vt: Add virtual console keyboard mode OFF

virtual console: add keyboard mode OFF

Add a new mode for the virtual console keyboard OFF in which all input
other than shift keys is ignored. Prevents vt input buffers from
overflowing when a program opens but doesn't read from a tty, like X11
using evdev for input.

Signed-off-by: Arthur Taylor <art@ified.ca>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index 1235ebd..6bcf05b 100644
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -688,6 +688,9 @@
 			kbd->kbdmode = VC_UNICODE;
 			compute_shiftstate();
 			break;
+		  case K_OFF:
+			kbd->kbdmode = VC_OFF;
+			break;
 		  default:
 			ret = -EINVAL;
 			goto out;