[PATCH 1/1] ptrace: do_notify_parent_cldstop: fix the wrong ->nsproxy usage

[Oleg Nesterov <oleg@redhat.com>]

If the non-traced sub-thread calls do_notify_parent_cldstop(), we send the
notification to group_leader->real_parent and we report group_leader's pid.

But, if group_leader is traced we use the wrong ->parent->nsproxy->pid_ns,
the tracer and parent can live in different namespaces. Change the code
to use "parent" instead of tsk->parent.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>

--- PTRACE/kernel/signal.c~CLDSTOP_NS	2009-05-25 20:24:50.000000000 +0200
+++ PTRACE/kernel/signal.c	2009-05-25 20:33:37.000000000 +0200
@@ -1496,7 +1496,7 @@ static void do_notify_parent_cldstop(str
 	 * see comment in do_notify_parent() abot the following 3 lines
 	 */
 	rcu_read_lock();
-	info.si_pid = task_pid_nr_ns(tsk, tsk->parent->nsproxy->pid_ns);
+	info.si_pid = task_pid_nr_ns(tsk, parent->nsproxy->pid_ns);
 	info.si_uid = __task_cred(tsk)->uid;
 	rcu_read_unlock();