linux-kernel - Re: [RFC PATCH 0/4] net/io_uring: pass a kernel pointer via optlen_t to proto[

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Message-ID: <Z-sDc-0qyfPZz9lv@mini-arch>
Date: Mon, 31 Mar 2025 14:04:51 -0700
From: Stanislav Fomichev <stfomichev@...il.com>
To: Stefan Metzmacher <metze@...ba.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
	Jens Axboe <axboe@...nel.dk>,
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Subject: Re: [RFC PATCH 0/4] net/io_uring: pass a kernel pointer via optlen_t
 to proto[_ops].getsockopt()

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?