Re: [PATCH 5.11] io_uring: don't take fs for recvmsg/sendmsg

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

On 07/11/2020 13:46, Stefan Metzmacher wrote:
> Hi Pavel,
> 
>> We don't even allow not plain data msg_control, which is disallowed in __sys_{send,revb}msg_sock().
> 
> Can't we better remove these checks and allow msg_control?
> For me it's a limitation that I would like to be removed.

We can grab fs only in specific situations as you mentioned, by e.g.
adding a switch(opcode) in io_prep_async_work(), but that's the easy
part. All msg_control should be dealt one by one as they do different
things. And it's not the fact that they ever require fs.

> 
> If there's a cost using IO_WQ_WORK_FS, would it be possible to use IO_WQ_WORK_FS only it msg_control is actually use> 
>   if (msg->msg_control || msg->msg_controllen) 
>       static const struct io_op_def sendmsg_control_op_def = {
>          ...
>       };
> 
>       something = &sendmsg_control_op_def;
>   }

-- 
Pavel Begunkov