igb: Fix NULL pointer dereference in ethtool loopback test

The igb driver currently causes a NULL pointer dereference when executing
the ethtool loopback test. This occurs because there is no associated
q_vector for the test ring when it is set up, as interrupts are typically
not added to the test rings.

Since commit 5ef44b3 removed the napi_id assignment in
__xdp_rxq_info_reg(), there is no longer a need to pass a napi_id to it.
Therefore, simply use 0 as the last parameter.

Fixes: 2c61960 ("igb: Add AF_XDP zero-copy Rx support")
Reviewed-by: Aleksandr Loktionov <[email protected]>
Reviewed-by: Joe Damato <[email protected]>
Signed-off-by: Tianyu Xu <[email protected]>
Reviewed-by: Paul Menzel <[email protected]>
Tested-by: Rinitha S <[email protected]> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <[email protected]>

Author: Tianyu Xu

drivers/net/ethernet/intel/igb/igb_main.c

@@ -4453,8 +4453,7 @@ int igb_setup_rx_resources(struct igb_ring *rx_ring)
 	if (xdp_rxq_info_is_reg(&rx_ring->xdp_rxq))
 		xdp_rxq_info_unreg(&rx_ring->xdp_rxq);
 	res = xdp_rxq_info_reg(&rx_ring->xdp_rxq, rx_ring->netdev,
-			       rx_ring->queue_index,
-			       rx_ring->q_vector->napi.napi_id);
+			       rx_ring->queue_index, 0);
 	if (res < 0) {
 		dev_err(dev, "Failed to register xdp_rxq index %u\n",
 			rx_ring->queue_index);