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Date: Tue, 25 Dec 2012 16:38:17 +0800
From: Gao feng <gaofeng@cn.fujitsu.com>
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To: canqun zhang <canqunzhang@gmail.com>
CC: Patrick McHardy <kaber@trash.net>, netfilter-devel@vger.kernel.org,
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Subject: Re: kernel panic when running /etc/init.d/iptables restart
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On 2012/12/25 15:25, canqun zhang wrote:
> Hi Gao feng
> The stack information is as follows. The kenel will panic because the
> nf_ct_destroy is NULL.
> 
> Reproduction:
> (1) starting a lxc container
> (2) iptables -t nat -A POSTROUTING -s 10.48.254.18 -o eth1 -j
> MASQUERADE (run it on host machine)
> (3) /etc/ini.d/iptables save (run it on host machine)
> (4)/etc/init.d/iptables restart (run it on host machine)
> 

Thanks!
It seems that nf_conntrack_l[3,4]proto_unregister doesn't make sure
nf_conns of the proto being destroyed.

If I'm right, there is another problem even your fix this panic problem.
the l3,14proto will be unregistered before all of it's nf_conns being destroyed.
So even nf_ct_destroy is not NULL,in destroy_conntrack we are not able to
find the right l4proto,the l4proto->destroy will be incorrect.resources will
not be released correctly.

So I think the root problem is we do register/unregister, set/unset both on the
first net (init_net), Maybe it's better to do register set on the first net, and
do unregister unset on the last net.