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From: Matt Parnell <mparnell@gmail.com>
To: Matthew Garrett <mjg59@google.com>
Cc: Kees Cook <keescook@chromium.org>,
	LSM List <linux-security-module@vger.kernel.org>,
	David Howells <dhowells@redhat.com>,
	matthew.garrett@nebula.com
Subject: Re: [PATCH] Kernel Lockdown: Add an option to allow raw MSR access even, in confidentiality mode.
Date: Mon, 2 Dec 2019 21:57:11 -0600
Message-ID: <337e64ca-f2da-d8ff-0b64-fce00c9e1994@gmail.com> (raw)
In-Reply-To: <b887b039-ebf6-5ef1-429e-04792f3cd664@gmail.com>

...possibly a bug on my older 4790k system, on my 8550u this doesn't
seem to happen. Strange.

Either way, I can stop bugging you if you'd like.

On 12/2/19 8:50 PM, Matt Parnell wrote:
> 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@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.

  reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-30  6:49 Matt Parnell
2019-11-30 18:36 ` Kees Cook
2019-11-30 19:09   ` Matt Parnell
2019-12-01 20:53     ` Matt Parnell
2019-12-02 18:29       ` Matt Parnell
2019-12-02 22:55         ` Jordan Glover
2019-12-02 23:13           ` Matt Parnell
2019-12-02 23:29           ` Matthew Garrett
2019-12-02 23:31             ` Matt Parnell
2019-12-03  2:13   ` Matt Parnell
2019-12-03  2:16     ` Matthew Garrett
2019-12-03  2:24       ` Matt Parnell
2019-12-03  2:50         ` Matt Parnell
2019-12-03  3:57           ` Matt Parnell [this message]
2019-12-02 19:43 ` Matthew Garrett
2019-12-02 20:39   ` Matt Parnell

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