[PATCH] Kernel Lockdown: Add an option to allow raw MSR access even, in confidentiality mode.

[Matt Parnell]

Correction: I'm out of caffeine, tired, and it has made me an idiot.

That message triggers regardless, it seems. I apologize.

On 12/2/19 8:24 PM, Matt Parnell wrote:
> For what it is worth, this doesn't happen with lockdown disabled.
>
> That message and the code that checks for mitigations is in
> arch/x86/kvm/vmx/vmx.c - for some reason locking down the MSRs is even
> making the kernel think that the MSR for the mitigation isn't there,
> meaning that it is also likely not mitigating the bug.
>
> On 12/2/19 8:16 PM, Matthew Garrett wrote:
>> On Mon, Dec 2, 2019 at 6:01 PM Matt Parnell <mparnell at gmail.com> wrote:
>>> I should also mention the kernel itself thinks it is vulnerable with the
>>> MSRs locked down:
>>>
>>> [    7.367922] L1TF CPU bug present and SMT on, data leak possible. See
>>> CVE-2018-3646 and
>>> https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for
>>> details.
>> The lockdown code doesn't touch any of the codepaths the kernel uses
>> to access MSRs itself (a *lot* would break in that case), so if the
>> kernel is asserting this inappropriately then that seems like a kernel
>> bug.