ext4: avoid modifying checksum fields directly during checksum verification
We temporally change checksum fields in buffers of some types of
metadata into '0' for verifying the checksum values. By doing this
without locking the buffer, some metadata's checksums, which are
being committed or written back to the storage, could be damaged.
In our test, several metadata blocks were found with damaged metadata
checksum value during recovery process. When we only verify the
checksum value, we have to avoid modifying checksum fields directly.
Signed-off-by: Daeho Jeong <daeho.jeong@samsung.com>
Signed-off-by: Youngjin Gil <youngjin.gil@samsung.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index e79bd32..39e9cfb 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -121,17 +121,18 @@
{
struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
__u32 csum;
- __le32 save_csum;
__le64 dsk_block_nr = cpu_to_le64(block_nr);
+ __u32 dummy_csum = 0;
+ int offset = offsetof(struct ext4_xattr_header, h_checksum);
- save_csum = hdr->h_checksum;
- hdr->h_checksum = 0;
csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&dsk_block_nr,
sizeof(dsk_block_nr));
- csum = ext4_chksum(sbi, csum, (__u8 *)hdr,
- EXT4_BLOCK_SIZE(inode->i_sb));
+ csum = ext4_chksum(sbi, csum, (__u8 *)hdr, offset);
+ csum = ext4_chksum(sbi, csum, (__u8 *)&dummy_csum, sizeof(dummy_csum));
+ offset += sizeof(dummy_csum);
+ csum = ext4_chksum(sbi, csum, (__u8 *)hdr + offset,
+ EXT4_BLOCK_SIZE(inode->i_sb) - offset);
- hdr->h_checksum = save_csum;
return cpu_to_le32(csum);
}