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

Wenjia Zhang
2023-10-18T20:29:32Z

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@linux.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@linux.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);
>>>   }
>