team: call RCU read lock when walking the port_list

Before reading the team port list, we need to acquire the RCU read lock.
Also change list_for_each_entry() to list_for_each_entry_rcu().

v2:
repost the patch to net-next and remove fixes flag as this is a cosmetic
change.

Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>

drivers/net/team/team.c

@@ -2066,7 +2066,8 @@ static int team_ethtool_get_link_ksettings(struct net_device *dev,
 	cmd->base.duplex = DUPLEX_UNKNOWN;
 	cmd->base.port = PORT_OTHER;
 
-	list_for_each_entry(port, &team->port_list, list) {
+	rcu_read_lock();
+	list_for_each_entry_rcu(port, &team->port_list, list) {
 		if (team_port_txable(port)) {
 			if (port->state.speed != SPEED_UNKNOWN)
 				speed += port->state.speed;
@@ -2075,6 +2076,8 @@ static int team_ethtool_get_link_ksettings(struct net_device *dev,
 				cmd->base.duplex = port->state.duplex;
 		}
 	}
+	rcu_read_unlock();
+
 	cmd->base.speed = speed ? : SPEED_UNKNOWN;
 
 	return 0;