Linux kernel (drivers/iommu/intel): Killing a VM that has a device attached through the VT-d nested/PASID path makes

Impact

Killing a VM that has a device attached through the VT-d nested/PASID path makes the host dereference past the end of a static blocked-domain object and take a general protection fault. A tenant kills its own qemu and the host kernel goes down, taking every other tenant sharing that node with it.

Who can reach it

A tenant VM (or its VMM) with a device bound through vfio + iommufd nested domains and a PASID attached simply exits or is killed - releasing the vfio device fd runs the reset path that hits the bug. Conditional on VT-d scalable mode with nested translation in use; no host root and no fabric access needed.

What to do

Update to a stable kernel carrying commits 88397fad / 1e659db4. Interim: avoid VT-d nested translation (vIOMMU) for tenant VMs on unpatched hosts, and drain co-tenants off nodes that run nested-PASID passthrough until the kernel is updated.

References