netfilter: flowtable: fix IPv6 tunnel addr match

Previously the IPv6 addresses in the key were clobbered and the mask was
left unset.

I haven't tested this; I noticed it while skimming the code to
understand an unrelated issue.

Fixes: cfab6dbd ("netfilter: flowtable: add tunnel match offload support")
Cc: wenxu <wenxu@ucloud.cn>
Signed-off-by: Will Mortensen <willmo@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_flow_table_offload.c

@@ -65,11 +65,11 @@ static void nf_flow_rule_lwt_match(struct nf_flow_match *match,
 		       sizeof(struct in6_addr));
 		if (memcmp(&key->enc_ipv6.src, &in6addr_any,
 			   sizeof(struct in6_addr)))
-			memset(&key->enc_ipv6.src, 0xff,
+			memset(&mask->enc_ipv6.src, 0xff,
 			       sizeof(struct in6_addr));
 		if (memcmp(&key->enc_ipv6.dst, &in6addr_any,
 			   sizeof(struct in6_addr)))
-			memset(&key->enc_ipv6.dst, 0xff,
+			memset(&mask->enc_ipv6.dst, 0xff,
 			       sizeof(struct in6_addr));
 		enc_keys |= BIT(FLOW_DISSECTOR_KEY_ENC_IPV6_ADDRS);
 		key->enc_control.addr_type = FLOW_DISSECTOR_KEY_IPV6_ADDRS;