File descriptor leak via executable DataSource engine causes plasmashell crash

[OmerFarukOruc]

Bug Description

KVitals causes plasmashell to crash repeatedly due to file descriptor (FD) exhaustion. The executable DataSource engine spawns a new QProcess (bash subprocess) every update interval, and the pipe FDs from these processes accumulate faster than they are cleaned up — especially under Wayland.

Once the per-process soft FD limit (typically 1024) is reached, plasmashell can no longer open pipes, shared libraries, or GPU buffers, and crashes with exit code 255.

Crash Sequence (from journalctl)

QProcess: Cannot create pipe (Too many open files)
Cannot load library /usr/lib64/qt6/plugins/...: Too many open files
eglSwapBuffers failed with 0x300c
The Wayland connection experienced a fatal error: Too many open files
plasmashell.service: Main process exited, code=exited, status=255/EXCEPTION

Root Cause

In main.qml:

Plasma5Support.DataSource {
    engine: "executable"
    connectedSources: ["bash " + scriptPath + " " + root.networkInterface]
    interval: Plasmoid.configuration.updateInterval
}

Each tick spawns a new bash process via QProcess, which creates 3+ pipe FDs (stdin/stdout/stderr). The script sys-stats.sh then forks ~15 additional subprocesses (awk x8, cat x3, free, grep, date, bc), each with their own FDs.

At the default 2-second interval, that is ~20+ pipe FDs created every 2 seconds. Under Wayland, QProcess cleanup can lag, causing FDs to accumulate until the soft limit (1024) is hit — typically within minutes.

Environment

• OS: Fedora 43 (KDE Plasma Desktop Edition)
• Plasma: 6.6.0
• Session: Wayland
• Widget version: Latest from GitHub (as of Feb 2026)

Reproduction

1. Install kvitals with default settings (2s update interval)
2. Start a Wayland session
3. Monitor FDs: watch -n 5 'ls /proc/$(pgrep -n plasmashell)/fd | wc -l'
4. Observe FD count climbing steadily
5. plasmashell crashes once it reaches ~1024 FDs

Suggested Fix

Replace engine: "executable" with KDE's native SystemMonitor DataSource (org.kde.ksystemstats), which provides CPU, RAM, temperature, battery, and network data without spawning any subprocesses.

Example:

import org.kde.ksystemstats as KSysStats

KSysStats.SensorDataModel {
    sensors: ["cpu/all/usage", "memory/physical/used", "memory/physical/total"]
}

This approach:

• Uses zero subprocesses — reads kernel data directly via D-Bus
• Creates zero pipe FDs — no QProcess involved
• Is the recommended KDE approach for system monitoring widgets

Alternatively, reading /proc/stat, /proc/meminfo, /sys/class/thermal/, etc. directly from QML via Qt.labs.platform file I/O would also eliminate the subprocess spawning.

Workaround

Users can mitigate the crash by raising plasmashell's soft FD limit:

mkdir -p ~/.config/systemd/user/plasma-plasmashell.service.d/
cat > ~/.config/systemd/user/plasma-plasmashell.service.d/override.conf << 'EOF'
[Service]
LimitNOFILESoft=65536
EOF
systemctl --user daemon-reload && systemctl --user restart plasma-plasmashell.service

This raises the limit from 1024 to 65536, buying significant headroom but not fixing the underlying leak.

[yassine20011]

Hi, thanks for pointing this out @OmerFarukOruc, I did try to watch -n 5 'ls /proc/$(pgrep -n plasmashell)/fd | wc -l.' It looks normal on my machine, but the problem statement is true. I was also hesitant to use the shell because of these problems.

The engine: "executable" to run a bash subprocess every tick is just fundamentally wrong for a long-running widget. I didn't know about the FD accumulation problem under Wayland, but the underlying problem you pointed out makes total sense.

Also, I didn't know that org.kde.ksystemstats was available as a QML import. I thought that to access system stats natively, I'd have to write a C++ plugin from scratch, which is why I ended up writing the shell script solution.

Plan of action:

• I'll be refactoring the widget to use org.kde.ksystemstats / KSysStats.SensorDataModel, which will remove the shell script solution and the QProcess spawning altogether.
• This will make KVitals consistent with how KDE's own System Monitor widget is implemented – no subprocesses, no pipe FDs, and direct D-Bus access to kernel data.
• I'll document your workaround (LimitNOFILESoft=65536) in the documentation as a temporary fix for users on the current version.

This is a breaking change, so it'll take a little while, but it's the correct