From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753580Ab2JVMAC (ORCPT ); Mon, 22 Oct 2012 08:00:02 -0400 Received: from mail.realvnc.com ([212.69.41.2]:25573 "EHLO mail.realvnc.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751864Ab2JVMAA (ORCPT ); Mon, 22 Oct 2012 08:00:00 -0400 X-Greylist: delayed 601 seconds by postgrey-1.27 at vger.kernel.org; Mon, 22 Oct 2012 08:00:00 EDT Message-ID: <508532DF.7050809@realvnc.com> Date: Mon, 22 Oct 2012 12:49:51 +0100 From: Simon Haggett User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120714 Thunderbird/14.0 MIME-Version: 1.0 To: Laurent Pinchart 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 References: <1350667166-3559-1-git-send-email-simon.haggett@realvnc.com> <20121019173718.GA2738@arwen.pp.htv.fi> <94F013E7935FF44C83EBE7784D62AD3F094730DB@039-SN2MPN1-023.039d.mgd.msft.net> <1535820.NU10ADjvOZ@avalon> In-Reply-To: <1535820.NU10ADjvOZ@avalon> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi On 22/10/12 11:47, Laurent Pinchart wrote: > Hi, > > 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. > >>>> spin_lock_irqsave(&ep->udc->lock, flags); > Many thanks Simon