netdev - Re: net: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected in skb_array

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Date:   Sat, 18 Feb 2017 18:28:39 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Cong Wang <xiyou.wangcong@...il.com>,
        netdev <netdev@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: net: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected in skb_array_produce

On Fri, Feb 10, 2017 at 6:17 AM, Jason Wang <jasowang@...hat.com> wrote:
>
>
> On 2017年02月10日 02:10, Michael S. Tsirkin wrote:
>>
>> On Thu, Feb 09, 2017 at 05:02:31AM -0500, Jason Wang wrote:
>>>
>>> ----- Original Message -----
>>>>
>>>> Hello,
>>>>
>>>> I've got the following report while running syzkaller fuzzer on mmotm
>>>> (git://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git)
>>>> remotes/mmotm/auto-latest ee4ba7533626ba7bf2f8b992266467ac9fdc045e:
>>>>
>>> [...]
>>>
>>>> other info that might help us debug this:
>>>>
>>>>   Possible interrupt unsafe locking scenario:
>>>>
>>>>         CPU0                    CPU1
>>>>         ----                    ----
>>>>    lock(&(&r->consumer_lock)->rlock);
>>>>                                 local_irq_disable();
>>>>                                 lock(&(&r->producer_lock)->rlock);
>>>>                                 lock(&(&r->consumer_lock)->rlock);
>>>>    <Interrupt>
>>>>      lock(&(&r->producer_lock)->rlock);
>>>>
>>> Thanks a lot for the testing.
>>>
>>> Looks like we could address this by using skb_array_consume_bh() instead.
>>>
>>> Could you pls verify if the following patch works?
>>
>> I think we should use _bh for the produce call as well,
>> since resizing takes the producer lock.
>
> Looks not since irq was disabled during resizing?


Hello,

Is there a fix for this that we can pick up?
This killed 10'000 VMs on our testing infra over the last day. Still
happening on linux-next.

Thanks