Boot failures because Dracut includes /etc/sysctl.d files with kernel.modprobe though 'systemd-sysctl'

[wiebeytec]

To combat all the recent local privilege escalations in various kernel components, we have:

kernel.modprobe = /usr/local/sbin/modprobe.filtered

in /etc/sysctl.d/90-modprobe.conf. This config file is included by Dracut in the initramfs (by /usr/lib/dracut/modules.d/11systemd-sysctl/module-setup.sh). But it doesn't include the argument (the script) for kernel.modprobe. Result: modprobe is broken, MD raid module can't be loaded on boot; boot failure. Probably applies to other modules too.

I think the only reasonable fix is to exclude kernel.modprobe from being included in the initramfs. One alternative is to also take the command, but that may have requirements that don't exist in the initramfs.

This was found on Ubuntu 26.04 (dracut 110-11), but applies broader.

[devkontrol]

CC @bdrung