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From: Andrey Konovalov <andreyknvl@google.com>
Date: Wed, 19 Sep 2018 20:53:52 +0200
Message-ID: <CAAeHK+x1MO4Q+11No8prngHCspy36EoPVv01SvQBsyuOYCKUcQ@mail.gmail.com>
Subject: Re: [PATCH v6 00/18] khwasan: kernel hardware assisted address sanitizer
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To: Will Deacon <will.deacon@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Andrey Ryabinin <aryabinin@virtuozzo.com>, Alexander Potapenko <glider@google.com>, Dmitry Vyukov <dvyukov@google.com>, Catalin Marinas <catalin.marinas@arm.com>, Christoph Lameter <cl@linux.com>, Mark Rutland <mark.rutland@arm.com>, Nick Desaulniers <ndesaulniers@google.com>, Marc Zyngier <marc.zyngier@arm.com>, Dave Martin <dave.martin@arm.com>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, "Eric W . Biederman" <ebiederm@xmission.com>, Ingo Molnar <mingo@kernel.org>, Paul Lawrence <paullawrence@google.com>, Geert Uytterhoeven <geert@linux-m68k.org>, Arnd Bergmann <arnd@arndb.de>, "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Kate Stewart <kstewart@linuxfoundation.org>, Mike Rapoport <rppt@linux.vnet.ibm.com>, kasan-dev <kasan-dev@googlegroups.com>, "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>, Linux ARM <linux-arm-kernel@lists.infradead.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>, Jann Horn <jannh@google.com>, Mark Brand <markbrand@google.com>, Chintan Pandya <cpandya@codeaurora.org>, Vishwath Mohan <vishwath@google.com>

On Fri, Sep 14, 2018 at 5:28 PM, Will Deacon <will.deacon@arm.com> wrote:
> On Thu, Sep 06, 2018 at 01:06:23PM +0200, Andrey Konovalov wrote:
>> On Thu, Sep 6, 2018 at 12:05 PM, Will Deacon <will.deacon@arm.com> wrote:
>> > On Wed, Sep 05, 2018 at 02:10:32PM -0700, Andrew Morton wrote:
>> >> On Wed, 29 Aug 2018 13:35:04 +0200 Andrey Konovalov <andreyknvl@google.com> wrote:
>> >>
>> >> > This patchset adds a new mode to KASAN [1], which is called KHWASAN
>> >> > (Kernel HardWare assisted Address SANitizer).
>> >>
>> >> We're at v6 and there are no reviewed-by's or acked-by's to be seen.
>> >> Is that a fair commentary on what has been happening, or have people
>> >> been remiss in sending and gathering such things?
>> >
>> > I still have concerns about the consequences of merging this as anything
>> > other than a debug option [1]. Unfortunately, merging it as a debug option
>> > defeats the whole point, so I think we need to spend more effort on developing
>> > tools that can help us to find and fix the subtle bugs which will arise from
>> > enabling tagged pointers in the kernel.
>>
>> I totally don't mind calling it a debug option. Do I need to somehow
>> specify it somewhere?
>
> Ok, sorry, I completely misunderstood you earlier on then! For some reason
> I thought you wanted this on by default.
>
> In which case, I'm ok with the overall idea as long as we make the caveats
> clear in the Kconfig text. In particular, that enabling this option may
> introduce problems relating to pointer casting and comparison, but can
> offer better coverage and lower memory consumption than a fully
> software-based KASAN solution.

Great! I'll explicitly call it debug feature and mention the caveats
in v7. Thanks!