linux-kernel - Re: [PATCH v6 00/18] khwasan: kernel hardware assisted address sanitizer

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Message-ID: <CAKwvOdk=F=kja-ZznrifTO8EASmPF0CoTPWbFxpMqLk-_KGEEQ@mail.gmail.com>
Date:   Thu, 6 Sep 2018 09:39:51 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Will Deacon <will.deacon@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Christoph Lameter <cl@...ux.com>,
        Mark Rutland <mark.rutland@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        Dave Martin <dave.martin@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Ingo Molnar <mingo@...nel.org>,
        Paul Lawrence <paullawrence@...gle.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-sparse@...r.kernel.org,
        Linux Memory Management List <linux-mm@...ck.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Kostya Serebryany <kcc@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Lee Smith <Lee.Smith@....com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@....com>,
        Jacob Bramley <Jacob.Bramley@....com>,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@....com>,
        Jann Horn <jannh@...gle.com>,
        Mark Brand <markbrand@...gle.com>,
        Chintan Pandya <cpandya@...eaurora.org>,
        Vishwath Mohan <vishwath@...gle.com>
Subject: Re: [PATCH v6 00/18] khwasan: kernel hardware assisted address sanitizer

On Thu, Sep 6, 2018 at 4:06 AM Andrey Konovalov <andreyknvl@...gle.com> wrote:
>
> On Thu, Sep 6, 2018 at 12:05 PM, Will Deacon <will.deacon@....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@...gle.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?
>
> Why does it defeat the point? The point is to ease KASAN-like testing
> on devices with limited memory.

I don't disagree with using it strictly for debug.  When I say I want
the series for Pixel phones, I should have been clearer that my intent
is for a limited pool of internal testers to walk around with KHWASAN
enabled devices; not general end users.  It's hard enough today to get
anyone to test KASAN/ASAN on their "daily driver" due to the memory
usage and resulting performance.

We don't ship KASAN or KUBSAN on by default to end users (nor plan
to); it's used strictly for fuzzing through syzkaller (or by brave
"dogfooders" on the internal kernel teams).  KHWASAN would let these
dogfooders go from being brave to fearless.

-- 
Thanks,
~Nick Desaulniers