rtnetlink: fix error code in rtnl_newlink()

If rtnl_get_peer_net() fails, then propagate the error code.  Don't
return success.

Fixes: 4832756 ("rtnetlink: fix double call of rtnl_link_get_net_ifla()")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/a2d20cd4-387a-4475-887c-bb7d0e88e25a@stanley.mountain
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Dan Carpenter

net/core/rtnetlink.c

@@ -3972,8 +3972,10 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 
 		if (ops->peer_type) {
 			peer_net = rtnl_get_peer_net(ops, data, extack);
-			if (IS_ERR(peer_net))
+			if (IS_ERR(peer_net)) {
+				ret = PTR_ERR(peer_net);
 				goto put_ops;
+			}
 			if (peer_net)
 				rtnl_nets_add(&rtnl_nets, peer_net);
 		}