Commit 5bfea2d9 authored Jun 04, 2020 by Fan Yang Committed by Linus Torvalds Jun 04, 2020

mm: Fix mremap not considering huge pmd devmap



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: 5c7fb56e ("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>

parent 15a2bc4d

arch/x86/include/asm/pgtable.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -257,6 +257,7 @@ 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;

mm/mremap.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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() */

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