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[76.102.12.149]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2ca7cae9e9esm3403523eec.23.2026.04.02.16.00.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Apr 2026 16:00:28 -0700 (PDT) Date: Thu, 2 Apr 2026 16:00:27 -0700 From: Stanislav Fomichev To: Breno Leitao Cc: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Kuniyuki Iwashima , Willem de Bruijn , metze@samba.org, axboe@kernel.dk, Stanislav Fomichev , io-uring@vger.kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org, Linus Torvalds , linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH net-next v2 2/4] net: call getsockopt_iter if available Message-ID: References: <20260401-getsockopt-v2-0-611df6771aff@debian.org> <20260401-getsockopt-v2-2-611df6771aff@debian.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On 04/02, Breno Leitao wrote: > Hello Stanislav, > > On Wed, Apr 01, 2026 at 11:10:22AM -0700, Stanislav Fomichev wrote: > > So maybe something like this is better to communicate your long term intent? > > > > } else if (ops->getsockopt_iter) { > > optval = sockptr_to_iter(optval) > > optlen = sockptr_to_iter(optlen) > > do_sock_getsockopt_iter(...) /* does not know what sockpt_t is */ > > } > > > > ? > > > > Then your new do_sock_getsockopt_iter is sockptr-free from the beginning > > and at some point we'll just drop/move those sockptr_to_iter calls? > > Sure, that would work as well. It would look like the following, from my > current implemention: > > +static int sockptr_to_sockopt(sockopt_t *opt, sockptr_t optval, > + sockptr_t optlen, struct kvec *kvec) > +{ > + int koptlen; > + > + if (copy_from_sockptr(&koptlen, optlen, sizeof(int))) > + return -EFAULT; > + > + if (optval.is_kernel) { > + kvec->iov_base = optval.kernel; > + kvec->iov_len = koptlen; > + iov_iter_kvec(&opt->iter_out, ITER_DEST, kvec, 1, koptlen); > + iov_iter_kvec(&opt->iter_in, ITER_SOURCE, kvec, 1, koptlen); > + } else { > + iov_iter_ubuf(&opt->iter_out, ITER_DEST, optval.user, koptlen); > + iov_iter_ubuf(&opt->iter_in, ITER_SOURCE, optval.user, > + koptlen); > + } > + opt->optlen = koptlen; > + > + return 0; > +} > + > int do_sock_getsockopt(struct socket *sock, bool compat, int level, > int optname, sockptr_t optval, sockptr_t optlen) > { > @@ -2366,15 +2390,31 @@ int do_sock_getsockopt(struct socket *sock, bool compat, int level, > > + } else if (ops->getsockopt_iter) { > + struct kvec kvec; > + sockopt_t opt; > + > + err = sockptr_to_sockopt(&opt, optval, optlen, &kvec); > + if (err) > + return err; > + > + err = ops->getsockopt_iter(sock, level, optname, &opt); > + > + /* Always write back optlen, even on failure. Some protocols > + * (e.g. CAN raw) return -ERANGE and set optlen to the > + * required buffer size so userspace can discover it. > + */ > + if (copy_to_sockptr(optlen, &opt.optlen, sizeof(int))) > + return -EFAULT; > + } else if (ops->getsockopt) { > .... > > > I hope this way it will be easier to review protocol handler changes. > > > > For example, looking at your AF_PACKET patch, you won't have to care > > about flipping the source and doing the revert. Most/all of the changes will > > be simple: > > - s/get_user(len, optlen)/len = opt->optlen/ > > - s/put_user(len, optlen)/opt->optlen = len/ > > - s/copy_from_user(xxx, optval, len)/copy_from_iter(xxx, len, &opt->iter_in)/ > > - s/copy_to_user(optval, xxx, len)/copy_to_iter(xxx, len, &opt->iter_out)/ > > That is, in fact, a great proposal. It will make the protocol changes review > way easier. > > This is what I have right now. > > typedef struct sockopt { > struct iov_iter iter_out; > struct iov_iter iter_in; > int optlen; > } sockopt_t; > > > And then, the drivers change would be as simple as: > > static int packet_getsockopt(struct socket *sock, int level, int optname, > - char __user *optval, int __user *optlen) > + sockopt_t *opt) > { > int len; > int val, lv = sizeof(val); > @@ -4065,8 +4066,7 @@ static int packet_getsockopt(struct socket *sock, int level, int optname, > if (level != SOL_PACKET) > return -ENOPROTOOPT; > > - if (get_user(len, optlen)) > - return -EFAULT; > + len = opt->optlen; > > if (len < 0) > return -EINVAL; > @@ -4115,7 +4115,7 @@ static int packet_getsockopt(struct socket *sock, int level, int optname, > len = sizeof(int); > if (len < sizeof(int)) > return -EINVAL; > - if (copy_from_user(&val, optval, len)) > + if (copy_from_iter(&val, len, &opt->iter_in) != len) > return -EFAULT; > switch (val) { > case TPACKET_V1: > @@ -4171,9 +4171,8 @@ static int packet_getsockopt(struct socket *sock, int level, int optname, > > if (len > lv) > len = lv; > - if (put_user(len, optlen)) > - return -EFAULT; > - if (copy_to_user(optval, data, len)) > + opt->optlen = len; > + if (copy_to_iter(data, len, &opt->iter_out) != len) > return -EFAULT; > return 0; > > This is not fully tested yet, but, in case you want to see how this looks like > so far, I have it in https://github.com/leitao/linux/tree/b4/getsockopt_v3. > > I will submit a newer version after I am done with the testing. > > Thanks for the insights, > --breno LGTM, thanks!