Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Vladimir Oltean <vladimir.oltean@nxp.com>
To:     netdev@vger.kernel.org
Cc:     Vinicius Costa Gomes <vinicius.gomes@intel.com>,
        Jamal Hadi Salim <jhs@mojatatu.com>,
        Cong Wang <xiyou.wangcong@gmail.com>,
        Jiri Pirko <jiri@resnulli.us>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Voon Weifeng <weifeng.voon@intel.com>,
        Vladimir Oltean <olteanv@gmail.com>,
        Kurt Kanzenbach <kurt@linutronix.de>,
        linux-kernel@vger.kernel.org
Subject: [PATCH v2 net-next 3/7] net/sched: taprio: use rtnl_dereference for oper and admin sched in taprio_destroy()
Date:   Thu, 15 Sep 2022 13:50:42 +0300
Message-Id: <20220915105046.2404072-4-vladimir.oltean@nxp.com>
In-Reply-To: <20220915105046.2404072-1-vladimir.oltean@nxp.com>
References: <20220915105046.2404072-1-vladimir.oltean@nxp.com>
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?aKklTgPfg8kkBc/Zt0SnmRWD15tinZiEP8l/NO4/4yA3ksHtO9EAHKcgMnvl?=
 =?us-ascii?Q?WN72446osBcDG5EOetloIUiJRKuQEMPVTDo3yPi89GA8VY6BpqaRdjo2LoWJ?=
 =?us-ascii?Q?MztSRqXPdShfRLhABKYXKmuL1ln3frD2k1EBWc9z36vCNTCiZynHRqK6yZQ1?=
 =?us-ascii?Q?cEJ09w0akAxXOfL7qsiD6lKsy/VCyy9AxLlMKr2z9OVRFTciuEZTOpi1f8rx?=
 =?us-ascii?Q?ahfYNL9G60FcUzpC/Zn02veH7zI98iVqYzkIYIUnajDktU6v6Hd8But1Hj5Q?=
 =?us-ascii?Q?Fe//6VS1Ps0dSzOco/QLpzvuvY2RoOx//j7yskOJjd6RI1fcCFEgJUhHt6mm?=
 =?us-ascii?Q?V6CYLzElVwY/sddwcxs8vTVCZgSFm+16F1knszsewCgxuHJSir7hHbf+Knfr?=
 =?us-ascii?Q?URWgr/k7pt2r0YxVfuw+LlK+F5o6o719OKL1gugNiwv7DKdDCoQ2mfYeEjDj?=
 =?us-ascii?Q?ToGkh1DHrrF9Omy2ayDyDEry7fM5ZK1S/M5aosONuPzoPhr3Yaz8GSXaDsP5?=
 =?us-ascii?Q?kqysEw9sxlG9GLbw3sYB4aOdVRpK4BIuZoaKUSkAG7eSdRDGC/P+jpKpm86L?=
 =?us-ascii?Q?SzPLZWMEz0ymWl7ptbFaQ/D0yTqOAYkXiqjbaq2kE20SkZ/Jqd4t6vJcpHrf?=
 =?us-ascii?Q?APfeEIXvAiRD+wHNnCmwZwL7GfkXICllFw8l2jBu2gTnDf7orW5OF7q4xQV/?=
 =?us-ascii?Q?8NaHjt+HnTn77e/OjHFKhSx5MXsrn13L1JkYIf5AxvCiDSAFeUATRqTZLyjz?=
 =?us-ascii?Q?m6m9yG/67NX+yAsYsyD8en7gu1REpRkJlYQUtoRvQOlQi+2IA/0+XnwCb6wN?=
 =?us-ascii?Q?zXM0wwBHyAxcPAd4sxbFBRq8GPpirOhsMqIwu2vf7kQRHISz7uJzJ1mGMmS6?=
 =?us-ascii?Q?YvybkcV0ojICyIOswoGe3+aTuWMDFN/iuCy8h9oE/KL68FmnOxW0LyX/iW1R?=
 =?us-ascii?Q?GgOi1EzGpZ/Wv/NWi4eWuGTCRG+i3rDC2HoBpXHHC/m4QGCMVzR+NvVWygIT?=
 =?us-ascii?Q?NfYn6hHPKzEdtcEjiKV4+PYc7KfMdGR+I10nDsdkvdSDXU+PQJo+8jvz/MWp?=
 =?us-ascii?Q?M5kJKNl6R8Ed3+vOemvcBZEY9GcRT2FSxKasIjdPWKUQWh/pAAGUmNbrntq+?=
 =?us-ascii?Q?iQyPPcrWBwdtXTfYv+5yiuvSEKWWgHoBP49Jyst0ARuTfRqFp0U7cyRPtky8?=
 =?us-ascii?Q?NuSkf8I6E6ckjSL4jJ+YjikoZgI84ys49+9fAsHPhGnM6OSfU35ZbYdGjLiQ?=
 =?us-ascii?Q?bUVnRpG+RKZyZMpBaF0lTla4kS+PCnNALgYykiBAauErPorkdXD5rm0LX5DM?=
 =?us-ascii?Q?sg7e0/ceQUwHDZwRF4SIO7sQxwJ64PIGrYHI6fomeLzV/Mqi3qGmG80OmxZ1?=
 =?us-ascii?Q?vTSVp/rHU5wEi2H8J5gV4kS9qJI5VpB6IwN9m9SQkfKPC3bWCMpC3KR7G3X1?=
 =?us-ascii?Q?I6OBXu8hO56yHimNRLx6HjVgh7gemQVDx5k6CLUAcZrIPLiHRdD85TunyNNb?=
 =?us-ascii?Q?vR0DtCXpb2jBBopQjf7qGsW1OJT6txNooxs1ICXGksYUppjH3l8eOmm+iRG9?=
 =?us-ascii?Q?Lir+Nw35oo+mq9wG/ECjazov/ybepjxbcWMIoWdF0+sFb4W4+CtzT9d+61OK?=
 =?us-ascii?Q?8Q=3D=3D?=
X-OriginatorOrg: nxp.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 1e34fa99-9322-4db5-56f2-08da97082c82
X-MS-Exchange-CrossTenant-AuthSource: VI1PR04MB5136.eurprd04.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Sep 2022 10:50:59.0649
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: qUct/gTwpaZNAH4Oeh98AHl0oFXziYXbF0cpweKZ/eZeTY0/ou6wLeL6I42FpYQjhau9xmnjTjjXKkZanTYtHA==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB8PR04MB7163
X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE,
        RCVD_IN_MSPIKE_H2,SPF_HELO_PASS,SPF_PASS autolearn=ham
        autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Sparse complains that taprio_destroy() dereferences q->oper_sched and
q->admin_sched without rcu_dereference(), since they are marked as __rcu
in the taprio private structure.

