usbip: usbip_host: fix to hold parent lock for device_attach() calls

BugLink: http://bugs.launchpad.net/bugs/1768825

commit 4bfb141b upstream.

usbip_host calls device_attach() without holding dev->parent lock.
Fix it.
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/usb/usbip/stub_main.c

@@ -201,7 +201,12 @@ static ssize_t rebind_store(struct device_driver *dev, const char *buf,
 	if (!bid)
 		return -ENODEV;
 
+	/* device_attach() callers should hold parent lock for USB */
+	if (bid->udev->dev.parent)
+		device_lock(bid->udev->dev.parent);
 	ret = device_attach(&bid->udev->dev);
+	if (bid->udev->dev.parent)
+		device_unlock(bid->udev->dev.parent);
 	if (ret < 0) {
 		dev_err(&bid->udev->dev, "rebind failed\n");
 		return ret;