CVE-2026-43258: In the Linux kernel, the following vulnerability has been resolved: alpha: fix user-space corruption during memory comp

Alpha Linux systems experience random user-space crashes and memory corruption when memory compaction (a process that reorganizes memory to reduce fragmentation) is enabled, with symptoms including segmentation faults and heap errors. The problem stems from incomplete TLB shootdown (flushing stale memory address translations across processors) during page migration, which Alpha's standard cache coherency method cannot fully prevent. The fix introduces a specialized migration helper that combines MM context invalidation, immediate per-CPU TLB flushing, and cross-CPU synchronization, along with updates to other memory functions for correct multi-processor memory ordering.