From 3e1bc8bf974e2d4e7beb842a4c801c2542eff3bd Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Wed, 13 Jun 2018 15:09:20 +0200 Subject: l2tp: prevent pppol2tp_connect() from creating kernel sockets If 'fd' is negative, l2tp_tunnel_create() creates a tunnel socket using the configuration passed in 'tcfg'. Currently, pppol2tp_connect() sets the relevant fields to zero, tricking l2tp_tunnel_create() into setting up an unusable kernel socket. We can't set 'tcfg' with the required fields because there's no way to get them from the current connect() parameters. So let's restrict kernel sockets creation to the netlink API, which is the original use case. Fixes: 789a4a2c61d8 ("l2tp: Add support for static unmanaged L2TPv3 tunnels") Signed-off-by: Guillaume Nault Signed-off-by: David S. Miller --- net/l2tp/l2tp_ppp.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'net') diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c index 8b3b6947a07d..1b24f76ae210 100644 --- a/net/l2tp/l2tp_ppp.c +++ b/net/l2tp/l2tp_ppp.c @@ -701,6 +701,15 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr, .encap = L2TP_ENCAPTYPE_UDP, .debug = 0, }; + + /* Prevent l2tp_tunnel_register() from trying to set up + * a kernel socket. + */ + if (fd < 0) { + error = -EBADF; + goto end; + } + error = l2tp_tunnel_create(sock_net(sk), fd, ver, tunnel_id, peer_tunnel_id, &tcfg, &tunnel); if (error < 0) goto end; -- cgit v1.2.3