[PATCH 1/2] netfilter: ip6t_SYNPROXY: fix NULL pointer dereference

[Phil Sutter <phil@nwl.cc>]

This happens when networking namespaces are enabled.

Suggested-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 net/ipv6/netfilter/ip6t_SYNPROXY.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/net/ipv6/netfilter/ip6t_SYNPROXY.c b/net/ipv6/netfilter/ip6t_SYNPROXY.c
index 6edb7b1..f5af323 100644
--- a/net/ipv6/netfilter/ip6t_SYNPROXY.c
+++ b/net/ipv6/netfilter/ip6t_SYNPROXY.c
@@ -40,9 +40,9 @@ static void
 synproxy_send_tcp(const struct sk_buff *skb, struct sk_buff *nskb,
 		  struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
 		  struct ipv6hdr *niph, struct tcphdr *nth,
-		  unsigned int tcp_hdr_size)
+		  unsigned int tcp_hdr_size, struct synproxy_net *snet)
 {
-	struct net *net = nf_ct_net((struct nf_conn *)nfct);
+	struct net *net = nf_ct_net(snet->tmpl);
 	struct dst_entry *dst;
 	struct flowi6 fl6;
 
@@ -84,7 +84,8 @@ free_nskb:
 
 static void
 synproxy_send_client_synack(const struct sk_buff *skb, const struct tcphdr *th,
-			    const struct synproxy_options *opts)
+			    const struct synproxy_options *opts,
+			    struct synproxy_net *snet)
 {
 	struct sk_buff *nskb;
 	struct ipv6hdr *iph, *niph;
@@ -120,7 +121,7 @@ synproxy_send_client_synack(const struct sk_buff *skb, const struct tcphdr *th,
 	synproxy_build_options(nth, opts);
 
 	synproxy_send_tcp(skb, nskb, skb->nfct, IP_CT_ESTABLISHED_REPLY,
-			  niph, nth, tcp_hdr_size);
+			  niph, nth, tcp_hdr_size, snet);
 }
 
 static void
@@ -164,7 +165,7 @@ synproxy_send_server_syn(const struct synproxy_net *snet,
 	synproxy_build_options(nth, opts);
 
 	synproxy_send_tcp(skb, nskb, &snet->tmpl->ct_general, IP_CT_NEW,
-			  niph, nth, tcp_hdr_size);
+			  niph, nth, tcp_hdr_size, snet);
 }
 
 static void
@@ -203,7 +204,7 @@ synproxy_send_server_ack(const struct synproxy_net *snet,
 
 	synproxy_build_options(nth, opts);
 
-	synproxy_send_tcp(skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
+	synproxy_send_tcp(skb, nskb, NULL, 0, niph, nth, tcp_hdr_size, snet);
 }
 
 static void
@@ -241,7 +242,7 @@ synproxy_send_client_ack(const struct synproxy_net *snet,
 
 	synproxy_build_options(nth, opts);
 
-	synproxy_send_tcp(skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
+	synproxy_send_tcp(skb, nskb, NULL, 0, niph, nth, tcp_hdr_size, snet);
 }
 
 static bool
@@ -301,7 +302,7 @@ synproxy_tg6(struct sk_buff *skb, const struct xt_action_param *par)
 					  XT_SYNPROXY_OPT_SACK_PERM |
 					  XT_SYNPROXY_OPT_ECN);
 
-		synproxy_send_client_synack(skb, th, &opts);
+		synproxy_send_client_synack(skb, th, &opts, snet);
 		return NF_DROP;
 
 	} else if (th->ack && !(th->fin || th->rst || th->syn)) {
-- 
2.1.2