linux-kernel - Re: [PATCH v4 3/5] kasan: support alloca() poisoning

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Date:   Tue, 5 Dec 2017 19:36:34 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Paul Lawrence <paullawrence@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, linux-kbuild@...r.kernel.org,
        Matthias Kaehlcke <mka@...omium.org>,
        Michael Davidson <md@...gle.com>,
        Greg Hackmann <ghackmann@...gle.com>
Subject: Re: [PATCH v4 3/5] kasan: support alloca() poisoning

On 12/04/2017 10:17 PM, Paul Lawrence wrote:
> clang's AddressSanitizer implementation adds redzones on either side of
> alloca()ed buffers.  These redzones are 32-byte aligned and at least 32
> bytes long.
> 
> __asan_alloca_poison() is passed the size and address of the allocated
> buffer, *excluding* the redzones on either side.  The left redzone will
> always be to the immediate left of this buffer; but AddressSanitizer may
> need to add padding between the end of the buffer and the right redzone.
> If there are any 8-byte chunks inside this padding, we should poison
> those too.
> 
> __asan_allocas_unpoison() is just passed the top and bottom of the
> dynamic stack area, so unpoisoning is simpler.
> 
> Signed-off-by: Greg Hackmann <ghackmann@...gle.com>
> Signed-off-by: Paul Lawrence <paullawrence@...gle.com>
> ---

Acked-by: Andrey Ryabinin <aryabinin@...tuozzo.com>