linux-kernel - Re: [PATCH RFC v2 05/21] kasan: allow VMAP_STACK for HW

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Date:   Tue, 27 Oct 2020 13:49:19 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Peter Collingbourne <pcc@...gle.com>,
        Serban Constantinescu <serbanc@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Elena Petrova <lenaptr@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v2 05/21] kasan: allow VMAP_STACK for HW_TAGS mode

On Thu, Oct 22, 2020 at 3:19 PM Andrey Konovalov <andreyknvl@...gle.com> wrote:
>
> Even though hardware tag-based mode currently doesn't support checking
> vmalloc allocations, it doesn't use shadow memory and works with
> VMAP_STACK as is.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> Link: https://linux-review.googlesource.com/id/I3552cbc12321dec82cd7372676e9372a2eb452ac
> ---
>  arch/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index af14a567b493..3caf7bcdcf93 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -868,7 +868,7 @@ config VMAP_STACK
>         default y
>         bool "Use a virtually-mapped stack"
>         depends on HAVE_ARCH_VMAP_STACK
> -       depends on !KASAN || KASAN_VMALLOC
> +       depends on !(KASAN_GENERIC || KASAN_SW_TAGS) || KASAN_VMALLOC

I find it a bit simpler to interpret:

    depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC

due to simpler structure. But maybe it's just me.

>         help
>           Enable this if you want the use virtually-mapped kernel stacks
>           with guard pages.  This causes kernel stack overflows to be
> --
> 2.29.0.rc1.297.gfa9743e501-goog
>