The Linux kernel is the backbone of numerous operating systems, so even a small bug can have catastrophic consequences. One such vulnerability, CVE-2024-27063, allowed a local attacker to trigger a kernel panic by exploiting how the LEDs subsystem interacts with network devices when their interfaces are renamed. Let's unpack the details behind this issue, how it was found, and what the patch changes.

What is the Vulnerability?

The bug resides in the leds-trigger-netdev subsystem of the Linux kernel, which allows LEDs (think Ethernet port blinks) to reflect network device states, like link activity or speed. Previous feature additions (in commit d5e01266e7f5) and logic refactoring (commit cee4bd16c319) accidentally introduced a serious flaw.

When a network device interface is *renamed* (for example, from eth to ens33), the kernel uses outdated pointers during state checks. This results in referencing a stale or freed device structure, causing an invalid memory access—which leads to a kernel panic (an immediate hard crash of the operating system).

Technical Breakdown

Where: drivers/leds/trigger/ledtrig-netdev.c

Netdev Trigger and Rename Event:

The LED trigger watches network interface events. You can rename an interface at runtime (ip link set eth name ens33).

Outdated Pointer Use:

The trigger data structure keeps a pointer to the associated net device. But on rename, the trigger event passes a *new* device pointer, which still needs to be updated and saved in the trigger_data struct (done when netdev gets registered).

Logic Bug:

After recent refactoring, the code mistakenly uses the *old* device (trigger_data->device) to check state (via get_device_state()), leading to an invalid pointer dereference.

Proof-of-Concept & Exploit Sketch

Though this bug mainly poses a DoS risk (crashing your own system), you can imagine a script that repeatedly renames an interface while manipulating triggers:

# Enable LED netdev trigger for 'eth'
echo netdev > /sys/class/leds/your_led/trigger
echo eth > /sys/class/leds/your_led/device_name

# In a tight loop, rename the interface
while true; do
    ip link set eth name temp
    ip link set temp name eth
done

With the buggy kernel, this can trigger a crash in seconds, especially if the LEDs subsystem is in use.

As described in the fix notes

> Move the call to get_device_state() after updating the new net_dev in trigger_data (in the NETDEV_REGISTER case).

Key Patch Diff _(simplified pseudocode)_

// Before: bug - get_device_state() called with outdated net_dev
trigger_data->device = old_net_dev;
state = get_device_state(trigger_data); // <- danger!
// ... then trigger_data updated

// After: correct - update trigger_data, then call get_device_state()
trigger_data->device = new_net_dev;
state = get_device_state(trigger_data); // <- safe!

Link to patch:
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1c460f2e6d923299aa81d4e145e6deb6b0288a40

References

- CVE Entry: CVE-2024-27063 at cve.org

Upstream Linux Patch:

1c460f2e6d92 – leds: trigger: netdev: Fix kernel panic on interface rename trig notify

Original Bug Report:

https://lore.kernel.org/lkml/20240225103202.19236-1-nicola.lanza@redhat.com/

Denial-of-service (system crash) when renaming network interfaces with LED triggers enabled.

- Mostly affects servers/systems using ledtrig-netdev.

Who is Affected?

- Any Linux distro using kernel 6.8 or affected commit range with LED netdev trigger enabled and frequent network interface renames.
- Physical servers, embedded devices, or virtual machines with automated naming scripts are most at risk.

Upgrade your kernel to a version including the above patch (post-March 2024 mainline).

- *Workaround*: Avoid renaming active interfaces with configured LED triggers until your kernel is patched.

Closing Thoughts

The CVE-2024-27063 case is a classic reminder: even non-core subsystems like blinking LEDs can trip up serious bugs in kernel land. Careful orchestration of resource updates—especially with asynchronous device events—remains critical. Thanks to quick community triage, this flaw was patched promptly in mainline.

Stay updated—both on patches and on which of your kernel features may open the door to rare but severe system crashes.


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Timeline

Published on: 05/01/2024 13:15:50 UTC
Last modified on: 09/18/2025 15:48:53 UTC