[HARMONY-6264] Need a new native method: VM.getStackClass()

• Type: New Feature
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 5.0M10
• Fix Version/s: 5.0M11
• Component/s: Classlib, DRLVM
• Environment: SVN Revision: 785439
• Patch Info: Patch Available
• Estimated Complexity: Advanced
• Assignee: Mark Hindess
• Reporter: Jesse Wilson
• Created: 08/Jul/09 21:58
• Updated: 14/Jul/09 07:59
• Resolved: 14/Jul/09 07:59

Description

We need a new native method, VM.getStackClass(int) to compliment VM.getStackClassLoader() and Class.getStackClasses(). It needs to be implemented in the VM vendors. I can fix Android's Dalvik VM, but I'll need a Harmony volunteer to fix DRLVM.

Background:
To implement AtomicReferenceFieldUpdater securely, it's necessary to capture the class of the caller, not just the class loader of the caller. Otherwise a rogue class (say, EvilBufferedInputStream) could use an AtomicReferenceFieldUpdater to modify protected fields of arbitrary instances (such as the buffer field of somebody else's BufferedInputStream).

This blocks HARMONY-6262, which updates of our copy of java.util.concurrent to Doug Lea's latest. The getStackClass() call is needed for line 181 and its result is used on line 262:
http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/main/java/util/concurrent/atomic/AtomicReferenceFieldUpdater.java?annotate=1.41