RDMA/cma: Fix crash in cma_req_handler

The RDMA CM uses the local qp_type to determine how to process an
incoming request.  This can result in an incoming REQ being treated as
a SIDR REQ and vice versa.  Fix this by switching off the event type
instead, and for good measure verify that the listener supports the
incoming connection request.

This problem showed up when a user space application mismatched the QP
types between a client and server app.
Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/core/cma.c

@@ -1179,6 +1179,15 @@ static void cma_set_req_event_data(struct rdma_cm_event *event,
 	event->param.conn.qp_num = req_data->remote_qpn;
 }
 
+static int cma_check_req_qp_type(struct rdma_cm_id *id, struct ib_cm_event *ib_event)
+{
+	return (((ib_event->event == IB_CM_REQ_RECEIVED) ||
+		 (ib_event->param.req_rcvd.qp_type == id->qp_type)) ||
+		((ib_event->event == IB_CM_SIDR_REQ_RECEIVED) &&
+		 (id->qp_type == IB_QPT_UD)) ||
+		(!id->qp_type));
+}
+
 static int cma_req_handler(struct ib_cm_id *cm_id, struct ib_cm_event *ib_event)
 {
 	struct rdma_id_private *listen_id, *conn_id;
@@ -1186,13 +1195,16 @@ static int cma_req_handler(struct ib_cm_id *cm_id, struct ib_cm_event *ib_event)
 	int offset, ret;
 
 	listen_id = cm_id->context;
+	if (!cma_check_req_qp_type(&listen_id->id, ib_event))
+		return -EINVAL;
+
 	if (cma_disable_callback(listen_id, RDMA_CM_LISTEN))
 		return -ECONNABORTED;
 
 	memset(&event, 0, sizeof event);
 	offset = cma_user_data_offset(listen_id->id.ps);
 	event.event = RDMA_CM_EVENT_CONNECT_REQUEST;
-	if (listen_id->id.qp_type == IB_QPT_UD) {
+	if (ib_event->event == IB_CM_SIDR_REQ_RECEIVED) {
 		conn_id = cma_new_udp_id(&listen_id->id, ib_event);
 		event.param.ud.private_data = ib_event->private_data + offset;
 		event.param.ud.private_data_len =