keyboard: integer underflow bug

commit b652277b upstream.

The "ct" variable should be an unsigned int.  Both struct kbdiacrs
->kb_cnt and struct kbd_data ->accent_table_size are unsigned ints.

Making it signed causes a problem in KBDIACRUC because the user could
set the signed bit and cause a buffer overflow.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/s390/char/keyboard.c

@@ -462,7 +462,8 @@ kbd_ioctl(struct kbd_data *kbd, struct file *file,
 	  unsigned int cmd, unsigned long arg)
 {
 	void __user *argp;
-	int ct, perm;
+	unsigned int ct;
+	int perm;
 
 	argp = (void __user *)arg;