libxfs: sanitize sb_inopblock in xfs_mount_validate_sb

[userspace port]

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: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/libxfs/xfs_sb.c b/libxfs/xfs_sb.c
index 16088a6cc640cefad8ac8989b0c11f9933665d84..4be73661de4da0649bbaf3faeb3b5679906c253b 100644 (file)
--- a/libxfs/xfs_sb.c
+++ b/libxfs/xfs_sb.c
@@ -258,6 +258,7 @@ 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)  ||