CVE-2026-19574 ARM64 MMU can assign an in-use ASID to a new memory domain, breaking user-mode memory isolation

The ARM64 MMU back-end allocated address space identifiers ASIDs for memory domains with a bare round-robin counter in archmemdomaininit arch/arm64/core/mmu.c. VMASIDBITS is 8, so only 255 ASIDs exist; once the counter wrapped, archmemdomaininit could hand an ASID to a new domain while a still-li...