netfilter: tproxy: properly refcount tcp listeners

inet_lookup_listener() and inet6_lookup_listener() no longer
take a reference on the found listener.

This minimal patch adds back the refcounting, but we might do
this differently in net-next later.

Fixes: 3b24d854cb35 ("tcp/dccp: do not touch listener sk_refcnt under synflood")
Reported-and-tested-by: Denys Fedoryshchenko <nuclearcat@nuclearcat.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/net/netfilter/xt_TPROXY.c b/net/netfilter/xt_TPROXY.c
index 7f4414d26a66..663c4c3c9072 100644
--- a/net/netfilter/xt_TPROXY.c
+++ b/net/netfilter/xt_TPROXY.c
@@ -127,6 +127,8 @@ nf_tproxy_get_sock_v4(struct net *net, struct sk_buff *skb, void *hp,
                                                     daddr, dport,
                                                     in->ifindex);
 
+                        if (sk && !atomic_inc_not_zero(&sk->sk_refcnt))
+                                sk = NULL;
                         /* NOTE: we return listeners even if bound to
                          * 0.0.0.0, those are filtered out in
                          * xt_socket, since xt_TPROXY needs 0 bound
@@ -195,6 +197,8 @@ nf_tproxy_get_sock_v6(struct net *net, struct sk_buff *skb, int thoff, void *hp,
                                                    daddr, ntohs(dport),
                                                    in->ifindex);
 
+                        if (sk && !atomic_inc_not_zero(&sk->sk_refcnt))
+                                sk = NULL;
                         /* NOTE: we return listeners even if bound to
                          * 0.0.0.0, those are filtered out in
                          * xt_socket, since xt_TPROXY needs 0 bound