package shim-signed 1.40.7+15.4-0ubuntu9 failed to install/upgrade: kernel segfault. Hard lock

[spec]

Ubuntu-Studio 20.04.3 LTS on MacPro 5,1, dual W3520
From /proc/version: Linux version 5.11.0-27-lowlatency (buildd@lcy01-amd64-019) (gcc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0, GNU ld (GNU Binutils for Ubuntu) 2.34) #29~20.04.1-Ubuntu SMP PREEMPT Wed Aug 11 17:06:56 UTC 2021

# apt-cache policy shim-signed
shim-signed:
  Installed: 1.40.7+15.4-0ubuntu9
  Candidate: 1.40.7+15.4-0ubuntu9
  Version table:
 *** 1.40.7+15.4-0ubuntu9 500
        500 http://us.archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     1.40.3+15+1533136590.3beb971-0ubuntu1 500
        500 http://us.archive.ubuntu.com/ubuntu focal/main amd64 Packages

>What you expected to happen

Running `apt upgrade` would complete without issue.

>What happened instead

System hard lock, becomes completely unresponsive both from the local terminal and over established SSH. Eventually memory is exhausted and the machine reboots.

Upon restart, running `apt upgrade` returns the error: "E: dpkg was interrupted, you must manually run 'dpkg --configure -a' to correct the problem."

Running `dpkg --configure -a` attempts to complete installation of shim-signed, segfaults, requiring a cold boot.

Only a fraction of the errors generated get written to the logs before the crash as the crash prevents a final flush to disk. From a remote machine I tailed several logs and triggered the crash again, then copied the results from the terminal and attached to report.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1941963

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[spec (playaspec)]

The only available logs are already attached. I have resolved my specific issue by removing the offending package, but the bug that triggered the segfault still remains when reinstalled.

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]