https://bugs.kde.org/show_bug.cgi?id=506658
Bug ID: 506658
Summary: kscreenlocker_greet breaks my fingerprint scanner,
until I restart it
Classification: Plasma
Product: plasmashell
Version First 6.4.2
Reported In:
Platform: Fedora RPMs
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Screen locking
Assignee: plasma-b...@kde.org
Reporter: cach...@yahoo.com
Target Milestone: 1.0
SUMMARY
I am not able to login at the screenlocker page with my fingerprint scanner,
unless I restart kscreenlocker_greet
STEPS TO REPRODUCE
1. Lock the screen with
sleep 1
dbus-send --session --print-reply --dest=org.kde.kglobalaccel
/component/org_kde_powerdevil org.kde.kglobalaccel.Component.invokeShortcut
string:'Turn Off Screen'
sleep 2
dbus-send --session --print-reply --dest=org.freedesktop.ScreenSaver
/ScreenSaver org.freedesktop.ScreenSaver.Lock
2. Wait a few seconds and then get the screen on by moving the mouse
3. I see the screenlocker window prompting for password, with the sentence "or
scan your fingerprint..." below the prompt, but only for a fraction of a
second. I hear an error message sound, and I cannot use the fingerprint.
OBSERVED RESULT
After logging with a password, in the console I see a libfprint kernel crash.
YET, I found a workaround: I created a service that checks for screen on/off.
If the screen turns on AND the screen is locked, I run the following command:
sleep 1 ; pkill -f kscreenlocker_greet
Then the screenlocker turns black, but when it comes back to life I do see the
line "or scan your fingerprint...", and I can use my fingerprint to log in,
strongly indicating that this is indeed a kscreenlocker_greet bug.
In addition, if I lock the screen without turning it off, with
sleep 2
dbus-send --session --print-reply --dest=org.freedesktop.ScreenSaver
/ScreenSaver org.freedesktop.ScreenSaver.Lock
then the screenlocker allows me to use the fingerprint scanner.
This journalctl extract seems to indicate that there is some ownership problem:
$ sudo journalctl -u fprintd.service -b -r
Jul 03 23:15:09 Orion systemd[1]: Starting fprintd.service - Fingerprint
Authentication Daemon...
Jul 03 23:15:09 Orion systemd[1]: fprintd.service: Failed with result
'core-dump'.
Jul 03 23:15:09 Orion systemd[1]: fprintd.service: Main process exited,
code=dumped, status=11/SEGV
Jul 03 23:15:09 Orion fprintd[91565]: BUG: (machine->completed):
fpi_ssm_next_state() ../libfprint/fpi-ssm.c:456
Jul 03 23:15:09 Orion fprintd[91565]: Error; expected 8 bytes but got 8000,
continuing
Jul 03 23:14:52 Orion fprintd[91565]: Read failed: device was disconnected,
aborting
Jul 03 23:14:22 Orion systemd[1]: Started fprintd.service - Fingerprint
Authentication Daemon.
This is the libfprint error in the console:
kernel: fprintd[81941]: segfault at 557324dea118 ip 00007f98ec20a75a sp
00007fff978d1ca0 error 4 in libfprint-2.so.2.0.0[a75a,7f98ec200000+5f000]
likely on CPU 10 (core 20, socket 0)
Jul 3 23:13:16 Orion kernel: Code: 5d 89 05 11 83 0a 00 c3 0f 1f 84 00 00 00
00 00 f3 0f 1e fa 55 48 89 e5 53 48 89 fb 48 83 ec 18 e8 fb 90 ff ff 48 85 db
74 36 <48> 8b 13 48 85 d2 74 05 48 3b 02 74 17 48 89 c6 48 89 df 48 89 55
Jul 3 23:13:16 Orion login[81830]: pam_fprintd(login:auth): fprintd name owner
changed during operation!
Jul 3 23:13:16 Orion login[81830]: pam_fprintd(login:auth): ReleaseDevice
failed: Object does not exist at path “/net/reactivated/Fprint/Device/1”
EXPECTED RESULT
Screenlocker asking for my fingerprint, no crashes.
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora 42
KDE Plasma Version: 6.4.2
Qt Version: 4.8.7
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