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From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Thu, 27 Aug 2020 14:02:25 +0200
Message-ID: <CAAeHK+yYeYJqkxiQD7F_VBzUmJ3Tx4W6huUUJ4Sk7auiA=UkoQ@mail.gmail.com>
Subject: Re: [PATCH 19/35] kasan: don't allow SW_TAGS with ARM64_MTE
To:     Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Marco Elver <elver@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        Elena Petrova <lenaptr@google.com>,
        Branislav Rankov <Branislav.Rankov@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Thu, Aug 27, 2020 at 11:52 AM Vincenzo Frascino
<vincenzo.frascino@arm.com> wrote:
>
> Hi Andrey,
>
> On 8/27/20 9:04 AM, Catalin Marinas wrote:
> > On Fri, Aug 14, 2020 at 07:27:01PM +0200, Andrey Konovalov wrote:
> >> Software tag-based KASAN provides its own tag checking machinery that
> >> can conflict with MTE. Don't allow enabling software tag-based KASAN
> >> when MTE is enabled.
> >>
> >> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> >> ---
> >>  lib/Kconfig.kasan | 1 +
> >>  1 file changed, 1 insertion(+)
> >>
> >> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> >> index b4cf6c519d71..e500c18cbe79 100644
> >> --- a/lib/Kconfig.kasan
> >> +++ b/lib/Kconfig.kasan
> >> @@ -69,6 +69,7 @@ config KASAN_GENERIC
> >>  config KASAN_SW_TAGS
> >>      bool "Software tag-based mode"
> >>      depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS
> >> +    depends on !ARM64_MTE
> >
> > I think that's better as:
> >
> > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> > index 10cf81d70657..736c32bd8905 100644
> > --- a/arch/arm64/Kconfig
> > +++ b/arch/arm64/Kconfig
> > @@ -131,7 +131,7 @@ config ARM64
> >       select HAVE_ARCH_JUMP_LABEL
> >       select HAVE_ARCH_JUMP_LABEL_RELATIVE
> >       select HAVE_ARCH_KASAN if !(ARM64_16K_PAGES && ARM64_VA_BITS_48)
> > -     select HAVE_ARCH_KASAN_SW_TAGS if HAVE_ARCH_KASAN
> > +     select HAVE_ARCH_KASAN_SW_TAGS if HAVE_ARCH_KASAN && !ARM64_MTE
> >       select HAVE_ARCH_KGDB
> >       select HAVE_ARCH_MMAP_RND_BITS
> >       select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
> >
>
> I agree with Catalin here, "select HAVE_ARCH_KASAN_SW_TAGS if HAVE_ARCH_KASAN &&
> !ARM64_MTE" should be sufficient.

Sounds good, will do in v2, thanks!