netdev - Re: [PATCH RFC 1/2] vsock/virtio: fix kernel panic after device hot-unplug

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Date:   Wed, 2 Jan 2019 11:01:27 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Stefan Hajnoczi <stefanha@...hat.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [PATCH RFC 1/2] vsock/virtio: fix kernel panic after device hot-unplug

On Wed, Jan 2, 2019 at 10:39 AM Stefan Hajnoczi <stefanha@...hat.com> wrote:
>
> On Thu, Dec 20, 2018 at 01:15:34PM +0100, Stefano Garzarella wrote:
> > diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
> > index 5d3cce9e8744..9dae54698737 100644
> > --- a/net/vmw_vsock/virtio_transport.c
> > +++ b/net/vmw_vsock/virtio_transport.c
> > @@ -75,6 +75,9 @@ static u32 virtio_transport_get_local_cid(void)
> >  {
> >       struct virtio_vsock *vsock = virtio_vsock_get();
> >
> > +     if (!vsock)
> > +             return VMADDR_CID_ANY;
> > +
> >       return vsock->guest_cid;
> >  }
>
> This looks unrelated to the rest of the patch.  Why is it necessary?

It is needed because the "the_virtio_vsock" returned by
virtio_vsock_get() is initialized during the probe and freed during
the removal.
So, if we move the vsock_core_exit() in the virtio_vsock_exit(), can
happen that the virtio_transport_get_local_cid() is called when the
"the_virtio_vsock" is NULL.

Do you think is better to split this patch?

Thanks,
Stefano

--
Stefano Garzarella
Red Hat