Comment 4 for bug 1775672

I am having the same problem. Ubuntu 18.04 installed with Windows 10 as dual boot. Secure boot enabled. The system has been working for years like this (since before 16.04). I have updated to every release since and it was working on all of them. It even worked on 18.04 before the latest kernel update. I suspect a work around could be to downgrade to a previous kernel or to disable module signing, but we should not have to.

 I sign my own modules with the following:

(only required once)
openssl req -new -x509 -newkey rsa:2048 -keyout MOK.priv -outform DER -out MOK.der -nodes -days 36500 -subj "/CN=Descriptive common name/"

After every kernel upgrade I sign the modules with:
#!/bin/bash

for f in $(dirname $(modinfo -n vboxdrv))/*.ko; do echo "Signing $f"; sudo /usr/src/linux-headers-$(uname -r)/scripts/sign-file sha256 ./MOK.priv ./MOK.der $f; done
modprobe vboxdrv

The kernel upgrade to 4.15.0-22 broke this process. Now the install of virtual box will stall on the following:
Building initial module for 4.15.0-22-generic