null terminate the converted LPStr at the right index (#17079)

diff --git a/src/vm/olevariant.cpp b/src/vm/olevariant.cpp
index 95c0b9b0cc861ae082b410acefbf972434d6f929..35936bbc5a0790249fe9a8d7e25e4a5bffb8141b 100644 (file)
--- a/src/vm/olevariant.cpp
+++ b/src/vm/olevariant.cpp
@@ -2310,8 +2310,9 @@ void OleVariant::MarshalLPSTRRArrayComToOle(BASEARRAYREF *pComArray, void *oleAr
                 ThrowOutOfMemory();
 
             // Convert the unicode string to an ansi string.
-            InternalWideToAnsi(stringRef->GetBuffer(), Length, lpstr, allocLength, fBestFitMapping, fThrowOnUnmappableChar);
-            lpstr[Length] = 0;
+            int bytesWritten = InternalWideToAnsi(stringRef->GetBuffer(), Length, lpstr, allocLength, fBestFitMapping, fThrowOnUnmappableChar);
+            _ASSERTE(bytesWritten >= 0 && bytesWritten < allocLength);
+            lpstr[bytesWritten] = 0;
         }
 
         *pOle++ = lpstr;