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Date:   Thu, 25 May 2023 09:03:02 -0600
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Subject: Re: [PATCH net-next v3] net: ioctl: Use kernel memory on protocol
 ioctl callbacks
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To:     Simon Horman <simon.horman@corigine.com>,
        Eric Dumazet <edumazet@google.com>
Cc:     Breno Leitao <leitao@debian.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
References: <20230525125503.400797-1-leitao@debian.org>
 <CANn89i+neca0ApNxRdZCiTMkwy-5=0mnOMM=9Z3u78VPNw4_fg@mail.gmail.com>
 <ZG92ox2BWE3rS1xR@corigine.com>
From:   David Ahern <dsahern@kernel.org>
In-Reply-To: <ZG92ox2BWE3rS1xR@corigine.com>
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On 5/25/23 8:54 AM, Simon Horman wrote:
> On Thu, May 25, 2023 at 04:19:32PM +0200, Eric Dumazet wrote:
>> On Thu, May 25, 2023 at 2:55 PM Breno Leitao <leitao@debian.org> 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" ???
> 
> Yes, indeed it does.
> 

phonet_sk_ioctl is simple enough to make an inline in which case this
should go in include//linux/phonet.h.