linux-kernel - Re: [PATCH] usb: gadget: f_uac2: fixup feedback endpoint stop

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Date:   Thu, 26 Aug 2021 09:23:42 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Ferry Toth <fntoth@...il.com>, Ferry Toth <ftoth@...londelft.nl>,
        Ruslan Bilovol <ruslan.bilovol@...il.com>,
        Felipe Balbi <balbi@...nel.org>,
        Pavel Hofman <pavel.hofman@...tera.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jack Pham <jackp@...eaurora.org>, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org, Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Subject: Re: [PATCH] usb: gadget: f_uac2: fixup feedback endpoint stop


On Wed 25 Aug 2021 at 22:07, Ferry Toth <fntoth@...il.com> wrote:

> Hi,
>
> Op 25-08-2021 om 11:21 schreef Jerome Brunet:
>> When the uac2 function is stopped, there seems to be an issue with some
>> platforms (Intel Merrifield at least)
>>
>> BUG: kernel NULL pointer dereference, address: 0000000000000008
>> ...
>> RIP: 0010:dwc3_gadget_del_and_unmap_request+0x19/0xe0
>> ...
>> Call Trace:
>>   dwc3_remove_requests.constprop.0+0x12f/0x170
>>   __dwc3_gadget_ep_disable+0x7a/0x160
>>   dwc3_gadget_ep_disable+0x3d/0xd0
>>   usb_ep_disable+0x1c/0x70
>>   u_audio_stop_capture+0x79/0x120 [u_audio]
>>   afunc_set_alt+0x73/0x80 [usb_f_uac2]
>>   composite_setup+0x224/0x1b90 [libcomposite]
>>
>> The issue happens only when the gadget is using the sync type "async", not
>> "adaptive". This indicates that problem is likely coming from the feedback
>> endpoint, which is only used with async synchronization mode.
>>
>> Update the feedback endpoint free function to release the endpoint the same
>> way it is done for the data endpoint.
>>
>> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
>> ---
>>
>>   Hi Ferry,
>>
>>   Would you mind trying this before reverting the whole thing ?
>>   The HW I have did not show the issue so far so I can't really check
>>   if it helps. Hopefully, it does ...
>
> Tested this evening and confirming that this resolves my issue. I can't say
> much about the code itself, maybe Thinh?
>
> Would be great if we could get this in instead of reverting the series.
>
> Tested-by:  Ferry Toth <ftoth@...londelft.nl> (dwc3 / Intel Merrifield)
>

Thanks for reporting and testing this.
I guess we should also add

Reported-by: Ferry Toth <ftoth@...londelft.nl>


>>   drivers/usb/gadget/function/u_audio.c | 15 +++++++++++----
>>   1 file changed, 11 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c
>> index 018dd0978995..63d9340f008e 100644
>> --- a/drivers/usb/gadget/function/u_audio.c
>> +++ b/drivers/usb/gadget/function/u_audio.c
>> @@ -230,7 +230,13 @@ static void u_audio_iso_fback_complete(struct usb_ep *ep,
>>   	int status = req->status;
>>     	/* i/f shutting down */
>> -	if (!prm->fb_ep_enabled || req->status == -ESHUTDOWN)
>> +	if (!prm->fb_ep_enabled) {
>> +		kfree(req->buf);
>> +		usb_ep_free_request(ep, req);
>> +		return;
>> +	}
>> +
>> +	if (req->status == -ESHUTDOWN)
>>   		return;
>>     	/*
>> @@ -421,9 +427,10 @@ static inline void free_ep_fback(struct uac_rtd_params *prm, struct usb_ep *ep)
>>   	prm->fb_ep_enabled = false;
>>     	if (prm->req_fback) {
>> -		usb_ep_dequeue(ep, prm->req_fback);
>> -		kfree(prm->req_fback->buf);
>> -		usb_ep_free_request(ep, prm->req_fback);
>> +		if (usb_ep_dequeue(ep, prm->req_fback)) {
>> +			kfree(prm->req_fback->buf);
>> +			usb_ep_free_request(ep, prm->req_fback);
>> +		}
>>   		prm->req_fback = NULL;
>>   	}
>>