Linux kernel (drivers/vfio/pci): A tenant holding a passthrough PCI device can make the kernel signal an interrupt

Impact

A tenant holding a passthrough PCI device can make the kernel signal an interrupt eventfd whose context has already been torn down, dereferencing a NULL/stale pointer from interrupt context. The host kernel corrupts or dies, and every other tenant sharing the node goes down with it.

Who can reach it

A container or VM holding /dev/vfio/<group> plus the device fd. The tenant deconfigures the INTx eventfd (VFIO_DEVICE_SET_IRQS with fd -1) while a device interrupt is pending, then drives the loopback trigger through SET_IRQS or the unmask irqfd - the irqfd path runs asynchronously to the ioctl mutex, so it is not serialized. Conditional on vfio-pci and a passthrough device that uses legacy INTx rather than MSI/MSI-X. No host root required.

What to do

The record lists no fixed release; boot a kernel carrying the stable fix commits below (backported across the 6.1/6.6/6.7 stable lines). Interim controls: only pass through devices using MSI/MSI-X, or remove the /dev/vfio device nodes from tenant containers.

References