UBUNTU: Ubuntu-4.15.0-96.97

[mirror_ubuntu-bionic-kernel.git] / mm / mprotect.c

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 58b629bb70de3024aba118000f83f52dd92e6d95..60864e19421e6836997d8993239d0943d8787731 100644 (file)
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -292,6 +292,42 @@ unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
        return pages;
 }
 
+static int prot_none_pte_entry(pte_t *pte, unsigned long addr,
+                              unsigned long next, struct mm_walk *walk)
+{
+       return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ?
+               0 : -EACCES;
+}
+
+static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask,
+                                  unsigned long addr, unsigned long next,
+                                  struct mm_walk *walk)
+{
+       return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ?
+               0 : -EACCES;
+}
+
+static int prot_none_test(unsigned long addr, unsigned long next,
+                         struct mm_walk *walk)
+{
+       return 0;
+}
+
+static int prot_none_walk(struct vm_area_struct *vma, unsigned long start,
+                          unsigned long end, unsigned long newflags)
+{
+       pgprot_t new_pgprot = vm_get_page_prot(newflags);
+       struct mm_walk prot_none_walk = {
+               .pte_entry = prot_none_pte_entry,
+               .hugetlb_entry = prot_none_hugetlb_entry,
+               .test_walk = prot_none_test,
+               .mm = current->mm,
+               .private = &new_pgprot,
+       };
+
+       return walk_page_range(start, end, &prot_none_walk);
+}
+
 int
 mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
        unsigned long start, unsigned long end, unsigned long newflags)
@@ -309,6 +345,19 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
                return 0;
        }
 
+       /*
+        * Do PROT_NONE PFN permission checks here when we can still
+        * bail out without undoing a lot of state. This is a rather
+        * uncommon case, so doesn't need to be very optimized.
+        */
+       if (arch_has_pfn_modify_check() &&
+           (vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
+           (newflags & (VM_READ|VM_WRITE|VM_EXEC)) == 0) {
+               error = prot_none_walk(vma, start, end, newflags);
+               if (error)
+                       return error;
+       }
+
        /*
         * If we make a private mapping writable we increase our commit;
         * but (without finer accounting) cannot reduce our commit if we