RE: [PATCH nf v3 1/1] netfilter: snmp: Fix one possible panic when snmp_trap_helper fail to register

Hi Pablo,

-----Original Message-----
From: netfilter-devel-owner@vger.kernel.org
[mailto:netfilter-devel-owner@vger.kernel.org] On Behalf Of Pablo Neira

Ayuso

Sent: Friday, March 24, 2017 8:23 PM
To: fgao@ikuai8.com
Cc: davem@davemloft.net; jolsa@redhat.com;

netfilter-devel@vger.kernel.org;

netdev@vger.kernel.org; gfree.wind@gmail.com
Subject: Re: [PATCH nf v3 1/1] netfilter: snmp: Fix one possible panic

when

snmp_trap_helper fail to register

On Fri, Mar 24, 2017 at 01:21:30PM +0100, Pablo Neira Ayuso wrote:

quoted

On Tue, Mar 21, 2017 at 08:22:29AM +0800, fgao@ikuai8.com wrote:

quoted

From: Gao Feng <redacted>

In the commit 93557f53e1fb ("netfilter: nf_conntrack: nf_conntrack
snmp helper"), the snmp_helper is replaced by nf_nat_snmp_hook. So
the snmp_helper is never registered. But it still tries to
unregister the snmp_helper, it could cause the panic.

This patch looks correct to me.

But probably for some reason I don't manage to trigger, how do you
reproduce this?

I'm refering to the panic.

[高峰] 
It is got by reviewing the codes.
When nf_conntrack_helper_unregister(&snmp_helper), but snmp_helper didn't
register actually.
And snmp_helper. hnode is not initialized, it would trigger the issue when
hlist_del_rcu in nf_conntrack_helper_unregister.

Best Regards
Feng

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