RFR 8017271: Crash may occur in java.net.DualStackPlainSocketImpl::initIDs due to unchecked values returned from JNI functions

[Chris Hegarty]

There is a remote possibility that FindClass can return NULL, for a 
class we expect to exist, OOM, etc. Best practice is to check the return 
value before attempting to use it.

CHECK_NULL [1] is a macro used in other places in the networking native 
code for such checks. There will be a pending exception on the stack if 
FindClass fails.

diff -r 4503e04141f7 src/windows/native/java/net/DualStackPlainSocketImpl.c
--- a/src/windows/native/java/net/DualStackPlainSocketImpl.c    Fri Jun 
21 18:26:13 2013 +0800
+++ b/src/windows/native/java/net/DualStackPlainSocketImpl.c    Fri Jun 
21 14:39:52 2013 +0100
@@ -43,6 +43,7 @@ JNIEXPORT void JNICALL Java_java_net_Dua
   (JNIEnv *env, jclass clazz) {

     jclass cls = (*env)->FindClass(env, "java/net/InetSocketAddress");
+    CHECK_NULL(cls);
     isa_class = (*env)->NewGlobalRef(env, cls);
     isa_ctorID = (*env)->GetMethodID(env, cls, "<init>",
                                      "(Ljava/net/InetAddress;I)V");

-Chris.

[1] #define CHECK_NULL(x) if ((x) == NULL) return;