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Date:   Thu, 9 Jan 2020 21:12:59 -0800
From:   Kees Cook <keescook@chromium.org>
To:     Christophe Leroy <christophe.leroy@c-s.fr>
Cc:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-mm@kvack.org
Subject: Re: [PATCH] init: fix misleading "This architecture does not have
 kernel memory protection" message
Message-ID: <202001092112.14F20C4DCE@keescook>
References: <62477e446d9685459d4f27d193af6ff1bd69d55f.1578557581.git.christophe.leroy@c-s.fr>
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On Thu, Jan 09, 2020 at 08:15:01AM +0000, Christophe Leroy wrote:
> This message leads to think that memory protection is not implemented
> for the said architecture, whereas absence of CONFIG_STRICT_KERNEL_RWX
> only means that memory protection has not been selected at
> compile time.
> 
> Don't print this message when CONFIG_ARCH_HAS_STRICT_KERNEL_RWX is
> selected by the architecture. Instead, print "Kernel memory protection
> not selected by kernel config."
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

Oh, yes, I like this. Should the message include a hint to the config
name?

Regardless:

Acked-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
>  init/main.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/init/main.c b/init/main.c
> index 2cd736059416..fd31b15cc910 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -1090,6 +1090,11 @@ static void mark_readonly(void)
>  	} else
>  		pr_info("Kernel memory protection disabled.\n");
>  }
> +#elif defined(CONFIG_ARCH_HAS_STRICT_KERNEL_RWX)
> +static inline void mark_readonly(void)
> +{
> +	pr_warn("Kernel memory protection not selected by kernel config.\n");
> +}
>  #else
>  static inline void mark_readonly(void)
>  {
> -- 
> 2.13.3
> 

-- 
Kees Cook