[Pkg-systemd-maintainers] Bug#733112: Bug#733112: libsystemd-login0: logind not found by gdm3

[Michael Stapelberg]

Hi Stig,

Stig Sandbeck Mathisen <ssm at debian.org> writes:
> I can reproduce this issue on my workstation now, I run systemd and
> gnome on a freshly updated and rebooted jessie workstation.
>
> When /proc is mounted with hidepid=1 or hidepid=2, I can log in with
> gdm3, but I get no gnome session, only a "Oh, no! Something went wrong"
> fullscreen message with a "log out" button on it.
>
> This only happens when the system is booted with init=/bin/systemd. If I
> boot with default init, I can run gnome with /proc mounted with
> hidepid=2 (not tested with hidepid=1)
That’s a good hint.

I found this in the Arch Linux bugtracker¹:

> Well after hours of debugging and just trying random things I could
> think of, I straced gdm... And wading through the megabytes of noise
> was worthwhile, I found this critical line: [pid 2063]
> open("/proc/1/cgroup", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file
> or directory)
> 
> I'm mounting /proc with options hidepid=2 -- which hides other users'
> processes. It never caused me a problem so far. But apparently Gnome
> 3.6 relies on poking around in the details of the init process. It
> would be sad to lose this security feature on all Gnome desktops. I'll
> try to bring this up with upstream.

So, I think the problem is in how gdm figures out whether it should talk
to logind in the first place, not in any systemd component. Can you
verify this? (And if so, can you please reassign the bug?)

① https://bugs.archlinux.org/task/31814

-- 
Best regards,
Michael