SAK broken since 2.4.3

I wanted to show someone how nice SAK works, pressed it twice, and lo! it not only killed the processes on the console, but also the kernel. Very effective.

The patch below (for a private, patched 2.4.3 - line numbers may differ) diminish this effectiveness a little. My kernel now survives.

Andries

[PS I intend to come with another SAK patch one of these days, but it may be for 2.5.]

@@ -1867,6 +1867,8 @@
  */
 void do_SAK(struct tty_struct *tty)
 {
+	if (!tty)
+		return;
 	PREPARE_TQUEUE(&tty->SAK_tq, __do_SAK, tty);
 	schedule_task(&tty->SAK_tq);
 }