Re: io_uring, IORING_OP_RECVMSG and ancillary data

[Jens Axboe <axboe@kernel.dk>]

On 4/25/20 11:29 AM, Andreas Smas wrote:
> Hi,
> 
> Tried to use io_uring with OP_RECVMSG with ancillary buffers (for my
> particular use case I'm using SO_TIMESTAMP for incoming UDP packets).
> 
> These submissions fail with EINVAL due to the check in __sys_recvmsg_sock().
> 
> The following hack fixes the problem for me and I get valid timestamps
> back. Not suggesting this is the real fix as I'm not sure what the
> implications of this is.
> 
> Any insight into this would be much appreciated.

It was originally disabled because of a security issue, but I do think
it's safe to enable again.

Adding the io-uring list and Jann as well, leaving patch intact below.

> diff --git a/net/socket.c b/net/socket.c
> index 2dd739fba866..689f41f4156e 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -2637,10 +2637,6 @@ long __sys_recvmsg_sock(struct socket *sock,
> struct msghdr *msg,
>                         struct user_msghdr __user *umsg,
>                         struct sockaddr __user *uaddr, unsigned int flags)
>  {
> -       /* disallow ancillary data requests from this path */
> -       if (msg->msg_control || msg->msg_controllen)
> -               return -EINVAL;
> -
>         return ____sys_recvmsg(sock, msg, umsg, uaddr, flags, 0);
>  }
> 


-- 
Jens Axboe