Kernel BUG at lib/list_debug.c on RHEL 8

Overview

Systems running certain Red Hat Enterprise Linux (RHEL) 8 kernel versions may encounter kernel panic events with the message:

kernel BUG at lib/list_debug.c:50!

This issue is observed primarily on RHEL 8.4 / 8.5-era kernels, especially 4.18.0-305.el8.x86_64.
The issue is resolved by upgrading to a kernel version containing the Red Hat–provided fixes.

Symptoms

• Unexpected kernel panic or server crash
• Crash dumps generated under /var/crash
• Repeated crash occurrences over time
• Error message present in crash logs:

  kernel BUG at lib/list_debug.c:50!
  

Affected Kernel Version

• 4.18.0-305.el8.x86_64 (Confirmed affected)

Later kernel versions include fixes and are not impacted.

How to Check

1. Verify the Running Kernel Version

Example (affected):

4.18.0-305.el8.x86_64

2. Check Crash Logs for the Error

Example output:

127.0.0.1-2026-01-24-05:58:09/vmcore-dmesg.txt:[565811.965600] kernel BUG at lib/list_debug.c:50!
127.0.0.1-2026-02-01-14:06:04/vmcore-dmesg.txt:[720457.055917] kernel BUG at lib/list_debug.c:50!
127.0.0.1-2026-02-04-07:35:08/vmcore-dmesg.txt:[235724.226457] kernel BUG at lib/list_debug.c:50!
127.0.0.1-2026-02-11-21:31:07/vmcore-dmesg.txt:[654935.054955] kernel BUG at lib/list_debug.c:50!
127.0.0.1-2026-02-26-01:10:08/vmcore-dmesg.txt:[226597.985699] kernel BUG at lib/list_debug.c:50!

If similar entries exist, the system is impacted.

Resolution

Preferred Recommendation

Upgrade to the latest available RHEL 8 kernel, which contains all stability, security, and bug fixes.

Recommended kernel (RHEL 8.10):

kernel-4.18.0-553.51.1.el8_10.x86_64

Minimum Required Kernel (If Staying on Older RHEL)

If the requestor must remain on a specific RHEL minor version, apply at least the following kernel versions:

RHEL 8.4

• Minimum kernel:

  kernel-4.18.0-305.12.1.el8_4
  

• Errata:
  • RHSA-2021:3057
    https://access.redhat.com/errata/RHSA-2021:3057

RHEL 8.5 and Above

• Minimum kernel:

  kernel-4.18.0-348.el8
  

• Errata:
  • RHSA-2021:4356
    https://access.redhat.com/errata/RHSA-2021:4356

Upgrade Procedure

1. Enable Update Repositories

Ensure the appropriate RHEL 8 update repositories are enabled based on the environment:

• Satellite
• PXE
• ISO or local mirror
• Red Hat CDN

2. Take Configuration Backup

Back up essential system configurations before proceeding:

(Optional: back up application-specific configuration files if required.)

3. Update the Server

Verify kernel installation:

4. Reboot the Server

Post‑Upgrade Validation

After reboot, perform the following checks:

1. Verify kernel version:
   uname -r
2. Confirm:
   • Network connectivity
   • Filesystems mounted correctly
   • Applications and services running as expected
3. Ensure no new crash files are generated under:
   /var/crash

Monitoring and Follow‑Up

• Request the requestor to monitor the system
• Watch for:
  • Reoccurrence of kernel panic
  • New lib/list_debug.c errors
• If the issue persists:
  • Collect sosreport
  • Gather latest crash logs
  • Open a case with Red Hat Support

Rollback (If Needed)

If issues occur after upgrade:

1. Reboot the system
2. Select a previous kernel from the GRUB menu
3. Boot and investigate compatibility or driver issues

Summary

The kernel BUG at lib/list_debug.c issue is resolved by upgrading the RHEL 8 kernel.
Best practice is to move to the latest RHEL 8.10 kernel for optimal stability and support.