[PATCH] clone-fix-2.5.34-A0, BK-curr

This fixes a clone-flags bug noticed by Roland McGrath.  The current
CLONE_DETACHED & CLONE_THREAD forcing code did things in the wrong
order, which makes it possible to force an oops the following way:

        main () { syscall(120, 0x00400000); }

instead of changing the order of CLONE_SIGHAND and CLONE_THREAD flag
forcing (which would fix the bug), the proper approach is to fail with
-EINVAL if invalid combinations of clone flags are detected.  This
change does not affect existing applications.

kernel/fork.c

@@ -672,16 +672,13 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 		return ERR_PTR(-EINVAL);
 
 	/*
-	 * Thread groups must share signals as well:
+	 * Thread groups must share signals as well, and detached threads
+	 * can only be started up within the thread group.
 	 */
-	if (clone_flags & CLONE_THREAD)
-		clone_flags |= CLONE_SIGHAND;
-	/*
-	 * Detached threads can only be started up within the thread
-	 * group.
-	 */
-	if (clone_flags & CLONE_DETACHED)
-		clone_flags |= CLONE_THREAD;
+	if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
+		return ERR_PTR(-EINVAL);
+	if ((clone_flags & CLONE_DETACHED) && !(clone_flags & CLONE_THREAD))
+		return ERR_PTR(-EINVAL);
 
 	retval = security_ops->task_create(clone_flags);
 	if (retval)