From 83a8441f8d8e2e47e9bf2aead3aca625ab95d5ad Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Wed, 6 Apr 2022 08:41:39 -0400 Subject: [PATCH] mm/huge_memory: Avoid calling pmd_page() on a non-leaf PMD Calling try_to_unmap() with TTU_SPLIT_HUGE_PMD and a folio that's not mapped by a PMD causes oopses on arm64 because we now call page_folio() on an invalid page. pmd_page() returns a valid page for non-leaf PMDs on some architectures, so this bug escaped testing before now. Fix this bug by delaying the call to pmd_page() until after we know the PMD is a leaf. Link: https://bugzilla.kernel.org/show_bug.cgi?id=215804 Fixes: af28a988b313 ("mm/huge_memory: Convert __split_huge_pmd() to take a folio") Reported-by: Zorro Lang Signed-off-by: Matthew Wilcox (Oracle) Tested-by: Zorro Lang --- mm/huge_memory.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 2fe38212e07c..c468fee595ff 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2145,15 +2145,14 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, * pmd against. Otherwise we can end up replacing wrong folio. */ VM_BUG_ON(freeze && !folio); - if (folio) { - VM_WARN_ON_ONCE(!folio_test_locked(folio)); - if (folio != page_folio(pmd_page(*pmd))) - goto out; - } + VM_WARN_ON_ONCE(folio && !folio_test_locked(folio)); if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) || - is_pmd_migration_entry(*pmd)) + is_pmd_migration_entry(*pmd)) { + if (folio && folio != page_folio(pmd_page(*pmd))) + goto out; __split_huge_pmd_locked(vma, pmd, range.start, freeze); + } out: spin_unlock(ptl); -- 2.34.1