Local denial of service via repeated TLB flushes

Denial of service in Linux kernel 6.9 through 6.12.3 allows local users to cause a CPU soft lockup during KASAN vmalloc cleanup. The purge_vmap_node path calls kasan_release_vmalloc for each vmap area, issuing thousands of separate cross-CPU TLB flushes instead of combining their address ranges. Exploitation requires a KASAN-enabled kernel and a heavy parallel kernel build; the observed consequence is a worker CPU stuck for more than 22 seconds, not data access or modification.