[9] RFR(S): 8139150: ClassVerifier frees exception message while it's still in use (original) (raw)

Daniel D. Daugherty daniel.daugherty at oracle.com
Thu Oct 8 16:08:43 UTC 2015

On 10/8/15 9:38 AM, Tobias Hartmann wrote:

Hi,

please review the following patch. https://bugs.openjdk.java.net/browse/JDK-8139150 http://cr.openjdk.java.net/~thartmann/8139150/webrev.00/

src/share/vm/classfile/stackMapTable.cpp No comments.

Thumbs up!

Did a quick audit and I don't see any other calls to class_format_error() with the same issue.

This bug is very old. That ResourceMark came from here:

$ sp -r1.17 src/share/vm/classfile/stackMapTable.cpp src/share/vm/classfile/SCCS/s.stackMapTable.cpp:

D 1.17 05/06/20 17:21:50 mingyao 18 17 00015/00008/00446 MRs: COMMENTS: Fixed 6275215, VM fails on StackMapTable jcod tests (VerifyError) Fixed 6275199, VM fails on StackMapTable jcod tests Fixed 6275153, VM fails on StackMapTable tests

And the code looked like this:

187a185,194

if (offset >= _code_length ||
    _code_data[offset] != ClassVerifier::NEW_OFFSET) {
  ResourceMark rm(THREAD);
  Exceptions::fthrow(
    THREAD_AND_LOCATION,
    vmSymbolHandles::java_lang_ClassFormatError(),
    "StackMapTable format error: bad offset for Uninitialized"
  );
  return NULL;
}

The class_format_error() call came from here:

D 1.21 06/04/13 11:43:50 km88527 23 22 00064/00108/00360 MRs: COMMENTS: fixed 6402717: Error verifying java.lang.Error causes VM to exit silently due to stack overflow

and the code changed to look like this:

 if (offset >= _code_length ||
     _code_data[offset] != ClassVerifier::NEW_OFFSET) {
   ResourceMark rm(THREAD);
   _verifier->class_format_error(
     "StackMapTable format error: bad offset for Uninitialized");
   return NULL;
 }

This fix should probably be backported... but I would check with Harold...

Dan

Problem: If class verification fails in StackMapReader::parseverificationtype(), ClassVerifier::classformaterror() is invoked to pass the error message. The method allocates a new string and saves it in ClassVerifier::message. The problem is that the caller creates a new ResourceMark that leads to message being deallocated after return. However, later in Verifier::verify() we call ClassVerifier::exceptionmessage() to get the message and pass it on. Solution: We should not create a ResourceMark here. There is a top level ResourceMark in Verifier::verify() that will take care of freeing the memory allocated in ClassVerifier::classformaterror(). Tested with JPRT and the failing testcase. Thanks, Tobias

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