CVE-2026-74573

In the Linux kernel, the following vulnerability has been resolved:

iommu/arm-smmu-v3-iommufd: Require exactly one Stream ID for a vDEVICE

armvsmmuvsidtosid() maps a guest's vSID to a single physical Stream ID

taken from master->streams[0], assuming a device has exactly one stream. A

device with several streams gets only its first one mapped, so a guest vSID

invalidation cannot reach the others' ATC and IOTLB entries; a device with

none makes master->streams a ZEROSIZEPTR, read out of bounds.

Add an armvsmmuvdevice_init() op to reject the vDEVICE with -EOPNOTSUPP

when master->num_streams is not one, rather than mapping it silently.