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

[Jeff Moyer <jmoyer@redhat.com>]

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

Cheers,
Jeff