netdev - Re: [PATCH 19/19] netfilter: gre: fix resource leak when unregister gre proto

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Date:	Mon, 07 Jan 2013 11:43:11 +0800
From:	Gao feng <gaofeng@...fujitsu.com>
To:	Pablo Neira Ayuso <pablo@...filter.org>
CC:	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
	canqunzhang@...il.com, kaber@...sh.net, ebiederm@...ssion.com
Subject: Re: [PATCH 19/19] netfilter: gre: fix resource leak when unregister
 gre proto

On 01/07/13 11:27, Pablo Neira Ayuso wrote:
> On Mon, Jan 07, 2013 at 11:05:12AM +0800, Gao feng wrote:
>> On 01/07/13 10:59, Gao feng wrote:
>>> On 01/07/13 10:38, Pablo Neira Ayuso wrote:
>>>> On Mon, Jan 07, 2013 at 03:15:17AM +0100, Pablo Neira Ayuso wrote:
>>>>> Hi Gao,
>>>>>
>>>>> On Mon, Jan 07, 2013 at 09:27:37AM +0800, Gao feng wrote:
>>>>>> Hi Pablo,
>>>>>>
>>>>>> On 01/05/13 11:50, Pablo Neira Ayuso wrote:
>>>>>>> Hi Gao,
>>>>>>>
>>>>>>> On Fri, Dec 28, 2012 at 10:36:46AM +0800, Gao feng wrote:
>>>>>>>> Currectly we unregister proto before all conntrack entries of
>>>>>>>> this proto being destroyed. so in function destroy_conntrack
>>>>>>>> we can't find proper l4proto to call l4proto->destroy.
>>>>>>>> this will cause resource leak.
>>>>>>>
>>>>>>> Good catch.
>>>>>>>
>>>>>>> But better to remove the entries before unregistering the protocol
>>>>>>> tracker, so l4proto->destroy is always called.
>>>>>>>
>>>>>>
>>>>>> I think the reason we unregister proto before remove all entries
>>>>>> is to avoid new entry for this protocol being created.
>>>>>>
>>>>>> If we remove all contrack entries before unregistration, there maybe
>>>>>> some new entries being created between nf_ct_iterate_cleanup and
>>>>>> nf_conntrack_l4proto_unregister_net.this will cause some terrible things.
>>>>>
>>>>> Leaks are less likely to happen, but may well still happen while
>>>>> racing with protocol removal, agreed.
>>>>>
>>>>>> SO I think we should make proto unavailable first,remove all entries next,
>>>>>> and remove proto from nf_ct_protos arrays finally.
>>>>>
>>>>> Your proposal adds a branch in the packet path to fix an issue that is
>>>>> specific of the GRE protocol tracker. In the current code, this fixes
>>>>> the memory leak while removing the nf_conntrack_proto_gre module,
>>>>> which is a rare operation.
>>>>>
>>>>> We have to come with a less intrusive solution.
>>>>
>>>> Wait. The existing code is calling nf_ct_gre_keymap_flush in
>>>> proto_gre_net_exit path, so those keymap objects are not leaked.
>>>
>>> Agree, it looks like nf_ct_gre_keymap_flush is added to solve this
>>> problem.
>>>
>>> Please ignore this patch.
>>
>> I mean ignore the codes of gre part.
>> I still think nf_ct_iterate_cleanup doesn't make sure all entries being
>> destroyed.
> 
> There is another round of nf_ct_iterate cleanup in
> nf_conntrack_cleanup_net. So I don't see any possible leak so far. Let
> me know if you find anything.
> 

Ok,I am wrong...
Please ignore this patch. ;)
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