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>

4 files changed, 9 insertions, 3 deletions

diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c
index e95d7876ca6b..6dd3c68c13ad 100644
--- a/drivers/tty/vt/keyboard.c
+++ b/drivers/tty/vt/keyboard.c
@@ -654,7 +654,8 @@ static void k_spec(struct vc_data *vc, unsigned char value, char up_flag)
         if (value >= ARRAY_SIZE(fn_handler))
                 return;
         if ((kbd->kbdmode == VC_RAW ||
-             kbd->kbdmode == VC_MEDIUMRAW) &&
+             kbd->kbdmode == VC_MEDIUMRAW ||
+             kbd->kbdmode == VC_OFF) &&
              value != KVAL(K_SAK))
                 return;         /* SAK is allowed even in raw mode */
         fn_handler[value](vc);
@@ -1295,7 +1296,7 @@ static void kbd_keycode(unsigned int keycode, int down, int hw_raw)
         if (rc == NOTIFY_STOP)
                 return;
 
-        if (raw_mode && type != KT_SPEC && type != KT_SHIFT)
+        if ((raw_mode || kbd->kbdmode == VC_OFF) && type != KT_SPEC && type != KT_SHIFT)
                 return;
 
         (*k_handler[type])(vc, keysym & 0xff, !down);
diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index 1235ebda6e1c..6bcf05bf4978 100644
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -688,6 +688,9 @@ int vt_ioctl(struct tty_struct *tty, struct file * file,
                         kbd->kbdmode = VC_UNICODE;
                         compute_shiftstate();
                         break;
+                  case K_OFF:
+                        kbd->kbdmode = VC_OFF;
+                        break;
                   default:
                         ret = -EINVAL;
                         goto out;
diff --git a/include/linux/kbd_kern.h b/include/linux/kbd_kern.h
index 506ad20c18f8..4b0761cc7dd9 100644
--- a/include/linux/kbd_kern.h
+++ b/include/linux/kbd_kern.h
@@ -50,11 +50,12 @@ struct kbd_struct {
 #define VC_CAPSLOCK     2       /* capslock mode */
 #define VC_KANALOCK     3       /* kanalock mode */
 
-        unsigned char kbdmode:2;        /* one 2-bit value */
+        unsigned char kbdmode:3;        /* one 3-bit value */
 #define VC_XLATE        0       /* translate keycodes using keymap */
 #define VC_MEDIUMRAW    1       /* medium raw (keycode) mode */
 #define VC_RAW          2       /* raw (scancode) mode */
 #define VC_UNICODE      3       /* Unicode mode */
+#define VC_OFF          4       /* disabled mode */
 
         unsigned char modeflags:5;
 #define VC_APPLIC       0       /* application key mode */
diff --git a/include/linux/kd.h b/include/linux/kd.h
index 15f2853ea58f..c36d8476db55 100644
--- a/include/linux/kd.h
+++ b/include/linux/kd.h
@@ -81,6 +81,7 @@ struct unimapinit {
 #define         K_XLATE         0x01
 #define         K_MEDIUMRAW     0x02
 #define         K_UNICODE       0x03
+#define         K_OFF           0x04
 #define KDGKBMODE       0x4B44  /* gets current keyboard mode */
 #define KDSKBMODE       0x4B45  /* sets current keyboard mode */