linux-kernel - Re: [PATCH] Kconfig: Make STRICT_DEVMEM default-y on x86 and arm64

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Message-ID: <20171204155610.GH29619@arm.com>
Date:   Mon, 4 Dec 2017 15:56:10 +0000
From:   Will Deacon <will.deacon@....com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com,
        Mark Rutland <mark.rutland@....com>,
        Laura Abbott <labbott@...hat.com>, x86@...nel.org
Subject: Re: [PATCH] Kconfig: Make STRICT_DEVMEM default-y on x86 and arm64

On Fri, Dec 01, 2017 at 12:10:00PM -0800, Kees Cook wrote:
> Distros have been shipping with CONFIG_STRICT_DEVMEM=y for years now. It
> is probably time to flip this default for x86 and arm64.

Should we be defaulting IO_STRICT_DEVMEM on as well?

Will

> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  lib/Kconfig.debug | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 947d3e2ed5c2..39b123d04a36 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -1985,7 +1985,7 @@ config STRICT_DEVMEM
>  	bool "Filter access to /dev/mem"
>  	depends on MMU && DEVMEM
>  	depends on ARCH_HAS_DEVMEM_IS_ALLOWED
> -	default y if TILE || PPC
> +	default y if TILE || PPC || X86 || ARM64
>  	---help---
>  	  If this option is disabled, you allow userspace (root) access to all
>  	  of memory, including kernel and userspace memory. Accidental
> -- 
> 2.7.4
> 
> 
> -- 
> Kees Cook
> Pixel Security