Merge branch 'l2tp-l2tp_ppp-must-ignore-non-PPP-sessions'

Guillaume Nault says:

====================
l2tp: l2tp_ppp must ignore non-PPP sessions

The original L2TP code was written for version 2 of the protocol, which
could only carry PPP sessions. Then L2TPv3 generalised the protocol so that
it could transport different kinds of pseudo-wires. But parts of the
l2tp_ppp module still break in presence of non-PPP sessions.

Assuming L2TPv2 tunnels can only transport PPP sessions is right, but
l2tp_netlink failed to ensure that (fixed in patch 1).
When retrieving a session from an arbitrary tunnel, l2tp_ppp needs to
filter out non-PPP sessions (last occurrence fixed in patch 2).
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

net/l2tp/l2tp_netlink.c

@@ -553,6 +553,12 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
 		goto out_tunnel;
 	}
 
+	/* L2TPv2 only accepts PPP pseudo-wires */
+	if (tunnel->version == 2 && cfg.pw_type != L2TP_PWTYPE_PPP) {
+		ret = -EPROTONOSUPPORT;
+		goto out_tunnel;
+	}
+
 	if (tunnel->version > 2) {
 		if (info->attrs[L2TP_ATTR_DATA_SEQ])
 			cfg.data_seq = nla_get_u8(info->attrs[L2TP_ATTR_DATA_SEQ]);

net/l2tp/l2tp_ppp.c

@@ -1201,7 +1201,7 @@ static int pppol2tp_tunnel_ioctl(struct l2tp_tunnel *tunnel,
 				l2tp_session_get(sock_net(sk), tunnel,
 						 stats.session_id);
 
-			if (session) {
+			if (session && session->pwtype == L2TP_PWTYPE_PPP) {
 				err = pppol2tp_session_ioctl(session, cmd,
 							     arg);
 				l2tp_session_dec_refcount(session);