Bug#773752: gdm3: GDM3 pollutes system logs with user session output under systemd

[Colomban Wendling]

Package: gdm3
Version: 3.14.1-3
Severity: important
Tags: upstream

Dear Maintainer,

On a system upgraded to systemd, GDM logs the stderr of the user's X
session in three (3!) log files through journald:

/var/log/user.log
/var/log/messages
/var/log/syslog

This fills up /var/log/ with huge journal files, because of the output
of a *user* application.

This is due to GDM3 logging to systemd instead of .xsession-errors (or
$XDG_CACHE_COME/gdm/session.log more recently).
See https://bugzilla.gnome.org/show_bug.cgi?id=676181

This behavior is extremely annoying as it continuously pollutes system
logs with most generally useless user application debugging or
unimpotant warnings (such as GTK warning messages from various
applications).

This can furthermore be a *serious* issue because it can easily lead to
DoS-like behavior when a user application misbehaves and spams its
stdout and/or stderr.  As mentioned above, the X session output ends up
in three system logs written by syslog (a root service), which doesn't
seem to be handling this kind of stress well by default, and leads to
filling /var/log beyond limits (using reserved blocks).

I know this kind of behavior can already be triggered with direct
syslog interaction (e.g. through `logger`), but it is quite different
since application would need to explicitly use syslog, while here it
affects random applications whom output was never expected to even be
logged.


So, please rebuild GDM3 with `--disable-systemd-journal`, as suggested
in a comment in the aforementioned bug:
https://bugzilla.gnome.org/show_bug.cgi?id=676181#c17
This should give back a sane logging behavior by logging to X session
output to $XDG_CACHE_HOME/gdm/session.log.


Regards,
Colomban

-- System Information:
Debian Release: 8.0
  APT prefers unstable
  APT policy: (500, 'unstable'), (500, 'testing'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.16.0-4-amd64 (SMP w/4 CPU cores)
Locale: LANG=fr_FR.utf8, LC_CTYPE=fr_FR.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages gdm3 depends on:
ii  accountsservice                              0.6.37-3+b1
ii  adduser                                      3.113+nmu3
ii  cinnamon [x-window-manager]                  2.2.16-5
ii  dconf-cli                                    0.22.0-1
ii  dconf-gsettings-backend                      0.22.0-1
ii  debconf [debconf-2.0]                        1.5.55
ii  gir1.2-gdm3                                  3.14.1-3
ii  gnome-session [x-session-manager]            3.14.0-2
ii  gnome-session-bin                            3.14.0-2
ii  gnome-session-flashback [x-session-manager]  3.8.1-7
ii  gnome-settings-daemon                        3.14.2-2
ii  gnome-shell                                  3.14.2-3
ii  gnome-terminal [x-terminal-emulator]         3.14.1-1
ii  gsettings-desktop-schemas                    3.14.1-1
ii  libaccountsservice0                          0.6.37-3+b1
ii  libaudit1                                    1:2.4-1+b1
ii  libc6                                        2.19-13
ii  libcanberra-gtk3-0                           0.30-2.1
ii  libcanberra0                                 0.30-2.1
ii  libgdk-pixbuf2.0-0                           2.31.1-2+b1
ii  libgdm1                                      3.14.1-3
ii  libglib2.0-0                                 2.42.1-1
ii  libglib2.0-bin                               2.42.1-1
ii  libgtk-3-0                                   3.14.5-1
ii  libpam-modules                               1.1.8-3.1
ii  libpam-runtime                               1.1.8-3.1
ii  libpam-systemd                               215-8
ii  libpam0g                                     1.1.8-3.1
ii  librsvg2-common                              2.40.5-1
ii  libselinux1                                  2.3-2
ii  libsystemd0                                  215-8
ii  libwrap0                                     7.6.q-25
ii  libx11-6                                     2:1.6.2-3
ii  libxau6                                      1:1.0.8-1
ii  libxdmcp6                                    1:1.1.1-1+b1
ii  libxrandr2                                   2:1.4.2-1+b1
ii  lsb-base                                     4.1+Debian13+nmu1
ii  marco [x-window-manager]                     1.8.2+dfsg1-4
ii  mate-session-manager [x-session-manager]     1.8.1-5
ii  mate-terminal [x-terminal-emulator]          1.8.1+dfsg1-3
ii  metacity [x-window-manager]                  1:3.14.3-1
ii  mutter [x-window-manager]                    3.14.2-1
ii  openbox [x-window-manager]                   3.5.2-8
ii  policykit-1                                  0.105-8
ii  twm [x-window-manager]                       1:1.0.8-1
ii  ucf                                          3.0030
ii  x11-common                                   1:7.7+7
ii  x11-xserver-utils                            7.7+3+b1
ii  xfce4-session [x-session-manager]            4.10.1-9
ii  xfce4-terminal [x-terminal-emulator]         0.6.3-1+b1
ii  xfwm4 [x-window-manager]                     4.10.1-3
ii  xterm [x-terminal-emulator]                  312-1

Versions of packages gdm3 recommends:
ii  at-spi2-core               2.14.0-1
ii  desktop-base               8.0.2
ii  gnome-icon-theme           3.12.0-1
ii  gnome-icon-theme-symbolic  3.12.0-1
ii  x11-xkb-utils              7.7+1
ii  xserver-xephyr             2:1.16.2.901-1
ii  xserver-xorg               1:7.7+7
ii  zenity                     3.14.0-1

Versions of packages gdm3 suggests:
ii  gnome-orca            3.14.0-2
ii  libpam-gnome-keyring  3.14.0-1+b1

-- debconf-show failed