From: Fan Yang Fan_Yang@sjtu.edu.cn
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: stable@vger.kernel.org Reported-by: Fan Yang Fan_Yang@sjtu.edu.cn Signed-off-by: Fan Yang Fan_Yang@sjtu.edu.cn Tested-by: Fan Yang Fan_Yang@sjtu.edu.cn Tested-by: Dan Williams dan.j.williams@intel.com Reviewed-by: Dan Williams dan.j.williams@intel.com Acked-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/include/asm/pgtable.h | 1 + mm/mremap.c | 2 +- 2 files changed, 2 insertions(+), 1 deletion(-)
--- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -256,6 +256,7 @@ 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; --- a/mm/mremap.c +++ b/mm/mremap.c @@ -266,7 +266,7 @@ unsigned long move_page_tables(struct vm 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() */