linux-kernel - Re: [PATCH v12 7/7] kasan: don't run tests in async mode

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Message-ID: <79183efe-ef9e-0a31-cdfa-e1bfae39b015@arm.com>
Date:   Tue, 9 Feb 2021 17:37:05 +0000
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     Andrey Konovalov <andreyknvl@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>
Cc:     Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Will Deacon <will@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Subject: Re: [PATCH v12 7/7] kasan: don't run tests in async mode

Hi Andrey,

On 2/9/21 5:26 PM, Andrey Konovalov wrote:
> On Tue, Feb 9, 2021 at 6:07 PM Catalin Marinas <catalin.marinas@....com> wrote:
>>
>> On Tue, Feb 09, 2021 at 04:02:25PM +0100, Andrey Konovalov wrote:
>>> On Tue, Feb 9, 2021 at 1:16 PM Vincenzo Frascino
>>> <vincenzo.frascino@....com> wrote:
>>>> On 2/9/21 12:02 PM, Catalin Marinas wrote:
>>>>> On Mon, Feb 08, 2021 at 04:56:17PM +0000, Vincenzo Frascino wrote:
>>>>>> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
>>>>>> index 7285dcf9fcc1..f82d9630cae1 100644
>>>>>> --- a/lib/test_kasan.c
>>>>>> +++ b/lib/test_kasan.c
>>>>>> @@ -51,6 +51,10 @@ static int kasan_test_init(struct kunit *test)
>>>>>>              kunit_err(test, "can't run KASAN tests with KASAN disabled");
>>>>>>              return -1;
>>>>>>      }
>>>>>> +    if (kasan_flag_async) {
>>>>>> +            kunit_err(test, "can't run KASAN tests in async mode");
>>>>>> +            return -1;
>>>>>> +    }
>>>>>>
>>>>>>      multishot = kasan_save_enable_multi_shot();
>>>>>>      hw_set_tagging_report_once(false);
>>>>>
>>>>> I think we can still run the kasan tests in async mode if we check the
>>>>> TFSR_EL1 at the end of each test by calling mte_check_tfsr_exit().
>>>>>
>>>>
>>>> IIUC this was the plan for the future. But I let Andrey comment for more details.
>>>
>>> If it's possible to implement, then it would be good to have. Doesn't
>>> have to be a part of this series though.
>>
>> I think it can be part of this series but after the 5.12 merging window
>> (we are a few days away from final 5.11 and I don't think we should
>> rush the MTE kernel async support in).
>>
>> It would be nice to have the kasan tests running with async by the time
>> we merge the patches (at a quick look, I think it's possible but, of
>> course, we may hit some blockers when implementing it).
> 
> OK, sounds good.
> 
> If it's possible to put an explicit check for tag faults at the end of
> each test, then adding async support shouldn't be hard.
> 
> Note, that some of the tests trigger bugs that are detected via
> explicit checks within KASAN. For example, KASAN checks that a pointer
> that's being freed points to a start of a slab object, or that the
> object is accessible when it gets freed, etc. I don't see this being a
> problem, so just FYI.
> 

Once you have your patches ready please send them to me and I will repost
another version. In the meantime I will address the remaining comments.

> Thanks!
> 

-- 
Regards,
Vincenzo