Re: [PATCH 1/1] io_uring/af_unix: disable sending io_uring over sockets

[Pavel Begunkov <asml.silence@gmail.com>]

On 12/8/23 16:06, Jeff Moyer wrote:
> Jann Horn <jannh@google.com> writes:
> 
>> On Fri, Dec 8, 2023 at 4:00 PM Jeff Moyer <jmoyer@redhat.com> wrote:
>>> Jens Axboe <axboe@kernel.dk> writes:
>>>
>>>> On Wed, 06 Dec 2023 13:26:47 +0000, Pavel Begunkov wrote:
>>>>> File reference cycles have caused lots of problems for io_uring
>>>>> in the past, and it still doesn't work exactly right and races with
>>>>> unix_stream_read_generic(). The safest fix would be to completely
>>>>> disallow sending io_uring files via sockets via SCM_RIGHT, so there
>>>>> are no possible cycles invloving registered files and thus rendering
>>>>> SCM accounting on the io_uring side unnecessary.
>>>>>
>>>>> [...]
>>>>
>>>> Applied, thanks!
>>>
>>> So, this will break existing users, right?
>>
>> Do you know of anyone actually sending io_uring FDs over unix domain
>> sockets?
> 
> I do not.  However, it's tough to prove no software is doing this.
> 
>> That seems to me like a fairly weird thing to do.
> 
> I am often surprised by what developers choose to do.  I attribute that
> to my lack of imagination.
> 
>> Thinking again about who might possibly do such a thing, the only
>> usecase I can think of is CRIU; and from what I can tell, CRIU doesn't
>> yet support io_uring anyway.
> 
> I'm not lobbying against turning this off, and I'm sure Pavel had
> already considered the potential impact before posting.  It would be

Jens already replied, but I wanted to add that it was discussed and
decided to go forward with, because there are no too obvious / known
users, and the benefits including safety outweigh it.

> good to include that information in the commit message, in my opinion.

Yeah, agree with that

-- 
Pavel Begunkov