From df4988aa1c9618d9c612639e96002cd4e772def2 Mon Sep 17 00:00:00 2001
From: Fan Yang <Fan_Yang@sjtu.edu.cn>
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: <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(-)
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() */