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Date:   Fri, 12 Mar 2021 16:08:24 +0100
From:   Marco Elver <elver@google.com>
To:     Andrey Konovalov <andreyknvl@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Alexander Potapenko <glider@google.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Dmitry Vyukov <dvyukov@google.com>, kasan-dev@googlegroups.com,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 05/11] kasan: docs: update boot parameters section
Message-ID: <YEuD6CIhVsSo9uqA@elver.google.com>
References: <c2bbb56eaea80ad484f0ee85bb71959a3a63f1d7.1615559068.git.andreyknvl@google.com>
 <01364952f15789948f0627d6733b5cdf5209f83a.1615559068.git.andreyknvl@google.com>
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On Fri, Mar 12, 2021 at 03:24PM +0100, Andrey Konovalov wrote:
> Update the "Boot parameters" section in KASAN documentation:
> 
> - Mention panic_on_warn.
> - Mention kasan_multi_shot and its interaction with panic_on_warn.
> - Clarify kasan.fault=panic interaction with panic_on_warn.
> - A readability clean-up.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

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

> ---
>  Documentation/dev-tools/kasan.rst | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
> index cd12c890b888..1189be9b4cb5 100644
> --- a/Documentation/dev-tools/kasan.rst
> +++ b/Documentation/dev-tools/kasan.rst
> @@ -174,10 +174,16 @@ call_rcu() and workqueue queuing.
>  Boot parameters
>  ~~~~~~~~~~~~~~~
>  
> +KASAN is affected by the generic ``panic_on_warn`` command line parameter.
> +When it is enabled, KASAN panics the kernel after printing a bug report.
> +
> +By default, KASAN prints a bug report only for the first invalid memory access.
> +With ``kasan_multi_shot``, KASAN prints a report on every invalid access. This
> +effectively disables ``panic_on_warn`` for KASAN reports.
> +
>  Hardware tag-based KASAN mode (see the section about various modes below) is
>  intended for use in production as a security mitigation. Therefore, it supports
> -boot parameters that allow to disable KASAN competely or otherwise control
> -particular KASAN features.
> +boot parameters that allow disabling KASAN or controlling its features.
>  
>  - ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``).
>  
> @@ -185,8 +191,8 @@ particular KASAN features.
>    traces collection (default: ``on``).
>  
>  - ``kasan.fault=report`` or ``=panic`` controls whether to only print a KASAN
> -  report or also panic the kernel (default: ``report``). Note, that tag
> -  checking gets disabled after the first reported bug.
> +  report or also panic the kernel (default: ``report``). The panic happens even
> +  if ``kasan_multi_shot`` is enabled.
>  
>  Implementation details
>  ----------------------
> -- 
> 2.31.0.rc2.261.g7f71774620-goog
>