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Tasklist

FS#58159 - [systemd]tty permissions changed to root after killing Xserver

Attached to Project: Arch Linux
Opened by stef204 (stef204) - Saturday, 07 April 2018, 21:00 GMT
Last edited by Andreas Radke (AndyRTR) - Tuesday, 10 December 2019, 11:05 GMT
Task Type Bug Report
Category Packages: Core
Status Assigned
Assigned To Dave Reisner (falconindy)
Christian Hesse (eworm)
Architecture All
Severity Medium
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 0%
Votes 2
Private No

Details

Description:

When dropping down to Linux Console after killing X server; the ownership of /dev/ttyX (whichever tty was used to "startx") is set to root:root as opposed to keeping it as $USER:tty (as it is when first logging in to system).
This creates permission problems: for example, after killing X and dropping back down to Linux Console, I can no longer edit files with emacsclient, as this change of ownership creates a permission error (cannot open display).
I start emacs server with a USER systemd unit on login. And before startx, when /dev/ttyX is owned by $USER:tty, emacsclient works as expected.
I have checked this ownership change on other distros and have not found this problem present in any, IOW, when killing X on Debian (and other tested distros), the ownership of /dev/ttX remains $USER:tty.
I have added myself to group "tty" but no change.

Additional info:
* package version(s)
coreutils 8.29-1
linux-zen 4.15.15-1
xorg-server 1.19.6+13+gd0d1a694f-1
i3-wm 4.15-1

* config and/or log files etc.
% uname -a
Linux archlinux 4.15.15-1-zen #1 ZEN SMP PREEMPT Sat Mar 31 23:59:18 UTC 2018 x86_64 GNU/Linux
(This problem is present with linux and linux-lts as well.)

% cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-linux-zen root=UUID=xxxxxxxxxxx rw acpi_backlight=video fbcon=scrollback:256k

% cat /etc/X11/Xwrapper.config
needs_root_rights=no
(I've tried to comment this line out, reboot but no change)

Steps to reproduce:
1) Boot into linux, linux-zen or linux-lts and login.

You can check ownership and perms at this point:
% ls -l /dev/tty1
crw------- 1 $USER:tty 4, 2 Apr 7 22:36 /dev/tty1
and the octal perm: crw------- 600 /dev/tty1

This is correct and expected.

2) % startx

Let X server and window manager start.
Exit X "gracefully" by using window manager's own method (or just kill X)

3) check ownership/permissions:
% ls -l /dev/tty1
crw------- 1 root:root 4, 2 Apr 7 25:36 /dev/tty1
and the octal perm: crw------- 600 /dev/tty1

4) try to open emacsclient: error, cannot open display, no permission

5) sudo chown $USER:tty /dev/tty1
5a) check ownership to make sure
% ls -l /dev/tty1
crw------- 1 $USER:tty 4, 2 Apr 7 25:36 /dev/tty1
and the octal perm: crw------- 600 /dev/tty1

6) % emacsclient somefile
This now works properly and opens the file, etc.

Again, I have checked this against 3 or 4 other distros, and none change ownership of/dev/ttyX, all return to same $USER:tty once X is killed.

It is difficult to identify where the problems lies, which package creates this ~edge case. It could be something local to my install but cannot figure out what,
This problem has been present for a at least 2 years if not longer and my system is pretty much always up to date.

I have tried with DWM as windows manager and the error and behavior is the same so I would tend to think not WM related.

(Note I have replaced ny actual user name with $USER in this bug report.)
This task depends upon

Comment by stef204 (stef204) - Sunday, 08 April 2018, 01:27 GMT
Correction: the ownership of /dev/ttyX once X is killed and one drops back down to Linux Console is: "root:tty" [not "root:root"]
Basically, during startx or after; the owner of /dev/ttyX from which X was started changes from "$USER:tty" to "root:tty" (probably by xorg-server or some related script or package) and stays that way, even once "X" is exited gracefully or not.

Additional info: a check using 'ps aux | grep xorg' reveals that "/usr/lib/xorg-server/Xorg" IS owned by $USER during X session.
Comment by Fabian Piribauer (piri) - Saturday, 22 September 2018, 08:04 GMT
Can confirm, after auditing the attribute changes it turns out that systemd-logind changes the ownership when Xorg is started/exited.
This also seems to happen on debian as someone has opened a github issue with systemd https://github.com/systemd/systemd/issues/10103.
Comment by stef204 (stef204) - Thursday, 27 September 2018, 12:19 GMT
Can this bug's status be changed to "confirmed"?

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