Fixed string size calculation in _validate_and_return_file_permission

Author: zezha-msft

azure-storage-file/azure/storage/file/_serialization.py

@@ -73,11 +73,11 @@ def _validate_and_format_range_headers(request, start_range, end_range, start_ra
 
 
 def _validate_and_return_file_permission(file_permission, file_permission_key, default_permission):
-    # if file_permission and file_permission are both empty, then use the default_permission value as file permission
-    # file_permission size should be <= 8KB, else file permission_key should be used
+    # if file_permission and file_permission_key are both empty, then use the default_permission
+    # value as file permission, file_permission size should be <= 8KB, else file permission_key should be used
     empty_file_permission = file_permission is None or len(file_permission) == 0
     empty_file_permission_key = file_permission_key is None or len(file_permission_key) == 0
-    file_permission_size_too_big = getsizeof(file_permission) > 8 * 1024
+    file_permission_size_too_big = False if file_permission is None else len(file_permission.encode('utf-8')) > 8 * 1024
 
     if file_permission_size_too_big:
         raise ValueError(_FILE_PERMISSION_TOO_LONG)