Bugfix: clear LITMUS^RT state on fork completely

When a real-time task forks, then its LITMUS^RT-specific fields should be cleared,
because we don't want real-time tasks to spawn new real-time tasks that bypass
the plugin's admission control (if any).

This was broken in three ways:
1) kernel/fork.c did not erase all of tsk->rt_param, only the first few bytes due to
   a wrong size argument to memset().
2) It should have been calling litmus_fork() instead anyway.
3) litmus_fork() was _also_ not clearing all of tsk->rt_param, due to another size
   argument bug.

Interestingly, 1) and 2) can be traced back to the 2007->2008 port,
whereas 3) was added by Mitchell much later on (to dead code, no less).

I'm really surprised that this never blew up before.

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 889730cce3ad..9fad346d7029 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -249,7 +249,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
         tsk->stack = ti;
 
         /* Don't let the new task be a real-time task. */
-        memset(&tsk->rt_param, 0, sizeof(struct rt_task));
+        litmus_fork(tsk);
 
         err = prop_local_init_single(&tsk->dirties);
         if (err)