netdev - Re: use-after-free in sctp_do

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Message-ID: <5660A951.4000808@akamai.com>
Date:	Thu, 3 Dec 2015 15:42:57 -0500
From:	Jason Baron <jbaron@...mai.com>
To:	Joe Perches <joe@...ches.com>, Aaron Conole <aconole@...hat.com>,
	Dmitry Vyukov <dvyukov@...gle.com>
Cc:	Eric Dumazet <edumazet@...gle.com>,
	syzkaller <syzkaller@...glegroups.com>,
	Vladislav Yasevich <vyasevich@...il.com>,
	linux-sctp@...r.kernel.org, netdev <netdev@...r.kernel.org>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: use-after-free in sctp_do_sm

On 12/03/2015 03:24 PM, Joe Perches wrote:
> On Thu, 2015-12-03 at 15:10 -0500, Jason Baron wrote:
>> On 12/03/2015 03:03 PM, Joe Perches wrote:
>>> On Thu, 2015-12-03 at 14:32 -0500, Jason Baron wrote:
>>>> On 12/03/2015 01:52 PM, Aaron Conole wrote:
>>>>> I think that as a minimum, the following patch should be evaluted,
>>>>> but am unsure to whom I should submit it (after I test):
>>> []
>>>> Agreed - the intention here is certainly to have no side effects. It
>>>> looks like 'no_printk()' is used in quite a few other places that would
>>>> benefit from this change. So we probably want a generic
>>>> 'really_no_printk()' macro.
>>>
>>> https://lkml.org/lkml/2012/6/17/231
>>
>> I don't see this in the tree.
> 
> It never got applied.
> 
>> Also maybe we should just convert
>> no_printk() to do what your 'eliminated_printk()'.
> 
> Some of them at least.
> 
>> So we can convert all users with this change?
> 
> I don't think so, I think there are some
> function evaluation/side effects that are
> required.  I believe some do hardware I/O.
> 
> It'd be good to at least isolate them.
> 
> I'm not sure how to find them via some
> automated tool/mechanism though.
> 
> I asked Julia Lawall about it once in this
> thread:  https://lkml.org/lkml/2014/12/3/696
> 

Seems rather fragile to have side effects that we rely
upon hidden in a printk().

Just convert them and see what breaks :)
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