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Date:   Fri, 5 Nov 2021 18:25:17 -0700
From:   Jack Pham <quic_jackp@quicinc.com>
To:     Albert Wang <albertccwang@google.com>
CC:     <balbi@kernel.org>, <gregkh@linuxfoundation.org>,
        <badhri@google.com>, <linux-usb@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        Wesley Cheng <quic_wcheng@quicinc.com>
Subject: Re: [PATCH] usb: dwc3: gadget: Fix null pointer exception
Message-ID: <20211106012513.GA19852@jackp-linux.qualcomm.com>
References: <20211104062616.948353-1-albertccwang@google.com>
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On Thu, Nov 04, 2021 at 02:26:16PM +0800, Albert Wang wrote:
> In the endpoint interrupt functions
> dwc3_gadget_endpoint_transfer_in_progress() and
> dwc3_gadget_endpoint_trbs_complete() will dereference the endpoint
> descriptor. But it could be cleared in __dwc3_gadget_ep_disable()
> when accessory disconnected. So we need to check whether it is null
> or not before dereferencing it.
> 
> Signed-off-by: Albert Wang <albertccwang@google.com>

Nice catch.  I think this might have been caused when the call to
dwc3_remove_requests() in __dwc3_gadget_ep_disable() was moved after
the endpoint descriptors is cleared.  So you can probably add:

Fixes: f09ddcfcb8c5 ("usb: dwc3: gadget: Prevent EP queuing while
stopping transfers").

Reviewed-by: Jack Pham <quic_jackp@quicinc.com>

> ---
>  drivers/usb/dwc3/gadget.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 23de2a5a40d6..83c7344888fd 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -3252,6 +3252,9 @@ static bool dwc3_gadget_endpoint_trbs_complete(struct dwc3_ep *dep,
>  	struct dwc3		*dwc = dep->dwc;
>  	bool			no_started_trb = true;
>  
> +	if (!dep->endpoint.desc)
> +		return no_started_trb;
> +
>  	dwc3_gadget_ep_cleanup_completed_requests(dep, event, status);
>  
>  	if (dep->flags & DWC3_EP_END_TRANSFER_PENDING)
> @@ -3299,6 +3302,9 @@ static void dwc3_gadget_endpoint_transfer_in_progress(struct dwc3_ep *dep,
>  {
>  	int status = 0;
>  
> +	if (!dep->endpoint.desc)
> +		return;
> +
>  	if (usb_endpoint_xfer_isoc(dep->endpoint.desc))
>  		dwc3_gadget_endpoint_frame_from_event(dep, event);
>  
> -- 
> 2.33.1.1089.g2158813163f-goog
>