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.

2 files changed, 2 insertions, 2 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)
diff --git a/litmus/litmus.c b/litmus/litmus.c
index 2dea340aea1d..d31a2ba030e4 100644
--- a/litmus/litmus.c
+++ b/litmus/litmus.c
@@ -285,7 +285,7 @@ static void reinit_litmus_state(struct task_struct* p, int restore)
 //      __setscheduler(p, p->rt_param.old_policy, p->rt_param.old_prio);
 
         /* Cleanup everything else. */
-        memset(&p->rt_param, 0, sizeof(user_config));
+        memset(&p->rt_param, 0, sizeof(p->rt_param));
 
         /* Restore preserved fields. */
         if (restore) {