--- x/net/smc/smc_core.c
+++ y/net/smc/smc_core.c
@@ -1893,10 +1893,22 @@ int smc_vlan_by_tcpsk(struct socket *clc
 		ini->vlan_id = vlan_dev_vlan_id(ndev);
 		goto out_rel;
 	}
+	rcu_read_lock();
+	if (ndev->reg_state == NETREG_UNREGISTERING || ndev->reg_state == NETREG_UNREGISTERED) {
+		rcu_read_unlock();
+		rc = -ENODEV;
+		goto out_rel;
+	}
+	rcu_read_unlock();
 
 	priv.data = (void *)&ini->vlan_id;
 	rtnl_lock();
-	netdev_walk_all_lower_dev(ndev, smc_vlan_by_tcpsk_walk, &priv);
+	rcu_read_lock();
+	if (ndev->reg_state == NETREG_UNREGISTERING || ndev->reg_state == NETREG_UNREGISTERED)
+		rc = -ENODEV;
+	else
+		netdev_walk_all_lower_dev(ndev, smc_vlan_by_tcpsk_walk, &priv);
+	rcu_read_unlock();
 	rtnl_unlock();
 
 out_rel: