Prevent dead task groups from regaining cfs_rq's in Kernel
Summary
GSD-2021-1002329: sched/fair: Prevent dead task groups from regaining cfs_rq's. Affects Kernel versions >= a7b359fc6a37faaf472125867c8dc5a068c90982, < 512e21c150c1c3ee298852660f3a796e267e62ec. No fix is published. How to fix ↓
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Background
The Kernel is a critical component of the Linux operating system that manages the system's resources and facilitates communication between hardware and software. It provides essential functionalities such as process scheduling, memory management, and device drivers. The vulnerability in question affects the scheduling subsystem of the Kernel, specifically the fair scheduler (sched/fair). This subsystem is responsible for distributing CPU resources fairly among tasks. The vulnerability allows dead task groups to regain control of the CPU's scheduling queue (cfs_rq), potentially leading to resource starvation and performance degradation.
Vulnerability Detail
The vulnerability arises from a flaw in the fair scheduler that allows dead task groups to regain control of the CPU's scheduling queue. This can occur when a task group is terminated but still holds a reference to the cfs_rq. As a result, the dead task group can reacquire the cfs_rq and potentially monopolize CPU resources, impacting the performance of other tasks. The vulnerability was introduced in version v5.13 of the Kernel and has been fixed in version v5.15.5.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
There is no known workaround for this vulnerability. It is essential to update the Kernel to the fixed version to mitigate the risk.
Conclusion
The vulnerability in the Kernel's fair scheduler allows dead task groups to regain control of the CPU's scheduling queue, potentially impacting system performance. To mitigate this vulnerability, it is crucial to update the Kernel to version v5.15.5 or later, which includes the necessary fix. For further support on vulnerability remediation, please contact DevNack.com.
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FAQ
The vulnerability can lead to resource starvation and performance degradation as dead task groups regain control of the CPU's scheduling queue, potentially monopolizing CPU resources.
You can use Vulert's playground at Vulert Scanner to check if your system is affected by this vulnerability. Vulert analyzes the manifest file (e.g., package-lock.json) of your application and alerts in real-time for open-source vulnerabilities, including this one.
At the time of this report, there is no known exploit for this vulnerability. However, it is crucial to apply the fix to prevent potential exploitation.
No, this vulnerability requires local access to the system. It cannot be exploited remotely.
Unfortunately, there are no known mitigations available for this vulnerability other than updating the Kernel to the fixed version. It is recommended to prioritize the update to ensure the system's security.
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