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From: Jakub Kicinski <kuba@kernel.org>
To: Kefeng Wang <wangkefeng.wang@huawei.com>, <gregkh@linuxfoundation.org>
Cc: <linux-kernel@vger.kernel.org>, <netdev@vger.kernel.org>,
	<hannes@stressinduktion.org>, <davem@davemloft.net>,
	<akpm@linux-foundation.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"Eric Dumazet" <edumazet@google.com>,
	Minmin chen <chenmingmin@huawei.com>
Subject: Re: [PATCH v2] once: Fix panic when module unload
Date: Fri, 6 Aug 2021 06:43:28 -0700	[thread overview]
Message-ID: <20210806064328.1b54a7f0@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <20210806082124.96607-1-wangkefeng.wang@huawei.com>

On Fri, 6 Aug 2021 16:21:24 +0800 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/

Seems reasonable. Greg does it look good to you?

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

  reply	other threads:[~2021-08-06 13:43 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-06  8:21 [PATCH v2] once: Fix panic when module unload Kefeng Wang
2021-08-06 13:43 ` Jakub Kicinski [this message]
2021-08-06 13:51   ` Greg KH
2021-08-09  1:15     ` Kefeng Wang
2021-08-06 15:22 ` Hannes Frederic Sowa
2021-08-09  1:13   ` Kefeng Wang

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