IB/mlx5: Fix NULL pointer dereference on debug print

commit a1ab8402 upstream.

For XRC QP CQs may not exist. Check before attempting dereference.

Fixes: e126ba97 ('mlx5: Add driver for Mellanox Connect-IB adapters')
Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Reviewed-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/infiniband/hw/mlx5/qp.c

@@ -1205,8 +1205,9 @@ struct ib_qp *mlx5_ib_create_qp(struct ib_pd *pd,
 			qp->ibqp.qp_num = qp->mqp.qpn;
 
 		mlx5_ib_dbg(dev, "ib qpnum 0x%x, mlx qpn 0x%x, rcqn 0x%x, scqn 0x%x\n",
-			    qp->ibqp.qp_num, qp->mqp.qpn, to_mcq(init_attr->recv_cq)->mcq.cqn,
-			    to_mcq(init_attr->send_cq)->mcq.cqn);
+			    qp->ibqp.qp_num, qp->mqp.qpn,
+			    init_attr->recv_cq ? to_mcq(init_attr->recv_cq)->mcq.cqn : -1,
+			    init_attr->send_cq ? to_mcq(init_attr->send_cq)->mcq.cqn : -1);
 
 		qp->xrcdn = xrcdn;