vdpa/mlx5: Fix double release of debugfs entry

The error path in setup_driver deletes the debugfs entry but doesn't
clear the pointer. During .dev_del the invalid pointer will be released
again causing a crash.

This patch fixes the issue by always clearing the debugfs entry in
mlx5_vdpa_remove_debugfs. Also, stop removing the debugfs entry in
.dev_del op: the debugfs entry is already handled within the
setup_driver/teardown_driver scope.

Cc: stable@vger.kernel.org
Fixes: f0417e72 ("vdpa/mlx5: Add and remove debugfs in setup/teardown driver")
Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Gal Pressman <gal@nvidia.com>
Message-Id: <20230829174014.928189-2-dtatulea@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

drivers/vdpa/mlx5/net/debug.c

@@ -146,7 +146,8 @@ void mlx5_vdpa_add_debugfs(struct mlx5_vdpa_net *ndev)
 		ndev->rx_dent = debugfs_create_dir("rx", ndev->debugfs);
 }
 
-void mlx5_vdpa_remove_debugfs(struct dentry *dbg)
+void mlx5_vdpa_remove_debugfs(struct mlx5_vdpa_net *ndev)
 {
-	debugfs_remove_recursive(dbg);
+	debugfs_remove_recursive(ndev->debugfs);
+	ndev->debugfs = NULL;
 }

drivers/vdpa/mlx5/net/mlx5_vnet.c

@@ -2713,7 +2713,7 @@ static int setup_driver(struct mlx5_vdpa_dev *mvdev)
 err_rqt:
 	teardown_virtqueues(ndev);
 err_setup:
-	mlx5_vdpa_remove_debugfs(ndev->debugfs);
+	mlx5_vdpa_remove_debugfs(ndev);
 out:
 	return err;
 }
@@ -2727,8 +2727,7 @@ static void teardown_driver(struct mlx5_vdpa_net *ndev)
 	if (!ndev->setup)
 		return;
 
-	mlx5_vdpa_remove_debugfs(ndev->debugfs);
-	ndev->debugfs = NULL;
+	mlx5_vdpa_remove_debugfs(ndev);
 	teardown_steering(ndev);
 	destroy_tir(ndev);
 	destroy_rqt(ndev);
@@ -3489,8 +3488,6 @@ static void mlx5_vdpa_dev_del(struct vdpa_mgmt_dev *v_mdev, struct vdpa_device *
 	struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
 	struct workqueue_struct *wq;
 
-	mlx5_vdpa_remove_debugfs(ndev->debugfs);
-	ndev->debugfs = NULL;
 	unregister_link_notifier(ndev);
 	_vdpa_unregister_device(dev);
 	wq = mvdev->wq;

drivers/vdpa/mlx5/net/mlx5_vnet.h

@@ -88,7 +88,7 @@ struct macvlan_node {
 };
 
 void mlx5_vdpa_add_debugfs(struct mlx5_vdpa_net *ndev);
-void mlx5_vdpa_remove_debugfs(struct dentry *dbg);
+void mlx5_vdpa_remove_debugfs(struct mlx5_vdpa_net *ndev);
 void mlx5_vdpa_add_rx_flow_table(struct mlx5_vdpa_net *ndev);
 void mlx5_vdpa_remove_rx_flow_table(struct mlx5_vdpa_net *ndev);
 void mlx5_vdpa_add_tirn(struct mlx5_vdpa_net *ndev);