CVE-2026-64514 userfaultfd: gate must_wait writability check on pte_present()

In the Linux kernel, the following vulnerability has been resolved: userfaultfd: gate mustwait writability check on ptepresent userfaultfdmustwait and userfaultfdhugemustwait read the PTE without taking the page table lock and then apply ptewrite / hugeptewrite to it. Those accessors decode bits...