RFR(S) 8160987: JDWP ClassType.InvokeMethod doesn't validate class

harold seigel harold.seigel at oracle.com
Thu Sep 15 18:10:20 UTC 2016

(Adding hotspot-runtime)

Hi Dan,

Thanks for looking at this.

I could pass NULL instead of clazz to ToReflectMethod() to ensure that 
the method object isn't being obtained from clazz.


On 9/15/2016 1:09 PM, Daniel D. Daugherty wrote:
> On 9/15/16 9:31 AM, harold seigel wrote:
>> Hi,
>> Please review this small fix for JDK-8160987.  The JDWP 
>> InvokeStatic() method was depending on the JNI function that it 
>> called to enforce the requirement that the specified method must be a 
>> member of the specified class or one of its super classes. But, JNI 
>> does not enforce this requirement.  This fix adds code to JDWP to do 
>> its own check that the specified method is a member of the specified 
>> class or one of its super classes.
>> JBS Bug: https://bugs.openjdk.java.net/browse/JDK-8160987
>> Open webrev: http://cr.openjdk.java.net/~hseigel/bug_8160987/
> src/jdk.jdwp.agent/share/native/libjdwp/invoker.c
>     Sorry I didn't think of this comment during the pre-review...
>     The only "strange" part of this fix is:
>     L374:     /* Get the method object from the method's jmethodID. */
>     L375:     method_object = JNI_FUNC_PTR(env,ToReflectedMethod)(env,
>     L376: clazz,
>     L377: method,
>     L378: JNI_TRUE /* isStatic */);
>     L379:     if (method_object == NULL) {
>     L380:         return JVMTI_ERROR_NONE; /* Bad jmethodID ? This 
> will be handled elsewhere */
>     L381:     }
>     Here we are using parameter 'clazz' to find the method_object for
>     parameter 'method' so that we can validate that 'clazz' refers to
>     method's class or superclass.
>     When a bogus 'clazz' value is passed in by a JCK test, the only
>     reason that JNI ToReflectedMethod() can still find the right
>     method_object is that our (HotSpot) implementation of JNI
>     ToReflectedMethod() doesn't really require the 'clazz' parameter
>     to find the right method_object. So the 'method_object' that we
>     return is the real one which has a 'clazz' field that doesn't
>     match the 'clazz' parameter.
>     Wow does that twist your head around or what?
>     So we're trusting JNI ToReflectedMethod() to return the right
>     method_object when we give it a potentially bad 'clazz' value.
>     So should we use JNI FromReflectedMethod() to convert the
>     method_object back into a jmethodID and verify that jmethodID
>     matches the one that we passed to check_methodClass()?
> I might be too paranoid here so feel free to say that enough is
> enough with this fix.
> Thumbs up!
> Dan
>> The fix was tested with the two failing JCK vm/jdwp tests listed in 
>> the bug, the JCK Lang, VM, and API tests, the hotspot JTReg tests, 
>> the java/lang, java/util and other JTReg tests, the co-located and 
>> non-colocated NSK tests, and with the RBT Tier2 tests.
>> Thanks, Harold

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