[PATCH 4.9 193/206] xfs: check for bogus values in btree block headers

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>

commit bb3be7e7c1c18e1b141d4cadeb98cc89ecf78099 upstream.

When we're reading a btree block, make sure that what we retrieved
matches the owner and level; and has a plausible number of records.

Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
Signed-off-by: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/xfs/libxfs/xfs_btree.c |   20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -1769,8 +1769,28 @@ xfs_btree_lookup_get_block(
 	if (error)
 		return error;
 
+	/* Check the inode owner since the verifiers don't. */
+	if (xfs_sb_version_hascrc(&cur->bc_mp->m_sb) &&
+	    (cur->bc_flags & XFS_BTREE_LONG_PTRS) &&
+	    be64_to_cpu((*blkp)->bb_u.l.bb_owner) !=
+			cur->bc_private.b.ip->i_ino)
+		goto out_bad;
+
+	/* Did we get the level we were looking for? */
+	if (be16_to_cpu((*blkp)->bb_level) != level)
+		goto out_bad;
+
+	/* Check that internal nodes have at least one record. */
+	if (level != 0 && be16_to_cpu((*blkp)->bb_numrecs) == 0)
+		goto out_bad;
+
 	xfs_btree_setbuf(cur, level, bp);
 	return 0;
+
+out_bad:
+	*blkp = NULL;
+	xfs_trans_brelse(cur->bc_tp, bp);
+	return -EFSCORRUPTED;
 }
 
 /*