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

[H. Peter Anvin]

On 02/12/2013 09:39 PM, Matthew Garrett wrote:
> On Tue, 2013-02-12 at 16:48 -0800, H. Peter Anvin wrote:
>
> > OK... what none of this gets into:
> >
> > Why should CAP_RAWIO be allowed on a secure boot system, when there are
> > 2^n known ways of compromise a system with CAP_RAWIO?
>
> CAP_SYS_RAWIO seems to have ended up being a catchall of "Maybe someone
> who isn't entirely root should be able to do this", and not everything
> it covers is equivalent to being able to compromise the running kernel.
> I wouldn't argue with the idea that maybe we should just reappraise most
> of the current uses of CAP_SYS_RAWIO, but removing capability checks
> from places that currently have them seems like an invitation for
> userspace breakage.

Sounds like you are thinking of CAP_SYS_ADMIN, but I don't really see a 
huge difference between MSRs and I/O control registers... just different 
address spaces.

	-hpa


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

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