CVE-2026-31397 mm/huge_memory: fix use of NULL folio in move_pages_huge_pmd()

In the Linux kernel, the following vulnerability has been resolved: mm/hugememory: fix use of NULL folio in movepageshugepmd movepageshugepmd handles UFFDIOMOVE for both normal THPs and huge zero pages. For the huge zero page path, srcfolio is explicitly set to NULL, and is used as a sentinel to...