linux-kernel - Re: [PATCH] framewarn: expand KASAN

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Date:   Fri, 21 Sep 2018 10:42:08 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Andy Lutomirski <luto@...nel.org>,
        kasan-dev <kasan-dev@...glegroups.com>
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] framewarn: expand KASAN_EXTRA exception to KASAN

On Fri, Sep 21, 2018 at 3:50 AM, Andy Lutomirski <luto@...nel.org> wrote:
> This patch seems reasonable, but you emailed the wrong people :)
>
> On Thu, Sep 20, 2018 at 5:15 PM Jason A. Donenfeld <Jason@...c4.com> wrote:
>>
>> It turns out that KASAN in general will bloat stack frames in unexpected
>> ways, not just KASAN_EXTRA. So, this patch trivially changes that
>> default to be associated with KASAN instead of KASAN_EXTRA.
>>
>> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
>> ---
>>  lib/Kconfig.debug | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>> index 4966c4fbe7f7..39078a080e29 100644
>> --- a/lib/Kconfig.debug
>> +++ b/lib/Kconfig.debug
>> @@ -222,7 +222,7 @@ config ENABLE_MUST_CHECK
>>  config FRAME_WARN
>>         int "Warn for stack frames larger than (needs gcc 4.4)"
>>         range 0 8192
>> -       default 3072 if KASAN_EXTRA
>> +       default 3072 if KASAN
>>         default 2048 if GCC_PLUGIN_LATENT_ENTROPY
>>         default 1280 if (!64BIT && PARISC)
>>         default 1024 if (!64BIT && !PARISC)


Looks fine to me.
KASAN always increases stack size too for exactly that reason, so it's
reasonable to allow larger frames rather than try to massage code
every here and there to fit into the normal frame size.

Acked-by: Dmitry Vyukov <dvyukov@...gle.com>

Thanks