geneve: rely on rtnl lock in geneve_offload_rx_ports

udp_tunnel_push_rx_port will grab mutex in the next patch so
we can't use rcu. geneve_offload_rx_ports is called
from geneve_netdevice_event for NETDEV_UDP_TUNNEL_PUSH_INFO and
NETDEV_UDP_TUNNEL_DROP_INFO which both have ASSERT_RTNL.
Entries are added to and removed from the sock_list under rtnl
lock as well (when adding or removing a tunneling device).

Signed-off-by: Stanislav Fomichev <[e-mail]>
Reviewed-by: Nikolay Aleksandrov <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/geneve.c

···
 /* per-network namespace private data for this module */
 struct geneve_net {
 	struct list_head	geneve_list;
+	/* sock_list is protected by rtnl lock */
 	struct list_head	sock_list;
 };
 
···
 	struct geneve_net *gn = net_generic(net, geneve_net_id);
 	struct geneve_sock *gs;
 
-	rcu_read_lock();
-	list_for_each_entry_rcu(gs, &gn->sock_list, list) {
+	ASSERT_RTNL();
+
+	list_for_each_entry(gs, &gn->sock_list, list) {
 		if (push) {
 			udp_tunnel_push_rx_port(dev, gs->sock,
 						UDP_TUNNEL_TYPE_GENEVE);
···
 						UDP_TUNNEL_TYPE_GENEVE);
 		}
 	}
-	rcu_read_unlock();
 }
 
 /* Initialize the device structure. */