CVE-2025-40174 x86/mm: Fix SMP ordering in switch_mm_irqs_off()

In the Linux kernel, the following vulnerability has been resolved: x86/mm: Fix SMP ordering in switchmmirqsoff Stephen noted that it is possible to not have an smpmb between the loadedmm store and the tlbgen load in switchmm, meaning the ordering against flushtlbmmrange goes out the window, and ...