linux-kernel - [PATCH net 7/9] net/mlx5e: Properly access RCU protected qdisc

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Message-ID: <20250610151514.1094735-8-mbloch@nvidia.com>
Date: Tue, 10 Jun 2025 18:15:12 +0300
From: Mark Bloch <mbloch@...dia.com>
To: "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>, Eric Dumazet <edumazet@...gle.com>, "Andrew
 Lunn" <andrew+netdev@...n.ch>, Simon Horman <horms@...nel.org>
CC: <saeedm@...dia.com>, <gal@...dia.com>, <leonro@...dia.com>,
	<tariqt@...dia.com>, Leon Romanovsky <leon@...nel.org>,
	<netdev@...r.kernel.org>, <linux-rdma@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Mark Bloch <mbloch@...dia.com>
Subject: [PATCH net 7/9] net/mlx5e: Properly access RCU protected qdisc_sleeping variable

From: Leon Romanovsky <leonro@...dia.com>

qdisc_sleeping variable is declared as "struct Qdisc __rcu" and
as such needs proper annotation while accessing it.

Without rtnl_dereference(), the following error is generated by smatch:

drivers/net/ethernet/mellanox/mlx5/core/en/qos.c:377:40: warning:
  incorrect type in initializer (different address spaces)
drivers/net/ethernet/mellanox/mlx5/core/en/qos.c:377:40:    expected
  struct Qdisc *qdisc
drivers/net/ethernet/mellanox/mlx5/core/en/qos.c:377:40:    got struct
  Qdisc [noderef] __rcu *qdisc_sleeping

Fixes: 214baf22870c ("net/mlx5e: Support HTB offload")
Signed-off-by: Leon Romanovsky <leonro@...dia.com>
Reviewed-by: Tariq Toukan <tariqt@...dia.com>
Signed-off-by: Mark Bloch <mbloch@...dia.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en/qos.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c b/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c
index f0744a45db92..2f32111210f8 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c
@@ -374,7 +374,9 @@ void mlx5e_reactivate_qos_sq(struct mlx5e_priv *priv, u16 qid, struct netdev_que
 void mlx5e_reset_qdisc(struct net_device *dev, u16 qid)
 {
 	struct netdev_queue *dev_queue = netdev_get_tx_queue(dev, qid);
-	struct Qdisc *qdisc = dev_queue->qdisc_sleeping;
+	struct Qdisc *qdisc;
+
+	qdisc = rtnl_dereference(dev_queue->qdisc_sleeping);
 
 	if (!qdisc)
 		return;
-- 
2.34.1