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

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Date:	Fri, 25 Sep 2015 17:02:33 +0800
From:	Peter Chen <peter.chen@...escale.com>
To:	Felipe Tonello <eu@...ipetonello.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

On Fri, Sep 25, 2015 at 09:27:49AM +0100, Felipe Tonello wrote:
> On Thu, Sep 24, 2015 at 2:20 AM, Peter Chen <peter.chen@...escale.com> 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@...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.
> >>
> >
> > 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.
> 

If it is not connected, the ep is not enabled, why we will call
usb_ep_queue? If it really does, there must be something wrong.

-- 

Best Regards,
Peter Chen
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