--- linux-3.3/fs/proc/base.c~	2012-03-19 21:44:42.000000000 +0100
+++ linux-3.3/fs/proc/base.c	2012-03-21 12:25:28.051092423 +0100
@@ -568,6 +568,8 @@
 				 struct task_struct *task,
 				 int hide_pid_min)
 {
+	if (vx_check(0, VS_WATCH_P))
+		return true;
 	if (pid->hide_pid < hide_pid_min)
 		return true;
 	if (in_group_p(pid->pid_gid))
--- linux-4.1.3-vs2.3.8.2/kernel/signal.c	2015-09-20 20:06:03.000000000 +0200
+++ testing41/kernel/signal.c	2015-12-05 13:01:00.599373873 +0100
@@ -1369,8 +1369,14 @@
 	for (;;) {
 		rcu_read_lock();
 		p = pid_task(pid, PIDTYPE_PID);
-		if (p && vx_check(vx_task_xid(p), VS_IDENT))
-			error = group_send_sig_info(sig, info, p);
+		if (p) {
+			if (vx_check(vx_task_xid(p), VS_IDENT))
+				error = group_send_sig_info(sig, info, p);
+			else {
+				rcu_read_unlock();
+				return -ESRCH;
+			}
+		}
 		rcu_read_unlock();
 		if (likely(!p || error != -ESRCH))
 			return error;