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[PATCH] xfs: sanitize sb_inopblock in xfs_mount_validate_sb

To: xfs-oss <xfs@xxxxxxxxxxx>
Subject: [PATCH] xfs: sanitize sb_inopblock in xfs_mount_validate_sb
From: Eric Sandeen <sandeen@xxxxxxxxxx>
Date: Tue, 28 Jan 2014 22:28:07 -0600
Delivered-to: xfs@xxxxxxxxxxx
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.2.0
xfs_mount_validate_sb doesn't check sb_inopblock for sanity
(as does its xfs_repair counterpart, FWIW).

If it's out of bounds, we can go off the rails in i.e.
xfs_inode_buf_verify(), which uses sb_inopblock as a loop
limit when stepping through a metadata buffer.

The problem can be demonstrated easily by corrupting
sb_inopblock with xfs_db and trying to mount the result:

# mkfs.xfs -dfile,name=fsfile,size=1g
# xfs_db -x fsfile 
xfs_db> sb 0
xfs_db> write inopblock 512
inopblock = 512
xfs_db> quit

# mount -o loop fsfile  mnt
and we blow up in xfs_inode_buf_verify().

With this patch, we get a (very noisy) corruption error,
and fail the mount as we should.

Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>

diff --git a/fs/xfs/xfs_sb.c b/fs/xfs/xfs_sb.c
index b7c9aea..511cce9 100644
--- a/fs/xfs/xfs_sb.c
+++ b/fs/xfs/xfs_sb.c
@@ -288,6 +288,7 @@ xfs_mount_validate_sb(
            sbp->sb_inodelog < XFS_DINODE_MIN_LOG                       ||
            sbp->sb_inodelog > XFS_DINODE_MAX_LOG                       ||
            sbp->sb_inodesize != (1 << sbp->sb_inodelog)                ||
+           sbp->sb_inopblock != howmany(sbp->sb_blocksize,sbp->sb_inodesize) ||
            (sbp->sb_blocklog - sbp->sb_inodelog != sbp->sb_inopblog)   ||
            (sbp->sb_rextsize * sbp->sb_blocksize > XFS_MAX_RTEXTSIZE)  ||
            (sbp->sb_rextsize * sbp->sb_blocksize < XFS_MIN_RTEXTSIZE)  ||

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