Re: [PATCH 1/2] x86/kasan: clear kasan_zero_page after TLB flush

From	Andy Lutomirski <luto@amacapital.net>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/2] x86/kasan: clear kasan_zero_page after TLB flush
Date	2016-01-18 23:30 +0100
Message-ID	<qSqtc-73V-5@gated-at.bofh.it> (permalink)
References	<qPtxg-8hk-17@gated-at.bofh.it> <qPKeK-2wl-3@gated-at.bofh.it> <qPKeL-2wl-23@gated-at.bofh.it>
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On Mon, Jan 11, 2016 at 4:51 AM, Andrey Ryabinin
<aryabinin@virtuozzo.com> wrote:
> Currently we clear kasan_zero_page before __flush_tlb_all(). This
> works with current implementation of native_flush_tlb[_global]()
> because it doesn't cause do any writes to kasan shadow memory.
> But any subtle change made in native_flush_tlb*() could break this.
> Also current code seems doesn't work for paravirt guests (lguest).
>
> Only after the TLB flush we can be sure that kasan_zero_page is not
> used as early shadow anymore (instrumented code will not write to it).
> So it should cleared it only after the TLB flush.

This seems to fix the issue with my patch set.  Thanks.

Tested-by: Andy Lutomirski <luto@kernel.org>

--Andy

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Re: [PATCH 1/2] x86/kasan: clear kasan_zero_page after TLB flush Andy Lutomirski <luto@amacapital.net> - 2016-01-18 23:30 +0100

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