"debug" kernel parameter causes "No buffer space available" Denial of Service

[TJ]

15.10/16.04 amd64

With the Linux kernel's "debug" parameter set systemd spams the logs to such a degree that boot fails with the plymouth progress indicator constantly cycling, only tty1 available, and no clear indication from the last messages displayed on console as to why.

Leaving aside the unresolved bug of systemd adopting the Linux 'debug' parameter, and thus being the direct cause of this, the complete failure to boot as a result is a serious regression and a Denial of Service. Needing to alter the Linux command-line to use "loglevel=7" is a distasteful workaround.

A boot without "debug" using the same GRUB menuitem starts fine which suggests the systemd debug-level logging is the direct cause.

Orignally it was not even clear if the system has transitioned from initrd to rootfs at this point as there's no way to interact.

Later systemic tests showed the transition had occurred and /var/log/syslog contained some clues:

$ grep 'No buffer space' /tmp/syslog-debug.log | wc -l
103

E.g.:

Jun 6 07:36:38 hephaestion whoopsie[1500]: [07:36:38] GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.Netwo
rkManager was not provided by any .service files
Jun 6 07:36:38 hephaestion systemd[1]: thermald.service: Failed to send unit change signal for thermald.service: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: grub-common.service: Failed to send unit change signal for grub-common.service: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: whoopsie.service: Failed to send unit change signal for whoopsie.service: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: rsyslog.service: Failed to send unit change signal for rsyslog.service: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: ofono.service: Failed to send unit change signal for ofono.service: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: dbus.socket: Failed to send unit change signal for dbus.socket: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: dbus.service: Failed to send unit change signal for dbus.service: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: systemd-logind.service: Failed to send unit change signal for systemd-logind.service: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: smartd.service: Failed to send unit change signal for smartd.service: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: ModemManager.service: Failed to send unit change signal for ModemManager.service: No buffer space available
Jun 6 07:36:38 hephaestion NetworkManager[1559]: <info> NetworkManager (version 1.0.4) is starting...
Jun 6 07:36:38 hephaestion systemd[1]: accounts-daemon.service: Failed to send unit change signal for accounts-daemon.service: No buffer space available
Jun 6 07:36:38 hephaestion NetworkManager[1559]: <info> Read config: /etc/NetworkManager/NetworkManager.conf
Jun 6 07:36:38 hephaestion systemd[1]: gpu-manager.service: Failed to send unit change signal for gpu-manager.service: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: binfmt-support.service: Failed to send unit change signal for binfmt-support.service: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: cups.socket: Failed to send unit change signal for cups.socket: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: cups.service: Failed to send unit change signal for cups.service: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: basic.target: Failed to send unit change signal for basic.target: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: sockets.target: Failed to send unit change signal for sockets.target: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 144: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 169: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 139: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 196: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 152: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 172: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 170: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 164: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 190: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 174: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 165: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 146: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 126: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 201: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 204: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: Failed to send job change signal for 166: No buffer space available
Jun 6 07:36:38 hephaestion systemd[1]: var-lib-lxcfs.mount: Changed dead -> mounted
Jun 6 07:36:38 hephaestion systemd[1]: run-cgmanager-fs.mount: Changed dead -> mounted
Jun 6 07:36:38 hephaestion systemd[1]: run-cgmanager-fs.mount: Failed to send unit change signal for run-cgmanager-fs.mount: No buffer space available

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.