l2tp: Correctly return -EBADF from pppol2tp_getname.

BugLink: https://bugs.launchpad.net/bugs/1874045

commit 4ac36a4a upstream.

If 'tunnel' is NULL we should return -EBADF but the 'end_put_sess' path
unconditionally sets 'error' back to zero. Rework the error path so it
more closely matches pppol2tp_sendmsg.

Fixes: fd558d18 ("l2tp: Split pppol2tp patch into separate l2tp and ppp parts")
Signed-off-by: Phil Turnbull <phil.turnbull@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

net/l2tp/l2tp_ppp.c

@@ -884,10 +884,8 @@ static int pppol2tp_getname(struct socket *sock, struct sockaddr *uaddr,
 
 	pls = l2tp_session_priv(session);
 	tunnel = l2tp_sock_to_tunnel(pls->tunnel_sock);
-	if (tunnel == NULL) {
-		error = -EBADF;
+	if (tunnel == NULL)
 		goto end_put_sess;
-	}
 
 	inet = inet_sk(tunnel->sock);
 	if ((tunnel->version == 2) && (tunnel->sock->sk_family == AF_INET)) {
@@ -965,12 +963,11 @@ static int pppol2tp_getname(struct socket *sock, struct sockaddr *uaddr,
 	}
 
 	*usockaddr_len = len;
+	error = 0;
 
 	sock_put(pls->tunnel_sock);
 end_put_sess:
 	sock_put(sk);
-	error = 0;
-
 end:
 	return error;
 }