In wait_task_stopped() exit_code already contains the right value for
the si_status member of siginfo, and this is simply set in the non
WNOWAIT case.
    
Pass it unchanged to wait_noreap_copyout();  we would only need to
shift it and add 0x7f if we were returning it in the user status field
and that isn't used for any function that permits WNOWAIT.
    
Signed-off-by: Scott James Remnant <scott@ubuntu.com>
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Roland McGrath <roland@redhat.com>

--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1389,7 +1389,7 @@ static int wait_task_stopped(struct task_struct
*p, int delayed_group_leader,
 		if (unlikely(!exit_code) || unlikely(p->exit_state))
 			goto bail_ref;
 		return wait_noreap_copyout(p, pid, uid,
-					   why, (exit_code << 8) | 0x7f,
+					   why, exit_code,
 					   infop, ru);
 	}