From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 01854C7112A for ; Sun, 14 Oct 2018 15:45:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C6EB820645 for ; Sun, 14 Oct 2018 15:45:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C6EB820645 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=decadent.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729453AbeJNX1A (ORCPT ); Sun, 14 Oct 2018 19:27:00 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:37150 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728141AbeJNX1A (ORCPT ); Sun, 14 Oct 2018 19:27:00 -0400 Received: from [2a02:8011:400e:2:cbab:f00:c93f:614] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.84_2) (envelope-from ) id 1gBiM1-0004cF-T5; Sun, 14 Oct 2018 16:30:54 +0100 Received: from ben by deadeye with local (Exim 4.91) (envelope-from ) id 1gBiLS-0000L2-HW; Sun, 14 Oct 2018 16:30:18 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "David S. Miller" , "Guillaume Nault" Date: Sun, 14 Oct 2018 16:25:41 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 145/366] l2tp: hold reference on tunnels in netlink dumps In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:cbab:f00:c93f:614 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.60-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Guillaume Nault commit 5846c131c39b6d0add36ec19dc8650700690f930 upstream. l2tp_tunnel_find_nth() is unsafe: no reference is held on the returned tunnel, therefore it can be freed whenever the caller uses it. This patch defines l2tp_tunnel_get_nth() which works similarly, but also takes a reference on the returned tunnel. The caller then has to drop it after it stops using the tunnel. Convert netlink dumps to make them safe against concurrent tunnel deletion. Fixes: 309795f4bec2 ("l2tp: Add netlink control API for L2TP") Signed-off-by: Guillaume Nault Signed-off-by: David S. Miller [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- net/l2tp/l2tp_core.c | 20 ++++++++++++++++++++ net/l2tp/l2tp_core.h | 2 ++ net/l2tp/l2tp_netlink.c | 11 ++++++++--- 3 files changed, 30 insertions(+), 3 deletions(-) --- a/net/l2tp/l2tp_core.c +++ b/net/l2tp/l2tp_core.c @@ -231,6 +231,26 @@ struct l2tp_tunnel *l2tp_tunnel_get(cons } EXPORT_SYMBOL_GPL(l2tp_tunnel_get); +struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth) +{ + const struct l2tp_net *pn = l2tp_pernet(net); + struct l2tp_tunnel *tunnel; + int count = 0; + + rcu_read_lock_bh(); + list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) { + if (++count > nth) { + l2tp_tunnel_inc_refcount(tunnel); + rcu_read_unlock_bh(); + return tunnel; + } + } + rcu_read_unlock_bh(); + + return NULL; +} +EXPORT_SYMBOL_GPL(l2tp_tunnel_get_nth); + /* Like l2tp_session_find() but takes a reference on the returned session. * Optionally calls session->ref() too if do_ref is true. */ --- a/net/l2tp/l2tp_core.h +++ b/net/l2tp/l2tp_core.h @@ -227,6 +227,8 @@ static inline void *l2tp_session_priv(st } struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id); +struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth); + void l2tp_tunnel_free(struct l2tp_tunnel *tunnel); struct l2tp_session *l2tp_session_get(const struct net *net, --- a/net/l2tp/l2tp_netlink.c +++ b/net/l2tp/l2tp_netlink.c @@ -395,14 +395,17 @@ static int l2tp_nl_cmd_tunnel_dump(struc struct net *net = sock_net(skb->sk); for (;;) { - tunnel = l2tp_tunnel_find_nth(net, ti); + tunnel = l2tp_tunnel_get_nth(net, ti); if (tunnel == NULL) goto out; if (l2tp_nl_tunnel_send(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq, NLM_F_MULTI, - tunnel) <= 0) + tunnel) <= 0) { + l2tp_tunnel_dec_refcount(tunnel); goto out; + } + l2tp_tunnel_dec_refcount(tunnel); ti++; } @@ -746,7 +749,7 @@ static int l2tp_nl_cmd_session_dump(stru for (;;) { if (tunnel == NULL) { - tunnel = l2tp_tunnel_find_nth(net, ti); + tunnel = l2tp_tunnel_get_nth(net, ti); if (tunnel == NULL) goto out; } @@ -754,6 +757,7 @@ static int l2tp_nl_cmd_session_dump(stru session = l2tp_session_get_nth(tunnel, si, false); if (session == NULL) { ti++; + l2tp_tunnel_dec_refcount(tunnel); tunnel = NULL; si = 0; continue; @@ -763,6 +767,7 @@ static int l2tp_nl_cmd_session_dump(stru cb->nlh->nlmsg_seq, NLM_F_MULTI, session) <= 0) { l2tp_session_dec_refcount(session); + l2tp_tunnel_dec_refcount(tunnel); break; } l2tp_session_dec_refcount(session);