From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753530Ab1IFIHz (ORCPT ); Tue, 6 Sep 2011 04:07:55 -0400 Received: from mail-qw0-f42.google.com ([209.85.216.42]:37907 "EHLO mail-qw0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753369Ab1IFIHu convert rfc822-to-8bit (ORCPT ); Tue, 6 Sep 2011 04:07:50 -0400 MIME-Version: 1.0 In-Reply-To: <20110905223102.GA26980@sucs.org> References: <20110829204846.GA14699@sucs.org> <201109051159.08268.laurent.pinchart@ideasonboard.com> <201109051213.26482.hverkuil@xs4all.nl> <201109051216.42579.hverkuil@xs4all.nl> <20110905223102.GA26980@sucs.org> Date: Tue, 6 Sep 2011 16:07:48 +0800 Message-ID: Subject: Re: BUG: unable to handle kernel paging request at 6b6b6bcb (v4l2_device_disconnect+0x11/0x30) From: Dave Young To: Sitsofe Wheeler Cc: Hans Verkuil , Laurent Pinchart , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Guennadi Liakhovetski , Mauro Carvalho Chehab Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 6, 2011 at 6:31 AM, Sitsofe Wheeler wrote: > On Mon, Sep 05, 2011 at 12:16:42PM +0200, Hans Verkuil wrote: >> On Monday, September 05, 2011 12:13:26 Hans Verkuil wrote: >> > >> > The original order is correct, but what I missed is that for drivers >> > that release (free) everything in the videodev release callback the >> > v4l2_device struct is also freed and v4l2_device_put will fail. >> > >> > To fix this, add this code just before the vdev->release call: >> > >> >     /* Do not call v4l2_device_put if there is no release callback set. */ >> >     if (v4l2_dev->release == NULL) >> >             v4l2_dev = NULL; >> > >> > If there is no release callback, then the refcounting is pointless >> > anyway. >> > >> > This should work. >> >> Note that in the long run using the v4l2_device release callback >> instead of the videodev release is better. But it's a lot of work to >> convert everything so that's long term. I'm quite surprised BTW that >> this bug wasn't found much earlier. > > This inline patch fixes the second "poison overwritten" problem so: > Tested-by: Sitsofe Wheeler Confirmed > > However, it does not prevent the original oops that was reported in the > original message. Yang Ruirui's patch in > https://lkml.org/lkml/2011/9/1/74 seems to be required to resolve > that initial problem - can it be ACK'd? Yang's patch is reproduced > inline below: Thanks, If it's ok, I can resend it as inline. > > For uvc device, dev->vdev.dev is the &intf->dev, > uvc_delete code is as below: >        usb_put_intf(dev->intf); >        usb_put_dev(dev->udev); > >        uvc_status_cleanup(dev); >        uvc_ctrl_cleanup_device(dev); > > ## the intf dev is released above, so below code will oops. > >        if (dev->vdev.dev) >                v4l2_device_unregister(&dev->vdev); > Fix it by get_device in v4l2_device_register and put_device in v4l2_device_disconnect > --- >  drivers/media/video/v4l2-device.c |    2 ++ >  1 file changed, 2 insertions(+) > diff --git a/drivers/media/video/v4l2-device.c b/drivers/media/video/v4l2-device.c > index c72856c..e6a2c3b 100644 > --- a/drivers/media/video/v4l2-device.c > +++ b/drivers/media/video/v4l2-device.c > @@ -38,6 +38,7 @@ int v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev) >        mutex_init(&v4l2_dev->ioctl_lock); >        v4l2_prio_init(&v4l2_dev->prio); >        kref_init(&v4l2_dev->ref); > +       get_device(dev); >        v4l2_dev->dev = dev; >        if (dev == NULL) { >                /* If dev == NULL, then name must be filled in by the caller */ > @@ -93,6 +94,7 @@ void v4l2_device_disconnect(struct v4l2_device *v4l2_dev) > >        if (dev_get_drvdata(v4l2_dev->dev) == v4l2_dev) >                dev_set_drvdata(v4l2_dev->dev, NULL); > +       put_device(v4l2_dev->dev); >        v4l2_dev->dev = NULL; >  } >  EXPORT_SYMBOL_GPL(v4l2_device_disconnect); > > -- > Sitsofe | http://sucs.org/~sits/ > -- Regards Yang RuiRui