ice: add NULL check in eswitch lag check

The function ice_lag_is_switchdev_running() is being called from outside of
the LAG event handler code.  This results in the lag->upper_netdev being
NULL sometimes.  To avoid a NULL-pointer dereference, there needs to be a
check before it is dereferenced.

Fixes: 776fe19 ("ice: block default rule setting on LAG interface")
Signed-off-by: Dave Ertman <[email protected]>
Reviewed-by: Aleksandr Loktionov <[email protected]>
Tested-by: Sujai Buvaneswaran <[email protected]>
Signed-off-by: Tony Nguyen <[email protected]>

Author: dmertman

drivers/net/ethernet/intel/ice/ice_lag.c

@@ -2226,7 +2226,8 @@ bool ice_lag_is_switchdev_running(struct ice_pf *pf)
 	struct ice_lag *lag = pf->lag;
 	struct net_device *tmp_nd;
 
-	if (!ice_is_feature_supported(pf, ICE_F_SRIOV_LAG) || !lag)
+	if (!ice_is_feature_supported(pf, ICE_F_SRIOV_LAG) ||
+	    !lag || !lag->upper_netdev)
 		return false;
 
 	rcu_read_lock();