linux-kernel - Re: [PATCH v2 04/20] kasan, arm64: unpoison stack only with CONFIG_KASAN

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Message-ID: <20201112095134.GI29613@gaia>
Date:   Thu, 12 Nov 2020 09:51:35 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Will Deacon <will.deacon@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev@...glegroups.com, linux-arm-kernel@...ts.infradead.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 04/20] kasan, arm64: unpoison stack only with
 CONFIG_KASAN_STACK

On Tue, Nov 10, 2020 at 11:20:08PM +0100, Andrey Konovalov wrote:
> There's a config option CONFIG_KASAN_STACK that has to be enabled for
> KASAN to use stack instrumentation and perform validity checks for
> stack variables.
> 
> There's no need to unpoison stack when CONFIG_KASAN_STACK is not enabled.
> Only call kasan_unpoison_task_stack[_below]() when CONFIG_KASAN_STACK is
> enabled.
> 
> Note, that CONFIG_KASAN_STACK is an option that is currently always
> defined when CONFIG_KASAN is enabled, and therefore has to be tested
> with #if instead of #ifdef.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> Link: https://linux-review.googlesource.com/id/If8a891e9fe01ea543e00b576852685afec0887e3
> ---
>  arch/arm64/kernel/sleep.S        |  2 +-
>  arch/x86/kernel/acpi/wakeup_64.S |  2 +-
>  include/linux/kasan.h            | 10 ++++++----
>  mm/kasan/common.c                |  2 ++
>  4 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
> index ba40d57757d6..bdadfa56b40e 100644
> --- a/arch/arm64/kernel/sleep.S
> +++ b/arch/arm64/kernel/sleep.S
> @@ -133,7 +133,7 @@ SYM_FUNC_START(_cpu_resume)
>  	 */
>  	bl	cpu_do_resume
>  
> -#ifdef CONFIG_KASAN
> +#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
>  	mov	x0, sp
>  	bl	kasan_unpoison_task_stack_below
>  #endif

I don't understand why CONFIG_KASAN_STACK is not a bool (do you plan to
add more values to it?) but for arm64:

Acked-by: Catalin Marinas <catalin.marinas@....com>