linux-kernel - Re: [PATCH V3 03/11] x86: Lock down IO port access when module security is enabled

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Date:	Thu, 05 Sep 2013 08:36:51 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Matthew Garrett <matthew.garrett@...ula.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"keescook@...omium.org" <keescook@...omium.org>
Subject: Re: [PATCH V3 03/11] x86: Lock down IO port access when module security is enabled

Sigh.  That capability really is fscked up.

Matthew Garrett <matthew.garrett@...ula.com> wrote:
>On Wed, 2013-09-04 at 20:52 -0700, H. Peter Anvin wrote:
>> On 09/03/2013 04:50 PM, Matthew Garrett wrote:
>> > IO port access would permit users to gain access to PCI
>configuration
>> > registers, which in turn (on a lot of hardware) give access to MMIO
>register
>> > space. This would potentially permit root to trigger arbitrary DMA,
>so lock
>> > it down by default.
>> > 
>> > Signed-off-by: Matthew Garrett <matthew.garrett@...ula.com>
>> 
>> Seriously... just deny CAP_SYS_RAWIO to any system in secure mode.
>
>No. CAP_SYS_RAWIO blocks things that we don't want blocked (x86
>microcode updates, various disk ioctls, *device firmware uploads* and a
>few others) - the semantics just don't match. We could relax those
>permissions, but then we'd potentially break someone else's security
>considerations.

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.
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