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

On 2021/8/6 21:51, Greg KH wrote:

On Fri, Aug 06, 2021 at 06:43:28AM -0700, Jakub Kicinski wrote:

quoted

On Fri, 6 Aug 2021 16:21:24 +0800 Kefeng Wang wrote:

quoted

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@huawei.com/ (local)

Seems reasonable. Greg does it look good to you?

Me?  I was not paying attention to this at all, sorry...

quoted

I think we can take it thru networking since nobody cared to pick up v1.

Thanks all ;)

Sure, I trust you :)
.