Local system hang via invalidation endpoint overflow

An infinite-loop flaw in the Linux Kernel RISC-V IOMMU driver allows local users to hang the system during IOTLB invalidation. The invalidation loop increments an address through gather->end; when that inclusive endpoint is ULONG_MAX, unsigned wraparound prevents termination, while the range-length expression can also overflow. Exploitation requires local low-privileged access and a RISC-V system using the affected IOMMU path, and the reported consequence is loss of availability rather than data access or modification.