On Thu, Feb 17, 2022 at 8:05 PM Hans Verkuil <hverkuil@xxxxxxxxx> wrote: > > On 17/02/2022 05:39, Dongliang Mu wrote: > > From: Dongliang Mu <mudongliangabcd@xxxxxxxxx> > > > > flush_work will throw one WARN if worker->func is NULL. So we should always > > initialize one worker before calling flush_work. When hdpvr_probe does not > > initialize its worker, the hdpvr_disconnect will encounter one WARN. The > > stack trace is in the following: > > > > hdpvr_disconnect+0xb8/0xf2 drivers/media/usb/hdpvr/hdpvr-core.c:425 > > usb_unbind_interface+0xbf/0x3a0 drivers/usb/core/driver.c:458 > > __device_release_driver drivers/base/dd.c:1206 [inline] > > device_release_driver_internal+0x22a/0x230 drivers/base/dd.c:1237 > > bus_remove_device+0x108/0x160 drivers/base/bus.c:529 > > device_del+0x1fe/0x510 drivers/base/core.c:3592 > > usb_disable_device+0xd1/0x1d0 drivers/usb/core/message.c:1419 > > usb_disconnect+0x109/0x330 drivers/usb/core/hub.c:2228 > > > > Fix this by adding a sanity check of the worker before flush_work. > > > > Reported-by: syzkaller <syzkaller@xxxxxxxxxxxxxxxx> > > Signed-off-by: Dongliang Mu <mudongliangabcd@xxxxxxxxx> > > --- > > drivers/media/usb/hdpvr/hdpvr-core.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/media/usb/hdpvr/hdpvr-core.c b/drivers/media/usb/hdpvr/hdpvr-core.c > > index 52e05a69c46e..d102b459d45d 100644 > > --- a/drivers/media/usb/hdpvr/hdpvr-core.c > > +++ b/drivers/media/usb/hdpvr/hdpvr-core.c > > @@ -422,7 +422,8 @@ static void hdpvr_disconnect(struct usb_interface *interface) > > mutex_unlock(&dev->io_mutex); > > v4l2_device_disconnect(&dev->v4l2_dev); > > msleep(100); > > - flush_work(&dev->worker); > > + if (dev->worker.func) > > + flush_work(&dev->worker); > > I don't think this is the right fix. Instead, move the INIT_WORK line from > hdpvr_start_streaming() to hdpvr_register_videodev(). That should initialize > the worker struct from the start instead of only when you start streaming, > as is the case today. I see your point. One small question: if we initialize worker at the beginning of hdpvr_register_videodev, but without schedule_work, will flush_work at hdpvr_disconnect lead to some issues? Or we need to verify if the work is pending or running at hdpvr_disconnect? > > Can you try that? > > Regards, > > Hans > > > mutex_lock(&dev->io_mutex); > > hdpvr_cancel_queue(dev); > > mutex_unlock(&dev->io_mutex); >
