From: tongtiangen <tongtiangen@huawei.com>
To: Jisheng Zhang <jszhang3@mail.ustc.edu.cn>
Cc: Andreas Schwab <schwab@linux-m68k.org>,
Atish Patra <atishp@atishpatra.org>,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Albert Ou <aou@eecs.berkeley.edu>,
linux-riscv <linux-riscv@lists.infradead.org>,
"linux-kernel@vger.kernel.org List"
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH -next v2] riscv: add VMAP_STACK overflow detection
Date: Fri, 23 Jul 2021 14:49:38 +0800 [thread overview]
Message-ID: <7775c6bd-dc55-bb0b-10d9-cde5099b149a@huawei.com> (raw)
In-Reply-To: <20210723124025.669cb4ec@xhacker>
On 2021/7/23 12:40, Jisheng Zhang wrote:
> On Fri, 23 Jul 2021 12:29:25 +0800
> Jisheng Zhang <jszhang3@mail.ustc.edu.cn> wrote:
>
>> On Fri, 23 Jul 2021 09:36:47 +0800
>> tongtiangen <tongtiangen@huawei.com> wrote:
>>
>>> On 2021/7/23 7:54, Jisheng Zhang wrote:
>>>> On Thu, 22 Jul 2021 17:42:52 +0200
>>>> Andreas Schwab <schwab@linux-m68k.org> wrote:
>>>>
>>>>> On Jul 22 2021, Jisheng Zhang wrote:
>>>>>
>>>>>> I think we need to pin the stack before calling get_wchan(), could you please
>>>>>> try below patch?
>>>>>
>>>>> Thanks, this fixes the crash for me.
>>>>>
>>>>> Andreas.
>>>>>
>>>>
>>>> Thanks for testing. I will send out formal patch later
>>>>
>>>> Thanks
>>>>
>>>> .
>>>>
>>>
>>> Hi all:
>>> I tried to reproduced this crash in openSUSE code repo(
>>> https://github.com/opensuse/kernel ), but not reproduced successfully.
>>>
>>> From the patch of problem repair, the crash is due to task->stack is
>>> released before calling get_wchan, the task state of maybe TASK_DEAD.
>>>
>>> VMAP_STACK is used to detect kernel stack overflow, there is no
>>> connection between the two, it makes me a little confused.
>>
>> I believe the bug exists from the first day of riscv mainlined.
>>
>> Since THREAD_INFO_IN_TASK=y in riscv, so when task stack can be freed
>> before being destroyed.
>
> typo: task stack can be freed before task is destroyed
>
>>
>> When VMAP_STACK=n, task's stack is allocated from linear mapping. When
>> task stack is freed, the corresponding mapping still exists, and since
>> get_wchan() only read, no harm is observed so far.
>>
>> When VMAP_STACK=y, task's stack is allocated from vmalloc area. When
>> task stack is freed, the corresponding mapping may not exist, so I expect
>> MMU fault here, thus the kernel panic.
>>
>> In summary, the bug isn't related with VMAP_STACK, but VMAP_STACK makes
>> the bug observable.
>>
>> Thanks
This explanation is understandable, it is necessary to perform a stack
validity check before walk_stackframe.
Thanks
>>
>>
>>
>> _______________________________________________
>> linux-riscv mailing list
>> linux-riscv@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-riscv
>
>
> .
>
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next prev parent reply other threads:[~2021-07-23 6:50 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-21 3:28 [PATCH -next v2] riscv: add VMAP_STACK overflow detection Tong Tiangen
2021-06-21 3:28 ` Tong Tiangen
2021-07-06 20:24 ` Palmer Dabbelt
2021-07-06 20:24 ` Palmer Dabbelt
2021-07-15 16:22 ` Andreas Schwab
2021-07-15 16:22 ` Andreas Schwab
2021-07-16 12:53 ` Jisheng Zhang
2021-07-16 12:53 ` Jisheng Zhang
2021-07-16 15:53 ` Andreas Schwab
2021-07-16 15:53 ` Andreas Schwab
2021-07-17 2:18 ` Jisheng Zhang
2021-07-17 2:18 ` Jisheng Zhang
2021-07-17 6:55 ` Andreas Schwab
2021-07-17 6:55 ` Andreas Schwab
2021-07-19 3:27 ` tongtiangen
2021-07-19 3:27 ` tongtiangen
2021-07-19 7:23 ` Andreas Schwab
2021-07-19 7:23 ` Andreas Schwab
2021-07-22 6:12 ` Palmer Dabbelt
2021-07-22 6:12 ` Palmer Dabbelt
2021-07-22 8:35 ` Atish Patra
2021-07-22 8:35 ` Atish Patra
2021-07-22 13:37 ` Jisheng Zhang
2021-07-22 13:37 ` Jisheng Zhang
2021-07-22 14:24 ` Jisheng Zhang
2021-07-22 14:24 ` Jisheng Zhang
2021-07-22 15:42 ` Andreas Schwab
2021-07-22 15:42 ` Andreas Schwab
2021-07-22 23:54 ` Jisheng Zhang
2021-07-22 23:54 ` Jisheng Zhang
2021-07-23 1:36 ` tongtiangen
2021-07-23 1:36 ` tongtiangen
2021-07-23 4:29 ` Jisheng Zhang
2021-07-23 4:29 ` Jisheng Zhang
2021-07-23 4:40 ` Jisheng Zhang
2021-07-23 4:40 ` Jisheng Zhang
2021-07-23 6:49 ` tongtiangen [this message]
2021-07-22 9:02 ` Andreas Schwab
2021-07-22 9:02 ` Andreas Schwab
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