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From:   Matthew Garrett <mjg59@google.com>
Date:   Fri, 8 Mar 2019 09:51:57 -0800
Message-ID: <CACdnJut3Y7CogvgtNsEcrEtA1WOxSb9OWP_wZ=3xNgCft2oeDw@mail.gmail.com>
Subject: Re: [PATCH 3/3] x86/ima: retry detecting secure boot mode
To:     Mimi Zohar <zohar@linux.ibm.com>
Cc:     Justin Forbes <jforbes@redhat.com>,
        linux-integrity <linux-integrity@vger.kernel.org>,
        LSM List <linux-security-module@vger.kernel.org>,
        linux-efi <linux-efi@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        David Howells <dhowells@redhat.com>,
        Seth Forshee <seth.forshee@canonical.com>,
        kexec@lists.infradead.org, Nayna Jain <nayna@linux.ibm.com>
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On Fri, Mar 8, 2019 at 5:40 AM Mimi Zohar <zohar@linux.ibm.com> wrote:
>
> On Thu, 2019-03-07 at 14:50 -0800, Matthew Garrett wrote:
> > 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.

Hm. And this only happens on certain firmware versions? If something's
stepping on boot_params then we have bigger problems.