Comment 13 for bug 2015400

Verification done on lunar-proposed.

$ lxc launch ubuntu:lunar lunar-loop --vm
$ lxc shell lunar-loop

# apt install -y gcc
# gcc -o test-loop test-loop.c

# add-apt-repository -y -p proposed
# apt-cache madison linux-image-6.2.0-30-generic
linux-image-6.2.0-30-generic | 6.2.0-30.30 | http://archive.ubuntu.com/ubuntu lunar-proposed/main amd64 Packages
linux-image-6.2.0-30-generic | 6.2.0-30.30 | http://security.ubuntu.com/ubuntu lunar-proposed/main amd64 Packages
# apt install -y linux-image-6.2.0-30-generic

# echo "GRUB_DEFAULT='Advanced options for Ubuntu>Ubuntu, with Linux 6.2.0-30-generic'" >/etc/default/grub.d/99-default.cfg
# update-grub
# reboot

# uname -rv
6.2.0-30-generic #30-Ubuntu SMP PREEMPT_DYNAMIC Wed Aug 9 13:33:35 UTC 2023

...

default: works (fixed)

# cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-6.2.0-30-generic root=PARTUUID=a335a269-dd48-4d3a-907a-2d2a2c6d53d7 ro console=tty1 console=ttyS0 panic=-1

# ./test-loop
#

max_loop=0: works (expected)

# echo 'GRUB_CMDLINE_LINUX_DEFAULT="$GRUB_CMDLINE_LINUX_DEFAULT max_loop=0"' >/etc/default/grub.d/99-maxloop.cfg
# update-grub && reboot

# cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-6.2.0-30-generic root=PARTUUID=a335a269-dd48-4d3a-907a-2d2a2c6d53d7 ro console=tty1 console=ttyS0 max_loop=0 panic=-1

# ./test-loop
#

max_loop=8: fails (expected)

# echo 'GRUB_CMDLINE_LINUX_DEFAULT="$GRUB_CMDLINE_LINUX_DEFAULT max_loop=8"' >/etc/default/grub.d/99-maxloop.cfg
# update-grub && reboot

# cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-6.2.0-30-generic root=PARTUUID=a335a269-dd48-4d3a-907a-2d2a2c6d53d7 ro console=tty1 console=ttyS0 max_loop=8 panic=-1

# ./test-loop
open: /dev/loop8: No such device or address