Commit 7ac6ab1f authored Jun 13, 2018 by Guillaume Nault Committed by David S. Miller Jun 14, 2018

l2tp: only accept PPP sessions in pppol2tp_connect()

l2tp_session_priv() returns a struct pppol2tp_session pointer only for
PPPoL2TP sessions. In particular, if the session is an L2TP_PWTYPE_ETH
pseudo-wire, l2tp_session_priv() returns a pointer to an l2tp_eth_sess
structure, which is much smaller than struct pppol2tp_session. This
leads to invalid memory dereference when trying to lock ps->sk_lock.

Fixes: d9e31d17 ("l2tp: Add L2TP ethernet pseudowire support")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 90904ff5

net/l2tp/l2tp_ppp.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -734,6 +734,12 @@ static int pppol2tp_connect(struct socket sock, struct sockaddr uservaddr,
		session = l2tp_session_get(sock_net(sk), tunnel, session_id);
		if (session) {
		drop_refcnt = true;

		if (session->pwtype != L2TP_PWTYPE_PPP) {
		error = -EPROTOTYPE;
		goto end;
		}

		ps = l2tp_session_priv(session);

		/* Using a pre-existing session is fine as long as it hasn't