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From: Andrey Konovalov <andreyknvl@google.com>
Date: Fri, 9 Mar 2018 19:42:19 +0100
Message-ID: <CAAeHK+zyGQtNxap6N5s11MWrQS-Y_uA7TRQnh5oP=HWZjPytsw@mail.gmail.com>
Subject: Re: [RFC PATCH 06/14] khwasan: enable top byte ignore for the kernel
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To: Marc Zyngier <marc.zyngier@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>, Andrey Ryabinin <aryabinin@virtuozzo.com>, Alexander Potapenko <glider@google.com>, Dmitry Vyukov <dvyukov@google.com>, Jonathan Corbet <corbet@lwn.net>, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will.deacon@arm.com>, Theodore Ts'o <tytso@mit.edu>, Jan Kara <jack@suse.com>, Christopher Li <sparse@chrisli.org>, Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Andrew Morton <akpm@linux-foundation.org>, Masahiro Yamada <yamada.masahiro@socionext.com>, Michal Marek <michal.lkml@markovi.net>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, Yury Norov <ynorov@caviumnetworks.com>, Nick Desaulniers <ndesaulniers@google.com>, Suzuki K Poulose <suzuki.poulose@arm.com>, Kristina Martsenko <kristina.martsenko@arm.com>, Punit Agrawal <punit.agrawal@arm.com>, Dave Martin <Dave.Martin@arm.com>, James Morse <james.morse@arm.com>, Julien Thierry <julien.thierry@arm.com>, Michael Weiser <michael.weiser@gmx.de>, Steve Capper <steve.capper@arm.com>, Ingo Molnar <mingo@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Sandipan Das <sandipan@linux.vnet.ibm.com>, Paul Lawrence <paullawrence@google.com>, David Woodhouse <dwmw@amazon.co.uk>, Kees Cook <keescook@chromium.org>, Geert Uytterhoeven <geert@linux-m68k.org>, Josh Poimboeuf <jpoimboe@redhat.com>, Arnd Bergmann <arnd@arndb.de>, kasan-dev <kasan-dev@googlegroups.com>, linux-doc@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>, Linux ARM <linux-arm-kernel@lists.infradead.org>, linux-ext4@vger.kernel.org, linux-sparse@vger.kernel.org, Linux Memory Management List <linux-mm@kvack.org>, Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>, Kostya Serebryany <kcc@google.com>, Evgeniy Stepanov <eugenis@google.com>, Lee Smith <Lee.Smith@arm.com>, Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>, Jacob Bramley <Jacob.Bramley@arm.com>, Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>, Kees Cook <keescook@google.com>, Jann Horn <jannh@google.com>, Mark Brand <markbrand@google.com>

On Fri, Mar 9, 2018 at 7:32 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
> Well, that's not quite how it works. KVM is an integral part of the
> kernel, and I don't really want to have to deal with regression (not to
> mention that KVM is an essential tool in our testing infrastructure).
>
> You could try and exclude KVM from the instrumentation (which we already
> have for invasive things such as KASAN), but I'm afraid that having a
> debugging option that conflicts with another essential part of the
> kernel is not an option.
>
> I'm happy to help you with that though.
>

Hm, KHWASAN instruments the very same parts of the kernel that KASAN
does (it reuses the same flag). I've checked, I actually have
CONFIG_KVM enabled in my test build, however I haven't tried to test
KVM yet. I'm planning to perform extensive fuzzing of the kernel with
syzkaller, so if there's any crashes caused by KHWASAN in kvm code
I'll see them. However if some bugs don't manifest as crashes, that
would be a difficult thing to detect for me.

Thanks!