USB: ldusb: fix memleak on disconnect

If disconnect() races with release() after a process has been
interrupted, release() could end up returning early and the driver would
fail to free its driver data.

Fixes: 2824bd25 ("[PATCH] USB: add ldusb driver")
Cc: stable <stable@vger.kernel.org>     # 2.6.13
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20191010125835.27031-2-johan@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/misc/ldusb.c

@@ -380,10 +380,7 @@ static int ld_usb_release(struct inode *inode, struct file *file)
 		goto exit;
 	}
 
-	if (mutex_lock_interruptible(&dev->mutex)) {
-		retval = -ERESTARTSYS;
-		goto exit;
-	}
+	mutex_lock(&dev->mutex);
 
 	if (dev->open_count != 1) {
 		retval = -ENODEV;