From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay3.corp.sgi.com [198.149.34.15]) by oss.sgi.com (Postfix) with ESMTP id C33C37F5F for ; Mon, 9 Sep 2013 15:33:36 -0500 (CDT) Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by relay3.corp.sgi.com (Postfix) with ESMTP id 52F00AC007 for ; Mon, 9 Sep 2013 13:33:33 -0700 (PDT) Received: from sandeen.net (sandeen.net [63.231.237.45]) by cuda.sgi.com with ESMTP id YodQfvDOMZkmR2JS for ; Mon, 09 Sep 2013 13:33:31 -0700 (PDT) Message-ID: <522E3099.1040503@sandeen.net> Date: Mon, 09 Sep 2013 15:33:29 -0500 From: Eric Sandeen MIME-Version: 1.0 Subject: [PATCH V2] xfs: be more forgiving of a v4 secondary sb w/ junk in v5 fields References: <520D1BA3.1050500@redhat.com> <20130815210018.GR6023@dastard> <520D44E7.1000905@sandeen.net> <520D592D.4040600@redhat.com> In-Reply-To: <520D592D.4040600@redhat.com> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: Eric Sandeen Cc: "'linux-xfs@oss.sgi.com'" 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 --- 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); _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs