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

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Date:	Wed, 23 Sep 2015 12:40:46 +0100
From:	Felipe Tonello <eu@...ipetonello.com>
To:	Peter Chen <peter.chen@...escale.com>
Cc:	USB list <linux-usb@...r.kernel.org>,
	Kernel development list <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

Hi Peter,

On Wed, Sep 23, 2015 at 8:09 AM, Peter Chen <peter.chen@...escale.com> wrote:
> 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.

Yes. Also there is the case where the usb cable is not conected, thus
failing to hardware enqueue the request, causing a memory leak on this
request.

Felipe
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