linux-kernel - Re: [PATCH] usb: misc: fix improper handling of refcount in uss720

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Date:   Wed, 6 Apr 2022 13:47:35 +0200
From:   Oliver Neukum <oneukum@...e.com>
To:     Hangyu Hua <hbh25y@...il.com>, gregkh@...uxfoundation.org,
        mudongliangabcd@...il.com
CC:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: misc: fix improper handling of refcount in
 uss720_probe()



On 06.04.22 09:33, Hangyu Hua wrote:
> usb_put_dev shouldn't be called when uss720_probe succeeds because of
> priv->usbdev. At the same time, priv->usbdev shouldn't be set to NULL
> before destroy_priv in uss720_disconnect because usb_put_dev is in
> destroy_priv.

Hi,

I am sorry, but that's a clear NACK.
> @@ -754,13 +753,13 @@ static void uss720_disconnect(struct usb_interface *intf)
>  	usb_set_intfdata(intf, NULL);
>  	if (pp) {
>  		priv = pp->private_data;
> -		priv->usbdev = NULL;
>  		priv->pp = NULL;
>  		dev_dbg(&intf->dev, "parport_remove_port\n");
>  		parport_remove_port(pp);
>  		parport_put_port(pp);
>  		kill_all_async_requests_priv(priv);
>  		kref_put(&priv->ref_count, destroy_priv);
> +		priv->usbdev = NULL;

That is a clear use after free The patch is no good in this state..

    HTH
        Oliver