offset);
                 }
+                csum = ext4_chksum(sbi, csum, (__u8 *)raw + offset,
+                                   EXT4_INODE_SIZE(inode->i_sb) - offset);
         }
 
         return csum;