RFR - 8190482: InnocuousThread creation should not require the caller to possess enableContextClassLoaderOverride

[Chris Hegarty]

Currently JDK code that wants to create innocuous threads is required to do so within a privileged context that has the "enableContextClassLoaderOverride" RuntimePermission ( since the InnocuousThread class overrides setContextClassLoader ). This permissions should not be required, especially if code in de-privileged modules wants to create innocuous threads. 

The factory methods for creating innocuous threads should assert privileges before constructing the thread.

diff --git a/src/java.base/share/classes/jdk/internal/misc/InnocuousThread.java b/src/java.base/share/classes/jdk/internal/misc/InnocuousThread.java
--- a/src/java.base/share/classes/jdk/internal/misc/InnocuousThread.java
+++ b/src/java.base/share/classes/jdk/internal/misc/InnocuousThread.java
@@ -62,10 +62,16 @@
      * set to the system class loader.
      */
     public static Thread newThread(String name, Runnable target) {
-        return new InnocuousThread(INNOCUOUSTHREADGROUP,
-                                   target,
-                                   name,
-                                   ClassLoader.getSystemClassLoader());
+        return AccessController.doPrivileged(
+                new PrivilegedAction<Thread>() {
+                    @Override
+                    public Thread run() {
+                        return new InnocuousThread(INNOCUOUSTHREADGROUP,
+                                                   target,
+                                                   name,
+                                                   ClassLoader.getSystemClassLoader());
+                    }
+                });
     }
 
     /**
@@ -80,8 +86,14 @@
      * Returns a new InnocuousThread with null context class loader.
      */
     public static Thread newSystemThread(String name, Runnable target) {
-        return new InnocuousThread(INNOCUOUSTHREADGROUP,
-                                   target, name, null);
+        return AccessController.doPrivileged(
+                new PrivilegedAction<Thread>() {
+                    @Override
+                    public Thread run() {
+                        return new InnocuousThread(INNOCUOUSTHREADGROUP,
+                                                   target, name, null);
+                    }
+                });
     }
 
-Chris.