Re: [PATCH net-next v3] net: ioctl: Use kernel memory on protocol ioctl callbacks

[Eric Dumazet]

On Thu, May 25, 2023 at 2:55 PM Breno Leitao <leitao@xxxxxxxxxx> wrote:
>
> 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 == PF_PHONET && sk->sk_protocol == PN_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, void __user *arg)
> +{
> +       return 1;
> +}
> +#endif
> +
>

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