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Subject: Re: [PATCH v2] once: Fix panic when module unload
To:     Hannes Frederic Sowa <hannes@stressinduktion.org>,
        <linux-kernel@vger.kernel.org>, <netdev@vger.kernel.org>,
        David Miller <davem@davemloft.net>
CC:     Andrew Morton <akpm@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        "Eric Dumazet" <edumazet@google.com>,
        Minmin chen <chenmingmin@huawei.com>
References: <20210806082124.96607-1-wangkefeng.wang@huawei.com>
 <7ae60193-0114-46d2-9770-697a2f88b85b@www.fastmail.com>
From:   Kefeng Wang <wangkefeng.wang@huawei.com>
Message-ID: <25dd38c6-39e7-8fb8-dff3-5062acf959c4@huawei.com>
Date:   Mon, 9 Aug 2021 09:13:47 +0800
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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@huawei.com/
>>
>> Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
>> Cc: Daniel Borkmann <daniel@iogearbox.net>
>> Cc: David S. Miller <davem@davemloft.net>
>> Cc: Eric Dumazet <edumazet@google.com>
>> Reported-by: Minmin chen <chenmingmin@huawei.com>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Thanks.
>
> Thanks,
> Hannes
> .
>