[PATCH] xfs: check da node magic in _node_lookup_int

["Darrick J. Wong" <darrick.wong@oracle.com>]

From: Darrick J. Wong <darrick.wong@oracle.com>

Before we start processing what we /think/ is a da3 node block, actually
check the magic to make sure that we're looking at a node block.  This
way we won't blow the asserts in _node_hdr_from_disk on corrupted
metadata.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/libxfs/xfs_da_btree.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
index 9efbd2038ffb..70e7da634f3e 100644
--- a/fs/xfs/libxfs/xfs_da_btree.c
+++ b/fs/xfs/libxfs/xfs_da_btree.c
@@ -1522,8 +1522,11 @@ xfs_da3_node_lookup_int(
 			break;
 		}
 
-		blk->magic = XFS_DA_NODE_MAGIC;
+		if (blk->magic != XFS_DA_NODE_MAGIC &&
+		    blk->magic != XFS_DA3_NODE_MAGIC)
+			return -EFSCORRUPTED;
 
+		blk->magic = XFS_DA_NODE_MAGIC;
 
 		/*
 		 * Search an intermediate node for a match.