1 files changed, 9 insertions, 7 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index 7a0707a48047..b3b74cc705ae 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -116,13 +116,15 @@ static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
 void vma_set_page_prot(struct vm_area_struct *vma)
 {
         unsigned long vm_flags = vma->vm_flags;
+        pgprot_t vm_page_prot;
 
-        vma->vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags);
-        if (vma_wants_writenotify(vma)) {
+        vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags);
+        if (vma_wants_writenotify(vma, vm_page_prot)) {
                 vm_flags &= ~VM_SHARED;
-                vma->vm_page_prot = vm_pgprot_modify(vma->vm_page_prot,
-                                                     vm_flags);
+                vm_page_prot = vm_pgprot_modify(vm_page_prot, vm_flags);
         }
+        /* remove_protection_ptes reads vma->vm_page_prot without mmap_sem */
+        WRITE_ONCE(vma->vm_page_prot, vm_page_prot);
 }
 
 /*
@@ -1386,7 +1388,7 @@ SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
  * to the private version (using protection_map[] without the
  * VM_SHARED bit).
  */
-int vma_wants_writenotify(struct vm_area_struct *vma)
+int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)
 {
         vm_flags_t vm_flags = vma->vm_flags;
         const struct vm_operations_struct *vm_ops = vma->vm_ops;
@@ -1401,8 +1403,8 @@ int vma_wants_writenotify(struct vm_area_struct *vma)
 
         /* The open routine did something to the protections that pgprot_modify
          * won't preserve? */
-        if (pgprot_val(vma->vm_page_prot) !=
-            pgprot_val(vm_pgprot_modify(vma->vm_page_prot, vm_flags)))
+        if (pgprot_val(vm_page_prot) !=
+            pgprot_val(vm_pgprot_modify(vm_page_prot, vm_flags)))
                 return 0;
 
         /* Do we need to track softdirty? */