l2tp: hold tunnel socket when handling control frames in l2tp_ip and l2tp_ip6

commit 94d7ee0baa8b764cf64ad91ed69464c1a6a0066b upstream.

The code following l2tp_tunnel_find() expects that a new reference is
held on sk. Either sk_receive_skb() or the discard_put error path will
drop a reference from the tunnel's socket.

This issue exists in both l2tp_ip and l2tp_ip6.

Fixes: a3c18422a4b4 ("l2tp: hold socket before dropping lock in l2tp_ip{, 6}_recv()")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
index 1a383eb7c7e63e3d44472a6ad2147fa1cce53b1f..38b2b95b0067d3b09d4ca2f638554ba2cd1dbb23 100644 (file)
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -178,9 +178,10 @@ pass_up:
 
        tunnel_id = ntohl(*(__be32 *) &skb->data[4]);
        tunnel = l2tp_tunnel_find(net, tunnel_id);
-       if (tunnel != NULL)
+       if (tunnel) {
                sk = tunnel->sock;
-       else {
+               sock_hold(sk);
+       } else {
                struct iphdr *iph = (struct iphdr *) skb_network_header(skb);
 
                read_lock_bh(&l2tp_ip_lock);

diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
index 2277b6b9e5b2df341c38053baf1fab5b4e30b75c..ce59bcf9f9ea5f704809204ccd481ad00cb4e4d5 100644 (file)
--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -190,9 +190,10 @@ pass_up:
 
        tunnel_id = ntohl(*(__be32 *) &skb->data[4]);
        tunnel = l2tp_tunnel_find(&init_net, tunnel_id);
-       if (tunnel != NULL)
+       if (tunnel) {
                sk = tunnel->sock;
-       else {
+               sock_hold(sk);
+       } else {
                struct ipv6hdr *iph = ipv6_hdr(skb);
 
                read_lock_bh(&l2tp_ip6_lock);