Commit 10e6e65d authored Sep 09, 2013 by Eric Sandeen Committed by Ben Myers Oct 30, 2013

xfs: be more forgiving of a v4 secondary sb w/ junk in v5 fields



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@vger.kernel.org
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Acked-by: Dave Chinner <david@fromorbit.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

parent 643f7c4e

fs/xfs/xfs_sb.c

+11 −2

Original line number	Diff line number	Diff line
		@@ -588,6 +588,11 @@ 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(
		@@ -608,10 +613,14 @@ xfs_sb_read_verify(

		if (!xfs_verify_cksum(bp->b_addr, be16_to_cpu(dsb->sb_sectsize),
		offsetof(struct xfs_sb, sb_crc))) {
		/* 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);

		out_error: