Re: [PATCH 3/3] usb: gadget: f_midi: free request when usb_ep_queue fails

[Felipe Tonello]

On Thu, Sep 24, 2015 at 2:20 AM, Peter Chen <peter.chen@xxxxxxxxxxxxx> wrote:
> On Wed, Sep 23, 2015 at 12:40:46PM +0100, Felipe Tonello wrote:
>> Hi Peter,
>>
>> On Wed, Sep 23, 2015 at 8:09 AM, Peter Chen <peter.chen@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxx>
>> >> ---
>> >>  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.
>>
>
> If the usb cable is not connected, the related endpoints should be
> not enabled. Would you really observe enqueue the request without
> cable connected?

The usb_ep_queue() returns an error if it is not connected, causing
the request never to be freed and never to be queued. Thus a memory
leak happens.

Felipe
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