Input: evdev - fix EVIOCG{type} ioctl

The 'max' size passed into the function is measured in number of bits
(KEY_MAX, LED_MAX, etc) so we need to convert it accordingly before trying
to copy the data out, otherwise we will try copying too much and end up
with up with a page fault.

Reported-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/evdev.c

@@ -738,20 +738,23 @@ static int evdev_handle_set_keycode_v2(struct input_dev *dev, void __user *p)
  */
 static int evdev_handle_get_val(struct evdev_client *client,
 				struct input_dev *dev, unsigned int type,
-				unsigned long *bits, unsigned int max,
-				unsigned int size, void __user *p, int compat)
+				unsigned long *bits, unsigned int maxbit,
+				unsigned int maxlen, void __user *p,
+				int compat)
 {
 	int ret;
 	unsigned long *mem;
+	size_t len;
 
-	mem = kmalloc(sizeof(unsigned long) * max, GFP_KERNEL);
+	len = BITS_TO_LONGS(maxbit) * sizeof(unsigned long);
+	mem = kmalloc(len, GFP_KERNEL);
 	if (!mem)
 		return -ENOMEM;
 
 	spin_lock_irq(&dev->event_lock);
 	spin_lock(&client->buffer_lock);
 
-	memcpy(mem, bits, sizeof(unsigned long) * max);
+	memcpy(mem, bits, len);
 
 	spin_unlock(&dev->event_lock);
 
@@ -759,7 +762,7 @@ static int evdev_handle_get_val(struct evdev_client *client,
 
 	spin_unlock_irq(&client->buffer_lock);
 
-	ret = bits_to_user(mem, max, size, p, compat);
+	ret = bits_to_user(mem, maxbit, maxlen, p, compat);
 	if (ret < 0)
 		evdev_queue_syn_dropped(client);