From patchwork Thu Apr 12 18:50:33 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Guillaume Nault X-Patchwork-Id: 897761 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=alphalink.fr Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 40MVNK54TZz9s3M for ; Fri, 13 Apr 2018 04:50:41 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753413AbeDLSuk (ORCPT ); Thu, 12 Apr 2018 14:50:40 -0400 Received: from zimbra.alphalink.fr ([217.15.80.77]:40465 "EHLO zimbra.alphalink.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753316AbeDLSug (ORCPT ); Thu, 12 Apr 2018 14:50:36 -0400 Received: from localhost (localhost [127.0.0.1]) by mail-2-cbv2.admin.alphalink.fr (Postfix) with ESMTP id 840382B52122; Thu, 12 Apr 2018 20:50:35 +0200 (CEST) Received: from zimbra.alphalink.fr ([127.0.0.1]) by localhost (mail-2-cbv2.admin.alphalink.fr [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id zgwjga8A65er; Thu, 12 Apr 2018 20:50:33 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by mail-2-cbv2.admin.alphalink.fr (Postfix) with ESMTP id CDE7E2B52093; Thu, 12 Apr 2018 20:50:33 +0200 (CEST) X-Virus-Scanned: amavisd-new at mail-2-cbv2.admin.alphalink.fr Received: from zimbra.alphalink.fr ([127.0.0.1]) by localhost (mail-2-cbv2.admin.alphalink.fr [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id iGNDl0fM_cxO; Thu, 12 Apr 2018 20:50:33 +0200 (CEST) Received: from c-dev-0.admin.alphalink.fr (94-84-15-217.reverse.alphalink.fr [217.15.84.94]) by mail-2-cbv2.admin.alphalink.fr (Postfix) with ESMTP id 69B362B5206F; Thu, 12 Apr 2018 20:50:33 +0200 (CEST) Received: by c-dev-0.admin.alphalink.fr (Postfix, from userid 1000) id 3FF74601B9; Thu, 12 Apr 2018 20:50:33 +0200 (CEST) Date: Thu, 12 Apr 2018 20:50:33 +0200 From: Guillaume Nault To: netdev@vger.kernel.org Cc: James Chapman Subject: [PATCH net 1/3] l2tp: hold reference on tunnels in netlink dumps Message-ID: References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Mutt-Fcc: =Sent User-Agent: Mutt/1.9.4 (2018-02-28) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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 --- 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(-) diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c index 0fbd3ee26165..c8c4183f0f37 100644 --- a/net/l2tp/l2tp_core.c +++ b/net/l2tp/l2tp_core.c @@ -183,6 +183,26 @@ struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id) } 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); + /* Lookup a session. A new reference is held on the returned session. */ struct l2tp_session *l2tp_session_get(const struct net *net, struct l2tp_tunnel *tunnel, diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h index ba33cbec71eb..e4896413b2b6 100644 --- a/net/l2tp/l2tp_core.h +++ b/net/l2tp/l2tp_core.h @@ -212,6 +212,8 @@ static inline void *l2tp_session_priv(struct l2tp_session *session) } 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, diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c index b05dbd9ffcb2..6616c9fd292f 100644 --- a/net/l2tp/l2tp_netlink.c +++ b/net/l2tp/l2tp_netlink.c @@ -487,14 +487,17 @@ static int l2tp_nl_cmd_tunnel_dump(struct sk_buff *skb, struct netlink_callback 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, L2TP_CMD_TUNNEL_GET) < 0) + tunnel, L2TP_CMD_TUNNEL_GET) < 0) { + l2tp_tunnel_dec_refcount(tunnel); goto out; + } + l2tp_tunnel_dec_refcount(tunnel); ti++; } @@ -848,7 +851,7 @@ static int l2tp_nl_cmd_session_dump(struct sk_buff *skb, struct netlink_callback for (;;) { if (tunnel == NULL) { - tunnel = l2tp_tunnel_find_nth(net, ti); + tunnel = l2tp_tunnel_get_nth(net, ti); if (tunnel == NULL) goto out; } @@ -856,6 +859,7 @@ static int l2tp_nl_cmd_session_dump(struct sk_buff *skb, struct netlink_callback session = l2tp_session_get_nth(tunnel, si); if (session == NULL) { ti++; + l2tp_tunnel_dec_refcount(tunnel); tunnel = NULL; si = 0; continue; @@ -865,6 +869,7 @@ static int l2tp_nl_cmd_session_dump(struct sk_buff *skb, struct netlink_callback cb->nlh->nlmsg_seq, NLM_F_MULTI, session, L2TP_CMD_SESSION_GET) < 0) { l2tp_session_dec_refcount(session); + l2tp_tunnel_dec_refcount(tunnel); break; } l2tp_session_dec_refcount(session);