Bug#966554: grub2-common: BootHole fixes in DSA-4735-1 break dual-boot with Windows

[Steve McIntyre]

Hi Jan,

Thanks very much for your report.

On Thu, Jul 30, 2020 at 03:56:08PM +0100, Jan Stolarek wrote:
>Package: grub2-common
>Version: 2.02+dfsg1-20+deb10u1
>Severity: important
>
>Dear Maintainer,
>
>After installing DSA-4735-1 security update (BootHole fixes) it is no longer
>possible to boot Windows from GRUB.  Running `update-grub2` correctly detects
>presence of Windows Boot Manager and creates GRUB entry for it.  However,
>selecting that entry on boot leads to black screen and nothing happens no matter
>how long I wait.  It is still possible to boot Windows directly from BIOS, i.e.
>by bypassing GRUB altogether.  Disabling Secure Boot does not help, neither does
>reinstalling GRUB.

Hmmm, that's worrying. Let's try to debug this.

Are you using Secure Boot on this machine? Reinstalling doesn't fix
the problem - ok. Can you please confirm if going back to the previous
versions of the Grub packages fixes the problem for you?

-- 
Steve McIntyre, Cambridge, UK.                                steve at einval.com
The two hard things in computing:
 * naming things
 * cache invalidation
 * off-by-one errors                  -- Stig Sandbeck Mathisen