Bug#929818: sddm crashes after VT switch (but switching works fine without sddm)

["J. Pfennig" <info@j-pfennig.de>]

Package: sddm
Version: 0.18.0-1
Severity: important

Concurrent X-Sessions can be started on other VTs (without sddm, just
xinit) and you can switch between these without any problem.

When switching back to the sddm VT (number 7) sddm crashes and so the
session is lost.

This behaviour is 100% reproducible on various notbooks.

(1) pam modification: the pam groups module now works fine with
    sddm (pam was fixed since stretch, sddm was not usable with
    stretch anyhow).

(2) here the trivial xinitrc used with startx to do testing:

#!/bin/sh
. /etc/X11/Xsession
if [ -x /usr/bin/startkde ] ; then
    startkde
elif [ -x /usr/bin/twm ] ; then
    twm &
    xclock -g 130x130+900+10 &
    xterm -g 120x35+10+10 -sb
fi

(3) Kernal taint: is virtual box, but the mentioned tests were
    run on a real machine.

---

Thanks for your attention and your Debian engagement
Jürgen

-- System Information:
Debian Release: 10.0
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 4.19.0-5-amd64 (SMP w/4 CPU cores)
Kernel taint flags: TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE= (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages sddm depends on:
ii  adduser                 3.118
ii  debconf [debconf-2.0]   1.5.71
ii  libc6                   2.28-10
ii  libgcc1                 1:8.3.0-6
ii  libpam0g                1.3.1-5
ii  libqt5core5a            5.11.3+dfsg1-1
ii  libqt5dbus5             5.11.3+dfsg1-1
ii  libqt5gui5              5.11.3+dfsg1-1
ii  libqt5network5          5.11.3+dfsg1-1
ii  libqt5qml5              5.11.3-4
ii  libqt5quick5            5.11.3-4
ii  libstdc++6              8.3.0-6
ii  libsystemd0             241-3
ii  libxcb-xkb1             1.13.1-2
ii  libxcb1                 1.13.1-2
ii  qml-module-qtquick2     5.11.3-4
ii  x11-common              1:7.7+19
ii  xnest [xserver]         2:1.20.3-1
ii  xserver-xorg [xserver]  1:7.7+19

Versions of packages sddm recommends:
ii  haveged                                1.9.1-7
ii  libpam-systemd                         241-3
ii  sddm-theme-breeze [sddm-theme]         4:5.14.5.1-1
ii  sddm-theme-debian-breeze [sddm-theme]  4:5.14.5.1-1
ii  sddm-theme-debian-elarun [sddm-theme]  0.18.0-1
ii  sddm-theme-debian-maui [sddm-theme]    0.18.0-1

Versions of packages sddm suggests:
pn  libpam-kwallet5           <none>
pn  qtvirtualkeyboard-plugin  <none>

-- Configuration Files:
/etc/pam.d/sddm changed:
auth    requisite       pam_nologin.so
auth    required        pam_succeed_if.so user != root quiet_success
@include common-auth
auth       optional   pam_group.so
-auth   optional        pam_gnome_keyring.so
-auth   optional        pam_kwallet5.so
@include common-account
session [success=ok ignore=ignore module_unknown=ignore default=bad] pam_selinux.so close
session optional        pam_keyinit.so force revoke
session required        pam_limits.so
session required        pam_loginuid.so
@include common-session
session [success=ok ignore=ignore module_unknown=ignore default=bad] pam_selinux.so open
-session optional       pam_gnome_keyring.so auto_start
-session optional       pam_kwallet5.so auto_start
@include common-password
session required        pam_env.so
session required        pam_env.so envfile=/etc/default/locale user_readenv=1


-- no debconf information