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From: Kees Cook <keescook@chromium.org>
Date: Thu, 6 Oct 2016 14:39:31 -0700
Message-ID: <CAGXu5jJew=YK6FtE7itQJiuF46YHSvoaUFYPX6PNg9iH6UquiA@mail.gmail.com>
Subject: Re: [PATCH] Let CONFIG_STRICT_DEVMEM depends on CONFIG_DEVMEM
To: Dave Young <dyoung@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@kernel.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>, Tejun Heo <tj@kernel.org>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Nikolay Aleksandrov <nikolay@cumulusnetworks.com>,
        Dmitry Vyukov <dvyukov@google.com>
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On Wed, Oct 5, 2016 at 10:12 PM, Dave Young <dyoung@redhat.com> wrote:
> With CONFIG_DEVMEM not set, CONFIG_STRICT_DEVMEM will be useless
> even if it is set =y, thus let's update the dependency in Kconfig.
>
> Signed-off-by: Dave Young <dyoung@redhat.com>

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

> ---
>  lib/Kconfig.debug |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- linux-x86.orig/lib/Kconfig.debug
> +++ linux-x86/lib/Kconfig.debug
> @@ -1980,7 +1980,7 @@ config ARCH_HAS_DEVMEM_IS_ALLOWED
>
>  config STRICT_DEVMEM
>         bool "Filter access to /dev/mem"
> -       depends on MMU
> +       depends on MMU && DEVMEM
>         depends on ARCH_HAS_DEVMEM_IS_ALLOWED
>         default y if TILE || PPC
>         ---help---

While we're at it, can we make DEVKMEM default=n? The help text even
suggests making it "n".

-Kees

-- 
Kees Cook
Nexus Security