linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Florian Westphal <fw@strlen.de>
To: Leonardo Bras <leonardo@linux.ibm.com>
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 <pablo@netfilter.org>,
	Jozsef Kadlecsik <kadlec@netfilter.org>,
	Florian Westphal <fw@strlen.de>,
	Roopa Prabhu <roopa@cumulusnetworks.com>,
	Nikolay Aleksandrov <nikolay@cumulusnetworks.com>,
	"David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH v4 2/2] net: br_netfiler_hooks: Drops IPv6 packets if IPv6 module is not loaded
Date: Fri, 30 Aug 2019 22:55:41 +0200	[thread overview]
Message-ID: <20190830205541.GR20113@breakpoint.cc> (raw)
In-Reply-To: <20190830181354.26279-3-leonardo@linux.ibm.com>

Leonardo Bras <leonardo@linux.ibm.com> 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 <leonardo@linux.ibm.com>
> ---
>  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.

  reply	other threads:[~2019-08-30 20:55 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-30 18:13 [PATCH v4 0/2] Drop IPV6 packets if IPv6 is disabled on boot Leonardo Bras
2019-08-30 18:13 ` [PATCH v4 1/2] netfilter: Terminate rule eval if protocol=IPv6 and ipv6 module is disabled Leonardo Bras
2019-08-30 20:58   ` Florian Westphal
2019-09-03 16:46     ` Leonardo Bras
2019-09-03 16:49       ` Pablo Neira Ayuso
2019-09-03 16:56         ` Leonardo Bras
2019-09-03 17:05         ` Florian Westphal
2019-09-03 19:31           ` Pablo Neira Ayuso
2019-09-03 19:48             ` Florian Westphal
2019-09-03 20:19               ` Pablo Neira Ayuso
2019-09-03 20:35                 ` Florian Westphal
2019-09-03 20:55                   ` Pablo Neira Ayuso
2019-09-03 20:55   ` Pablo Neira Ayuso
2019-08-30 18:13 ` [PATCH v4 2/2] net: br_netfiler_hooks: Drops IPv6 packets if IPv6 module is not loaded Leonardo Bras
2019-08-30 20:55   ` Florian Westphal [this message]
2019-08-31  4:42     ` Leonardo Bras
2019-08-31  8:43       ` Florian Westphal

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190830205541.GR20113@breakpoint.cc \
    --to=fw@strlen.de \
    --cc=bridge@lists.linux-foundation.org \
    --cc=coreteam@netfilter.org \
    --cc=davem@davemloft.net \
    --cc=kadlec@netfilter.org \
    --cc=leonardo@linux.ibm.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=netdev@vger.kernel.org \
    --cc=netfilter-devel@vger.kernel.org \
    --cc=nikolay@cumulusnetworks.com \
    --cc=pablo@netfilter.org \
    --cc=roopa@cumulusnetworks.com \
    --subject='Re: [PATCH v4 2/2] net: br_netfiler_hooks: Drops IPv6 packets if IPv6 module is not loaded' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).