netfilter: flowtable: fix NULL pointer dereference in tunnel offload support

The tc ct action does not cache the route in the flowtable entry.

Fixes: 88bf6e41 ("netfilter: flowtable: add tunnel encap/decap action offload support")
Fixes: cfab6dbd ("netfilter: flowtable: add tunnel match offload support")
Signed-off-by: wenxu <wenxu@ucloud.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_flow_table_offload.c

@@ -92,7 +92,7 @@ static int nf_flow_rule_match(struct nf_flow_match *match,
 	NF_FLOW_DISSECTOR(match, FLOW_DISSECTOR_KEY_TCP, tcp);
 	NF_FLOW_DISSECTOR(match, FLOW_DISSECTOR_KEY_PORTS, tp);
 
-	if (other_dst->lwtstate) {
+	if (other_dst && other_dst->lwtstate) {
 		tun_info = lwt_tun_info(other_dst->lwtstate);
 		nf_flow_rule_lwt_match(match, tun_info);
 	}
@@ -483,7 +483,7 @@ static void flow_offload_encap_tunnel(const struct flow_offload *flow,
 	struct dst_entry *dst;
 
 	dst = flow->tuplehash[dir].tuple.dst_cache;
-	if (dst->lwtstate) {
+	if (dst && dst->lwtstate) {
 		struct ip_tunnel_info *tun_info;
 
 		tun_info = lwt_tun_info(dst->lwtstate);
@@ -503,7 +503,7 @@ static void flow_offload_decap_tunnel(const struct flow_offload *flow,
 	struct dst_entry *dst;
 
 	dst = flow->tuplehash[!dir].tuple.dst_cache;
-	if (dst->lwtstate) {
+	if (dst && dst->lwtstate) {
 		struct ip_tunnel_info *tun_info;
 
 		tun_info = lwt_tun_info(dst->lwtstate);