linux-kernel - Re: [PATCH v5 6/6] kasan: Forbid kunit tests when async mode is enabled

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Date:   Thu, 21 Jan 2021 18:40:35 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Vincenzo Frascino <vincenzo.frascino@....com>
Cc:     Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>
Subject: Re: [PATCH v5 6/6] kasan: Forbid kunit tests when async mode is enabled

On Thu, Jan 21, 2021 at 5:40 PM Vincenzo Frascino
<vincenzo.frascino@....com> wrote:
>
> Architectures supported by KASAN_HW_TAGS can provide a sync or async
> mode of execution. KASAN KUNIT tests can be executed only when sync
> mode is enabled.
>
> Forbid the execution of the KASAN KUNIT tests when async mode is
> enabled.
>
> Cc: Dmitry Vyukov <dvyukov@...gle.com>
> Cc: Andrey Ryabinin <aryabinin@...tuozzo.com>
> Cc: Alexander Potapenko <glider@...gle.com>
> Cc: Andrey Konovalov <andreyknvl@...gle.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@....com>
> ---
>  lib/test_kasan.c | 5 +++++
>  mm/kasan/kasan.h | 2 ++
>  2 files changed, 7 insertions(+)
>
> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> index 7285dcf9fcc1..1306f707b4fe 100644
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -52,6 +52,11 @@ static int kasan_test_init(struct kunit *test)
>                 return -1;
>         }
>
> +       if (!hw_is_mode_sync()) {
> +               kunit_err(test, "can't run KASAN tests in async mode");
> +               return -1;
> +       }

I'd rather implement this check at the KASAN level, than in arm64
code. Just the way kasan_stack_collection_enabled() is implemented.

Feel free to drop this change and the previous patch, I'll implement
this myself later.

> +
>         multishot = kasan_save_enable_multi_shot();
>         hw_set_tagging_report_once(false);
>         return 0;
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 3923d9744105..3464113042ab 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -296,6 +296,7 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
>
>  #define hw_enable_tagging_sync()               arch_enable_tagging_sync()
>  #define hw_enable_tagging_async()              arch_enable_tagging_async()
> +#define hw_is_mode_sync()                      arch_is_mode_sync()
>  #define hw_init_tags(max_tag)                  arch_init_tags(max_tag)
>  #define hw_set_tagging_report_once(state)      arch_set_tagging_report_once(state)
>  #define hw_get_random_tag()                    arch_get_random_tag()
> @@ -306,6 +307,7 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
>
>  #define hw_enable_tagging_sync()
>  #define hw_enable_tagging_async()
> +#define hw_is_mode_sync()
>  #define hw_set_tagging_report_once(state)
>
>  #endif /* CONFIG_KASAN_HW_TAGS */
> --
> 2.30.0
>