Скачать или смотреть Fixing General Protection Fault in Linux Kernel Module for Acer Nitro Fan and RGB Control

Learn how to resolve kernel panics caused by improper memory handling in a Linux kernel module controlling Acer Nitro 16 fans and RGB keyboard.
---
This video is based on the question https://stackoverflow.com/q/79358782/ asked by the user 'Detux' ( https://stackoverflow.com/u/20625863/ ) and on the answer https://stackoverflow.com/a/79359029/ provided by the user 'stark' ( https://stackoverflow.com/u/1216776/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: My Linux kernel module to control fan speeds and rgb keyboard of Acer Nitro 16 causes kernel panic

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to drop me a comment under this video.
---
Problem Overview

When writing a Linux kernel module to control the fan speeds and RGB keyboard brightness on an Acer Nitro 16 laptop, users have encountered persistent kernel panics. Specifically, inserting the module with insmod leads to system freezes accompanied by blinking Caps Lock lights and General protection fault messages in dmesg logs.

This issue is often mistaken for faulty memory hardware but is actually rooted in improper memory management within the kernel module code.



Root Cause Analysis

The kernel panic traces back to unsafe usage of dynamically allocated memory:

[[See Video to Reveal this Text or Code Snippet]]

Key issues here include:

Using strlen() on uninitialized kernel memory: kbfr is freshly allocated and contains garbage data. Calling strlen() before copying user data can cause undefined behavior, leading to kernel crashes.

No null-termination guarantee: copy_from_user() copies raw bytes without ensuring a null terminator, so string functions may run out of bounds.

Checking for NULL after using the pointer: The NULL check should happen immediately after allocation.



Corrected and Safer Approach

To avoid kernel panics and safely handle user input strings in a kernel module:

[[See Video to Reveal this Text or Code Snippet]]

Highlights:

Check kmalloc success immediately

Copy user data before using it

Use strnlen to safely detect string length within limits

Guarantee null-termination before any string operations

Free allocated memory when done to avoid leaks (not shown here but important)



Additional Tips for Kernel Module Stability

Always verify that copy_from_user returns zero (success) before using the data.

Use fixed-size buffers if possible, or clearly define maximum input size.

Avoid complex string operations in kernel space; prefer numeric parsing with well-defined input formats.

Use printk judiciously for debugging but remove or reduce logs after verification.



Summary

Kernel panics caused by general protection faults often stem from unsafe memory handling. In this example, the panic was triggered by reading uninitialized kmalloc memory as a string. Ensuring proper null-termination, verifying allocation success, and safely copying user data prevent such kernel crashes.

By adopting these best practices, Linux kernel modules for hardware control like fans and RGB lighting can operate reliably and safely.