In fixing bugid 4898868 it was discovered that AWT sometimes does not check
for null values of env at the beginning of JNI calls. E.g. in
/src/win32/native/sun/windows/awt_new.cpp the code read:

int
NewHandler::handler(size_t) {
    JNIEnv *env = (JNIEnv *)JNU_GetEnv(jvm, JNI_VERSION_1_2);
    if (env->EnsureLocalCapacity(1) < 0) {
        return 0;
    }

and the pointer "env" was dereferenced without checking to see if it was valid.

The doc for JNU_GetEnv() in src/share/native/common/jni_util.h reads:

/*
  * Check if the current thread is attached to the VM, and returns
  * the JNIEnv of the specified version if the thread is attached.
  *
  * If the current thread is not attached, this function returns 0.
  *
  * If the current thread is attached, this function returns the
  * JNI environment, or returns (void *)JNI_ERR if the specified
  * version is not suppored.
  */
JNIEXPORT void * JNICALL
JNU_GetEnv(JavaVM *vm, jint version);

We should audit the AWT JNI code and handle error conditions such as this one.
I imagine we should do it for the unix native code as well as windows.