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

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Message-ID: <511C1284.6080304@zytor.com>
Date:	Wed, 13 Feb 2013 14:24:04 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
CC:	Matthew Garrett <matthew.garrett@...ula.com>,
	Borislav Petkov <bp@...en8.de>,
	Kees Cook <keescook@...omium.org>,
	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 02/13/2013 11:55 AM, Paolo Bonzini wrote:
> Il 13/02/2013 18:22, H. Peter Anvin ha scritto:
>>>
>>> On non-x86 machines CAP_SYS_RAWIO is much less dangerous, especially
>>> when coupled with file DAC.
>
> Discretionary Access Control.
>
>> Either way, I think you are at best deluded and more like you just
>> completely wrong about CAP_SYS_RAWIO being "less dangerous on non-x86
>> machines".  With the possible exception of s390 I suspect it is, in
>> fact, more dangerous.
>
> I may well be wrong, but as a quick data point CAP_SYS_RAWIO has no
> occurrences in arch/ except arch/x86.  Of course a lot of driver
> functionality will be limited to CAP_SYS_RAWIO, but usually this
> requires having a file descriptor for some file.
>

Well, yes, although that could include /dev/mem.

	-hpa


-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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