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/super.c b/fs/ext4/super.c
index 3822a5a..6e2f9d6 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2068,23 +2068,25 @@
static __le16 ext4_group_desc_csum(struct super_block *sb, __u32 block_group,
struct ext4_group_desc *gdp)
{
- int offset;
+ int offset = offsetof(struct ext4_group_desc, bg_checksum);
__u16 crc = 0;
__le32 le_group = cpu_to_le32(block_group);
struct ext4_sb_info *sbi = EXT4_SB(sb);
if (ext4_has_metadata_csum(sbi->s_sb)) {
/* Use new metadata_csum algorithm */
- __le16 save_csum;
__u32 csum32;
+ __u16 dummy_csum = 0;
- save_csum = gdp->bg_checksum;
- gdp->bg_checksum = 0;
csum32 = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&le_group,
sizeof(le_group));
- csum32 = ext4_chksum(sbi, csum32, (__u8 *)gdp,
- sbi->s_desc_size);
- gdp->bg_checksum = save_csum;
+ csum32 = ext4_chksum(sbi, csum32, (__u8 *)gdp, offset);
+ csum32 = ext4_chksum(sbi, csum32, (__u8 *)&dummy_csum,
+ sizeof(dummy_csum));
+ offset += sizeof(dummy_csum);
+ if (offset < sbi->s_desc_size)
+ csum32 = ext4_chksum(sbi, csum32, (__u8 *)gdp + offset,
+ sbi->s_desc_size - offset);
crc = csum32 & 0xFFFF;
goto out;
@@ -2094,8 +2096,6 @@
if (!ext4_has_feature_gdt_csum(sb))
return 0;
- offset = offsetof(struct ext4_group_desc, bg_checksum);
-
crc = crc16(~0, sbi->s_es->s_uuid, sizeof(sbi->s_es->s_uuid));
crc = crc16(crc, (__u8 *)&le_group, sizeof(le_group));
crc = crc16(crc, (__u8 *)gdp, offset);