7171703: JNI DefineClass crashes client VM when first parameter is NULL

Reviewed-by: acorn, kamg, sspitsyn, dholmes

src/share/vm/prims/jni.cpp

 /*
- * Copyright (c) 1997, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -378,6 +378,7 @@ JNI_ENTRY(jclass, jni_DefineClass(JNIEnv *env, const char *name, jobject loaderR
   jclass cls = NULL;
   DT_RETURN_MARK(DefineClass, jclass, (const jclass&)cls);
 
+  TempNewSymbol class_name = NULL;
   // Since exceptions can be thrown, class initialization can take place
   // if name is NULL no check for class name in .class stream has to be made.
   if (name != NULL) {
@@ -387,9 +388,8 @@ JNI_ENTRY(jclass, jni_DefineClass(JNIEnv *env, const char *name, jobject loaderR
       // into the constant pool.
       THROW_MSG_0(vmSymbols::java_lang_NoClassDefFoundError(), name);
     }
+    class_name = SymbolTable::new_symbol(name, CHECK_NULL);
   }
-  TempNewSymbol class_name = SymbolTable::new_symbol(name, THREAD);
-
   ResourceMark rm(THREAD);
   ClassFileStream st((u1*) buf, bufLen, NULL);
   Handle class_loader (THREAD, JNIHandles::resolve(loaderRef));