1 files changed, 9 insertions, 2 deletions

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 14f93e62270f..638edabaff71 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -123,6 +123,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
         unsigned long oldflags = vma->vm_flags;
         long nrpages = (end - start) >> PAGE_SHIFT;
         unsigned long charged = 0;
+        unsigned int mask;
         pgprot_t newprot;
         pgoff_t pgoff;
         int error;
@@ -149,8 +150,6 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
                 }
         }
 
-        newprot = protection_map[newflags & 0xf];
-
         /*
          * First try to merge with previous and/or next vma.
          */
@@ -177,6 +176,14 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
         }
 
 success:
+        /* Don't make the VMA automatically writable if it's shared, but the
+         * backer wishes to know when pages are first written to */
+        mask = VM_READ|VM_WRITE|VM_EXEC|VM_SHARED;
+        if (vma->vm_ops && vma->vm_ops->page_mkwrite)
+                mask &= ~VM_SHARED;
+
+        newprot = protection_map[newflags & mask];
+
         /*
          * vm_flags and vm_page_prot are protected by the mmap_sem
          * held in write mode.