netdev - Re: crash in __xfrm_state

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Message-ID: <70a8c07d-effc-012d-5513-656e172e882e@akamai.com>
Date:   Mon, 16 Dec 2019 12:34:30 -0800
From:   Josh Hunt <johunt@...mai.com>
To:     Steffen Klassert <steffen.klassert@...unet.com>,
        Florian Westphal <fw@...len.de>
Cc:     herbert@...dor.apana.org.au, David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>
Subject: Re: crash in __xfrm_state_lookup on 4.19 LTS

On 12/13/19 3:13 AM, Steffen Klassert wrote:
> On Fri, Dec 13, 2019 at 11:25:12AM +0100, Florian Westphal wrote:
>> Steffen Klassert <steffen.klassert@...unet.com> wrote:
>>>
>>> We destroy the states with a workqueue by doing schedule_work().
>>> I think we should better use call_rcu to make sure that a
>>> rcu grace period has elapsed before the states are destroyed.
>>
>> xfrm_state_gc_task calls synchronize_rcu after stealing the gc list and
>> before destroying those states, so I don't think this is a problem.
> 
> That's true, I've missed this. In that case, I don't
> have an idea what is the root cause of these crashes.
> We need to find a way to reproduce it.
> 

Thanks. I will try reproducing. Please let me know if you have any 
suggestions on how I may be able to trigger this behavior.

Josh