linux-kernel - Re: [PATCH net-next v4] net: ioctl: Use kernel memory on protocol ioctl callbacks

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Message-ID: <ZHoWeiDVoLV1VMpT@gmail.com>
Date:   Fri, 2 Jun 2023 09:19:06 -0700
From:   Breno Leitao <leitao@...ian.org>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     dsahern@...nel.org, 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>,
        Matthieu Baerts <matthieu.baerts@...sares.net>,
        Mat Martineau <martineau@...nel.org>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Xin Long <lucien.xin@...il.com>, leit@...com, axboe@...nel.dk,
        asml.silence@...il.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 v4] net: ioctl: Use kernel memory on protocol
 ioctl callbacks

On Wed, May 31, 2023 at 03:01:56AM -0400, Willem de Bruijn wrote:
> Breno Leitao wrote:
> > +int ip6mr_sk_ioctl(struct sock *sk, unsigned int cmd, void __user *arg);
> > +static inline int sk_is_ip6mr(struct sock *sk)
> > +{
> > +	return sk->sk_family == AF_INET6 &&
> > +		inet_sk(sk)->inet_num == IPPROTO_ICMPV6;
> > +}
 
> Technically, this is just sk_is_icmpv6, which is broader than IPv6
> multicast routing.

Right, let me rename it to reflect this properly.

> No other concerns from me.

Thanks for the detailed review.

> Two small asides, that are fine to ignore.
> 
> The $PROTO_sk_ioctl functions could conceivably call directly into
> the $PROTO_ioctl functions without the indirect function pointer.
> But that would require open coding the sock_sk_ioctl_inout helpers.
> 
> The demux now first checks relatively unlikely multicast routing
> and phonet before falling through to the more common protocols. But
> ioctl is not a hot path operation.

I am more than happy to open code sock_sk_ioctl_inout into protocol
functions, but, I would prefer to do it in a follow up patch, since this
one is close (I hope) to address the original problem. I hope it works
for you.

Thanks!