linux-kernel - Re: [PATCH 29/31] kasan, arm64: allow KASAN_VMALLOC with HW

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Message-ID: <CA+fCnZdJCCRNLWD0QdgrXTocwDMroQ_MsBNi36N3JBG-UiVNvw@mail.gmail.com>
Date:   Mon, 6 Dec 2021 22:10:29 +0100
From:   Andrey Konovalov <andreyknvl@...il.com>
To:     Marco Elver <elver@...gle.com>
Cc:     andrey.konovalov@...ux.dev,
        Alexander Potapenko <glider@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Peter Collingbourne <pcc@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Will Deacon <will@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Evgenii Stepanov <eugenis@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH 29/31] kasan, arm64: allow KASAN_VMALLOC with HW_TAGS

On Wed, Dec 1, 2021 at 12:35 PM Marco Elver <elver@...gle.com> wrote:
>
> On Tue, Nov 30, 2021 at 11:08PM +0100, andrey.konovalov@...ux.dev wrote:
> > From: Andrey Konovalov <andreyknvl@...gle.com>
> >
> > vmalloc tagging support for HW_TAGS KASAN is now complete.
> >
> > Allow enabling CONFIG_KASAN_VMALLOC.
>
> This actually doesn't "allow" enabling it, it unconditionally enables it
> and a user can't disable CONFIG_KASAN_VMALLOC.
>
> I found some background in acc3042d62cb9 why arm64 wants this.

Indeed. Will adjust the description in v2.

> > Also adjust CONFIG_KASAN_VMALLOC description:
> >
> > - Mention HW_TAGS support.
> > - Remove unneeded internal details: they have no place in Kconfig
> >   description and are already explained in the documentation.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> > ---
> >  arch/arm64/Kconfig |  3 +--
> >  lib/Kconfig.kasan  | 20 ++++++++++----------
> >  2 files changed, 11 insertions(+), 12 deletions(-)
> >
> > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> > index c05d7a06276f..5981e5460c51 100644
> > --- a/arch/arm64/Kconfig
> > +++ b/arch/arm64/Kconfig
> > @@ -205,8 +205,7 @@ config ARM64
> >       select IOMMU_DMA if IOMMU_SUPPORT
> >       select IRQ_DOMAIN
> >       select IRQ_FORCED_THREADING
> > -     select KASAN_VMALLOC if KASAN_GENERIC
> > -     select KASAN_VMALLOC if KASAN_SW_TAGS
> > +     select KASAN_VMALLOC
>
> This produces the following warning when making an arm64 defconfig:
>
>  | WARNING: unmet direct dependencies detected for KASAN_VMALLOC
>  |   Depends on [n]: KASAN [=n] && HAVE_ARCH_KASAN_VMALLOC [=y]
>  |   Selected by [y]:
>  |   - ARM64 [=y]
>  |
>  | WARNING: unmet direct dependencies detected for KASAN_VMALLOC
>  |   Depends on [n]: KASAN [=n] && HAVE_ARCH_KASAN_VMALLOC [=y]
>  |   Selected by [y]:
>  |   - ARM64 [=y]
>
> To unconditionally select KASAN_VMALLOC, it should probably be
>
>         select KASAN_VMALLOC if KASAN

Will fix in v2.

Thanks!