Linux kernel (drivers/vfio/fsl-mc): The eventfd trigger for a vfio-fsl-mc interrupt starts out NULL and becomes NULL

Impact

The eventfd trigger for a vfio-fsl-mc interrupt starts out NULL and becomes NULL again if the tenant sets it to -1, but the loopback test path fires the handler without checking. A tenant holding the device fd dereferences NULL in the kernel interrupt path and downs the host for everyone on the node.

Who can reach it

A container or VM holding a vfio-fsl-mc device fd, invoking the loopback interrupt trigger through VFIO_DEVICE_SET_IRQS before setting an eventfd or after clearing it to -1. No host root. Conditional on the NXP DPAA2 fsl-mc bus and its vfio driver - NXP SoC hardware, not present in x86 or ARM GPU fleets.

What to do

The record lists no fixed release; boot a kernel carrying the stable fix commits below. Interim control: blacklist vfio-fsl-mc on any fleet that does not assign DPAA2 objects.

References