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

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Date:	Thu, 24 Sep 2015 09:20:02 +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 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?

-- 

Best Regards,
Peter Chen
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