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Date: Fri, 8 Feb 2013 22:45:35 -0800
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Subject: Re: [PATCH] x86: Lock down MSR writing in secure boot
From: Kees Cook <keescook@chromium.org>
To: Matthew Garrett <matthew.garrett@nebula.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Borislav Petkov <bp@alien8.de>,
        LKML <linux-kernel@vger.kernel.org>,
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On Fri, Feb 8, 2013 at 5:29 PM, Matthew Garrett
<matthew.garrett@nebula.com> wrote:
> On Fri, 2013-02-08 at 17:22 -0800, H. Peter Anvin wrote:
>
>> You don't have to build the kernel twice to exclude a loadable module.
>
> I guess you could just strip the signatures off any modules you don't
> want to support under Secure Boot, but that breaks some other use cases.

Also, _reading_ MSRs from userspace arguably has utility that doesn't
compromise ring-0. So excluding the driver entirely seems like
overkill.

-Kees

--
Kees Cook
Chrome OS Security