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Date:   Wed, 3 Apr 2019 19:44:41 +0200
From:   Pablo Neira Ayuso <pablo@netfilter.org>
To:     Rundong Ge <rdong.ge@gmail.com>
Cc:     kadlec@blackhole.kfki.hu, fw@strlen.de, roopa@cumulusnetworks.com,
        nikolay@cumulusnetworks.com, davem@davemloft.net,
        netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
        bridge@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] netfilter:bridge: Hold bridge dev for fake_rtable to
 avoid  the dangling pointer
Message-ID: <20190403174441.2l7xyk5o2hftrdm3@salvia>
References: <20190402125609.30313-1-rdong.ge@gmail.com>
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On Tue, Apr 02, 2019 at 12:56:09PM +0000, Rundong Ge wrote:
> Problem:
> When bridge-nf-call-iptables is enabled, skb_dst(skb) of packets that
> in the nfqueue may be a dangling pointer if user delete the bridge.
> Because packets go through the br_nf_pre_routing_finish will set the dst
> pointer to the br->fake_rtable. But the br struct will be freed
> without the reference check for these skbs.
> 
> User impact:
> Kernel panic may happen when user delete the bridge if there are
> continuous traffics go through the nfqueue.
> Here is a panic in my device which using kernel v3.10.

This kernel is _very old_.

Could you provide the steps to reproduce this issue?

Holding the device doesn't seem the way to go to me, we have a of
netdevice_notifier that is dropping packets for an interface that is
gone in nfnetlink_queue. We also drop packets whenever a hook in gone.

So I wonder if this is still a problem in mainline kernels.