Re: [PATCH 4/6] usbip: fix stub_dev usbip_sockfd_store() races leading to gpf

[Tetsuo Handa]

On 2021/03/09 1:27, Shuah Khan wrote:
> Yes. We might need synchronization between events, threads, and shutdown
> in usbip_host side and in connection polling and threads in vhci.
> 
> I am also looking at the shutdown sequences closely as well since the
> local state is referenced without usbip_device lock in these paths.
> 
> I am approaching these problems as peeling the onion an expression so
> we can limit the changes and take a spot fix approach. We have the
> goal to address these crashes and not introduce regressions.

I think my [PATCH v4 01/12]-[PATCH v4 06/12] simplify your further changes
without introducing regressions. While ud->lock is held when checking ud->status,
current attach/detach code is racy about read/update of ud->status . I think we
can close race in attach/detach code via a simple usbip_event_mutex serialization.