mmap a VM_MIXEDMAP region whose ->huge_fault installs a PMD through vmf_insert_pfn_pmd() - mshv_vtl_low does this, and needs CAP_SYS_ADMIN to open - then: madvise(p, PMD_SIZE, MADV_PAGEOUT); With a stand-in module for the driver: BUG: unable to handle page fault for address: fffff587c0000008 RIP: 0010:madvise_cold_or_pageout_pte_range+0x410/0x9b0 walk_pgd_range+0x52b/0xaf0 __walk_page_range+0x6a/0x1d0 walk_page_range_vma_unsafe+0x8e/0x120 madvise_pageout+0xb2/0x180 madvise_vma_behavior+0x46b/0xa90 do_madvise+0x108/0x190 __x64_sys_madvise+0x26/0x30 Nothing validates the pfn on the way in: can_madv_lru_vma() rejects VM_PFNMAP, but not VM_MIXEDMAP can_fault() *pfn = vmf->pgoff & ~(mask >> PAGE_SHIFT); vmf_insert_pfn_pmd() no pfn_valid() check pmd_folio() pfn_to_page() -> unpopulated vmemmap Even with a valid pfn the path is wrong. The mapping carries no rmap, so folio_maybe_mapped_shared() sees mapcount 0, and the walker goes on to folio_deactivate(), or folio_isolate_lru() plus reclaim_pages(), against a folio this mapping does not own. Use vm_normal_folio_pmd() and skip on NULL, as the PTE half of this same walker already does with vm_normal_folio(). This also filters the huge zero PMD, so its separate check is no longer needed. Fixes: 3c8e44c9b369 ("mm: mark special bits for huge pfn mappings when inject") Reported-by: sashiko-bot Closes: https://sashiko.dev/#/patchset/20260817220810.1175596-1-gourry%40gourry.net Cc: stable@vger.kernel.org # v6.19+ Assisted-by: LLM Signed-off-by: Gregory Price (Meta) Reviewed-by: Lorenzo Stoakes (ARM) Acked-by: David Hildenbrand (Arm) Reviewed-by: Zi Yan --- mm/madvise.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index 61e15d9502ca..85ab9bc76e06 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -395,16 +395,15 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, return 0; orig_pmd = *pmd; - if (is_huge_zero_pmd(orig_pmd)) - goto huge_unlock; - if (unlikely(!pmd_present(orig_pmd))) { VM_WARN_ON_ONCE(!pmd_is_migration_entry(orig_pmd) && !pmd_is_device_private_entry(orig_pmd)); goto huge_unlock; } - folio = pmd_folio(orig_pmd); + folio = vm_normal_folio_pmd(vma, addr, orig_pmd); + if (!folio) + goto huge_unlock; if (folio_is_zone_device(folio)) goto huge_unlock; -- 2.55.0