Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20230525125503.400797-1-leitao@debian.org>
In-Reply-To: <20230525125503.400797-1-leitao@debian.org>
From:   Eric Dumazet <edumazet@google.com>
Date:   Thu, 25 May 2023 16:19:32 +0200
Message-ID: <CANn89i+neca0ApNxRdZCiTMkwy-5=0mnOMM=9Z3u78VPNw4_fg@mail.gmail.com>
Subject: Re: [PATCH net-next v3] net: ioctl: Use kernel memory on protocol
 ioctl callbacks
To:     Breno Leitao <leitao@debian.org>
Cc:     dsahern@kernel.org, willemdebruijn.kernel@gmail.com,
        Remi Denis-Courmont <courmisch@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Alexander Aring <alex.aring@gmail.com>,
        Stefan Schmidt <stefan@datenfreihafen.org>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Matthieu Baerts <matthieu.baerts@tessares.net>,
        Mat Martineau <martineau@kernel.org>,
        Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>,
        Xin Long <lucien.xin@gmail.com>, leit@fb.com, axboe@kernel.dk,
        asml.silence@gmail.com, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, dccp@vger.kernel.org,
        linux-wpan@vger.kernel.org, mptcp@lists.linux.dev,
        linux-sctp@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Thu, May 25, 2023 at 2:55=E2=80=AFPM Breno Leitao <leitao@debian.org> wr=
ote:
>
> Most of the ioctls to net protocols operates directly on userspace
> argument (arg). Usually doing get_user()/put_user() directly in the
> ioctl callback.  This is not flexible, because it is hard to reuse these
> functions without passing userspace buffers.
>
> Change the "struct proto" ioctls to avoid touching userspace memory and
> operate on kernel buffers, i.e., all protocol's ioctl callbacks is
> adapted to operate on a kernel memory other than on userspace (so, no
> more {put,get}_user() and friends being called in the ioctl callback).
>

 diff --git a/include/net/phonet/phonet.h b/include/net/phonet/phonet.h
> index 862f1719b523..93705d99f862 100644
> --- a/include/net/phonet/phonet.h
> +++ b/include/net/phonet/phonet.h
> @@ -109,4 +109,23 @@ void phonet_sysctl_exit(void);
>  int isi_register(void);
>  void isi_unregister(void);
>
> +#ifdef CONFIG_PHONET
> +int phonet_sk_ioctl(struct sock *sk, unsigned int cmd, void __user *arg)=
;
> +
> +static inline bool phonet_is_sk(struct sock *sk)
> +{
> +       return sk->sk_family =3D=3D PF_PHONET && sk->sk_protocol =3D=3D P=
N_PROTO_PHONET;
> +}
> +#else
> +static inline bool phonet_is_sk(struct sock *sk)
> +{
> +       return 0;
> +}
> +
> +static inline int phonet_sk_ioctl(struct sock *sk, unsigned int cmd, voi=
d __user *arg)
> +{
> +       return 1;
> +}
> +#endif
> +
>

PHONET can be built as a module, so I guess the compiler would
complain if "CONFIG_PHONET=3Dm" ???