diff --git a/nova/virt/disk/api.py b/nova/virt/disk/api.py
index af14e3f..4808bb4 100644
--- a/nova/virt/disk/api.py
+++ b/nova/virt/disk/api.py
@@ -335,10 +335,11 @@ def _join_and_check_path_within_fs(fs, *args):
     mounted guest fs.  Trying to be clever and specifying a
     path with '..' in it will hit this safeguard.
     '''
-    absolute_path = os.path.realpath(os.path.join(fs, *args))
-    if not absolute_path.startswith(os.path.realpath(fs) + '/'):
+    abs_path, _err = utils.execute('readlink', '-m', os.path.join(fs, *args),
+                                   run_as_root=True)
+    if not abs_path.startswith(os.path.realpath(fs) + '/'):
         raise exception.Invalid(_('injected file path not valid'))
-    return absolute_path
+    return abs_path
 
 
 def _inject_file_into_fs(fs, path, contents, append=False):