l2tp: cleanup eth/ppp pseudowire setup code

l2tp eth/ppp pseudowire setup/cleanup uses kfree() in some error
paths. Drop the refcount instead such that the session object is
always freed when the refcount reaches 0.
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/l2tp/l2tp_eth.c

@@ -322,7 +322,7 @@ static int l2tp_eth_create(struct net *net, struct l2tp_tunnel *tunnel,
 	l2tp_session_dec_refcount(session);
 	free_netdev(dev);
 err_sess:
-	kfree(session);
+	l2tp_session_dec_refcount(session);
 err:
 	return rc;
 }

net/l2tp/l2tp_ppp.c

@@ -770,6 +770,8 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
 			goto end;
 		}
 
+		drop_refcnt = true;
+
 		pppol2tp_session_init(session);
 		ps = l2tp_session_priv(session);
 		l2tp_session_inc_refcount(session);
@@ -778,10 +780,10 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
 		error = l2tp_session_register(session, tunnel);
 		if (error < 0) {
 			mutex_unlock(&ps->sk_lock);
-			kfree(session);
+			l2tp_session_dec_refcount(session);
 			goto end;
 		}
-		drop_refcnt = true;
+
 		new_session = true;
 	}
 
@@ -875,7 +877,7 @@ static int pppol2tp_session_create(struct net *net, struct l2tp_tunnel *tunnel,
 	return 0;
 
 err_sess:
-	kfree(session);
+	l2tp_session_dec_refcount(session);
 err:
 	return error;
 }