[concurrency-interest] FutureTask.cancel(true) should run thread.interrupt within doPrivileged

[Doug Lea]

On 10/02/2013 12:29 PM, Martin Buchholz wrote:
> FutureTask.cancel(true) invokes thread.interrupt on the thread (if any)
> currently running the task.
> This should succeed even if modifyThread permission is denied by the security
> manager.
>

We haven't interpreted "should" in this way in the past here or in
related contexts, but I don't see are reason not to,  pending any
objections by security folks.

-Doug


> Here's a proposed fix for jdk8+:
>
> --- src/main/java/util/concurrent/FutureTask.java15 May 2013 02:39:59 -00001.103
> +++ src/main/java/util/concurrent/FutureTask.java2 Oct 2013 16:25:23 -0000
> @@ -132,6 +132,12 @@
>           return state != NEW;
>       }
> +    private static void privilegedInterrupt(Thread t) {
> +        java.security.PrivilegedAction<Void> doInterrupt =
> +            () -> { t.interrupt(); return null; };
> +        java.security.AccessController.doPrivileged(doInterrupt);
> +    }
> +
>       public boolean cancel(boolean mayInterruptIfRunning) {
>           if (!(state == NEW &&
>                 UNSAFE.compareAndSwapInt(this, stateOffset, NEW,
> @@ -142,7 +148,11 @@
>                   try {
>                       Thread t = runner;
>                       if (t != null)
> -                        t.interrupt();
> +                        try {
> +                            t.interrupt();
> +                        } catch (SecurityException e) {
> +                            privilegedInterrupt(t);
> +                        }
>                   } finally { // final state
>                       UNSAFE.putOrderedInt(this, stateOffset, INTERRUPTED);
>                   }
>
>
>
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