diff --git a/drivers/usb/misc/ldusb.c b/drivers/usb/misc/ldusb.c
index cd92ae1231bc..457fc0ae70e1 100644
--- a/drivers/usb/misc/ldusb.c
+++ b/drivers/usb/misc/ldusb.c
@@ -498,11 +498,11 @@ static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count,
 		retval = -EFAULT;
 		goto unlock_exit;
 	}
-	dev->ring_tail = (dev->ring_tail+1) % ring_buffer_size;
-
 	retval = bytes_to_read;
 
 	spin_lock_irq(&dev->rbsl);
+	dev->ring_tail = (dev->ring_tail + 1) % ring_buffer_size;
+
 	if (dev->buffer_overflow) {
 		dev->buffer_overflow = 0;
 		spin_unlock_irq(&dev->rbsl);