On 18/02/2022 06:58, Dongliang Mu wrote: > 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? No, flush_work already checks if there is anything to do. If nothing was scheduled, it will just return. Regards, Hans > >> >> Can you try that? > > >> >> Regards, >> >> Hans >> >>> mutex_lock(&dev->io_mutex); >>> hdpvr_cancel_queue(dev); >>> mutex_unlock(&dev->io_mutex); >>
