linux-kernel - Re: kernel BUG at mm/mempolicy.c:1699!

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Date:	Fri, 29 Jul 2016 21:16:29 +0200
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	Vegard Nossum <vegard.nossum@...cle.com>
Cc:	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Alexander Potapenko <glider@...gle.com>,
	kasan-dev <kasan-dev@...glegroups.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>
Subject: Re: kernel BUG at mm/mempolicy.c:1699!

On Fri, Jul 29, 2016 at 9:10 PM, Vegard Nossum <vegard.nossum@...cle.com> wrote:
> On 07/29/2016 08:05 PM, Dmitry Vyukov wrote:
>>
>> On Fri, Jul 29, 2016 at 7:57 PM, Vegard Nossum <vegard.nossum@...cle.com>
>> wrote:
>>>
>>> ------------[ cut here ]------------
>>> kernel BUG at mm/mempolicy.c:1699!
>
> [...]
>>>
>>> In particular, it's interesting that the kernel/exit.c line is
>>>
>>>      mpol_put(tsk->mempolicy);
>>>
>>> and alloc_pages_current() does (potentially):
>>>
>>>      pol = get_task_policy(current);.
>>>
>>> The bug seems very new or very rare or both.
>>
>>
>> This is https://github.com/google/kasan/issues/35
>> It is introduced with stackdepot.
>
>
> Ah, cool.
>
> Would it be enough to set __GFP_THISNODE in depot_save_stack() so it
> uses &default_policy instead of current->mempolicy?

I don't have deep understanding of that code. But looks at the code,
using &default_policy should help.