netdev - Re: [PATCH v4 00/10] io_uring: Initial support for {s,g}etsockopt commands

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Date: Mon, 9 Oct 2023 03:11:05 -0700
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Breno Leitao <leitao@...ian.org>
Cc: Jakub Kicinski <kuba@...nel.org>, sdf@...gle.com, axboe@...nel.dk, 
	asml.silence@...il.com, martin.lau@...ux.dev, krisman@...e.de, 
	bpf@...r.kernel.org, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
	io-uring@...r.kernel.org, pabeni@...hat.com
Subject: Re: [PATCH v4 00/10] io_uring: Initial support for {s,g}etsockopt commands

On Fri, Oct 6, 2023 at 10:45 AM Breno Leitao <leitao@...ian.org> wrote:
>
> Hello Jakub,
>
> On Tue, Sep 05, 2023 at 03:49:51PM -0700, Jakub Kicinski wrote:
> > On Mon,  4 Sep 2023 09:24:53 -0700 Breno Leitao wrote:
> > > Patches 1-2: Modify the BPF hooks to support sockptr_t, so, these functions
> > > become flexible enough to accept user or kernel pointers for optval/optlen.
> >
> > Have you seen:
> >
> > https://lore.kernel.org/all/CAHk-=wgGV61xrG=gO0=dXH64o2TDWWrXn1mx-CX885JZ7h84Og@mail.gmail.com/
> >
> > ? I wasn't aware that Linus felt this way, now I wonder if having
> > sockptr_t spread will raise any red flags as this code flows back
> > to him.
>
> Thanks for the heads-up. I've been thinking about it for a while and I'd
> like to hear what are the next steps here.
>
> Let me first back up and state where we are, and what is the current
> situation:
>
> 1) __sys_getsockopt() uses __user pointers for both optval and optlen
> 2) For io_uring command, Jens[1] suggested we get optlen from the io_uring
> sqe, which is a kernel pointer/value.
>
> Thus, we need to make the common code (callbacks) able to handle __user
> and kernel pointers (for optlen, at least).
>
> From a proto_ops callback perspective, ->setsockopt() uses sockptr.
>
>           int             (*setsockopt)(struct socket *sock, int level,
>                                         int optname, sockptr_t optval,
>                                         unsigned int optlen);
>
> Getsockopt() uses sockptr() for level=SOL_SOCKET:
>
>         int sk_getsockopt(struct sock *sk, int level, int optname,
>                     sockptr_t optval, sockptr_t optlen)
>
> But not for the other levels:
>
>         int             (*getsockopt)(struct socket *sock, int level,
>                                       int optname, char __user *optval, int __user *optlen);
>
>
> That said, if this patchset shouldn't use sockptr anymore, what is the
> recommendation?
>
> If we move this patchset to use iov_iter instead of sockptr, then I
> understand we want to move *all* these callbacks to use iov_vec. Is this
> the right direction?
>
> Thanks for the guidance!
>
> [1] https://lore.kernel.org/all/efe602f1-8e72-466c-b796-0083fd1c6d82@kernel.dk/

Since sockptr_t is already used by __sys_setsockopt and
__sys_setsockopt, patches 1 and 2 don't introduce any new sockptr code
paths.

setsockopt callbacks also already use sockptr as of commit
a7b75c5a8c41 ("net: pass a sockptr_t into ->setsockopt").

getsockopt callbacks do take user pointers, just not sockptr.

Is the only issue right now the optlen kernel pointer?