[PATCH] media: hdpvr: call flush_work only if initialized

[PATCH] media: hdpvr: call flush_work only if initialized

[Dongliang Mu]

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);
 	mutex_lock(&dev->io_mutex);
 	hdpvr_cancel_queue(dev);
 	mutex_unlock(&dev->io_mutex);
-- 
2.25.1

Re: [PATCH] media: hdpvr: call flush_work only if initialized

[Hans Verkuil]

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);

Re: [PATCH] media: hdpvr: call flush_work only if initialized

[Dongliang Mu]

On Thu, Feb 17, 2022 at 8:05 PM Hans Verkuil <hverkuil@xs4all.nl> wrote:
>
> 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.

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);
>

Re: [PATCH] media: hdpvr: call flush_work only if initialized

[Hans Verkuil]

On 18/02/2022 06:58, Dongliang Mu wrote:
> On Thu, Feb 17, 2022 at 8:05 PM Hans Verkuil <hverkuil@xs4all.nl> wrote:
>>
>> 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.
> 
> 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);
>>