xfs: don't return garbage buffers in xfs_da3_node_read

If we're reading a node in a dir/attr btree and the buffer comes off the
disk with a magic number we don't recognize, don't ASSERT and don't set
a garbage buffer type (0 also triggers ASSERTs).  Instead, report the
corruption, release the buffer, and return -EFSCORRUPTED because that's
what the dabtree is -- corrupt.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/libxfs/xfs_da_btree.c

@@ -305,9 +305,11 @@ xfs_da3_node_read(
 			type = XFS_BLFT_DIR_LEAFN_BUF;
 			break;
 		default:
-			type = 0;
-			ASSERT(0);
-			break;
+			XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW,
+					tp->t_mountp, info);
+			xfs_trans_brelse(tp, *bpp);
+			*bpp = NULL;
+			return -EFSCORRUPTED;
 		}
 		xfs_trans_buf_set_type(tp, *bpp, type);
 	}