https://bugs.kde.org/show_bug.cgi?id=520483
Bug ID: 520483
Summary: On a multiseat setup (two seats, two GPUs), PLM spawns
greeters on both seats, but the seat1 session is not
isolated from seat0: on login attempt, the session is
launched "for VT 2" — the VT already used by seat0 —
and authenticates the seat0 user. The se
Classification: Plasma
Product: plasma-login-manager
Version First 6.6.0
Reported In:
Platform: CachyOS
OS: Linux
Status: REPORTED
Severity: grave
Priority: NOR
Component: general
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Target Milestone: ---
## Hardware / Environment
- CPU: AMD Ryzen 9 7900X
- seat0 (office): NVIDIA GTX 1660 SUPER, proprietary driver 595.71.05,
nvidia_drm.modeset=Y, fbdev=Y
- seat1 (TV): AMD Raphael iGPU (amdgpu, KMS)
- Distro: CachyOS (Arch-based)
- Plasma: 6.6 — Plasma Login Manager (PLM)
- Session type: Wayland on both seats
- Boot: systemd-boot
## Steps to reproduce
1. Assign a second GPU + USB input device to seat1 via loginctl attach
(drm/cardX node + usb node).
2. `loginctl list-seats` shows seat0 and seat1; seat1 has its GPU (MASTER) and
input devices.
3. Reboot. PLM spawns greeters on both seats (sessions c1 and c2, class
greeter).
4. Attempt to log in on the seat1 greeter.
## Observed behaviour
- Both greeters start successfully.
- On login from the seat1 greeter, the log shows the session started "for VT 2"
— the same VT as seat0's user session.
- The authenticated user is the seat0 user (uid=1000), not a separate seat
user.
- Session exits with HelperExitStatus(255).
- Many portal errors: `Could not register app ID: Unable to open
/proc/<pid>/root`.
- seat1 display stays black throughout.
## Expected behaviour
Each seat's greeter and session should be isolated: the seat1 session should
start on its own VT, independent of seat0, and render on the seat1 GPU/display.
## Logs
```
=== plasmalogin log ===
may 21 13:28:22 HOSTNAME plasmalogin[1095]: Socket server started.
may 21 13:28:22 HOSTNAME plasmalogin[1095]: Greeter starting...
may 21 13:28:22 HOSTNAME plasmalogin[1095]: Display server started.
may 21 13:28:22 HOSTNAME plasmalogin[1095]: Greeter starting...
may 21 13:28:22 HOSTNAME plasmalogin-helper[1097]:
pam_unix(plasmalogin-greeter:session): session opened for user
plasmalogin(uid=959) by (uid=0)
may 21 13:28:23 HOSTNAME plasmalogin-helper[1098]: Starting Wayland user
session: "/usr/share/plasmalogin/scripts/wayland-session"
"/usr/bin/startplasma-login-wayland"
may 21 13:28:23 HOSTNAME plasmalogin[1095]: Greeter session started
successfully
may 21 13:28:24 HOSTNAME plasmalogin[1095]: Message received from greeter:
Connect
may 21 13:28:46 HOSTNAME plasmalogin[1095]: Message received from greeter:
Login
may 21 13:28:46 HOSTNAME plasmalogin[1095]: Session
"/usr/share/wayland-sessions/plasma.desktop" selected, command:
"/usr/lib/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland" for
VT 2 "wayland"
may 21 13:28:46 HOSTNAME plasmalogin[1095]: Authentication for user "user"
successful
may 21 13:28:46 HOSTNAME plasmalogin-helper[1250]:
pam_unix(plasmalogin:session): session opened for user user(uid=USER_UID) by
user(uid=0)
may 21 13:28:46 HOSTNAME plasmalogin-helper[1250]: Starting Wayland user
session: "/usr/share/plasmalogin/scripts/wayland-session"
"/usr/lib/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland"
may 21 13:28:46 HOSTNAME plasmalogin[1095]: Session started true
may 21 13:28:51 HOSTNAME plasmalogin[1095]: Greeter stopping...
may 21 13:28:51 HOSTNAME plasmalogin[1095]: Auth: plasmalogin-helper exited
with 255
may 21 13:28:51 HOSTNAME plasmalogin[1095]: Greeter stopped.
PLASMALOGIN::Auth::HelperExitStatus(255)
=== session VT conflict evidence ===
may 21 13:28:46 HOSTNAME plasmalogin[1095]: Session
"/usr/share/wayland-sessions/plasma.desktop" selected, command:
"/usr/lib/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland" for
VT 2 "wayland"
may 21 13:28:46 HOSTNAME systemd[1256]: Reload requested from client PID 1277
('startplasma-way')...
may 21 13:28:51 HOSTNAME plasmalogin[1095]: Greeter stopped.
PLASMALOGIN::Auth::HelperExitStatus(255)
may 21 13:28:52 HOSTNAME kwin_wayland[1320]: Failed to register with host
portal QDBusError("org.freedesktop.portal.Error.Failed", "Could not register
app ID: Unable to open /proc/1320/root")
may 21 13:28:52 HOSTNAME polkit-kde-authentication-agent-1[1494]: Failed to
register with host portal QDBusError("org.freedesktop.portal.Error.Failed",
"Could not register app ID: Unable to open /proc/1494/root")
```
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