A flaw in the Linux kernel’s iommufd/viommu component causes the igroup lock to remain held when allocating a virtual device whose requested size exceeds the core structure size. The error handling path jumps past the mutex unlock, leaving the lock held and blocking all subsequent vDEVICE operations on that group. The problem manifests as a deadlock in the kernel and can halt services that rely on the affected modules.

The vulnerability affects any Linux kernel installation that includes the iommufd and viommu modules. Specific version information is not provided, so all kernel configurations with these modules that contain the unpatched code are potentially impacted across distributions. The CPE indicates the general Linux kernel as the affected product.

The EPSS score is less than 1%, indicating very low exploitation probability, and the vulnerability is not listed in CISA KEV. Because the defect results in a kernel lock deadlock, the primary impact is a local denial of service. Exploitation requires triggering the allocation path that checks vdevice_size, typically by loading a driver that performs such an allocation. The lack of an exploitable remote vector or privilege escalation path means the risk is confined to attackers who can run or install kernel modules, yet the CVSS score of 5.5 indicates a medium severity. A patched kernel removes the deadlock path and restores normal operation.