netdev - [PATCH net 2/4] l2tp: only accept PPP sessions in pppol2tp

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 13 Jun 2018 15:09:19 +0200
From:   Guillaume Nault <g.nault@...halink.fr>
To:     netdev@...r.kernel.org
Cc:     James Chapman <jchapman@...alix.com>
Subject: [PATCH net 2/4] 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: d9e31d17ceba ("l2tp: Add L2TP ethernet pseudowire support")
Signed-off-by: Guillaume Nault <g.nault@...halink.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
-- 
2.17.1