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

From: Mimi Zohar
Date: Fri Mar 08 2019 - 08:40:00 EST

On Thu, 2019-03-07 at 14:50 -0800, Matthew Garrett wrote:
> On Thu, Mar 7, 2019 at 2:48 PM Mimi Zohar <zohar@xxxxxxxxxxxxx> 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. ÂOn 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. Âefi_get_secureboot() returns the
secure_boot mode correctly as enabled. ÂThe problem seems to be in
saving the secure_boot mode for later use.