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

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Date:   Fri, 08 Mar 2019 08:39:37 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Matthew Garrett <mjg59@...gle.com>
Cc:     Justin Forbes <jforbes@...hat.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, 2019-03-07 at 14:50 -0800, Matthew Garrett wrote:
> On Thu, Mar 7, 2019 at 2:48 PM Mimi Zohar <zohar@...ux.ibm.com> wrote:
> > I added this last attempt because I'm seeing this on my laptop, with
> > some older, buggy firmware.
> 
> Is the issue that it gives incorrect results on the first read, or is
> the issue that it gives incorrect results before ExitBootServices() is
> called? If the former then we should read twice in the boot stub, if
> the latter then we should figure out a way to do this immediately
> after ExitBootServices() instead.

Detecting the secure boot mode isn't the problem.  On boot, I am
seeing "EFI stub: UEFI Secure Boot is enabled", but setup_arch() emits
"Secure boot could not be determined".

In efi_main() the secure_boot mode is initially unset, so
efi_get_secureboot() is called.  efi_get_secureboot() returns the
secure_boot mode correctly as enabled.  The problem seems to be in
saving the secure_boot mode for later use.

Mimi