releases/4.19.35/mm-huge_memory.c-fix-modifying-of-page-protection-by-insert_pfn_pmd.patch

   1 From c6f3c5ee40c10bb65725047a220570f718507001 Mon Sep 17 00:00:00 2001
   2 From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
   3 Date: Fri, 5 Apr 2019 18:39:10 -0700
   4 Subject: mm/huge_memory.c: fix modifying of page protection by insert_pfn_pmd()
   5
   6 From: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
   7
   8 commit c6f3c5ee40c10bb65725047a220570f718507001 upstream.
   9
  10 With some architectures like ppc64, set_pmd_at() cannot cope with a
  11 situation where there is already some (different) valid entry present.
  12
  13 Use pmdp_set_access_flags() instead to modify the pfn which is built to
  14 deal with modifying existing PMD entries.
  15
  16 This is similar to commit cae85cb8add3 ("mm/memory.c: fix modifying of
  17 page protection by insert_pfn()")
  18
  19 We also do similar update w.r.t insert_pfn_pud eventhough ppc64 don't
  20 support pud pfn entries now.
  21
  22 Without this patch we also see the below message in kernel log "BUG:
  23 non-zero pgtables_bytes on freeing mm:"
  24
  25 Link: http://lkml.kernel.org/r/20190402115125.18803-1-aneesh.kumar@linux.ibm.com
  26 Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
  27 Reported-by: Chandan Rajendra <chandan@linux.ibm.com>
  28 Reviewed-by: Jan Kara <jack@suse.cz>
  29 Cc: Dan Williams <dan.j.williams@intel.com>
  30 Cc: <stable@vger.kernel.org>
  31 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  32 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  33 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  34
  35 ---
  36  mm/huge_memory.c |   36 ++++++++++++++++++++++++++++++++++++
  37  1 file changed, 36 insertions(+)
  38
  39 --- a/mm/huge_memory.c
  40 +++ b/mm/huge_memory.c
  41 @@ -734,6 +734,21 @@ static void insert_pfn_pmd(struct vm_are
  42         spinlock_t *ptl;
  43
  44         ptl = pmd_lock(mm, pmd);
  45 +       if (!pmd_none(*pmd)) {
  46 +               if (write) {
  47 +                       if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
  48 +                               WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
  49 +                               goto out_unlock;
  50 +                       }
  51 +                       entry = pmd_mkyoung(*pmd);
  52 +                       entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
  53 +                       if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
  54 +                               update_mmu_cache_pmd(vma, addr, pmd);
  55 +               }
  56 +
  57 +               goto out_unlock;
  58 +       }
  59 +
  60         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
  61         if (pfn_t_devmap(pfn))
  62                 entry = pmd_mkdevmap(entry);
  63 @@ -745,11 +760,16 @@ static void insert_pfn_pmd(struct vm_are
  64         if (pgtable) {
  65                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
  66                 mm_inc_nr_ptes(mm);
  67 +               pgtable = NULL;
  68         }
  69
  70         set_pmd_at(mm, addr, pmd, entry);
  71         update_mmu_cache_pmd(vma, addr, pmd);
  72 +
  73 +out_unlock:
  74         spin_unlock(ptl);
  75 +       if (pgtable)
  76 +               pte_free(mm, pgtable);
  77  }
  78
  79  vm_fault_t vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
  80 @@ -800,6 +820,20 @@ static void insert_pfn_pud(struct vm_are
  81         spinlock_t *ptl;
  82
  83         ptl = pud_lock(mm, pud);
  84 +       if (!pud_none(*pud)) {
  85 +               if (write) {
  86 +                       if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
  87 +                               WARN_ON_ONCE(!is_huge_zero_pud(*pud));
  88 +                               goto out_unlock;
  89 +                       }
  90 +                       entry = pud_mkyoung(*pud);
  91 +                       entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
  92 +                       if (pudp_set_access_flags(vma, addr, pud, entry, 1))
  93 +                               update_mmu_cache_pud(vma, addr, pud);
  94 +               }
  95 +               goto out_unlock;
  96 +       }
  97 +
  98         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
  99         if (pfn_t_devmap(pfn))
 100                 entry = pud_mkdevmap(entry);
 101 @@ -809,6 +843,8 @@ static void insert_pfn_pud(struct vm_are
 102         }
 103         set_pud_at(mm, addr, pud, entry);
 104         update_mmu_cache_pud(vma, addr, pud);
 105 +
 106 +out_unlock:
 107         spin_unlock(ptl);
 108  }
 109