usb: yurex: Fix inconsistent locking bug in yurex_read()

Unlock before returning on the error path.

Fixes: 86b20af1 ("usb: yurex: Replace snprintf() with the safer scnprintf() variant")
Reported-by: Dan Carpenter <error27@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/r/202312170252.3udgrIcP-lkp@intel.com/Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Link: https://lore.kernel.org/r/20231219063639.450994-1-harshit.m.mogalapalli@oracle.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/misc/yurex.c

@@ -414,8 +414,10 @@ 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_irqsave(&dev->lock, flags);
 	scnprintf(in_buffer, MAX_S64_STRLEN, "%lld\n", dev->bbu);