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

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Date:   Wed, 25 Aug 2021 22:07:21 +0200
From:   Ferry Toth <fntoth@...il.com>
To:     Jerome Brunet <jbrunet@...libre.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

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)

>   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;
>   	}
>