Re: [PATCH 5.11] io_uring: NULL files dereference by SQPOLL

Jens Axboe
2020-11-07T22:28:50Z

On 11/7/20 2:54 PM, Pavel Begunkov wrote:
> On 07/11/2020 21:18, Pavel Begunkov wrote:
>> On 07/11/2020 21:16, Pavel Begunkov wrote:
>>> SQPOLL task may find sqo_task->files == NULL, so
>>> __io_sq_thread_acquire_files() would left it unset and so all the
>>> following fails, e.g. attempts to submit. Fail if sqo_task doesn't have
>>> files.
>>
>> Josef, could you try this one?
>
> Hmm, as you said it happens often... IIUC there is a drawback with
> SQPOLL -- after the creator process/thread exits most of subsequent
> requests will start failing.
> I'd say from application correctness POV such tasks should exit
> only after their SQPOLL io_urings got killed.

I don't think there's anything wrong with that - if you submit requests
and exit before they have completed, then you by definition are not
caring about the result of them.

--
Jens Axboe