ia64: Pin controlling tty for unaligned fault message

Prevent destruction of the controlling tty before tty_write_message()
can determine if the tty is safe to use.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/ia64/kernel/unaligned.c

@@ -1336,8 +1336,11 @@ ia64_handle_unaligned (unsigned long ifa, struct pt_regs *regs)
 			 * Don't call tty_write_message() if we're in the kernel; we might
 			 * be holding locks...
 			 */
-			if (user_mode(regs))
-				tty_write_message(current->signal->tty, buf);
+			if (user_mode(regs)) {
+				struct tty_struct *tty = get_current_tty();
+				tty_write_message(tty, buf);
+				tty_kref_put(tty);
+			}
 			buf[len-1] = '\0';	/* drop '\r' */
 			/* watch for command names containing %s */
 			printk(KERN_WARNING "%s", buf);