From: Guillaume Nault <g.nault@alphalink.fr>
Date: Fri, 13 Oct 2017 19:22:35 +0200
Subject: l2tp: check ps->sock before running pppol2tp_session_ioctl()
Patch-mainline: v4.14-rc6
Git-commit: 5903f594935a3841137c86b9d5b75143a5b7121c
References: bsc#1076830

When pppol2tp_session_ioctl() is called by pppol2tp_tunnel_ioctl(),
the session may be unconnected. That is, it was created by
pppol2tp_session_create() and hasn't been connected with
pppol2tp_connect(). In this case, ps->sock is NULL, so we need to check
for this case in order to avoid dereferencing a NULL pointer.

Fixes: 309795f4bec2 ("l2tp: Add netlink control API for L2TP")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Michal Kubecek <mkubecek@suse.cz>

---
 net/l2tp/l2tp_ppp.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index 32ea0f3d868c..2ec137d8eb99 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -993,6 +993,9 @@ static int pppol2tp_session_ioctl(struct l2tp_session *session,
 		 session->name, cmd, arg);
 
 	sk = ps->sock;
+	if (!sk)
+		return -EBADR;
+
 	sock_hold(sk);
 
 	switch (cmd) {
-- 
2.16.1