https://bugs.kde.org/show_bug.cgi?id=497501
Bug ID: 497501
Summary: startplasma reads "LANG" at the wrong moment in time,
leading to a wrong value for "LANG" on a multi-locale
system
Classification: Plasma
Product: plasmashell
Version: 6.2.4
Platform: Gentoo Packages
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Startup process
Assignee: plasma-b...@kde.org
Reporter: matthias.na...@mhnnet.de
CC: k...@davidedmundson.co.uk
Target Milestone: 1.0
SUMMARY
On a multi-locale system, which uses a different locale for system daemons and
user sessions, Plasma/KDE uses the wrong locale upon initial login if
`plasma-localerc` has not yet been created. The function `runStartupConfig`
reads the environment variable `LANG` at a wrong moment in time which leads to
a faulty value for a system with a multi-locale setup, i.e. a system which uses
a different locale for system processes and user processes (i.e. those started
by `systemd --user`).
This bug can either be solved within Plasma/KDE or by SDDM or even both. The
bug is the result of an unlucky interaction between Plasma/KDE and SDDM and bad
timing.
STEPS TO REPRODUCE
**Prerequisites**
This bug only becomes apparent if one uses different locales as the system's
default and for user processes. The system's default locale is set as
`LANG=C.UTF-8` in `/etc/locale.conf`. This ensures to get unlocalized messages
in the system log.
The file `/etc/locale-users.conf` sets `LANG=de_DE.UTF-8` as the default for
ordinary user accounts. This file is used used in various places. The file
`/etc/environment.d/20-locale.conf` is a symbolic link to
`/etc/locale-users.conf`. The PAM module `pam_env.so` and the user's systemd
process `systemd --user` parses the directory `/etc/environment.d/` upon
session creation. Moreover, certain user-facing system services uses the file
`/etc/locale-users.conf` to setup a localized environment via systemd service
drop-ins. For `user@.service` and `sddm.service`, there is
`/etc/systemd/system/{user@.service.d,sddm.service.d}/override.conf` with
```
[Service]
EnvironmentFile=-/etc/locale-users.conf
```
This way, SDDM greets user with a localized UI.
**The actual bug**
For the Plasma/KDE part the relevant code snippet is in
"startkde/startplasma.cpp:Backend::openSession() (lines 177-217). At the end of
that method, the LANG variable gets a special treatment: If the variable LANG
is not set in formatsConfig (aka plasma-localerc), but set as an environment
variable, then the **current** value of that environment variable is written to
plasma-localerc and synced. I stress the word “current”, because timing is
crucial.
For SDDM, the relevant part is somewhere in the sddm-helper application.
sddm-helper clears the environment variables and then re-constructs a
“cleansed” environment.
Here is what happens. A typical pstree looks like
systemd,1 --switched-root --system --deserialize=50 splash
├─sddm,711
│ └─sddm-helper,886 --socket
/tmp/sddm-auth-65c418cf-f7c6-4130-8213-9d60d6c82829 --id 1 --start
/usr/libexec/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland
--user matthias
│ └─startplasma-wayland,935
└─systemd,908 --user
└─plasmashell,1221 --no-respawn
sddm (PID 711) creates the initial login screen. Although this process runs as
a child of the system's systemd (PID 1), the environment is fine:
```
/proc # cat 711/environ | tr '\0' '\n' | egrep LANG
LANG=de_DE.UTF-8
GDM_LANG=de_DE.UTF-8
LANGUAGE=de_DE:en_US
```
(Because of that service drop-in for sddm.service.) When the user attempts to
authenticate, sddm spawns sddm-helper. This sddm-helper clears the environment
and creates a “cleansed” one:
/proc # cat 886/environ | tr '\0' '\n'
LANG="C.UTF-8"
(Note: I did not even use egrep here to filter for LANG. That is everything
which is set.) sddm-helper spawns startplasma-wayland. Now, this is the unlucky
moment in time, when startplasma-wayland picks up the wrong initial value for
LANG due to the code in void runStartupConfig().
The environment for the user’s systemd (PID 908) is fine again:
/proc # cat 908/environ | tr '\0' '\n' | egrep LANG
LANG=de_DE.UTF-8
GDM_LANG=de_DE.UTF-8
LANGUAGE=de_DE:en_US
Unfortunately, this is too late, because Plasma has already read and written
the wrong value for LANG.
This is a bug in either SDDM or Plasma or both. I do not know, why SDDM clears
the environment. Maybe as a safety measure to clear any potentially harmful
environment variables a user might have been set. But in doing so, SDDM goes a
little over the edge. Or it is a bug in Plasma, because Plasma tries to read
LANG at the wrong moment in time.
I see to possible solutions for that bug:
1. Maybe Plasma should postpone reading the `LANG` variable until Plasma runs
within the user’s SystemD session after everything is “proper” again.
2. Maybe sddm-helper should not clear all environment variables, but stash away
the values of harmless environment variables (such as `LANG`) and restore them
to their original value.
Obviously, both fixes can also be combined.
OBSERVED RESULT
On a multi-locale system, which uses a different locale for system daemons and
user sessions, Plasma/KDE uses the wrong locale upon initial login if
`plasma-localerc` has not yet been created.
EXPECTED RESULT
Plasma/KDE should use the correct value for LANG from the user's environment
upon initial login.
SOFTWARE/OS VERSIONS
Linux: Gentoo Linux 2.17
KDE Plasma Version: 6.2.4
KDE Frameworks Version: 6.7.0
Qt Version: 6.7.3
Kernel: 6.12.4-gentoo
Graphics Platform: Wayland
--
You are receiving this mail because:
You are watching all bug changes.
