linux-kernel - Re: [PATCH 3/3] usb: gadget: f_midi: free request when usb_ep

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Date:	Wed, 23 Sep 2015 15:09:18 +0800
From:	Peter Chen <peter.chen@...escale.com>
To:	"Felipe F. Tonello" <eu@...ipetonello.com>
CC:	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
	Felipe Balbi <balbi@...com>,
	Andrzej Pietrasiewicz <andrzej.p@...sung.com>
Subject: Re: [PATCH 3/3] usb: gadget: f_midi: free request when usb_ep_queue
 fails

On Tue, Sep 22, 2015 at 07:59:10PM +0100, Felipe F. Tonello wrote:
> This fix a memory leak that will occur in this case.
> 
> Signed-off-by: Felipe F. Tonello <eu@...ipetonello.com>
> ---
>  drivers/usb/gadget/function/f_midi.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c
> index e92aff5..e6a114b 100644
> --- a/drivers/usb/gadget/function/f_midi.c
> +++ b/drivers/usb/gadget/function/f_midi.c
> @@ -550,9 +550,11 @@ static void f_midi_transmit(struct f_midi *midi, struct usb_request *req)
>  		int err;
>  
>  		err = usb_ep_queue(ep, req, GFP_ATOMIC);
> -		if (err < 0)
> +		if (err < 0) {
>  			ERROR(midi, "%s queue req: %d\n",
>  			      midi->in_ep->name, err);
> +			free_ep_req(ep, req);
> +		}
>  	} else {
>  		free_ep_req(ep, req);
>  	}
> -- 
> 2.1.4
> 

I may know your problem, current midi library, alsa and this driver
allow device sends as much data as possible, but without block the
sending until host reads data, it only allocates the request buffer
(using midi_alloc_ep_req), but without free, so after you send
enough data, it is out of memory.

-- 

Best Regards,
Peter Chen
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