From mboxrd@z Thu Jan 1 00:00:00 1970 From: "=?UTF-8?q?Maciej=20=C5=BBenczykowski?=" Subject: [PATCH] net: do not allow changing SO_REUSEADDR/SO_REUSEPORT on bound sockets Date: Sun, 3 Jun 2018 10:47:05 -0700 Message-ID: <20180603174705.51802-1-zenczykowski@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Cc: Eric Dumazet , netdev@vger.kernel.org To: "=?UTF-8?q?Maciej=20=C5=BBenczykowski?=" , "David S . Miller" Return-path: Received: from mail-ua0-f202.google.com ([209.85.217.202]:42203 "EHLO mail-ua0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751057AbeFCRrK (ORCPT ); Sun, 3 Jun 2018 13:47:10 -0400 Received: by mail-ua0-f202.google.com with SMTP id m2-v6so16930921uab.9 for ; Sun, 03 Jun 2018 10:47:10 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: From: Maciej Żenczykowski It is not safe to do so because such sockets are already in the hash tables and changing these options can result in invalidating the tb->fastreuse(port) caching. This can have later far reaching consequences wrt. bind conflict checks which rely on these caches (for optimization purposes). Not to mention that you can currently end up with two identical non-reuseport listening sockets bound to the same local ip:port by clearing reuseport on them after they've already both been bound. There is unfortunately no EISBOUND error or anything similar, and EISCONN seems to be misleading for a bound-but-not-connected socket, so use EUCLEAN 'Structure needs cleaning' which AFAICT is the closest you can get to meaning 'socket in bad state'. (although perhaps EINVAL wouldn't be a bad choice either?) This does unfortunately run the risk of breaking buggy userspace programs... Signed-off-by: Maciej Żenczykowski Cc: Eric Dumazet Change-Id: I77c2b3429b2fdf42671eee0fa7a8ba721c94963b --- net/core/sock.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/net/core/sock.c b/net/core/sock.c index 435a0ba85e52..feca4c98f8a0 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -728,9 +728,22 @@ int sock_setsockopt(struct socket *sock, int level, int optname, sock_valbool_flag(sk, SOCK_DBG, valbool); break; case SO_REUSEADDR: - sk->sk_reuse = (valbool ? SK_CAN_REUSE : SK_NO_REUSE); + val = (valbool ? SK_CAN_REUSE : SK_NO_REUSE); + if ((sk->sk_family == PF_INET || sk->sk_family == PF_INET6) && + inet_sk(sk)->inet_num && + (sk->sk_reuse != val)) { + ret = (sk->sk_state == TCP_ESTABLISHED) ? -EISCONN : -EUCLEAN; + break; + } + sk->sk_reuse = val; break; case SO_REUSEPORT: + if ((sk->sk_family == PF_INET || sk->sk_family == PF_INET6) && + inet_sk(sk)->inet_num && + (sk->sk_reuseport != valbool)) { + ret = (sk->sk_state == TCP_ESTABLISHED) ? -EISCONN : -EUCLEAN; + break; + } sk->sk_reuseport = valbool; break; case SO_TYPE: -- 2.17.1.1185.g55be947832-goog