From de9bada5d389903f4faf33980e6a95a2911c7e6d Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Fri, 15 Jun 2018 15:39:17 +0200 Subject: l2tp: reject creation of non-PPP sessions on L2TPv2 tunnels The /proc/net/pppol2tp handlers (pppol2tp_seq_*()) iterate over all L2TPv2 tunnels, and rightfully expect that only PPP sessions can be found there. However, l2tp_netlink accepts creating Ethernet sessions regardless of the underlying tunnel version. This confuses pppol2tp_seq_session_show(), which expects that l2tp_session_priv() returns a pppol2tp_session structure. When the session is an Ethernet pseudo-wire, a struct l2tp_eth_sess is returned instead. This leads to invalid memory access when pppol2tp_session_get_sock() later tries to dereference ps->sk. Fixes: d9e31d17ceba ("l2tp: Add L2TP ethernet pseudowire support") Signed-off-by: Guillaume Nault Signed-off-by: David S. Miller --- net/l2tp/l2tp_netlink.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'net/l2tp/l2tp_netlink.c') diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c index 6616c9fd292f..5b9900889e31 100644 --- a/net/l2tp/l2tp_netlink.c +++ b/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]); -- cgit v1.2.3-59-g8ed1b