Medium [CVE-2026-74520] Fix IOPF group ownership UAF

In the Linux kernel, the following vulnerability has been resolved: iommu/iommufd: Fix IOPF group ownership UAF iopf_group_alloc() links each last-page IOPF group into the generic IOPF pending list before invoking the domain fault handler. iommufd_fault_iopf_handler() also queued an accepted group in the IOMMUFD deliver list without removing it from the generic pending list.

When detach or HWPT replacement drops the device's IOPF reference count to zero, an IOMMU driver may call iopf_queue_remove_device(). That function responds to and frees groups through the generic pending list without removing the same groups from IOMMUFD's deliver list or response xarray.

A later read, response, or cleanup can then access the freed group and cause a UAF. Make iopf_group_response() send a response regardless of pending-list membership, so the dequeued group can still be completed by IOMMUFD.

A flaw was found in the Linux kernel's IOMMU (Input/Output Memory Management Unit) and IOMMUFD (IOMMU File Descriptor) components. This vulnerability is a Use-After-Free (UAF), which means the system attempts to use memory that has already been released.

Specifically, during device detachment or hardware page table replacement, an IOMMU Page Fault (IOPF) group can be freed while still being referenced by other parts of the system.