From 31fcbef62d8142c0c173b0b8255e9b0c28a7a038 Mon Sep 17 00:00:00 2001 From: Eric Sandeen Date: Mon, 9 Sep 2013 15:33:29 -0500 Subject: [PATCH] xfs: be more forgiving of a v4 secondary sb w/ junk in v5 fields commit 10e6e65dfcedff63275c3d649d329c044caa8e26 upstream. 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. Signed-off-by: Eric Sandeen Acked-by: Dave Chinner Reviewed-by: Mark Tinguely Signed-off-by: Ben Myers Signed-off-by: Greg Kroah-Hartman --- fs/xfs/xfs_sb.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/fs/xfs/xfs_sb.c b/fs/xfs/xfs_sb.c index a5b59d9..0397081 100644 --- a/fs/xfs/xfs_sb.c +++ b/fs/xfs/xfs_sb.c @@ -596,6 +596,11 @@ 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( @@ -616,8 +621,12 @@ 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); -- 2.7.4