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

From	Dmitry Vyukov <dvyukov@google.com>
Newsgroups	linux.kernel
Subject	Re: kernel BUG at mm/mempolicy.c:1699!
Date	2016-07-29 21:20 +0200
Message-ID	<s0lua-qL-7@gated-at.bofh.it> (permalink)
References	<s0keK-7S4-25@gated-at.bofh.it> <s0koq-8aN-25@gated-at.bofh.it> <s0lua-qL-9@gated-at.bofh.it>
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On Fri, Jul 29, 2016 at 9:10 PM, Vegard Nossum <vegard.nossum@oracle.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@oracle.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.

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kernel BUG at mm/mempolicy.c:1699! Vegard Nossum <vegard.nossum@oracle.com> - 2016-07-29 20:00 +0200
  Re: kernel BUG at mm/mempolicy.c:1699! Dmitry Vyukov <dvyukov@google.com> - 2016-07-29 20:10 +0200
    Re: kernel BUG at mm/mempolicy.c:1699! Vegard Nossum <vegard.nossum@oracle.com> - 2016-07-29 21:20 +0200
      Re: kernel BUG at mm/mempolicy.c:1699! Dmitry Vyukov <dvyukov@google.com> - 2016-07-29 21:20 +0200

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