shim's fallback hangs in CopyMem, can't boot ISOs

[valdikss]

I'm getting black screen trying to boot KDE Neon Unstable neon-unstable-20220130-0332.iso, which uses
shim-signed 1.40.7+15.4-0ubuntu9

This is due to a bug in shim 15.4 fallback (fbx64.efi), it fails on CopyMem inside add_to_boot_list on my Lenovo X220 in this place of fallback.c:

    CopyMem(newbootorder + 1, bootorder, sizeof (CHAR16) * option);
    CopyMem(newbootorder + option + 1, bootorder + option + 1,
        sizeof (CHAR16) * (nbootorder - option - 1));

The fix already present in upstream:
https://github.com/rhboot/shim/commit/41319e14c9144063605750baccd5bb332a3cf4fc

Kindly asking to apply this patch or update shim to current git master.

[Steve Langasek (vorlon)]

This appears to be a valid bug report against shim based on the described problematic behavior of the upstream binary. However, fbx64.efi should not be included on ISO images; there is also a bug in the mastering of this (non-Ubuntu) ISO image. fbx64.efi is intended to be installed only on fixed disks as part of a *fallback* boot path in the event that the boot variables have been wiped from the firmware's nvram. It should not be installed on removable media.

[valdikss (valdikss1)]

>However, fbx64.efi should not be included on ISO images

Sorry, my fault, there's no fbx64.efi in that ISO, and it doesn't boot due to unrelated issue.
However, I got an issue with fallback on Fedora, and Ubuntu also buggy version of shim.