Executive Summary

This vulnerability exists in the Linux kernel's iommu/vt-d component. It involves the improper order of operations when handling a PASID (Process Address Space ID) table. Specifically, the CPU cache flush for a freshly allocated zero-initialized PASID table was done after writing its address to a PASID directory entry, rather than before. This creates a time window where non-coherent IOMMU hardware might use the PASID table while its contents in RAM still contain random old data instead of being zero-initialized, potentially leading to incorrect or unexpected behavior.

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Impact Analysis

The vulnerability can lead to the use of stale or uninitialized data in the PASID table by the IOMMU hardware. This may cause unpredictable system behavior, potential data corruption, or security issues related to memory management and device isolation. Since the PASID table controls address translations for devices, improper initialization could affect system stability or security in environments relying on IOMMU for device isolation.

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