Bug#897654: libpam-systemd: "Failed to create session: No such process"

[Michael Gold]

Package: libpam-systemd
Version: 238-4
Severity: important

At some point in the past, I was able to shut down my system as a
non-root user:
	dbus-send --system --print-reply --dest=org.freedesktop.login1 /org/freedesktop/login1 "org.freedesktop.login1.Manager.PowerOff" boolean:true

But it now gives me this error:
	Error org.freedesktop.DBus.Error.InteractiveAuthorizationRequired: Interactive authentication required.

...probably because I have no loginctl session:
	$ loginctl
	   SESSION        UID USER             SEAT             TTY
	
	0 sessions listed.
	$ loginctl session-status
	Could not get properties: No such process
	$ strace -f loginctl session-status 2>&1|grep ESRCH
	$ 

I log in via lightdm and run an xsession script.  It may have worked in
the past because I was running ck-launch-session, which apparently no
longer exists.  pam_systemd also logs "No such process":
	Apr 09 11:37:30 golbez lightdm[14767]: pam_systemd(lightdm:session): pam-systemd initializing
	Apr 09 11:37:30 golbez lightdm[14767]: pam_systemd(lightdm:session): Asking logind to create session: uid=1000 pid=14767 service=lightdm type=x11 class=user desktop=lightdm-xsession seat=seat0 vtnr=7 tty= display=:0 remote=no remote_user= remote_host=
	Apr 09 11:37:30 golbez lightdm[14767]: pam_systemd(lightdm:session): Failed to create session: No such process

The same happens if I log in on a tty rather than X11:
	Apr 09 12:07:58 golbez login[16106]: pam_systemd(login:session): pam-systemd initializing
	Apr 09 12:07:58 golbez login[16106]: pam_systemd(login:session): Asking logind to create session: uid=1000 pid=16106 service=login type=tty class=user desktop= seat= vtnr=0 tty=tty3 display= remote=no remote_user= remote_host=
	Apr 09 12:07:58 golbez login[16106]: pam_systemd(login:session): Failed to create session: No such process

logind is running:
	root     15741  0.0  0.0  64304  5808 ?        Ss   11:59   0:00 /lib/systemd/systemd-logind
(I restarted it after the first failure.)

strace shows that logind fails to open a 'cgroup' file:
	openat(AT_FDCWD, "/proc/16134/cgroup", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
	sendmsg(12, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base=..., iov_len=104}, {iov_base="\17\0\0\0No such process\0", iov_len=20}], msg_iovlen=2, msg_controllen=0, msg_flags=0}, MSG_DONTWAIT|MSG_NOSIGNAL) = 124

I'm marking this "important" because, according to the package
description, registering this session is the only purpose of the
package.  But on another system, I do seem to get a valid session.

- Michael


-- System Information:
Debian Release: buster/sid
  APT prefers testing
  APT policy: (900, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.15.0-2-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_CA.UTF-8, LC_CTYPE=en_CA.UTF-8 (charmap=UTF-8), LANGUAGE=en_CA:en (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages libpam-systemd depends on:
ii  dbus            1.12.6-2
ii  libc6           2.27-3
ii  libpam-runtime  1.1.8-3.7
ii  libpam0g        1.1.8-3.7
ii  systemd         238-4
ii  systemd-sysv    238-4

libpam-systemd recommends no packages.

libpam-systemd suggests no packages.

-- no debconf information
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