diff --git a/drivers/usb/misc/yurex.c b/drivers/usb/misc/yurex.c
index 494db0178..4eb30089d 100755
--- a/drivers/usb/misc/yurex.c
+++ b/drivers/usb/misc/yurex.c
@@ -412,8 +412,10 @@ static ssize_t yurex_read(struct file *file, char __user *buffer, size_t count,
 		return -ENODEV;
 	}
 
-	if (WARN_ON_ONCE(dev->bbu > S64_MAX || dev->bbu < S64_MIN))
+	if (WARN_ON_ONCE(dev->bbu > S64_MAX || dev->bbu < S64_MIN)) {
+		mutex_unlock(&dev->io_mutex);
 		return -EIO;
+	}
 
 	spin_lock_irq(&dev->lock);
 	scnprintf(in_buffer, MAX_S64_STRLEN, "%lld\n", dev->bbu);