Linux Kernel Lockdown for eBPF Applications
Issue Description
eBPF applications may fail to load or run properly when the Linux kernel lockdown feature is enabled. This guide will help you diagnose and resolve issues related to kernel lockdown, particularly for Qpoint eBPF applications.
Symptoms
eBPF programs fail to load with errors mentioning "invalid argument" or "unknown func".
Qpoint Tap fails to start with a panic message similar to:
panic: failed to load BPF programs and maps: field MonitorCertOpenEntry: program monitor_cert_open_entry: load program: invalid argument: unknown func bpf_probe_write_user#36
Diagnosis Steps
Check current lockdown status:
cat /sys/kernel/security/lockdown
The output will show the current mode in square brackets, e.g.,
none [integrity] confidentiality
.Verify GRUB configuration:
cat /etc/default/grub
Look for the
GRUB_CMDLINE_LINUX
line and check iflockdown=none
is present.If lockdown is not set to "none" or the GRUB configuration doesn't match the current status, proceed to the fix.
Fix
Edit the GRUB configuration:
sudo nano /etc/default/grub
Modify the
GRUB_CMDLINE_LINUX
line to includelockdown=none
:GRUB_CMDLINE_LINUX="console=ttyS0,19200n8 net.ifnames=0 lockdown=none"
Ensure there's a space between parameters.
Save the file and exit the editor.
Update GRUB:
sudo update-grub
Reboot the system:
sudo reboot
After reboot, verify the lockdown status again:
cat /sys/kernel/security/lockdown
It should now show
[none] integrity confidentiality
.
Additional Troubleshooting
If the issue persists after following these steps:
Check kernel version:
uname -r
Ensure you're running a kernel version that supports the eBPF features you're using.
Verify eBPF system requirements:
sudo sysctl kernel.unprivileged_bpf_disabled
If this returns 1, unprivileged eBPF is disabled and may need to be enabled.
Check for any security modules (e.g., SELinux, AppArmor) that might be interfering:
sestatus aa-status
Review system logs for any related errors:
sudo journalctl -b | grep -i bpf
Further Assistance
If you continue to experience issues after following this guide, please contact Qpoint support with the following information:
Output of the diagnosis steps
Complete error message from Qpoint Tap
Kernel version (
uname -r
)Any relevant entries from system logs
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