From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8FDB3C3A59B for ; Fri, 30 Aug 2019 20:55:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6825623429 for ; Fri, 30 Aug 2019 20:55:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728225AbfH3Uzv (ORCPT ); Fri, 30 Aug 2019 16:55:51 -0400 Received: from Chamillionaire.breakpoint.cc ([193.142.43.52]:58868 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727992AbfH3Uzv (ORCPT ); Fri, 30 Aug 2019 16:55:51 -0400 Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1i3nvp-0006RE-4L; Fri, 30 Aug 2019 22:55:41 +0200 Date: Fri, 30 Aug 2019 22:55:41 +0200 From: Florian Westphal To: Leonardo Bras Cc: netfilter-devel@vger.kernel.org, coreteam@netfilter.org, bridge@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Pablo Neira Ayuso , Jozsef Kadlecsik , Florian Westphal , Roopa Prabhu , Nikolay Aleksandrov , "David S. Miller" Subject: Re: [PATCH v4 2/2] net: br_netfiler_hooks: Drops IPv6 packets if IPv6 module is not loaded Message-ID: <20190830205541.GR20113@breakpoint.cc> References: <20190830181354.26279-1-leonardo@linux.ibm.com> <20190830181354.26279-3-leonardo@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190830181354.26279-3-leonardo@linux.ibm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Leonardo Bras wrote: > A kernel panic can happen if a host has disabled IPv6 on boot and have to > process guest packets (coming from a bridge) using it's ip6tables. > > IPv6 packets need to be dropped if the IPv6 module is not loaded. > > Signed-off-by: Leonardo Bras > --- > net/bridge/br_netfilter_hooks.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c > index d3f9592f4ff8..5e8693730df1 100644 > --- a/net/bridge/br_netfilter_hooks.c > +++ b/net/bridge/br_netfilter_hooks.c > @@ -493,6 +493,8 @@ static unsigned int br_nf_pre_routing(void *priv, > brnet = net_generic(state->net, brnf_net_id); > if (IS_IPV6(skb) || is_vlan_ipv6(skb, state->net) || > is_pppoe_ipv6(skb, state->net)) { > + if (!ipv6_mod_enabled()) > + return NF_DROP; > if (!brnet->call_ip6tables && > !br_opt_get(br, BROPT_NF_CALL_IP6TABLES)) > return NF_ACCEPT; No, thats too aggressive and turns the bridge into an ipv6 blackhole. There are two solutions: 1. The above patch, but use NF_ACCEPT instead 2. keep the DROP, but move it below the call_ip6tables test, so that users can tweak call-ip6tables to accept packets. Perhaps it would be good to also add a pr_warn_once() that tells that ipv6 was disabled on command line and call-ip6tables isn't supported in this configuration. I would go with option two.