Critical Vulnerability in Linux Kernel: rcu/nocb WARN_ON_ONCE() Trigger
Summary
DEBIAN-CVE-2024-35929: In the Linux kernel, the following vulnerability has been resolved: rcu/nocb: Fix WARN_ON_ONCE() in the rcu_nocb_bypass_lock() For the kernels built with CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y and CONFIG_RCU_LAZY=y, the follo... Affects linux versions < 6.8.9-1. Fixed in 6.8.9-1. How to fix ↓
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Background
The Linux kernel is the core component of many operating systems, responsible for managing hardware and system resources. It provides essential services for all other parts of the operating system. The kernel is highly configurable and can be optimized for various environments, including servers, desktops, and embedded systems. However, like any complex software, it is susceptible to vulnerabilities that can affect system stability and security.
Vulnerability Detail
In the Linux kernel, a vulnerability has been identified in the rcu/nocb subsystem that can lead to a WARN_ON_ONCE() trigger in the rcu_nocb_bypass_lock() and rcu_nocb_wait_contended() functions. This issue arises when the kernel is built with CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y and CONFIG_RCU_LAZY=y. Under certain conditions, this can cause system instability and unexpected behavior, particularly when specific operations are performed concurrently. The vulnerability can be reproduced by executing 'echo 3 > /proc/sys/vm/drop_caches', which may lead to warnings and potential system performance degradation.
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 workaround, avoid executing the command 'echo 3 > /proc/sys/vm/drop_caches' while the kernel is running with the vulnerable configuration. This can help prevent triggering the WARN_ON_ONCE() warnings until the kernel is updated.
Conclusion
The vulnerability in the Linux kernel related to the rcu/nocb subsystem poses a risk of system instability. It is crucial to update to the patched version 6.8.9-1 or later to mitigate this risk. Users are also encouraged to utilize tools like Vulert for ongoing vulnerability monitoring.
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FAQ
The vulnerability can lead to system instability and unexpected behavior, particularly under specific concurrent operations.
You can check your kernel version with the command 'uname -r' and compare it with the patched version 6.8.9-1 or later.
Yes, you can use Vulert, which monitors and alerts in real-time for open-source vulnerabilities in your software using a manifest file like package-lock.json.
Yes, you can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without any signup.
If an immediate update is not possible, avoid executing the command that triggers the vulnerability and monitor your system for any unusual behavior.
References
Related vulnerabilities
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