linux-kernel - Re: [PATCH v4 12/12] mm/kasan: make kasan=on|off take effect for all three modes

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Message-ID: <CA+fCnZfw5V4HqHepJUbH5cFSEj1G4yvJMb=1Tjd_7WDBP7uUfQ@mail.gmail.com>
Date: Thu, 4 Dec 2025 17:40:48 +0100
From: Andrey Konovalov <andreyknvl@...il.com>
To: Baoquan He <bhe@...hat.com>
Cc: linux-mm@...ck.org, ryabinin.a.a@...il.com, glider@...gle.com, 
	dvyukov@...gle.com, vincenzo.frascino@....com, akpm@...ux-foundation.org, 
	kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org, 
	kexec@...ts.infradead.org, elver@...gle.com, sj@...nel.org, 
	lorenzo.stoakes@...cle.com, snovitoll@...il.com, christophe.leroy@...roup.eu
Subject: Re: [PATCH v4 12/12] mm/kasan: make kasan=on|off take effect for all
 three modes

On Fri, Nov 28, 2025 at 4:35 AM 'Baoquan He' via kasan-dev
<kasan-dev@...glegroups.com> wrote:
>
> Now everything is ready, set kasan=off can disable kasan for all
> three modes.
>
> Signed-off-by: Baoquan He <bhe@...hat.com>
> ---
>  include/linux/kasan-enabled.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
> index b05ec6329fbe..b33c92cc6bd8 100644
> --- a/include/linux/kasan-enabled.h
> +++ b/include/linux/kasan-enabled.h
> @@ -4,6 +4,7 @@
>
>  #include <linux/static_key.h>
>
> +#ifdef CONFIG_KASAN
>  extern bool kasan_arg_disabled;
>
>  /*
> @@ -12,7 +13,6 @@ extern bool kasan_arg_disabled;
>   */
>  DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
>
> -#if defined(CONFIG_ARCH_DEFER_KASAN) || defined(CONFIG_KASAN_HW_TAGS)

So do we still need CONFIG_ARCH_DEFER_KASAN? If not, it needs to be removed.

But if we only allow kasan=off for x86/arm64 after all (see my comment
to the cover letter), I believe we need to keep it.


>  /*
>   * Runtime control for shadow memory initialization or HW_TAGS mode.
>   * Uses static key for architectures that need deferred KASAN or HW_TAGS.
> @@ -30,7 +30,7 @@ static inline void kasan_enable(void)
>  /* For architectures that can enable KASAN early, use compile-time check. */
>  static __always_inline bool kasan_enabled(void)
>  {
> -       return IS_ENABLED(CONFIG_KASAN);
> +       return false;
>  }
>
>  static inline void kasan_enable(void) {}
> --
> 2.41.0
>
> --
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