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Message-ID: <1757326026-536849-2-git-send-email-tariqt@nvidia.com>
Date: Mon, 8 Sep 2025 13:07:04 +0300
From: Tariq Toukan <tariqt@...dia.com>
To: Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David
 S. Miller" <davem@...emloft.net>
CC: Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>,
	Tariq Toukan <tariqt@...dia.com>, Mark Bloch <mbloch@...dia.com>,
	<netdev@...r.kernel.org>, <linux-rdma@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Gal Pressman <gal@...dia.com>, Jianbo Liu
	<jianbol@...dia.com>
Subject: [PATCH net 1/3] net/mlx5e: Harden uplink netdev access against device unbind

From: Jianbo Liu <jianbol@...dia.com>

The function mlx5_uplink_netdev_get() gets the uplink netdevice
pointer from mdev->mlx5e_res.uplink_netdev. However, the netdevice can
be removed and its pointer cleared when unbound from the mlx5_core.eth
driver. This results in a NULL pointer, causing a kernel panic.

 BUG: unable to handle page fault for address: 0000000000001300
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page
 PGD 0 P4D 0
 Oops: Oops: 0000 [#1] SMP
 CPU: 5 UID: 0 PID: 1420 Comm: devlink Not tainted 6.16.0-rc7+ #1 NONE
 Hardware name: ...
 RIP: 0010:mlx5e_vport_rep_load+0x22a/0x270 [mlx5_core]
 Code: ...
 RSP: 0018:ffff8881142b78f0 EFLAGS: 00010246
 RAX: ffff888104652150 RBX: ffff88810215a6c0 RCX: 0000000000000000
 RDX: ffff888104652000 RSI: ffffffffa02b0cc0 RDI: 0000000000000000
 RBP: ffff888104652000 R08: ffff8884edaad5c0 R09: 0000000000000000
 R10: ffff8881142b78f0 R11: ffff888100716480 R12: ffff88810f1e0000
 R13: ffff88810215a6c0 R14: ffff888104652000 R15: ffff8881095301a0
 FS:  00007fa008742740(0000) GS:ffff88856a9f6000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000001300 CR3: 0000000106fb6001 CR4: 0000000000372eb0
 Call Trace:
  <TASK>
  mlx5_esw_offloads_rep_load+0x68/0xe0 [mlx5_core]
  esw_offloads_enable+0x593/0x910 [mlx5_core]
  mlx5_eswitch_enable_locked+0x341/0x420 [mlx5_core]
  ? is_mp_supported+0x4b/0xa0 [mlx5_core]
  mlx5_devlink_eswitch_mode_set+0x17e/0x3a0 [mlx5_core]
  devlink_nl_eswitch_set_doit+0x60/0xd0
  genl_family_rcv_msg_doit+0xe0/0x130
  genl_rcv_msg+0x183/0x290
  ? devlink_get_from_attrs_lock+0x180/0x180
  ? devlink_nl_eswitch_get_doit+0x290/0x290
  ? devlink_nl_pre_doit_port_optional+0x40/0x40
  ? genl_family_rcv_msg_dumpit+0xf0/0xf0
  netlink_rcv_skb+0x4b/0xf0
  genl_rcv+0x24/0x40
  netlink_unicast+0x255/0x380
  ? __alloc_skb+0x120/0x1b0
  netlink_sendmsg+0x1f3/0x420
  __sock_sendmsg+0x38/0x60
  __sys_sendto+0x119/0x180
  ? count_memcg_events+0xec/0x150
  ? __rseq_handle_notify_resume+0xa9/0x460
  ? handle_mm_fault+0x12e/0x260
  ? do_user_addr_fault+0x2a4/0x680
  __x64_sys_sendto+0x20/0x30
  do_syscall_64+0x53/0x1d0
  entry_SYSCALL_64_after_hwframe+0x4b/0x53

Ensure the pointer is valid before use by checking it for NULL. If it
is valid, immediately call netdev_hold() to take a reference, and
preventing the netdevice from being freed while it is in use.

