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

From: Breno Leitao <leitao@debian.org>
To: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc: Jakub Kicinski <kuba@kernel.org>,
	sdf@google.com, axboe@kernel.dk, asml.silence@gmail.com,
	martin.lau@linux.dev, krisman@suse.de, bpf@vger.kernel.org,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	io-uring@vger.kernel.org, pabeni@redhat.com
Subject: Re: [PATCH v4 00/10] io_uring: Initial support for {s,g}etsockopt commands
Date: Mon, 9 Oct 2023 06:28:00 -0700	[thread overview]
Message-ID: <ZSP/4GVaQiFuDizz@gmail.com> (raw)
In-Reply-To: <CAF=yD-Lr3238obe-_omnPBvgdv2NLvdK5be-5F7YyV3H7BkhSg@mail.gmail.com>

On Mon, Oct 09, 2023 at 03:11:05AM -0700, Willem de Bruijn wrote:
> On Fri, Oct 6, 2023 at 10:45 AM Breno Leitao <leitao@debian.org> wrote:
> > 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?

Correct. The current discussion is only related to optlen in the
getsockopt() callbacks (invoked when level != SOL_SOCKET). Everything
else (getsockopt(level=SOL_SOCKET..) and setsockopt) is using sockptr.

Is it bad if we review/merge this code as is (using sockptr), and start
the iov_iter/getsockopt() refactor in a follow-up thread?

Thanks!