linux-kernel - [PATCH] vdpa/mlx5: Fix double release of debugfs entry

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Date:   Tue, 29 Aug 2023 20:40:09 +0300
From:   Dragos Tatulea <dtatulea@...dia.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
CC:     Dragos Tatulea <dtatulea@...dia.com>,
        Gal Pressman <gal@...dia.com>,
        <virtualization@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH] 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.

Fixes: f0417e72add5 ("vdpa/mlx5: Add and remove debugfs in setup/teardown driver")
Signed-off-by: Dragos Tatulea <dtatulea@...dia.com>
Reviewed-by: Gal Pressman <gal@...dia.com>
---
 drivers/vdpa/mlx5/net/debug.c     | 5 +++--
 drivers/vdpa/mlx5/net/mlx5_vnet.c | 7 ++-----
 drivers/vdpa/mlx5/net/mlx5_vnet.h | 2 +-
 3 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/vdpa/mlx5/net/debug.c b/drivers/vdpa/mlx5/net/debug.c
index 60d6ac68cdc4..9c85162c19fc 100644
--- a/drivers/vdpa/mlx5/net/debug.c
+++ b/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;
 }
diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index 37be945a0230..f91c938b4be1 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/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;
diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.h b/drivers/vdpa/mlx5/net/mlx5_vnet.h
index 36c44d9fdd16..60cdbc903037 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.h
+++ b/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);
-- 
2.41.0