Re: [PATCH v3 3/3] uio: fix crash after the device is unregistered

[Xiubo Li]

On 2018/7/7 2:58, Mike Christie wrote:
> On 07/05/2018 09:57 PM, xiubli@xxxxxxxxxx wrote:
> >   void uio_event_notify(struct uio_info *info)
> >   {
> > -	struct uio_device *idev = info->uio_dev;
> > +	struct uio_device *idev;
> > +
> > +	if (!info)
> > +		return;
> > +
> > +	idev = info->uio_dev;
> >   
> For this one too, I am not sure if it is needed.
>
> uio_interrupt -> uio_event_notify. See other mail.
>
> driver XYZ -> uio_event_notify. I think drivers need to handle this and
> set some bits and/or perform some cleanup to make sure they are not
> calling uio_event_notify after it has called uio_unregister_device. The
> problem with the above test is if they do not they could have called
> uio_unregister_device right after the info test so you could still hit
> the problem.

When we are tcmu_destroy_device(), if the netlink notify event to 
userspace is not successful then the TCMU will call the uio unregister, 
which will set the idev->info = NULL, without close and deleting the 
device in userspace. But the TCMU could still queue cmds to the ring 
buffer, then the uio_event_notify will be called.

For this case only when using idev->info it would happen. And currently 
there is no need to check this, I will remove it for now.

Thanks,

BRs