[PATCH] initialise vma->vm_next in do_mmap_pgoff()

We end up inspecting this field in zap_page_range(), on the mmap error path.
Best initialise it to something...

mm/mmap.c

@@ -677,6 +677,7 @@ unsigned long do_mmap_pgoff(struct file * file, unsigned long addr,
 	vma->vm_pgoff = pgoff;
 	vma->vm_file = NULL;
 	vma->vm_private_data = NULL;
+	vma->vm_next = NULL;
 	INIT_LIST_HEAD(&vma->shared);
 
 	if (file) {