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SubjectRe: [PATCH] media: hdpvr: call flush_work only if initialized
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On 17/02/2022 05:39, Dongliang Mu wrote:
> From: Dongliang Mu <mudongliangabcd@gmail.com>
>
> 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@googlegroups.com>
> Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
> ---
> 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.

Can you try that?

Regards,

Hans

> mutex_lock(&dev->io_mutex);
> hdpvr_cancel_queue(dev);
> mutex_unlock(&dev->io_mutex);

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