linux-kernel - Re: [PATCH v3 09/12] usb: misc: lvstest: update to use the usb_control_msg

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Date:   Wed, 27 Jan 2021 16:15:03 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Anant Thazhemadam <anant.thazhemadam@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Evgeny Novikov <novikov@...ras.ru>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 09/12] usb: misc: lvstest: update to use the
 usb_control_msg_{send|recv}() API

On Wed, Jan 27, 2021 at 12:09:43AM +0530, Anant Thazhemadam wrote:
> The newer usb_control_msg_{send|recv}() API are an improvement on the
> existing usb_control_msg() as it ensures that a short read/write is treated
> as an error, data can be used off the stack, and raw usb pipes need not be
> created in the calling functions.
> For this reason, instances of usb_control_msg() have been replaced with
> usb_control_msg_{recv|send}() and the return value checking conditions have
> also been modified appropriately.
> 
> Signed-off-by: Anant Thazhemadam <anant.thazhemadam@...il.com>
> ---
>  drivers/usb/misc/lvstest.c | 38 ++++++++++++++++----------------------
>  1 file changed, 16 insertions(+), 22 deletions(-)

> @@ -336,10 +330,10 @@ static void lvs_rh_work(struct work_struct *work)
>  
>  	/* Examine each root port */
>  	for (i = 1; i <= descriptor->bNbrPorts; i++) {
> -		ret = usb_control_msg(hdev, usb_rcvctrlpipe(hdev, 0),
> +		ret = usb_control_msg_recv(hdev, 0,
>  			USB_REQ_GET_STATUS, USB_DIR_IN | USB_RT_PORT, 0, i,
> -			port_status, sizeof(*port_status), 1000);
> -		if (ret < 4)
> +			port_status, sizeof(*port_status), 1000, GFP_KERNEL);
> +		if (ret < 0)
>  			continue;

I'm afraid this may introduce a regression as well since the
sizeof(*port_status) is 8 for some devices and the driver only cares
about the first 4 that all devices use (i.e. it is written to handle
short reads).

>  		portchange = le16_to_cpu(port_status->wPortChange);
> @@ -420,13 +414,13 @@ static int lvs_rh_probe(struct usb_interface *intf,
>  	usb_set_intfdata(intf, lvs);
>  
>  	/* how many number of ports this root hub has */
> -	ret = usb_control_msg(hdev, usb_rcvctrlpipe(hdev, 0),
> +	ret = usb_control_msg_recv(hdev, 0,
>  			USB_REQ_GET_DESCRIPTOR, USB_DIR_IN | USB_RT_HUB,
>  			USB_DT_SS_HUB << 8, 0, &lvs->descriptor,
> -			USB_DT_SS_HUB_SIZE, USB_CTRL_GET_TIMEOUT);
> -	if (ret < (USB_DT_HUB_NONVAR_SIZE + 2)) {
> +			USB_DT_SS_HUB_SIZE, USB_CTRL_GET_TIMEOUT, GFP_KERNEL);
> +	if (ret < 0) {
>  		dev_err(&hdev->dev, "wrong root hub descriptor read %d\n", ret);
> -		return ret < 0 ? ret : -EINVAL;
> +		return ret;
>  	}

This looks like it may break for similar reasons.

Johan