On 09/09/13 15:33, Eric Sandeen wrote:
Today, if xfs_sb_read_verify encounters a v4 superblock
with junk past v4 fields which includes data in sb_crc,
it will be treated as a failing checksum and a significant
corruption.
There are known prior bugs which leave junk at the end
of the V4 superblock; we don't need to actually fail the
verification in this case if other checks pan out ok.
So if this is a secondary superblock, and the primary
superblock doesn't indicate that this is a V5 filesystem,
don't treat this as an actual checksum failure.
We should probably check the garbage condition as
we do in xfs_repair, and possibly warn about it
or self-heal, but that's a different scope of work.
Stable folks: This can go back to v3.10, which is what
introduced the sb CRC checking that is tripped up by old,
stale, incorrect V4 superblocks w/ unzeroed bits.
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Eric Sandeen<sandeen@xxxxxxxxxx>
---
V2: Comment changes: More! (No code changes)
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 2b0ba35..b2deab1 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -749,6 +749,11 @@ xfs_sb_verify(
* single bit error could clear the feature bit and unused parts of the
* superblock are supposed to be zero. Hence a non-null crc field indicates that
* we've potentially lost a feature bit and we should check it anyway.
+ *
+ * However, past bugs (i.e. in growfs) left non-zeroed regions beyond the
+ * last field in V4 secondary superblocks. So for secondary superblocks,
+ * we are more forgiving, and ignore CRC failures if the primary doesn't
+ * indicate that the fs version is V5.
*/
static void
xfs_sb_read_verify(
@@ -769,8 +774,12 @@ xfs_sb_read_verify(
if (!xfs_verify_cksum(bp->b_addr, be16_to_cpu(dsb->sb_sectsize),
offsetof(struct xfs_sb, sb_crc))) {
- error = EFSCORRUPTED;
- goto out_error;
+ /* Only fail bad secondaries on a known V5 filesystem */
+ if (bp->b_bn != XFS_SB_DADDR&&
+ xfs_sb_version_hascrc(&mp->m_sb)) {
+ error = EFSCORRUPTED;
+ goto out_error;
+ }
}
}
error = xfs_sb_verify(bp, true);
This moved to fs/xfs/xfs_sb.c in TOT, but the patch looks good to me.
Reviewed-by: Mark Tinguely <tinguely@xxxxxxx>
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