[net,2/4] l2tp: only accept PPP sessions in pppol2tp_connect()

Message ID 89a39d08a4722ac050d28b07333ca096786812f6.1528887257.git.g.nault@alphalink.fr
State Accepted
Delegated to: David Miller
Headers show
  • l2tp: pppol2tp_connect() fixes
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Commit Message

Guillaume Nault June 13, 2018, 1:09 p.m.
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: d9e31d17ceba ("l2tp: Add L2TP ethernet pseudowire support")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
 net/l2tp/l2tp_ppp.c | 6 ++++++
 1 file changed, 6 insertions(+)


diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index 270a0a999eaf..8b3b6947a07d 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -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