linux-kernel - Re: [PATCH 2/2] usb: dwc2: forbid queuing request to a disabled ep

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Message-ID: <87wpsmi582.fsf@saruman.tx.rr.com>
Date:	Thu, 10 Dec 2015 11:27:41 -0600
From:	Felipe Balbi <balbi@...com>
To:	<changbin.du@...el.com>, <johnyoun@...opsys.com>
CC:	<gregkh@...uxfoundation.org>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	"Du, Changbin" <changbin.du@...el.com>
Subject: Re: [PATCH 2/2] usb: dwc2: forbid queuing request to a disabled ep


Hi,

changbin.du@...el.com writes:
> From: "Du, Changbin" <changbin.du@...el.com>
>
> Queue a request to disabled ep  doesn't make sense, and induce caller
> make mistakes.
>
> Here is a example for the android mtp gadget function driver. A mem
> corruption can happen on below senario.
> 1) On disconnect, mtp driver disable its EPs,
> 2) During send_file_work and receive_file_work, mtp queues a request
>    to ep. (The mtp driver need improve its synchronization logic!)
> 3) mtp_function_unbind is invoked and all mtp requests are freed.
> 4) when dwc2 process the request queued on step 2, will cause kernel
>    NULL pointer dereference exception.
>
> Signed-off-by: Du, Changbin <changbin.du@...el.com>
> ---
>  drivers/usb/dwc2/gadget.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
> index 586bbcd..4d637ab 100644
> --- a/drivers/usb/dwc2/gadget.c
> +++ b/drivers/usb/dwc2/gadget.c
> @@ -786,6 +786,12 @@ static int dwc2_hsotg_ep_queue(struct usb_ep *ep, struct usb_request *req,
>  		ep->name, req, req->length, req->buf, req->no_interrupt,
>  		req->zero, req->short_not_ok);
>  
> +	if (!hs_ep->enabled) {
> +		dev_warn(hs->dev, "%s: cannot queue to disabled ep\n",
> +				__func__);

similar comment to previous patch:

	if (dev_WARN_ONCE(hs->dev, !hs_ep->enabled,
        	"cannot queue to disabled ep %s\n", hs_ep->name))

> +		return -ESHUTDOWN;
> +	}
> +
>  	/* Prevent new request submission when controller is suspended */
>  	if (hs->lx_state == DWC2_L2) {
>  		dev_dbg(hs->dev, "%s: don't submit request while suspended\n",
> -- 
> 2.5.0
>
> --
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-- 
balbi

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