netdev - Re: [PATCH net] bridge: drop netfilter fake rtable unconditionally

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Message-ID: <20170313165124.GA32021@salvia>
Date:   Mon, 13 Mar 2017 17:51:24 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Florian Westphal <fw@...len.de>
Cc:     netdev@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: Re: [PATCH net] bridge: drop netfilter fake rtable unconditionally

On Mon, Mar 13, 2017 at 05:38:17PM +0100, Florian Westphal wrote:
> Andreas reports kernel oops during rmmod of the br_netfilter module.
> Hannes debugged the oops down to a NULL rt6info->rt6i_indev.
> 
> Problem is that br_netfilter has the nasty concept of adding a fake
> rtable to skb->dst; this happens in a br_netfilter prerouting hook.
> 
> A second hook (in bridge LOCAL_IN) is supposed to remove these again
> before the skb is handed up the stack.
> 
> However, on module unload hooks get unregistered which means an
> skb could traverse the prerouting hook that attaches the fake_rtable,
> while the 'fake rtable remove' hook gets removed from the hooklist
> immediately after.
> 
> Fixes: 34666d467cbf1e2e3c7 ("netfilter: bridge: move br_netfilter out of the core")
> Reported-by: Andreas Karis <akaris@...hat.com>
> Debugged-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
> Signed-off-by: Florian Westphal <fw@...len.de>
> ---
>  David, I know you *love* the fake_rtable turd, but I think
>  this patch should go directly via net and not nf tree.
>  After all, this adds to bridge and removes from the netfilter part.

If this helps speed up this.

Acked-by: Pablo Neira Ayuso <pablo@...filter.org>

I also love this bridge netfilter Frankenstein a lot. Looking forward
you kill this via native bridge conntrack support for nf_tables.

Thanks.