Linux kernel (drivers/vfio/pci/pds): The pds VFIO variant driver shipped without a detach_ioas operation, so it had no

Impact

The pds VFIO variant driver shipped without a detach_ioas operation, so it had no way to detach the device from the iommufd address space it was attached to. VFIO core's registration check catches this and refuses to load the driver, which is the fail-closed outcome - but the hazard the check exists to prevent is precisely a passthrough device left attached to an IOAS after the tenant that owned it is gone, i.e. a DMA window that outlives its owner. As shipped, the operator-visible symptom is that pds passthrough simply does not work when iommufd is enabled.

Who can reach it

Not directly attacker-triggered in the released form: the missing op makes probe fail with a WARN when CONFIG_IOMMUFD is enabled and a device is bound to pds_vfio_pci. Worth carrying because it is a completeness gap in the IOAS attach/detach contract on a passthrough driver, and because it silently removes AMD Pensando DPU/SmartNIC passthrough from any node running an iommufd-enabled kernel. Conditional on CONFIG_IOMMUFD and pds_vfio_pci being bound.

What to do

No fixed release is listed in this record; apply the linked stable commits or run a current stable/LTS kernel on nodes with Pensando/pds SR-IOV VFs. Interim: if pds passthrough is required, keep those nodes on the legacy VFIO type1 container path rather than iommufd until the kernel is patched.

References