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 <sitsofe@xxxxxxxxx> 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: 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/ -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
