linux-kernel - [PATCH 3.2 063/147] l2tp: remove useless duplicate session detection in l2tp

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Message-ID: <lsq.1510009387.681100674@decadent.org.uk>
Date:   Mon, 06 Nov 2017 23:03:07 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Guillaume Nault" <g.nault@...halink.fr>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.2 063/147] l2tp: remove useless duplicate session
 detection in l2tp_netlink

3.2.95-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Guillaume Nault <g.nault@...halink.fr>

commit af87ae465abdc070de0dc35d6c6a9e7a8cd82987 upstream.

There's no point in checking for duplicate sessions at the beginning of
l2tp_nl_cmd_session_create(); the ->session_create() callbacks already
return -EEXIST when the session already exists.

Furthermore, even if l2tp_session_find() returns NULL, a new session
might be created right after the test. So relying on ->session_create()
to avoid duplicate session is the only sane behaviour.

Signed-off-by: Guillaume Nault <g.nault@...halink.fr>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.2: also delete the now-unused local variable]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -361,7 +361,6 @@ static int l2tp_nl_cmd_session_create(st
 	u32 peer_session_id;
 	int ret = 0;
 	struct l2tp_tunnel *tunnel;
-	struct l2tp_session *session;
 	struct l2tp_session_cfg cfg = { 0, };
 	struct net *net = genl_info_net(info);
 
@@ -381,11 +380,6 @@ static int l2tp_nl_cmd_session_create(st
 		goto out;
 	}
 	session_id = nla_get_u32(info->attrs[L2TP_ATTR_SESSION_ID]);
-	session = l2tp_session_find(net, tunnel, session_id);
-	if (session) {
-		ret = -EEXIST;
-		goto out;
-	}
 
 	if (!info->attrs[L2TP_ATTR_PEER_SESSION_ID]) {
 		ret = -EINVAL;