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Subject: Re: [PATCH] usb: dwc3: gadget: Fail request submission if it was
 already queued
To:     Felipe Balbi <balbi@kernel.org>
Cc:     linux-arm-msm@vger.kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "open list:DESIGNWARE USB3 DRD IP DRIVER" <linux-usb@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>
References: <20190111060212.7390-1-mgautam@codeaurora.org>
 <87pnt3od02.fsf@linux.intel.com>
 <d0f73188-7943-146f-5944-1bfd74bdce77@codeaurora.org>
 <87k1jbo8hm.fsf@linux.intel.com>
From:   Manu Gautam <mgautam@codeaurora.org>
Message-ID: <5ede621a-b1da-bf46-2b9e-938897a728e3@codeaurora.org>
Date:   Wed, 16 Jan 2019 10:04:08 +0530
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Hi,

On 1/11/2019 2:51 PM, Felipe Balbi wrote:
> Hi,
>
> Manu Gautam <mgautam@codeaurora.org> writes:
>>> Manu Gautam <mgautam@codeaurora.org> writes:
>>>> If a function driver tries to re-submit an already queued request,
>>>> it can results in corruption of pending/started request lists.
>>>> Catch such conditions and fail the request submission to DCD.
>>>>
>>>> Signed-off-by: Manu Gautam <mgautam@codeaurora.org>
>>>> ---
>>>>  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 679c12e14522..51716c6b286a 100644
>>>> --- a/drivers/usb/dwc3/gadget.c
>>>> +++ b/drivers/usb/dwc3/gadget.c
>>>> @@ -1290,6 +1290,12 @@ static int __dwc3_gadget_ep_queue(struct dwc3_ep *dep, struct dwc3_request *req)
>>>>  				&req->request, req->dep->name))
>>>>  		return -EINVAL;
>>>>  
>>>> +	if (req->request.status == -EINPROGRESS) {
>>> this test is really not enough. What if gadget driver set status to
>>> EINPROGRESS before submission? A better check would involve making sure
>>> req isn't part of dep->pending_list or dep->started_list or
>>> dep->cancelled_list. It's clear that this won't work very well as the
>>> amount of requests grow.
>> Thanks for quick review.
>> 'request.status' check can be replaced:
>> +if (!list_empty(&req->list) {
>>
>> And replace list_del with list_del_init from dwc3_gadget_giveback()
> I would rather avoid this. We could start tracking our own internal
> dwc3_request status. Something along the lines of:

Thanks for this quick patch.

[snip]

>  
> With this, we can remove some of the other request flags, such as "started".
>
>>> Anyway, which gadget driver did this? Why is it only affecting dwc3?
>> Function driver is not in upstream (f_mtp.c).
> So this could happen with any UDC, right? Why is f_mtp.c queueing the
> same request twice?


Looks like chipidea UDC already has such a check.
It is not yet clear that why f_mtp queued same request twice.
However, having a safeguard check in UDC should be helpful.


>
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