[Debian-on-mobile-maintainers] Bug#1026998: mmsd-tng shouldn't run for _greetd user

[Andrey Skvortsov]

Package: mmsd-tng
Version: 2.0.0-1
Severity: normal

Dear Maintainer,

on latest Mobian build on OG PP with phog/greetd enabled mmsdtng crashes, when it starts under
_greetd user.

```
mobian at mobian:~$ journalctl -b | grep mmsd
Dec 25 23:51:35 mobian mmsdtng[712]: MMSD-TNG version 2.0.0
Dec 25 23:51:35 mobian mmsdtng[712]: Using cross-namespace EXTERNAL authentication (this will deadlock if server is GDBus < 2.73.3)
Dec 25 23:51:35 mobian mmsdtng[712]: ../src/main.c:on_bus_acquired() Dbus Bus acquired!
Dec 25 23:51:35 mobian mmsdtng[712]: ../src/service.c:__mms_service_init() Starting Up MMSD Service Manager
Dec 25 23:51:35 mobian mmsdtng[712]: ../src/plugin.c:__mms_plugin_init() 
Dec 25 23:51:35 mobian mmsdtng[712]: ../plugins/modemmanager.c:modemmanager_init() Starting Modem Manager Plugin!
Dec 25 23:51:35 mobian mmsdtng[712]: ../src/service.c:mms_service_create() service 0x55b4ed0280
Dec 25 23:51:35 mobian mmsdtng[712]: ../src/service.c:mms_service_set_identity() service 0x55b4ed0280 identity modemmanager
Dec 25 23:51:35 mobian mmsdtng[712]: Failed to create path /etc/greetd/.mms/modemmanager/mms
Dec 25 23:51:35 mobian mmsdtng[712]: g_key_file_get_string: assertion 'key_file != NULL' failed
Dec 25 23:51:35 mobian mmsdtng[712]: g_key_file_get_string: assertion 'key_file != NULL' failed
Dec 25 23:51:35 mobian mmsdtng[712]: g_key_file_get_string: assertion 'key_file != NULL' failed
Dec 25 23:51:35 mobian systemd-coredump[732]: Removed old coredump core.mmsdtng.119.46cdb79a83e646dda6153a968ac63680.1390.1672001039000000.zst.
Dec 25 23:51:37 mobian systemd-coredump[732]: Process 712 (mmsdtng) of user 119 dumped core.
                                              #0  0x0000005578ac85ec n/a (mmsdtng + 0x185ec)
                                              #1  0x0000005578ac68bc n/a (mmsdtng + 0x168bc)
                                              #2  0x0000005578ac6988 __mms_plugin_init (mmsdtng + 0x16988)
                                              #12 0x0000005578ab99cc main (mmsdtng + 0x99cc)
                                              #15 0x0000005578ab9b70 _start (mmsdtng + 0x9b70)
Dec 25 23:51:37 mobian systemd[659]: mmsd-tng.service: Main process exited, code=dumped, status=11/SEGV
Dec 25 23:51:37 mobian systemd[659]: mmsd-tng.service: Failed with result 'core-dump'.

```

And /etc/greetd is read-only home directory for _greetd user.
```
mobian at mobian:~$ ls -l /etc/ | grep greetd
drwxr-xr-x 2 root root    4096 Dec 25 23:29 greetd
```
IMHO, mmsd-tng shouldn't run in greetd session.
Link to upstream discussuion: https://gitlab.com/kop316/mmsd/-/issues/86

-- System Information:
Debian Release: bookworm/sid
  APT prefers testing-debug
  APT policy: (500, 'testing-debug'), (500, 'testing')
Architecture: arm64 (aarch64)
Foreign Architectures: armhf

Kernel: Linux 5.15.44-sunxi64-page-debug (SMP w/4 CPU threads)
Kernel taint flags: TAINT_CRAP, TAINT_UNSIGNED_MODULE
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages mmsd-tng depends on:
ii  init-system-helpers                           1.65.2
ii  libc-ares2                                    1.18.1-1+b2
ii  libc6                                         2.36-6
ii  libgcc-s1                                     12.2.0-10
ii  libglib2.0-0                                  2.74.2-1
ii  libmm-glib0                                   1.20.0-1
ii  libphonenumber8 [libphonenumber8-protobuf32]  8.12.57+ds-3
ii  libsoup-3.0-0                                 3.2.2-1
ii  libstdc++6                                    12.2.0-10

Versions of packages mmsd-tng recommends:
ii  modemmanager  1.20.0-1

mmsd-tng suggests no packages.

-- no debconf information