Fixes: 7a9fb35e8c3a ("net/mlx5e: Do not reload ethernet ports when changing eswitch mode")
Signed-off-by: Jianbo Liu <jianbol@...dia.com>
Reviewed-by: Cosmin Ratiu <cratiu@...dia.com>
Reviewed-by: Jiri Pirko <jiri@...dia.com>
Reviewed-by: Dragos Tatulea <dtatulea@...dia.com>
Signed-off-by: Tariq Toukan <tariqt@...dia.com>
---
 .../net/ethernet/mellanox/mlx5/core/en_rep.c  | 26 +++++++++++++++----
 .../net/ethernet/mellanox/mlx5/core/esw/qos.c |  1 +
 .../ethernet/mellanox/mlx5/core/lib/mlx5.h    | 15 ++++++++++-
 include/linux/mlx5/driver.h                   |  1 +
 4 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rep.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rep.c
index 63a7a788fb0d..912887376824 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rep.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rep.c
@@ -1506,12 +1506,20 @@ static const struct mlx5e_profile mlx5e_uplink_rep_profile = {
 static int
 mlx5e_vport_uplink_rep_load(struct mlx5_core_dev *dev, struct mlx5_eswitch_rep *rep)
 {
-	struct mlx5e_priv *priv = netdev_priv(mlx5_uplink_netdev_get(dev));
 	struct mlx5e_rep_priv *rpriv = mlx5e_rep_to_rep_priv(rep);
+	struct net_device *netdev = mlx5_uplink_netdev_get(dev);
+	struct mlx5e_priv *priv;
+	int err;
+
+	if (!netdev)
+		return 0;
 
+	priv = netdev_priv(netdev);
 	rpriv->netdev = priv->netdev;
-	return mlx5e_netdev_change_profile(priv, &mlx5e_uplink_rep_profile,
-					   rpriv);
+	err = mlx5e_netdev_change_profile(priv, &mlx5e_uplink_rep_profile,
+					  rpriv);
+	mlx5_uplink_netdev_put(dev, netdev);
+	return err;
 }
 
 static void
@@ -1638,8 +1646,16 @@ mlx5e_vport_rep_unload(struct mlx5_eswitch_rep *rep)
 {
 	struct mlx5e_rep_priv *rpriv = mlx5e_rep_to_rep_priv(rep);
 	struct net_device *netdev = rpriv->netdev;
-	struct mlx5e_priv *priv = netdev_priv(netdev);
-	void *ppriv = priv->ppriv;
+	struct mlx5e_priv *priv;
+	void *ppriv;
+
+	if (!netdev) {
+		ppriv = rpriv;
+		goto free_ppriv;
+	}
+
+	priv = netdev_priv(netdev);
+	ppriv = priv->ppriv;
 
 	if (rep->vport == MLX5_VPORT_UPLINK) {
 		mlx5e_vport_uplink_rep_unload(rpriv);
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/esw/qos.c b/drivers/net/ethernet/mellanox/mlx5/core/esw/qos.c
index 8b4977650183..5f2d6c35f1ad 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/esw/qos.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/esw/qos.c
@@ -1515,6 +1515,7 @@ static u32 mlx5_esw_qos_lag_link_speed_get_locked(struct mlx5_core_dev *mdev)
 		speed = lksettings.base.speed;
 
 out:
+	mlx5_uplink_netdev_put(mdev, slave);
 	return speed;
 }
 
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lib/mlx5.h b/drivers/net/ethernet/mellanox/mlx5/core/lib/mlx5.h
index b111ccd03b02..74ea5da58b7e 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/lib/mlx5.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/mlx5.h
@@ -47,7 +47,20 @@ int mlx5_crdump_collect(struct mlx5_core_dev *dev, u32 *cr_data);
 
 static inline struct net_device *mlx5_uplink_netdev_get(struct mlx5_core_dev *mdev)
 {
-	return mdev->mlx5e_res.uplink_netdev;
+	struct mlx5e_resources *mlx5e_res = &mdev->mlx5e_res;
+	struct net_device *netdev;
+
+	mutex_lock(&mlx5e_res->uplink_netdev_lock);
+	netdev = mlx5e_res->uplink_netdev;
+	netdev_hold(netdev, &mlx5e_res->tracker, GFP_KERNEL);
+	mutex_unlock(&mlx5e_res->uplink_netdev_lock);
+	return netdev;
+}
+
+static inline void mlx5_uplink_netdev_put(struct mlx5_core_dev *mdev,
+					  struct net_device *netdev)
+{
+	netdev_put(netdev, &mdev->mlx5e_res.tracker);
 }
 
 struct mlx5_sd;
diff --git a/include/linux/mlx5/driver.h b/include/linux/mlx5/driver.h
index 8c5fbfb85749..10fe492e1fed 100644
--- a/include/linux/mlx5/driver.h
+++ b/include/linux/mlx5/driver.h
@@ -663,6 +663,7 @@ struct mlx5e_resources {
 		bool			   tisn_valid;
 	} hw_objs;
 	struct net_device *uplink_netdev;
+	netdevice_tracker tracker;
 	struct mutex uplink_netdev_lock;
 	struct mlx5_crypto_dek_priv *dek_priv;
 };
-- 
2.31.1


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