[RFC PATCH 0/4] net/io_uring: pass a kernel pointer via optlen_t to proto[_ops].getsockopt()

[Stanislav Fomichev]

On 03/31, Stefan Metzmacher wrote:
> The motivation for this is to remove the SOL_SOCKET limitation
> from io_uring_cmd_getsockopt().
> 
> The reason for this limitation is that io_uring_cmd_getsockopt()
> passes a kernel pointer as optlen to do_sock_getsockopt()
> and can't reach the ops->getsockopt() path.
> 
> The first idea would be to change the optval and optlen arguments
> to the protocol specific hooks also to sockptr_t, as that
> is already used for setsockopt() and also by do_sock_getsockopt()
> sk_getsockopt() and BPF_CGROUP_RUN_PROG_GETSOCKOPT().
> 
> But as Linus don't like 'sockptr_t' I used a different approach.
> 
> @Linus, would that optlen_t approach fit better for you?

[..]

> Instead of passing the optlen as user or kernel pointer,
> we only ever pass a kernel pointer and do the
> translation from/to userspace in do_sock_getsockopt().

At this point why not just fully embrace iov_iter? You have the size
now + the user (or kernel) pointer. Might as well do
s/sockptr_t/iov_iter/ conversion?