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ext4: avoid modifying checksum fields directly during checksum verification

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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>
This commit is contained in:
Daeho Jeong
2016-07-03 17:51:39 -04:00
committed by Theodore Ts'o
parent f70749ca42
commit b47820edd1
4 changed files with 42 additions and 36 deletions
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13
fs/ext4/xattr.c
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@@ -121,17 +121,18 @@ static __le32 ext4_xattr_block_csum(struct inode *inode,
{
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);
}