Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933111Ab2JYAcq (ORCPT ); Wed, 24 Oct 2012 20:32:46 -0400 Received: from perceval.ideasonboard.com ([95.142.166.194]:45292 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753836Ab2JYAco (ORCPT ); Wed, 24 Oct 2012 20:32:44 -0400 From: Laurent Pinchart To: Simon Haggett Cc: Li Yang-R58472 , "balbi@ti.com" , Greg Kroah-Hartman , "linux-usb@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/1] usb: gadget: Don't attempt to dequeue requests for a disabled USB endpoint on Freescale hardware Date: Thu, 25 Oct 2012 02:33:34 +0200 Message-ID: <270227469.pLqYTv1WEV@avalon> User-Agent: KMail/4.9.2 (Linux/3.5.7-gentoo; KDE/4.9.2; x86_64; ; ) In-Reply-To: <508532DF.7050809@realvnc.com> References: <1350667166-3559-1-git-send-email-simon.haggett@realvnc.com> <1535820.NU10ADjvOZ@avalon> <508532DF.7050809@realvnc.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3851 Lines: 98 Hi Simon, On Monday 22 October 2012 12:49:51 Simon Haggett wrote: > On 22/10/12 11:47, Laurent Pinchart wrote: > > On Monday 22 October 2012 03:33:19 Li Yang-R58472 wrote: > >> On Saturday, October 20, 2012 1:37 AM Felipe Balbi wrote: > >>> On Fri, Oct 19, 2012 at 06:19:26PM +0100, Simon Haggett wrote: > >>>> Some gadget drivers may attempt to dequeue requests for an endpoint > >>>> that has already been disabled. For example, in the UVC gadget driver, > >>>> uvc_function_set_alt() will call usb_ep_disable() when alt setting 0 > >>>> is selected. When the userspace application subsequently issues the > >>>> VIDIOC_STREAMOFF ioctl, uvc_video_enable() invokes usb_ep_dequeue() to > >>> > >>> ensure that all requests have been cancelled. > >>> > >>> bug is on uvc gadget, then. Laurent ? > > > > We've discussed this topic a couple of months before. I believe that's not > > a bug. > > > > http://68.183.106.108/lists/linux-usb/msg68869.html > > > >>> Also, fsl should be removed from the tree, I'm trying to persuade iMX > >>> folks to use drivers/usb/chipidea instead. > >> > >> Besides the iMX usage, the driver is also being used by many Freescale > >> PowerPC/Coldfire SoCs. I agree that it's ideal to move to a common > >> driver. > >> But it is a large task to make the chipidea driver works for all the > >> hardware that fsl_udc had supported and been tested on. > >> > >>>> For the Freescale High Speed Dual-Role USB controller, > >>>> fsl_ep_dequeue() provides the implementation of usb_ep_dequeue(). If > >>>> this is called for a disabled endpoint, a kernel oops will occur when > >>> > >>> the ep->ep.desc field is dereferenced (by ep_index()). > >>> > >>>> fsl_ep_disable() sets this field to NULL, as well as deleting all > >>>> pending requests for the endpoint. > >>>> > >>>> This patch adds an additional check to fsl_ep_dequeue() to ensure that > >>>> the endpoint has not already been disabled before attempting to dequeue > >>> > >>> requests. > >>> > >>>> Signed-off-by: Simon Haggett > >>>> --- > >>>> > >>>> drivers/usb/gadget/fsl_udc_core.c | 5 ++++- > >>>> 1 files changed, 4 insertions(+), 1 deletions(-) > >>>> > >>>> diff --git a/drivers/usb/gadget/fsl_udc_core.c > >>>> b/drivers/usb/gadget/fsl_udc_core.c > >>>> index 6ae70cb..acd513b 100644 > >>>> --- a/drivers/usb/gadget/fsl_udc_core.c > >>>> +++ b/drivers/usb/gadget/fsl_udc_core.c > >>>> @@ -955,7 +955,10 @@ static int fsl_ep_dequeue(struct usb_ep *_ep, > >>> > >>> struct usb_request *_req) > >>> > >>>> int ep_num, stopped, ret = 0; > >>>> u32 epctrl; > >>>> > >>>> - if (!_ep || !_req) > >>>> + /* Ensure that the ep and request are valid, and the ep is not > >>>> + * disabled > >>>> + */ > >>>> + if (!_ep || !_req || !ep->ep.desc) > >>>> > >>>> return -EINVAL; > > > > Shouldn't that last check be done with a lock taken ? > > I had presumed a lock wasn't necessary because ep->ep.desc is only set > to NULL by fsl_ep_disable() which, since it is called by > usb_ep_disable(), should only be invoked when no other task is using the > endpoint (according to include/linux/usb/gadget.h). Furthermore, the > chipidea UDC driver does check the equivalent of this field is not NULL > without taking a lock (ep_dequeue() in drivers/usb/chipidea/udc.c). > > However, it is possible that I'm misunderstanding something here, so > apologies if I am. I might be wrong as well :-) I just wanted to point out something that appeared to me as a possible issue. > >>>> spin_lock_irqsave(&ep->udc->lock, flags); -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/