netdev - Re: [PATCH net 5/5] net/smc: put sk reference if close work was canceled

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <ad5e4191-227e-4a62-a110-472618ef7de1@linux.ibm.com>
Date: Wed, 18 Oct 2023 22:26:25 +0200
From: Wenjia Zhang <wenjia@...ux.ibm.com>
To: "D. Wythe" <alibuda@...ux.alibaba.com>, kgraul@...ux.ibm.com,
        jaka@...ux.ibm.com, wintera@...ux.ibm.com
Cc: kuba@...nel.org, davem@...emloft.net, netdev@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [PATCH net 5/5] net/smc: put sk reference if close work was
 canceled



On 17.10.23 04:06, D. Wythe wrote:
> 
> 
> On 10/13/23 3:04 AM, Wenjia Zhang wrote:
>>
>>
>> On 11.10.23 09:33, D. Wythe wrote:
>>> From: "D. Wythe" <alibuda@...ux.alibaba.com>
>>>
>>> Note that we always hold a reference to sock when attempting
>>> to submit close_work. 
>> yes
>> Therefore, if we have successfully
>>> canceled close_work from pending, we MUST release that reference
>>> to avoid potential leaks.
>>>
>> Isn't the corresponding reference already released inside the 
>> smc_close_passive_work()?
>>
> 
> Hi Wenjia,
> 
> If we successfully cancel the close work from the pending state,
> it means that smc_close_passive_work() has never been executed.
> 
> You can find more details here.
> 
> /**
> * cancel_work_sync - cancel a work and wait for it to finish
> * @work:the work to cancel
> *
> * Cancel @work and wait for its execution to finish. This function
> * can be used even if the work re-queues itself or migrates to
> * another workqueue. On return from this function, @work is
> * guaranteed to be not pending or executing on any CPU.
> *
> * cancel_work_sync(&delayed_work->work) must not be used for
> * delayed_work's. Use cancel_delayed_work_sync() instead.
> *
> * The caller must ensure that the workqueue on which @work was last
> * queued can't be destroyed before this function returns.
> *
> * Return:
> * %true if @work was pending, %false otherwise.
> */
> boolcancel_work_sync(structwork_struct *work)
> {
> return__cancel_work_timer(work, false);
> }
> 
> Best wishes,
> D. Wythe
As I understand, queue_work() would wake up the work if the work is not 
already on the queue. And the sock_hold() is just prio to the 
queue_work(). That means, cancel_work_sync() would cancel the work 
either before its execution or after. If your fix refers to the former 
case, at this moment, I don't think the reference can be hold, thus it 
is unnecessary to put it.
> 
>>> Fixes: 42bfba9eaa33 ("net/smc: immediate termination for SMCD link 
>>> groups")
>>> Signed-off-by: D. Wythe <alibuda@...ux.alibaba.com>
>>> ---
>>>   net/smc/smc_close.c | 3 ++-
>>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/net/smc/smc_close.c b/net/smc/smc_close.c
>>> index 449ef45..10219f5 100644
>>> --- a/net/smc/smc_close.c
>>> +++ b/net/smc/smc_close.c
>>> @@ -116,7 +116,8 @@ static void smc_close_cancel_work(struct smc_sock 
>>> *smc)
>>>       struct sock *sk = &smc->sk;
>>>         release_sock(sk);
>>> -    cancel_work_sync(&smc->conn.close_work);
>>> +    if (cancel_work_sync(&smc->conn.close_work))
>>> +        sock_put(sk);
>>>       cancel_delayed_work_sync(&smc->conn.tx_work);
>>>       lock_sock(sk);
>>>   }
>