Critical RCU Usage Vulnerability in Linux Kernel Package
Summary
DEBIAN-CVE-2025-21876: In the Linux kernel, the following vulnerability has been resolved: iommu/vt-d: Fix suspicious RCU usage Commit ("iommu/vt-d: Allocate DMAR fault interrupts locally") moved the call to enable_drhd_fault_handling() to a c... 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 the Linux operating system, responsible for managing hardware resources and providing essential services to applications. It is widely used across various platforms, including servers, desktops, and embedded systems. This vulnerability affects the Linux kernel versions in Debian 13 and 14, specifically related to the IOMMU (Input-Output Memory Management Unit) subsystem, which is crucial for managing memory access for devices.
Vulnerability Detail
In the Linux kernel, a vulnerability has been identified in the IOMMU subsystem, specifically in the handling of DMAR (DMA Remapping) fault interrupts. The issue arises from a commit that moved the call to enable_drhd_fault_handling() to a code path that does not hold any lock while traversing the drhd list. This can lead to a warning about suspicious RCU (Read-Copy-Update) usage, indicating potential race conditions and instability in the kernel. If left unaddressed, this vulnerability could lead to system crashes or unpredictable behavior, especially under high load or during device probing.
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
Currently, there are no specific workarounds available for this vulnerability other than applying the patch by updating the kernel version.
Conclusion
The identified vulnerability in the Linux kernel poses significant risks to system stability and security. It is crucial for users of Debian 13 and 14 to update their kernel to the patched version 6.12.19-1 to mitigate these risks effectively.
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FAQ
The vulnerability involves improper handling of RCU usage in the IOMMU subsystem, which can lead to system instability.
The vulnerability affects Linux kernel versions prior to 6.12.19-1 in both Debian 13 and 14.
You can use tools like Vulert to monitor and alert for open-source vulnerabilities in your software. Visit Vulert Scanner to check if your application is affected.
If exploited, this vulnerability could lead to system crashes, unpredictable behavior, and potential data loss.
Currently, there are no known workarounds to mitigate this risk other than updating to the patched version.
References
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