linux-kernel - Re: [PATCH] kasan: add support for kasan.fault=panic_on

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Message-ID: <CA+fCnZdy4TmMacvsPkoenCynUYsyKZ+kU1fx7cDpbh_6=cEPAQ@mail.gmail.com>
Date:   Tue, 20 Jun 2023 12:57:39 +0200
From:   Andrey Konovalov <andreyknvl@...il.com>
To:     Marco Elver <elver@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Taras Madan <tarasmadan@...gle.com>,
        Aleksandr Nogikh <nogikh@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Jonathan Corbet <corbet@....net>, kasan-dev@...glegroups.com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH] kasan: add support for kasan.fault=panic_on_write

On Wed, Jun 14, 2023 at 11:52 AM Marco Elver <elver@...gle.com> wrote:
>
> @@ -597,7 +614,11 @@ void kasan_report_async(void)
>         pr_err("Asynchronous fault: no details available\n");
>         pr_err("\n");
>         dump_stack_lvl(KERN_ERR);
> -       end_report(&flags, NULL);
> +       /*
> +        * Conservatively set is_write=true, because no details are available.
> +        * In this mode, kasan.fault=panic_on_write is like kasan.fault=panic.
> +        */
> +       end_report(&flags, NULL, true);

Hi Marco,

When asymm mode is enabled, kasan_report_async should only be called
for read accesses. I think we could check the mode and panic
accordingly.

Please also update the documentation to describe the flag behavior wrt
async/asymm modes.

On a related note, it looks like we have a typo in KASAN
documentation: it states that asymm mode detects reads synchronously,
and writes - asynchronously. Should be the reverse.

Thanks!