linux-kernel - Re: [PATCH] netfilter:bridge: Hold bridge dev for fake

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Date:   Wed, 3 Apr 2019 19:44:41 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Rundong Ge <rdong.ge@...il.com>
Cc:     kadlec@...ckhole.kfki.hu, fw@...len.de, roopa@...ulusnetworks.com,
        nikolay@...ulusnetworks.com, davem@...emloft.net,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        bridge@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] netfilter:bridge: Hold bridge dev for fake_rtable to
 avoid  the dangling pointer

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.