swapops-0004-mm-ksm-handle-protnone-saved-writes-when-making-page.patch

   1 From 361de9fb44163c4e693022786af380a2b2298c6d Mon Sep 17 00:00:00 2001
   2 From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
   3 Date: Fri, 24 Feb 2017 14:59:19 -0800
   4 Subject: [PATCH 4/4] mm/ksm: handle protnone saved writes when making page
   5  write protect
   6
   7 Without this KSM will consider the page write protected, but a numa
   8 fault can later mark the page writable.  This can result in memory
   9 corruption.
  10
  11 Link: http://lkml.kernel.org/r/1487498625-10891-3-git-send-email-aneesh.kumar@linux.vnet.ibm.com
  12 Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
  13 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  14 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  15 (backported from commit 595cd8f256d24face93b2722927ec9c980419c26)
  16 Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
  17 ---
  18  include/asm-generic/pgtable.h | 8 ++++++++
  19  mm/ksm.c                      | 9 +++++++--
  20  2 files changed, 15 insertions(+), 2 deletions(-)
  21
  22 diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
  23 index b6f3a8a4b738..8c8ba48bef0b 100644
  24 --- a/include/asm-generic/pgtable.h
  25 +++ b/include/asm-generic/pgtable.h
  26 @@ -200,6 +200,10 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres
  27  #define pte_mk_savedwrite pte_mkwrite
  28  #endif
  29
  30 +#ifndef pte_clear_savedwrite
  31 +#define pte_clear_savedwrite pte_wrprotect
  32 +#endif
  33 +
  34  #ifndef pmd_savedwrite
  35  #define pmd_savedwrite pmd_write
  36  #endif
  37 @@ -208,6 +212,10 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres
  38  #define pmd_mk_savedwrite pmd_mkwrite
  39  #endif
  40
  41 +#ifndef pmd_clear_savedwrite
  42 +#define pmd_clear_savedwrite pmd_wrprotect
  43 +#endif
  44 +
  45  #ifndef __HAVE_ARCH_PMDP_SET_WRPROTECT
  46  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  47  static inline void pmdp_set_wrprotect(struct mm_struct *mm,
  48 diff --git a/mm/ksm.c b/mm/ksm.c
  49 index fed4afd8293b..099dfa45d596 100644
  50 --- a/mm/ksm.c
  51 +++ b/mm/ksm.c
  52 @@ -878,7 +878,8 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page,
  53         if (!ptep)
  54                 goto out_mn;
  55
  56 -       if (pte_write(*ptep) || pte_dirty(*ptep)) {
  57 +       if (pte_write(*ptep) || pte_dirty(*ptep) ||
  58 +           (pte_protnone(*ptep) && pte_savedwrite(*ptep))) {
  59                 pte_t entry;
  60
  61                 swapped = PageSwapCache(page);
  62 @@ -903,7 +904,11 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page,
  63                 }
  64                 if (pte_dirty(entry))
  65                         set_page_dirty(page);
  66 -               entry = pte_mkclean(pte_wrprotect(entry));
  67 +
  68 +               if (pte_protnone(entry))
  69 +                       entry = pte_mkclean(pte_clear_savedwrite(entry));
  70 +               else
  71 +                       entry = pte_mkclean(pte_wrprotect(entry));
  72                 set_pte_at_notify(mm, addr, ptep, entry);
  73         }
  74         *orig_pte = *ptep;
  75 --
  76 2.7.4
  77