Critical Vulnerability in Linux Kernel: RDMA/mlx5 Implicit ODP Hang
Summary
DEBIAN-CVE-2025-21886: In the Linux kernel, the following vulnerability has been resolved: RDMA/mlx5: Fix implicit ODP hang on parent deregistration Fix the destroy_unused_implicit_child_mr() to prevent hanging during parent deregistration as... Affects linux versions < 6.12.19-1. Fixed in 6.12.19-1. How to fix ↓
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Background
The Linux kernel is the core component of many operating systems, providing essential services for hardware management and system resources. It is known for its stability and performance, supporting a wide range of hardware architectures. However, vulnerabilities can arise, impacting system reliability and security. This specific vulnerability affects the RDMA (Remote Direct Memory Access) subsystem, particularly the mlx5 driver, which is used for high-performance networking.
Vulnerability Detail
In the Linux kernel, a vulnerability has been identified in the RDMA/mlx5 subsystem that causes an implicit ODP (On-Demand Paging) hang during parent deregistration. The issue arises when the reference count for the implicit Memory Region (MR) parent is not properly managed, leading to potential system hangs. This can result in tasks being blocked for extended periods, as evidenced by the reported case where a Python process was blocked for over 120 seconds. The vulnerability is critical as it can disrupt system operations and affect applications relying on RDMA functionalities.
How To Fix
Minimum fixed version
6.12.19-1
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 disable the hung task timeout message by executing the command: 'echo 0 > /proc/sys/kernel/hung_task_timeout_secs'. However, this does not fix the underlying issue and should only be used as a short-term measure until the package is updated.
Conclusion
The vulnerability in the Linux kernel's RDMA/mlx5 subsystem poses significant risks, including potential system hangs and application disruptions. Users are advised to update their packages to the patched version to mitigate these risks. Temporary workarounds are available but should not replace proper updates.
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FAQ
The vulnerability involves a hang in the RDMA/mlx5 subsystem during parent deregistration, potentially blocking tasks for extended periods.
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The risks include system hangs and disruptions in applications that rely on RDMA functionalities, which can lead to degraded performance and reliability.
Yes, updating the Linux package to version 6.12.19-1 or later will permanently fix the vulnerability.
If immediate updates are not possible, consider applying the temporary workaround to disable hung task timeout messages until a proper update can be performed.
References
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