dccp: call inet_add_protocol after register_pernet_subsys in dccp_v6_init

Patch "call inet_add_protocol after register_pernet_subsys in dccp_v4_init"
fixed a null pointer dereference issue for dccp_ipv4 module.

The same fix is needed for dccp_ipv6 module.
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/dccp/ipv6.c

@@ -1098,33 +1098,33 @@ static int __init dccp_v6_init(void)
 {
 	int err = proto_register(&dccp_v6_prot, 1);
 
-	if (err != 0)
+	if (err)
 		goto out;
 
-	err = inet6_add_protocol(&dccp_v6_protocol, IPPROTO_DCCP);
-	if (err != 0)
-		goto out_unregister_proto;
-
 	inet6_register_protosw(&dccp_v6_protosw);
 
 	err = register_pernet_subsys(&dccp_v6_ops);
-	if (err != 0)
+	if (err)
 		goto out_destroy_ctl_sock;
+
+	err = inet6_add_protocol(&dccp_v6_protocol, IPPROTO_DCCP);
+	if (err)
+		goto out_unregister_proto;
+
 out:
 	return err;
-
+out_unregister_proto:
+	unregister_pernet_subsys(&dccp_v6_ops);
 out_destroy_ctl_sock:
-	inet6_del_protocol(&dccp_v6_protocol, IPPROTO_DCCP);
 	inet6_unregister_protosw(&dccp_v6_protosw);
-out_unregister_proto:
 	proto_unregister(&dccp_v6_prot);
 	goto out;
 }
 
 static void __exit dccp_v6_exit(void)
 {
-	unregister_pernet_subsys(&dccp_v6_ops);
 	inet6_del_protocol(&dccp_v6_protocol, IPPROTO_DCCP);
+	unregister_pernet_subsys(&dccp_v6_ops);
 	inet6_unregister_protosw(&dccp_v6_protosw);
 	proto_unregister(&dccp_v6_prot);
 }