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From:   Andrey Konovalov <andreyknvl@gmail.com>
Date:   Tue, 20 Jun 2023 19:19:06 +0200
Message-ID: <CA+fCnZe4cetv53bGM0cOxLGB+ZDiNU7eeSb2LKNkO2j4xCPkYQ@mail.gmail.com>
Subject: Re: [PATCH] kasan, doc: note kasan.fault=panic_on_write behaviour for
 async modes
To:     Marco Elver <elver@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Taras Madan <tarasmadan@google.com>,
        Aleksandr Nogikh <nogikh@google.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Jonathan Corbet <corbet@lwn.net>, kasan-dev@googlegroups.com,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, Catalin Marinas <catalin.marinas@arm.com>
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On Tue, Jun 20, 2023 at 7:17=E2=80=AFPM Marco Elver <elver@google.com> wrot=
e:
>
> Note the behaviour of kasan.fault=3Dpanic_on_write for async modes, since
> all asynchronous faults will result in panic (even if they are reads).
>
> Fixes: 452c03fdbed0 ("kasan: add support for kasan.fault=3Dpanic_on_write=
")
> Signed-off-by: Marco Elver <elver@google.com>
> ---
>  Documentation/dev-tools/kasan.rst | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/=
kasan.rst
> index 7f37a46af574..f4acf9c2e90f 100644
> --- a/Documentation/dev-tools/kasan.rst
> +++ b/Documentation/dev-tools/kasan.rst
> @@ -110,7 +110,9 @@ parameter can be used to control panic and reporting =
behaviour:
>  - ``kasan.fault=3Dreport``, ``=3Dpanic``, or ``=3Dpanic_on_write`` contr=
ols whether
>    to only print a KASAN report, panic the kernel, or panic the kernel on
>    invalid writes only (default: ``report``). The panic happens even if
> -  ``kasan_multi_shot`` is enabled.
> +  ``kasan_multi_shot`` is enabled. Note that when using asynchronous mod=
e of
> +  Hardware Tag-Based KASAN, ``kasan.fault=3Dpanic_on_write`` always pani=
cs on
> +  asynchronously checked accesses (including reads).
>
>  Software and Hardware Tag-Based KASAN modes (see the section about vario=
us
>  modes below) support altering stack trace collection behavior:
> --
> 2.41.0.185.g7c58973941-goog
>

Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>