linux-kernel - Re: [PATCH] x86: Lock down MSR writing in secure boot

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Date:	Fri, 8 Feb 2013 22:45:35 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Matthew Garrett <matthew.garrett@...ula.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	linux-security-module <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH] x86: Lock down MSR writing in secure boot

On Fri, Feb 8, 2013 at 5:29 PM, Matthew Garrett
<matthew.garrett@...ula.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
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