[PPP] L2TP: Disallow non-UDP datagram sockets

With the addition of UDP-Lite we need to refine the socket check so
that only genuine UDP sockets are allowed through.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 5 deletions

diff --git a/drivers/net/pppol2tp.c b/drivers/net/pppol2tp.c
index 266e8b38fe10..ed8ead432d77 100644
--- a/drivers/net/pppol2tp.c
+++ b/drivers/net/pppol2tp.c
@@ -1326,12 +1326,14 @@ static struct sock *pppol2tp_prepare_tunnel_socket(int fd, u16 tunnel_id,
                 goto err;
         }
 
+        sk = sock->sk;
+
         /* Quick sanity checks */
-        err = -ESOCKTNOSUPPORT;
-        if (sock->type != SOCK_DGRAM) {
+        err = -EPROTONOSUPPORT;
+        if (sk->sk_protocol != IPPROTO_UDP) {
                 PRINTK(-1, PPPOL2TP_MSG_CONTROL, KERN_ERR,
-                       "tunl %hu: fd %d wrong type, got %d, expected %d\n",
-                       tunnel_id, fd, sock->type, SOCK_DGRAM);
+                       "tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
+                       tunnel_id, fd, sk->sk_protocol, IPPROTO_UDP);
                 goto err;
         }
         err = -EAFNOSUPPORT;
@@ -1343,7 +1345,6 @@ static struct sock *pppol2tp_prepare_tunnel_socket(int fd, u16 tunnel_id,
         }
 
         err = -ENOTCONN;
-        sk = sock->sk;
 
         /* Check if this socket has already been prepped */
         tunnel = (struct pppol2tp_tunnel *)sk->sk_user_data;