netdev - Re: [RFC PATCH] net: cgroup: null ptr dereference in netprio cgroup during init

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Message-ID: <50064E95.7020503@intel.com>
Date:	Tue, 17 Jul 2012 22:50:13 -0700
From:	John Fastabend <john.r.fastabend@...el.com>
To:	Gao feng <gaofeng@...fujitsu.com>
CC:	davem@...emloft.net, nhorman@...driver.com,
	mark.d.rustad@...el.com, netdev@...r.kernel.org,
	eric.dumazet@...il.com
Subject: Re: [RFC PATCH] net: cgroup: null ptr dereference in netprio cgroup
 during init

On 7/17/2012 6:59 PM, Gao feng wrote:
> 于 2012年07月18日 08:33, John Fastabend 写道:
>> When the netprio cgroup is built in the kernel cgroup_init will call
>> cgrp_create which eventually calls update_netdev_tables. This is
>> being called before do_initcalls() so a null ptr dereference occurs
>> on init_net.
>>

[...]

>
>
> Thanks John.
> It's my mistake.
>
> Can we make sure init_net.count is zero here?
> I can't find some places to initialize it to zero.
>

Its defined in net_namespace.c so it's zeroed by virtue
of being global. And initialized in setup_net via
pure_initcall() always after cgroup_init() if I've done
my accounting correctly.

.John
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