[ https://issues.apache.org/jira/browse/HARMONY-6264?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12730282#action_12730282 ] 

Alexey Varlamov commented on HARMONY-6264:
------------------------------------------

Ah, indeed - this is even easier than I thought :)


> Need a new native method: VM.getStackClass()
> --------------------------------------------
>
>                 Key: HARMONY-6264
>                 URL: https://issues.apache.org/jira/browse/HARMONY-6264
>             Project: Harmony
>          Issue Type: New Feature
>          Components: Classlib, DRLVM
>    Affects Versions: 5.0M10
>         Environment: SVN Revision: 785439
>            Reporter: Jesse Wilson
>            Priority: Minor
>         Attachments: getStackClass.patch, getStackClass_Implementation.patch
>
>   Original Estimate: 2h
>  Remaining Estimate: 2h
>
> 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

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