1671:28: warning: incorrect type in argument 1 (different address spaces)
1671:28:    expected struct callback_head *head
1671:28:    got struct callback_head [noderef] __rcu *
1674:28: warning: incorrect type in argument 1 (different address spaces)
1674:28:    expected struct callback_head *head
1674:28:    got struct callback_head [noderef] __rcu *

To silence that build warning, do actually use rtnl_dereference(), since
we know the rtnl_mutex is held at the time of q->destroy().

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
v1->v2: resend to net-next, use rtnl_dereference() instead of opening an
        rcu_read_lock()

 net/sched/sch_taprio.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 63cbf856894a..6113c6646559 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -1636,6 +1636,7 @@ static void taprio_destroy(struct Qdisc *sch)
 {
 	struct taprio_sched *q = qdisc_priv(sch);
 	struct net_device *dev = qdisc_dev(sch);
+	struct sched_gate_list *oper, *admin;
 	unsigned int i;
 
 	spin_lock(&taprio_list_lock);
@@ -1659,11 +1660,14 @@ static void taprio_destroy(struct Qdisc *sch)
 
 	netdev_reset_tc(dev);
 
-	if (q->oper_sched)
-		call_rcu(&q->oper_sched->rcu, taprio_free_sched_cb);
+	oper = rtnl_dereference(q->oper_sched);
+	admin = rtnl_dereference(q->admin_sched);
+
+	if (oper)
+		call_rcu(&oper->rcu, taprio_free_sched_cb);
 
-	if (q->admin_sched)
-		call_rcu(&q->admin_sched->rcu, taprio_free_sched_cb);
+	if (admin)
+		call_rcu(&admin->rcu, taprio_free_sched_cb);
 }
 
 static int taprio_init(struct Qdisc *sch, struct nlattr *opt,
-- 
2.34.1