linux-kernel - Re: [PATCH v9 3/4] kasan: Add report for async mode

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Date:   Fri, 29 Jan 2021 18:40:57 +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>,
        Andrew Morton <akpm@...ux-foundation.org>,
        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 v9 3/4] kasan: Add report for async mode

On Tue, Jan 26, 2021 at 2:46 PM Vincenzo Frascino
<vincenzo.frascino@....com> wrote:
>
> KASAN provides an asynchronous mode of execution.
>
> Add reporting functionality for this mode.
>
> Cc: Dmitry Vyukov <dvyukov@...gle.com>
> Cc: Andrey Ryabinin <aryabinin@...tuozzo.com>
> Cc: Alexander Potapenko <glider@...gle.com>
> Cc: Andrey Konovalov <andreyknvl@...gle.com>
> Reviewed-by: Andrey Konovalov <andreyknvl@...gle.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@....com>
> ---
>  include/linux/kasan.h |  6 ++++++
>  mm/kasan/report.c     | 13 +++++++++++++
>  2 files changed, 19 insertions(+)
>
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index bb862d1f0e15..b6c502dad54d 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -360,6 +360,12 @@ static inline void *kasan_reset_tag(const void *addr)
>
>  #endif /* CONFIG_KASAN_SW_TAGS || CONFIG_KASAN_HW_TAGS*/
>
> +#ifdef CONFIG_KASAN_HW_TAGS
> +
> +void kasan_report_async(void);
> +
> +#endif /* CONFIG_KASAN_HW_TAGS */
> +
>  #ifdef CONFIG_KASAN_SW_TAGS
>  void __init kasan_init_sw_tags(void);
>  #else
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index 87b271206163..69bad9c01aed 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -360,6 +360,19 @@ void kasan_report_invalid_free(void *object, unsigned long ip)
>         end_report(&flags, (unsigned long)object);
>  }
>
> +#ifdef CONFIG_KASAN_HW_TAGS
> +void kasan_report_async(void)
> +{
> +       unsigned long flags;
> +
> +       start_report(&flags);
> +       pr_err("BUG: KASAN: invalid-access\n");
> +       pr_err("Asynchronous mode enabled: no access details available\n");
> +       dump_stack();
> +       end_report(&flags);

This conflicts with "kasan: use error_report_end tracepoint" that's in mm.

I suggest to call end_report(&flags, 0) here and check addr !=0 in
end_report() before calling trace_error_report_end().

> +}
> +#endif /* CONFIG_KASAN_HW_TAGS */
> +
>  static void __kasan_report(unsigned long addr, size_t size, bool is_write,
>                                 unsigned long ip)
>  {
> --
> 2.30.0
>