linux-kernel - Re: [PATCH 3/3] x86/ima: retry detecting secure boot mode

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Date:   Thu, 7 Mar 2019 14:44:55 -0800
From:   Matthew Garrett <mjg59@...gle.com>
To:     Justin Forbes <jforbes@...hat.com>
Cc:     Mimi Zohar <zohar@...ux.ibm.com>,
        linux-integrity <linux-integrity@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Howells <dhowells@...hat.com>,
        Seth Forshee <seth.forshee@...onical.com>,
        kexec@...ts.infradead.org, Nayna Jain <nayna@...ux.ibm.com>
Subject: Re: [PATCH 3/3] x86/ima: retry detecting secure boot mode

On Thu, Mar 7, 2019 at 2:38 PM Justin Forbes <jforbes@...hat.com> wrote:
> On Thu, Mar 7, 2019 at 4:29 PM Matthew Garrett <mjg59@...gle.com> wrote:
>>
>> On Mon, Nov 19, 2018 at 11:57 AM Mimi Zohar <zohar@...ux.ibm.com> wrote:
>> >
>> > The secure boot mode may not be detected on boot for some reason (eg.
>> > buggy firmware).  This patch attempts one more time to detect the
>> > secure boot mode.
>>
>> Do we have cases where this has actually been seen? I'm not sure what
>> the circumstances are that would result in this behaviour.
>
>
> We have never seen it in practice, though we only ever do anything with it with x86, so it is possible that some other platforms maybe?

I'm not sure that it buys us anything to check this in both the boot
stub and the running kernel. If a platform *is* giving us different
results, anything else relying on the information from the boot stub
is also going to be broken, so we should do this centrally rather than
in the IMA code.