Re: [PATCH v2 04/20] kasan, arm64: unpoison stack only with CONFIG_KASAN_STACK

From: Catalin Marinas
Date: Thu Nov 12 2020 - 04:51:44 EST


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@xxxxxxxxxx>
> 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@xxxxxxx>