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

Matt Parnell mparnell at gmail.com
Tue Dec 3 02:24:54 UTC 2019

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.

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