Index: /trunk/src/VBox/Additions/common/VBoxService/VBoxServiceAutoMount.cpp
===================================================================
--- /trunk/src/VBox/Additions/common/VBoxService/VBoxServiceAutoMount.cpp	(revision 75946)
+++ /trunk/src/VBox/Additions/common/VBoxService/VBoxServiceAutoMount.cpp	(revision 75947)
@@ -1371,6 +1371,7 @@
     AssertRC(rc);
 
-    PRTUTF16 pwszName = &wszPrefixedName[RTUtf16Len(wszPrefixedName)];
-    rc = RTStrToUtf16Ex(pEntry->pszName, RTSTR_MAX, &pwszName, pwszName - wszPrefixedName, NULL);
+    size_t const offName = RTUtf16Len(wszPrefixedName);
+    PRTUTF16 pwszName = &wszPrefixedName[offName];
+    rc = RTStrToUtf16Ex(pEntry->pszName, RTSTR_MAX, &pwszName, sizeof(wszPrefixedName) - offName, NULL);
     if (RT_FAILURE(rc))
     {