What were you trying to do that didn't work?

On RHEL 9.6, if an invalid option prefixed with -- is present in the kernel command line, the system remains bootable but crashes fatally when systemd re-execs itself. This happens during certain package updates (e.g. glibc), leading to system instability and multiple failed services.

The expectation is that systemd should gracefully ignore invalid/unknown kernel command line options and not crash when reloading.

Please provide the package NVR for which the bug is seen:

systemd-252-51.el9_6.1

How reproducible is this bug?:

Steps to reproduce

• Start with a clean, updated RHEL 9.6 system. 

  Kernel cmdline is simple:
  # grep "^GRUB_CMDLINE_LINUX" /etc/default/grub
  GRUB_CMDLINE_LINUX="ipv6.disable=1"
  # cat /proc/cmdline
  ... ro ipv6.disable=1
  

• Install glibc.i686:

# yum install glibc.i686

Works fine, system remains stable. 

• Add an invalid string prefixed with --

# vi /etc/default/grub
GRUB_CMDLINE_LINUX="ipv6.disable=1 --randomstring"

# grub2-mkconfig -o /boot/grub2/grub.cfg --update-bls-cmdline
# reboot  

• After reboot:

# cat /proc/cmdline ... ro ipv6.disable=1 --randomstring

System still boots and runs.

• Install glibc.i686 :

# yum install glibc.i686

System fatally destabilizes.

• Observed state:

# systemctl status | grep -m1 State
    State: starting
# systemctl list-units --state=failed |grep "^●"
● atd.service loaded failed failed Deferred execution scheduler
● chronyd.service loaded failed failed NTP client/server
● mcelog.service loaded failed failed Machine Check Exception Logging Daemon
● plymouth-start.service loaded failed failed Show Plymouth Boot Screen
● polkit.service loaded failed failed Authorization Manager
● salt-minion.service loaded failed failed The Salt Minion
● saphostagent.service loaded failed failed SAP Host Agent
● tuned.service loaded failed failed Dynamic System Tuning Daemon

 systemd-journald loses connection and logs errors

Expected results

• Invalid kernel cmdline options should be ignored with a warning.

• System should remain stable and glibc updates should not cause crashes.

Actual results

• System fatally destabilizes when systemd re-execs after glibc update.

• Multiple services fail.

• Journald errors occur.