In the Linux kernel, the following vulnerability has been resolved:
iommu/vt-d: Fix iopf_refcount leak on RID domain replacement
intel_iommu_attach_device() enables IOPF for the new domain but never
disables it for the old one. device_block_translation(), called at the
start of the function, tears down translation but does not touch any IOPF
state; blocking_domain_attach_dev() has to call iopf_for_domain_remove()
explicitly before invoking it for exactly this reason.
identity_domain_attach_dev() has the same problem. Its comment claims
that no PRI handling is needed because the device has been put in the
blocking state, but the blocking state and the IOPF reference count are
independent of each other.
As a result, replacing a domain that has an iopf_handler with another
domain at RID level leaks a reference in info->iopf_refcount. The count
never drops back to zero, so iopf_queue_remove_device() is never called
and iommu_disable_pci_pri() triggers its WARN_ON(info->iopf_refcount)
when the device is released.
The PASID paths already handle this correctly by way of
iopf_for_domain_replace(); convert the two RID paths to do the same.
Using the replace helper rather than a bare remove keeps the enable
before the disable, so the reference count does not transiently reach
zero and evict the device from the IOPF queue.