https://bugs.kde.org/show_bug.cgi?id=518755
Bug ID: 518755
Summary: Wayland lock screen fails to authenticate (pam_unix
“user unknown”) with no user feedback; SDDM login
works
Classification: Plasma
Product: plasmashell
Version First 6.6.4
Reported In:
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Screen locking
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: 1.0
Wayland lock screen fails to authenticate (pam_unix “user unknown”) with no
user feedback; SDDM login works
On a Plasma Wayland session, the lock screen consistently fails to unlock even
with the correct password. There is no visible error message or feedback in the
UI — the lock screen does not react or indicate that login failed.
Authentication via SDDM works normally, and unlocking the session via loginctl
unlock-session also works, which indicates that PAM and the user account are
functioning correctly.
Steps to Reproduce:
Log into a Plasma Wayland session
Lock the screen
Enter the correct password
Press Enter
Expected Result:
Session unlocks successfully, or at least shows an error message if
authentication fails.
Actual Result:
Lock screen does not unlock
No feedback or error message is shown in the UI
Selecting "switch user" allows for successful login.
Logs show authentication failure
Relevant Logs:
unix_chkpwd: check pass; user unknown
unix_chkpwd: password check failed for user (myuser)
kscreenlocker_greet: pam_unix(kde:auth): authentication failure
Shortly after:
kwin_wayland: Atomic modeset test failed! Permission denied
Applying output configuration failed!
Additional Information:
PAM configuration was tested and simplified (even minimal pam_unix only) →
issue persists
SDDM login works correctly
loginctl unlock-session works correctly
Issue occurs consistently
No visible error message or feedback from lock screen
System Information:
Arch Linux
KDE Plasma 6.6.4
Wayland session
GPU: NVIDIA RTX 3080
Driver: nvidia-open (DRM KMS enabled, modeset=Y, fbdev=Y)
Notes:
This appears to be a problem specific to kscreenlocker’s authentication
handling under Wayland, rather than a system or PAM configuration issue.
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