Critical NULL Dereference Vulnerability in Linux Kernel: Impacting Debian Packages
Summary
DEBIAN-CVE-2024-35846: In the Linux kernel, the following vulnerability has been resolved: mm: zswap: fix shrinker NULL crash with cgroup_disable=memory Christian reports a NULL deref in zswap that he bisected down to the zswap shrinker. Affects linux versions < 6.8.9-1. Fixed in 6.8.9-1. How to fix ↓
Check if this vulnerability affects your application
Upload a manifest or SBOM and we'll show whether you're affected, plus every other risky package in the same scan.
No signup required · Results in about 60 seconds
Background
The Linux kernel is the core component of the Linux operating system, responsible for managing system resources and hardware communication. It provides essential services for all other software running on the system. The kernel is modular, allowing for various functionalities to be added or removed as needed. However, vulnerabilities in the kernel can lead to severe security issues, including system crashes and unauthorized access. This specific vulnerability affects the zswap feature, which is designed to improve memory management by compressing pages before they are swapped out to disk.
Vulnerability Detail
In the Linux kernel, a vulnerability has been identified in the zswap shrinker, which can lead to a NULL dereference crash when the memory control group (memcg) is disabled via the boot-time flag. This occurs because the zswap shrinker may be called with a NULL memcg pointer, causing a crash in the memcg_page_state function. This issue has been reported in various bug trackers and can severely impact systems running with the memory control group feature disabled, leading to potential system instability and crashes.
How To Fix
Minimum fixed version
6.8.9-1
This is the first release that contains the fix.
sudo apt-get install --only-upgrade linuxTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, users can enable the memory control group feature by removing the boot-time flag that disables it. This can prevent the NULL dereference crash until the system can be updated to the patched version.
Conclusion
The identified vulnerability in the Linux kernel's zswap feature poses a significant risk to systems running Debian 13 and 14 with the memory control group feature disabled. Users are strongly encouraged to update to the patched version to mitigate potential crashes and data loss. Utilizing tools like Vulert can help monitor and alert for such vulnerabilities in real-time.
See every vulnerability recorded for linux →
FAQ
Zswap is a compressed cache for swap pages in the Linux kernel, which helps improve performance by reducing the amount of data written to disk.
If your system has the memory control group feature disabled, it may crash due to a NULL dereference in the zswap shrinker, leading to potential data loss and instability.
Yes, if the system crashes as a result of this vulnerability, there is a risk of data loss, especially if unsaved work is present.
You can use Vulert, which monitors open-source vulnerabilities in your software. By uploading your manifest file like package-lock.json, you can check for vulnerabilities without needing to access the code.
If an immediate update is not possible, consider enabling the memory control group feature as a temporary workaround to prevent crashes.
References
Related vulnerabilities
Recent vulnerabilities recorded for linux.
