https://bugs.kde.org/show_bug.cgi?id=466118
Bug ID: 466118
Summary: Selecting Switch User in Plasma 5.27.0 resulted in a
black screen with sddm errors
Classification: Plasma
Product: plasmashell
Version: 5.27.0
Platform: Fedora RPMs
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Application Launcher (Kickoff)
Assignee: plasma-b...@kde.org
Reporter: matt.fagn...@bell.net
CC: mikel5...@gmail.com, noaha...@gmail.com
Target Milestone: 1.0
Created attachment 156523
--> https://bugs.kde.org/attachment.cgi?id=156523&action=edit
Journal for the boot of Fedora-KDE-Live-x86_64-38-20230218.n.0.iso on bare
metal in which I saw the black screen problem twice
SUMMARY
I booted the Fedora 38 KDE Plasma live image
Fedora-KDE-Live-x86_64-38-20230218.n.0.iso in a QEMU/KVM VM in GNOME Boxes with
3 GB RAM and 3D acceleration disabled using the llvmpipe driver in a Fedora 37
KDE Plasma installation. I noticed that Switch User was shown in the Leave menu
of the Application Launcher menu in Plasma 5.27.0. The Switch User option had
been missing in previous Plasma versions. When I selected Switch User, a black
screen occurred. I tried to switch VTs by clicking on ctrl+alt+f2, ctrl+alt+f3
in the Keyboard menu in GNOME Boxes but the VT logins didn't appear. I shutdown
the VM.
I booted Fedora-KDE-Live-x86_64-38-20230218.n.0.iso from a USB flash drive
written with Fedora Media Writer on bare metal with sysrq_always_enabled on the
kernel command line. When I selected Switch User, a black screen occurred with
a mouse cursor that I could move for a second then froze. I pressed sysrq+alt+e
to stop all processes which restarted Plasma. The journal around the time of
the black screen showed sddm-helper exited with the error code 5 and sddm
"Couldn't initiate jump to VT 0: No such device or address" I didn't think
there was a VT 0 which might be the reason for the problem.
Feb 19 15:51:15 systemd[1]: Started session-c1.scope - Session c1 of User sddm.
Feb 19 15:51:15 audit[2754]: USER_START pid=2754 uid=0 auid=4294967295
ses=4294967295 subj=system_u:system_r:xdm_t:s0-s0:c0.c1023
msg='op=PAM:session_open grantors=pam_unix,pam_systemd acct="sddm"
exe="/usr/libexec/sddm-helper" hostname=localhost-live addr=?
terminal=/dev/tty1 res=success'
Feb 19 15:51:15 sddm-helper[2754]: pam_unix(sddm-greeter:session): session
closed for user sddm
Feb 19 15:51:15 audit[2754]: USER_END pid=2754 uid=0 auid=4294967295
ses=4294967295 subj=system_u:system_r:xdm_t:s0-s0:c0.c1023
msg='op=PAM:session_close grantors=pam_unix,pam_systemd acct="sddm"
exe="/usr/libexec/sddm-helper" hostname=localhost-live addr=?
terminal=/dev/tty1 res=success'
Feb 19 15:51:15 audit[2754]: CRED_DISP pid=2754 uid=0 auid=4294967295
ses=4294967295 subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:setcred
grantors=pam_permit acct="sddm" exe="/usr/libexec/sddm-helper"
hostname=localhost-live addr=? terminal=/dev/tty1 res=success'
Feb 19 15:51:15 systemd[1]: session-c1.scope: Deactivated successfully.
Feb 19 15:51:15 sddm[1426]: Auth: sddm-helper exited with 5
Feb 19 15:51:15 sddm[1426]: Couldn't initiate jump to VT 0: No such device or
address
Feb 19 15:51:15 systemd-logind[1241]: Session c1 logged out. Waiting for
processes to exit.
Feb 19 15:51:15 systemd-logind[1241]: Removed session c1.
I'll attach the journal for the boot in which I saw the black screen problem
twice with the same sddm errors. I'm not sure if Switch User was intended to be
enabled again. Plasma might have been trying to start sddm on VT 0 which didn't
exist, or the problem might be with sddm. Selecting Switch User resulted in a
black screen 6/8 times. I had switched to VT2 in VMs and logged in as the
liveuser user before selecting Switch User in the two cases when the lock
screen appeared instead of a black screen.
STEPS TO REPRODUCE
1. Download Fedora-KDE-Live-x86_64-38-20230218.n.0.iso from
https://koji.fedoraproject.org/koji/buildinfo?buildID=2154783
2. boot Fedora-KDE-Live-x86_64-38-20230218.n.0.iso in a QEMU/KVM VM in GNOME
Boxes with 3 GB RAM and 3D acceleration disabled or on bare metal
3. in the VM case, I disabled automatic login from sddm in System Settings. I'm
not sure if this is needed.
4. Select the Application Launcher menu in the lower left corner of Plasma
5.27.0 on Wayland
5. Select the Leave menu
6. Select Switch User
OBSERVED RESULT
Selecting Switch User in Plasma 5.27.0 in F38 resulted in a black screen with
sddm errors
EXPECTED RESULT
sddm would appear normally without a black screen
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora 38
(available in About System)
KDE Plasma Version: 5.27.0
KDE Frameworks Version: 5.103.0
Qt Version: 5.15.8
ADDITIONAL INFORMATION
Switch User doesn't appear in the Leave menu in Plasma 5.27.0 of my Fedora 37
KDE Plasma installation. I reported this problem at
https://bugzilla.redhat.com/show_bug.cgi?id=2171316 There's a report about user
switching problems involving two users at
https://github.com/sddm/sddm/issues/1660
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