Potential Crash in SFQ Queueing due to GSO Handling in Linux Kernel
Summary
CVE-2025-38115: In the Linux kernel, the following vulnerability has been resolved: net_sched: sch_sfq: fix a potential crash on gso_skb handling SFQ has an assumption of always being able to queue at least one packet. Affects linux versions 5.10.103-1 – 6.9.9-1. No fix is published. How to fix ↓
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Background
The Linux kernel is the core component of many operating systems, providing essential services for hardware and software interaction. It manages system resources, facilitates communication between hardware and software, and ensures efficient operation of applications. The kernel is critical for system stability and performance. This vulnerability affects the SFQ (Stochastic Fairness Queueing) queuing discipline, which is designed to manage packet scheduling in network traffic. The issue arises from an assumption in SFQ that it can always queue at least one packet, leading to potential crashes under specific conditions.
Vulnerability Detail
In the Linux kernel, a vulnerability has been identified in the SFQ queuing discipline related to the handling of GSO (Generic Segmentation Offload) packets. After a specific commit, the length of the queue (sch->q.len) can be inflated by packets in sch->gso_skb. This can result in an enqueue operation on an empty SFQ queue being followed by an immediate drop, potentially causing a crash. The vulnerability stems from improper handling of the queue's tail, which can lead to instability in network operations.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
As a temporary workaround, users can disable GSO on the affected network interface to prevent the issue from occurring. This can be done using the following command:
ethtool -K <interface_name> tso off
Replace <interface_name> with the name of your network interface, such as 'to-lb'.
Conclusion
The vulnerability CVE-2025-38115 in the Linux kernel's SFQ queuing discipline poses a risk of crashes due to improper handling of GSO packets. Users are advised to update their kernel to the patched version to mitigate this risk. Temporary workarounds are available, but updating is the recommended solution for long-term stability.
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FAQ
The vulnerability can lead to potential crashes in the network scheduling system, affecting the stability of network operations.
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Yes, a patch has been released for the Linux kernel to address this vulnerability. Users should update their kernel to the latest version.
SFQ stands for Stochastic Fairness Queueing, a queuing discipline used in network traffic management.
GSO stands for Generic Segmentation Offload, a technique used to improve network performance by offloading the segmentation of large packets to the network interface card.
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