IB/mlx4: Verify net device validity on port change event

Processing an event is done in a different context from the one when
the event was dispatched. This requires a check that the slave
net device is still valid when the event is being processed. The check is done
under the iboe lock which ensure correctness.

Fixes: a5750090 ('IB/mlx4: Add port aggregation support')
Signed-off-by: NMoni Shoua <monis@mellanox.com>
Signed-off-by: NOr Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/infiniband/hw/mlx4/main.c

@@ -2697,8 +2697,12 @@ static void handle_bonded_port_state_event(struct work_struct *work)
 	spin_lock_bh(&ibdev->iboe.lock);
 	for (i = 0; i < MLX4_MAX_PORTS; ++i) {
 		struct net_device *curr_netdev = ibdev->iboe.netdevs[i];
+		enum ib_port_state curr_port_state;
 
-		enum ib_port_state curr_port_state =
+		if (!curr_netdev)
+			continue;
+
+		curr_port_state =
 			(netif_running(curr_netdev) &&
 			 netif_carrier_ok(curr_netdev)) ?
 			IB_PORT_ACTIVE : IB_PORT_DOWN;