linux-kernel - Re: [RFC PATCHv2 1/1] usb: f_rndis: Avoid to use ERROR macro if cdev can be null

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Date:	Tue, 19 Mar 2013 14:22:56 +0100
From:	Michal Nazarewicz <mina86@...a86.com>
To:	oskar.andero@...ymobile.com, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Felipe Balbi <balbi@...com>, Radovan.Lekanovic@...ymobile.com,
	Truls Bengtsson <truls.bengtsson@...ymobile.com>,
	Oskar Andero <oskar.andero@...ymobile.com>
Subject: Re: [RFC PATCHv2 1/1] usb: f_rndis: Avoid to use ERROR macro if cdev can be null

On Tue, Mar 19 2013, oskar.andero@...ymobile.com wrote:
> The udc_irq service runs the isr_tr_complete_handler which in turn
> "nukes" the endpoints, including a call to rndis_response_complete,
> if appropriate. If the rndis_msg_parser fails here, an error will
> be printed using a dev_err call (through the ERROR() macro).
>
> However, if the usb cable was just disconnected the device (cdev)
> might not be available and will be null. Since the dev_err macro will
> dereference the cdev pointer we get a null pointer exception.
>
> Reviewed-by: Radovan Lekanovic <radovan.lekanovic@...ymobile.com>
> Signed-off-by: Truls Bengtsson <truls.bengtsson@...ymobile.com>
> Signed-off-by: Oskar Andero <oskar.andero@...ymobile.com>

Acked-by: Michal Nazarewicz <mina86@...a86.com>

I think this is the best solution.  Adding if statements around it would
just add noise.

> ---
>  drivers/usb/gadget/f_rndis.c |    3 +--
>  1 files changed, 1 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/gadget/f_rndis.c b/drivers/usb/gadget/f_rndis.c
> index 71beeb8..cc9c49c 100644
> --- a/drivers/usb/gadget/f_rndis.c
> +++ b/drivers/usb/gadget/f_rndis.c
> @@ -447,14 +447,13 @@ static void rndis_response_complete(struct usb_ep *ep, struct usb_request *req)
>  static void rndis_command_complete(struct usb_ep *ep, struct usb_request *req)
>  {
>  	struct f_rndis			*rndis = req->context;
> -	struct usb_composite_dev	*cdev = rndis->port.func.config->cdev;
>  	int				status;
>  
>  	/* received RNDIS command from USB_CDC_SEND_ENCAPSULATED_COMMAND */
>  //	spin_lock(&dev->lock);
>  	status = rndis_msg_parser(rndis->config, (u8 *) req->buf);
>  	if (status < 0)
> -		ERROR(cdev, "RNDIS command error %d, %d/%d\n",
> +		pr_err("RNDIS command error %d, %d/%d\n",
>  			status, req->actual, req->length);
>  //	spin_unlock(&dev->lock);
>  }

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +----<email/xmpp: mpn@...gle.com>--------------ooO--(_)--Ooo--

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