RDS: check for valid cm_id before initiating connection

Connection could have been dropped while the route is being resolved
so check for valid cm_id before initiating the connection.
Reviewed-by: Ajaykumar Hotchandani <ajaykumar.hotchandani@oracle.com>
Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/rds/rdma_transport.c

@@ -34,6 +34,7 @@
 #include <rdma/rdma_cm.h>
 
 #include "rdma_transport.h"
+#include "ib.h"
 
 static struct rdma_cm_id *rds_rdma_listen_id;
 
@@ -82,8 +83,18 @@ int rds_rdma_cm_event_handler(struct rdma_cm_id *cm_id,
 		break;
 
 	case RDMA_CM_EVENT_ROUTE_RESOLVED:
-		/* XXX worry about racing with listen acceptance */
+		/* Connection could have been dropped so make sure the
+		 * cm_id is valid before proceeding
+		 */
+		if (conn) {
+			struct rds_ib_connection *ibic;
+
+			ibic = conn->c_transport_data;
+			if (ibic && ibic->i_cm_id == cm_id)
 				ret = trans->cm_initiate_connect(cm_id);
+			else
+				rds_conn_drop(conn);
+		}
 		break;
 
 	case RDMA_CM_EVENT_ESTABLISHED: