A recently resolved vulnerability, CVE-2021-46945, in the Linux kernel affects how it handles ext4 panic errors. This blog post will discuss the vulnerability, code snippet, and links to original references. It will also provide exploit details for a better understanding of the issue.
Vulnerability
The vulnerability affects how the Linux kernel handles panic errors in the ext4 file system. It specifically relates to the kernel's inconsistent behavior when specific commands are issued in sequence. The inconsistency is due to a change in the behavior of the ext4 file system after commit 014c9caa29d3. As a result, the ext4_abort() function doesn't reliably panic in all instances when it should, which could lead to further issues and potential exploits.
The following series of commands would trigger a panic before commit 014c9caa29d3
1. mount /dev/sda -o ro,errors=panic test
2. mount /dev/sda -o remount,abort test
However, after commit 014c9caa29d3, remounting a file system using the "abort" test mount option no longer triggers a panic.
Original References
- Linux Kernel Mailing List
- Kernel Git Commit
Exploit Details
The following sequence of commands leads to a panic due to the vulnerability in handling ext4 panic errors:
1. mount /dev/sda -o ro,errors=panic test
2. echo test > /sys/fs/ext4/sda/trigger_fs_error
Previously, these commands would not cause a panic. The resolution of CVE-2021-46945 makes ext4's behavior more consistent, which ultimately strengthens the kernel's overall security.
Conclusion
CVE-2021-46945 highlights the importance of consistent behavior within the Linux kernel's ext4 file system to prevent potential exploits. The resolution of this vulnerability now ensures that panic errors are appropriately handled. Users are encouraged to update to the latest Linux kernel version to benefit from these security improvements.
Timeline
Published on: 02/27/2024 19:04:06 UTC
Last modified on: 04/10/2024 20:11:52 UTC