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References: <20210626100931.22794-1-Kuan-Ying.Lee@mediatek.com> <20210626100931.22794-4-Kuan-Ying.Lee@mediatek.com>
In-Reply-To: <20210626100931.22794-4-Kuan-Ying.Lee@mediatek.com>
From:   Marco Elver <elver@google.com>
Date:   Mon, 28 Jun 2021 08:00:00 +0200
Message-ID: <CANpmjNMyHQuUF1KwGj7cMgWVL-TifC52uZu54GgtS9SziyuXdg@mail.gmail.com>
Subject: Re: [PATCH v4 3/3] kasan: add memory corruption identification
 support for hardware tag-based mode
To:     Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
Cc:     Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Alexander Potapenko <glider@google.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, wsd_upstream@mediatek.com,
        chinwen.chang@mediatek.com, nicholas.tang@mediatek.com
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On Sat, 26 Jun 2021 at 12:09, Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> wrote:
>
> Add memory corruption identification support for hardware tag-based
> mode. We store one old free pointer tag and free backtrace instead
> of five because hardware tag-based kasan only has 16 different tags.
>
> If we store as many stacks as SW tag-based kasan does(5 stacks),
> there is high probability to find the same tag in the stacks when
> out-of-bound issues happened and we will mistake out-of-bound
> issue for use-after-free.
>
> Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
> Suggested-by: Marco Elver <elver@google.com>
> Reviewed-by: Alexander Potapenko <glider@google.com>
> Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>

Reviewed-by: Marco Elver <elver@google.com>


> ---
>  lib/Kconfig.kasan | 2 +-
>  mm/kasan/kasan.h  | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index fdb4a08dba83..1e2d10f86011 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -169,7 +169,7 @@ config KASAN_STACK
>
>  config KASAN_TAGS_IDENTIFY
>         bool "Enable memory corruption identification"
> -       depends on KASAN_SW_TAGS
> +       depends on KASAN_SW_TAGS || KASAN_HW_TAGS
>         help
>           This option enables best-effort identification of bug type
>           (use-after-free or out-of-bounds) at the cost of increased
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 952df2db7fdd..f58672f6029a 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -153,7 +153,7 @@ struct kasan_track {
>         depot_stack_handle_t stack;
>  };
>
> -#ifdef CONFIG_KASAN_TAGS_IDENTIFY
> +#if defined(CONFIG_KASAN_TAGS_IDENTIFY) && defined(CONFIG_KASAN_SW_TAGS)
>  #define KASAN_NR_FREE_STACKS 5
>  #else
>  #define KASAN_NR_FREE_STACKS 1
> --
> 2.18.0