Input: uinput - support injecting multiple events in one write() call

Rework the code in uinput_inject_event so that it matches the code in
evdev_write and allows injecting more than one event, or zero events.
Signed-off-by: Ryan Mallon <rmallon@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/misc/uinput.c

@@ -430,20 +430,30 @@ static int uinput_setup_device(struct uinput_device *udev,
 	return retval;
 }
 
-static ssize_t uinput_inject_event(struct uinput_device *udev,
+static ssize_t uinput_inject_events(struct uinput_device *udev,
 				    const char __user *buffer, size_t count)
 {
 	struct input_event ev;
+	size_t bytes = 0;
 
-	if (count < input_event_size())
+	if (count != 0 && count < input_event_size())
 		return -EINVAL;
 
-	if (input_event_from_user(buffer, &ev))
+	while (bytes + input_event_size() <= count) {
+		/*
+		 * Note that even if some events were fetched successfully
+		 * we are still going to return EFAULT instead of partial
+		 * count to let userspace know that it got it's buffers
+		 * all wrong.
+		 */
+		if (input_event_from_user(buffer + bytes, &ev))
 			return -EFAULT;
 
 		input_event(udev->dev, ev.type, ev.code, ev.value);
+		bytes += input_event_size();
+	}
 
-	return input_event_size();
+	return bytes;
 }
 
 static ssize_t uinput_write(struct file *file, const char __user *buffer,
@@ -460,7 +470,7 @@ static ssize_t uinput_write(struct file *file, const char __user *buffer,
 		return retval;
 
 	retval = udev->state == UIST_CREATED ?
-			uinput_inject_event(udev, buffer, count) :
+			uinput_inject_events(udev, buffer, count) :
 			uinput_setup_device(udev, buffer, count);
 
 	mutex_unlock(&udev->mutex);