net/mlx5e: Harden uplink netdev access against device unbind

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
 at RIP: 0010:mlx5e_vport_rep_load+0x22a/0x270 [mlx5_core]
 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]
  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
  netlink_rcv_skb+0x4b/0xf0
  genl_rcv+0x24/0x40
  netlink_unicast+0x255/0x380
  netlink_sendmsg+0x1f3/0x420
  __sock_sendmsg+0x38/0x60
  __sys_sendto+0x119/0x180
  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: 7a9fb35 ("net/mlx5e: Do not reload ethernet ports when changing eswitch mode")
Signed-off-by: Jianbo Liu <jianbol@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/1757939074-617281-2-git-send-email-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Jianbo Liu

drivers/net/ethernet/mellanox/mlx5/core/en_rep.c

@@ -1506,12 +1506,21 @@ 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;
+	struct mlx5e_priv *priv;
+	int err;
+
+	netdev = mlx5_uplink_netdev_get(dev);
+	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 +1647,16 @@ 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);

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;
 }
 

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;

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;
 };