linux-kernel - Re: [PATCH net-next v5] net: ioctl: Use kernel memory on protocol ioctl callbacks

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Message-ID: <ZHxEX0TlXX7VV9kX@gmail.com>
Date:   Sun, 4 Jun 2023 00:59:27 -0700
From:   Breno Leitao <leitao@...ian.org>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     Remi Denis-Courmont <courmisch@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexander Aring <alex.aring@...il.com>,
        Stefan Schmidt <stefan@...enfreihafen.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        David Ahern <dsahern@...nel.org>,
        Matthieu Baerts <matthieu.baerts@...sares.net>,
        Mat Martineau <martineau@...nel.org>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Xin Long <lucien.xin@...il.com>, axboe@...nel.dk,
        asml.silence@...il.com, leit@...com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, dccp@...r.kernel.org,
        linux-wpan@...r.kernel.org, mptcp@...ts.linux.dev,
        linux-sctp@...r.kernel.org
Subject: Re: [PATCH net-next v5] net: ioctl: Use kernel memory on protocol
 ioctl callbacks

Hello Willem 

On Sat, Jun 03, 2023 at 10:21:50AM +0200, Willem de Bruijn wrote:
> On Fri, Jun 2, 2023 at 6:31 PM Breno Leitao <leitao@...ian.org> wrote:
> > Signed-off-by: Breno Leitao <leitao@...ian.org>
> 
> Please check the checkpatch output
> 
> https://patchwork.hopto.org/static/nipa/753609/13265673/checkpatch/stdout

I am checking my current checkpatch before sending the patch, but I am
not seeing the problems above.

My tree is at 44c026a73be8038 ("Linux 6.4-rc3"), and I am not able to
reproduce the problems above.

	$ scripts/checkpatch.pl v5/v5-0001-net-ioctl-Use-kernel-memory-on-protocol-ioctl-cal.patch
	total: 0 errors, 0 warnings, 0 checks, 806 lines checked
	v5/v5-0001-net-ioctl-Use-kernel-memory-on-protocol-ioctl-cal.patch has no obvious style problems and is ready for submission.

Let me investigate what options I am missing when running checkpatch.

> > +/* A wrapper around sock ioctls, which copies the data from userspace
> > + * (depending on the protocol/ioctl), and copies back the result to userspace.
> > + * The main motivation for this function is to pass kernel memory to the
> > + * protocol ioctl callbacks, instead of userspace memory.
> > + */
> > +int sk_ioctl(struct sock *sk, unsigned int cmd, void __user *arg)
> > +{
> > +       int rc = 1;
> > +
> > +       if (sk_is_ipmr(sk))
> > +               rc = ipmr_sk_ioctl(sk, cmd, arg);
> > +       else if (sk_is_icmpv6(sk))
> > +               rc = ip6mr_sk_ioctl(sk, cmd, arg);
> > +       else if (sk_is_phonet(sk))
> > +               rc = phonet_sk_ioctl(sk, cmd, arg);
> 
> Does this handle all phonet ioctl cases correctly?
> 
> Notably pn_socket_ioctl has a SIOCPNGETOBJECT that reads and writes a u16.

We are not touching  "struct proto_ops" in this patch at all.  And
pn_socket_ioctl() is part of "struct proto_ops".

	const struct proto_ops phonet_stream_ops = {
		  ...
		  .ioctl          = pn_socket_ioctl,
	}

That said, all the "struct proto_ops" ioctl calls backs continue to use
"unsigned long arg" with userspace information, at least for now.

	struct proto_ops {
		...
		int             (*ioctl)     (struct socket *sock, unsigned int cmd,
					      unsigned long arg);
	}

This patch only changes the "struct proto".