From df4988aa1c9618d9c612639e96002cd4e772def2 Mon Sep 17 00:00:00 2001 From: Fan Yang Date: Thu, 4 Jun 2020 18:22:07 +0800 Subject: [PATCH] mm: Fix mremap not considering huge pmd devmap commit 5bfea2d9b17f1034a68147a8b03b9789af5700f9 upstream. The original code in mm/mremap.c checks huge pmd by: if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd)) { However, a DAX mapped nvdimm is mapped as huge page (by default) but it is not transparent huge page (_PAGE_PSE | PAGE_DEVMAP). This commit changes the condition to include the case. This addresses CVE-2020-10757. Fixes: 5c7fb56e5e3f ("mm, dax: dax-pmd vs thp-pmd vs hugetlbfs-pmd") Cc: Reported-by: Fan Yang Signed-off-by: Fan Yang Tested-by: Fan Yang Tested-by: Dan Williams Reviewed-by: Dan Williams Acked-by: Kirill A. Shutemov Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/pgtable.h | 1 + mm/mremap.c | 2 +- 2 files changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 1e6bb4c25334..ea85f23d9e22 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -253,6 +253,7 @@ static inline int pmd_large(pmd_t pte) } #ifdef CONFIG_TRANSPARENT_HUGEPAGE +/* NOTE: when predicate huge page, consider also pmd_devmap, or use pmd_large */ static inline int pmd_trans_huge(pmd_t pmd) { return (pmd_val(pmd) & (_PAGE_PSE|_PAGE_DEVMAP)) == _PAGE_PSE; diff --git a/mm/mremap.c b/mm/mremap.c index 245bf9c555b2..8005d0b2b843 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -266,7 +266,7 @@ unsigned long move_page_tables(struct vm_area_struct *vma, new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr); if (!new_pmd) break; - if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd)) { + if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) || pmd_devmap(*old_pmd)) { if (extent == HPAGE_PMD_SIZE) { bool moved; /* See comment in move_ptes() */