linux-kernel - Re: RFC: Tainting the kernel on raw I/O access

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Message-ID: <20140903221547.GA21800@srcf.ucam.org>
Date:	Wed, 3 Sep 2014 23:15:47 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	"H. Peter Anvin" <h.peter.anvin@...el.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Kees Cook <keescook@...omium.org>
Subject: Re: RFC: Tainting the kernel on raw I/O access

(Cc: Kees)

On Wed, Sep 03, 2014 at 02:20:59PM -0700, H. Peter Anvin wrote:
> In a meeting earlier today, we discussed MSR access and that it could be
> used to do bad things.  The same applies to other forms of raw I/O
> (/dev/mem, /dev/port, ioperm, iopl, etc.)
> 
> This is basically the same problem with which the secure boot people
> have been struggling.
> 
> Peter Z. suggested we should taint the kernel on raw I/O access, and I
> tend to concur.
> 
> So what I would like to suggest is that we create a new kernel helper
> function which can return an error in secure boot mode and otherwise
> taints the kernel with a raw I/O taint.
> 
> What do people think?

Not a bad plan, but there's a couple of places where you'd want to 
forbid stuff in Secure Boot without tainting the kernel in the generic 
use-case, so there's still some problem to solve there.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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