netdev - Re: [Patch net] nfc: check sock state in llcp_sock

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Date:	Sun, 3 Jan 2016 14:36:17 -0800
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Dmitry Vyukov <dvyukov@...gle.com>
Cc:	netdev <netdev@...r.kernel.org>, linux-wireless@...r.kernel.org,
	Lauro Ramos Venancio <lauro.venancio@...nbossa.org>,
	Aloisio Almeida Jr <aloisio.almeida@...nbossa.org>,
	Samuel Ortiz <sameo@...ux.intel.com>
Subject: Re: [Patch net] nfc: check sock state in llcp_sock_getname()

On Sat, Jan 2, 2016 at 12:03 AM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
> On Sat, Jan 2, 2016 at 1:34 AM, Cong Wang <xiyou.wangcong@...il.com> wrote:
>> llcp_sock_getname() checks llcp_sock->dev to make sure
>> llcp_sock is already connected or bound, however, we could
>> be in the middle of llcp_sock_bind() where llcp_sock->dev
>> is bound and llcp_sock->service_name_len is set,
>> but llcp_sock->service_name is not, in this case we would
>> lead to copy some bytes from a NULL pointer.
>>
>> We should just check if sk->sk_state is still closed since
>> both connect() and bind() will update this state at the end.
>
> Hi Cong,
>
> This is still racy. If you want to play lock-free then you also need
> proper memory barriers. Stores to sk_state need to be
> smp_store_release, while the load needs to be smp_load_acquire.
> Otherwise getname still can see partially initialized socket.
>

Right... Or just lock sock perhaps. I will update my patch.

Thanks!
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