Re: [PATCH v2] once: Fix panic when module unload

[Kefeng Wang]

On 2021/8/6 23:22, Hannes Frederic Sowa wrote:
> On Fri, Aug 6, 2021, at 10:21, Kefeng Wang wrote:
> > DO_ONCE
> > DEFINE_STATIC_KEY_TRUE(___once_key);
> > __do_once_done
> >    once_disable_jump(once_key);
> >      INIT_WORK(&w->work, once_deferred);
> >      struct once_work *w;
> >      w->key = key;
> >      schedule_work(&w->work);                     module unload
> >                                                     //*the key is
> > destroy*
> > process_one_work
> >    once_deferred
> >      BUG_ON(!static_key_enabled(work->key));
> >         static_key_count((struct static_key *)x)    //*access key, crash*
> >
> > When module uses DO_ONCE mechanism, it could crash due to the above
> > concurrency problem, we could reproduce it with link[1].
> >
> > Fix it by add/put module refcount in the once work process.
> >
> > [1]
> > https://lore.kernel.org/netdev/eaa6c371-465e-57eb-6be9-f4b16b9d7cbf@xxxxxxxxxx/
> >
> > Cc: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>
> > Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> > Cc: David S. Miller <davem@xxxxxxxxxxxxx>
> > Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> > Reported-by: Minmin chen <chenmingmin@xxxxxxxxxx>
> > Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> Acked-by: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>
Thanks.
> Thanks,
> Hannes
> .