IB/iser: Fix a possible race in iser connection states transition

In some circumstances (multiple targets), RDMA_CM ESTABLISHED event
and ep_disconnect may race. In this case, the iser connection state
may transition to UP (after ep_disconnect transitioned it to
TERMINATING), while the connection is being torn down.

Upon RDMA_CM event ESTABLISHED we allow iser connection state to
transition to UP only from PENDING. We also make sure to protect this
state change (done under the connection lock).

Signed-off-by: Ariel Nahum <arieln@mellanox.com>
Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/ulp/iser/iser_verbs.c

@@ -732,8 +732,8 @@ static void iser_connected_handler(struct rdma_cm_id *cma_id)
 	iser_info("remote qpn:%x my qpn:%x\n", attr.dest_qp_num, cma_id->qp->qp_num);
 
 	ib_conn = (struct iser_conn *)cma_id->context;
-	ib_conn->state = ISER_CONN_UP;
-	wake_up_interruptible(&ib_conn->wait);
+	if (iser_conn_state_comp_exch(ib_conn, ISER_CONN_PENDING, ISER_CONN_UP))
+		wake_up_interruptible(&ib_conn->wait);
 }
 
 static void iser_disconnected_handler(struct rdma_cm_id *cma_id)