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

[Matthew Garrett]

On Fri, 2013-02-08 at 11:21 -0800, Kees Cook wrote:
> On Fri, Feb 8, 2013 at 11:17 AM, Matthew Garrett
> <matthew.garrett@xxxxxxxxxx> wrote:
> > On Fri, 2013-02-08 at 11:12 -0800, Kees Cook wrote:
> >> Writing to MSRs should not be allowed unless CAP_COMPROMISE_KERNEL is
> >> set since it could lead to execution of arbitrary code in kernel mode.
> >
> > Willing to buy this, but do you have a description of one potential
> > approach? We should probably also figure out what's writing to MSRs at
> > the moment (anything other than energy_perf_bias?) and decide what the
> > best thing to do there is.
> 
> Yes, change the SYSENTER entry point to where-ever you like. There are
> examples already written:
> http://grsecurity.net/~spender/msr32.c

Cool. Yup, this sounds like a good plan.
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