How to Report Linux Kernel Bugs: A Comprehensive Guide

Reporting bugs in the Linux kernel is a crucial task for maintaining system stability and security. This guide will walk you through the process of documenting and submitting bugs to ensure they are addressed promptly and effectively. Additionally, we will explore how to use relevant tools to bisect kernel revisions and identify the problematic commit.

Step-by-Step Guide to Bug Reporting

When you encounter a bug in the Linux kernel, the first step is to document it thoroughly. This includes:

Identifying the exact environment where the bug occurs (e.g., distribution, hardware configuration, version of the kernel). Describing the symptoms and reproduction steps in detail. Capturing any relevant logs and error messages. Providing any additional information that might help in understanding and fixing the issue.

Once you have gathered all this information, you need to prepare your documentation in a format that can be easily shared. This typically involves:

Writing a clear and concise description of the bug. Attaching any relevant files or logs. Describing the expected behavior vs. the actual behavior.

Submitting Bug Reports

After thorough documentation, you should submit your bug report via a mailing list. The linux-kernel@ mailing list is the primary channel for discussing kernel issues. However, it's important to note that this list does not accept HTML emails. Therefore, ensure your mailer is configured to send only plain text emails.

When submitting your report, consider including the following:

Your complete documentation from the previous steps. Cc-ing the maintainer of the component affected by the bug. If you have already bisected the kernel to a specific commit, cc-ing the author of that patch and all sign-offs.

To further enhance your chances of a quick resolution, here are some additional tips:

Using a clear and descriptive subject line for your email. Mentioning the severity of the bug and how it affects users. Attaching any necessary source code or backtraces.

Using the MAINTAINERS File for Better Feedback

The MAINTAINERS file, available in the source directory of the kernel, is a valuable resource. It lists maintainers responsible for various kernel subsystems. By Cc-ing the appropriate maintainer, you can direct your bug report to the right individuals who are best suited to investigate and address it.

If you have successfully bisected the bug to a specific commit, it is particularly beneficial to:

Cc-ing the author of the problematic commit. Cc-ing the sign-offs of that commit.

This not only helps in identifying the responsible party but also speeds up the response time, as the issue can be tackled more efficiently.

Example Scenarios

Let's consider a practical example where you encountered a bug in a specific module of the Linux kernel. Assume:

You have documented the environment and reproduced the bug. You have bisected the kernel to a single problematic commit. The bug is related to the 'network' subsystem.

Your email to the linux-kernel@ mailing list might look like this:

Subject: Bug Report: Network Module Crash [PATCH/bisect]
Dear linux-kernel mailing list members,
I am reporting a critical issue in the network module of the Linux kernel. Here is a detailed description of the bug: [Detailed description and reproduction steps].
I have encountered this issue on the following environment:
- Distribution: Ubuntu 20.04 LTS
- Kernel Version: 5.4.0-1040
- Hardware Configuration: Intel i7-8700   16GB RAM   NVMe SSD
The symptoms of the issue are as follows: [Symptoms]. I was able to pinpoint the problematic commit using the bisect tool, and it turns out to be [Commit hash].
For more information, please find the attachment containing the backtrace and relevant log files.
Specifically, I would like to request the attention of the maintainers of the 'network' subsystem. The Cc recipients are:
- [Maintainer1's email]
- [Maintainer2's email]
- [Author of problematic commit's email]
- [Sign-offs of the commit]
I would appreciate any assistance in resolving this issue as soon as possible. Thank you for your time and effort.
Best regards,
[Your Name]

In conclusion, the Linux kernel community values detailed and well-structured bug reports. By following these guidelines and making use of the MAINTAINERS file, you can significantly contribute to the efficiency and effectiveness of the kernel development process.