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

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Date:   Thu, 14 Sep 2023 09:40:20 +0000
From:   Dragos Tatulea <dtatulea@...dia.com>
To:     "mst@...hat.com" <mst@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "xuanzhuo@...ux.alibaba.com" <xuanzhuo@...ux.alibaba.com>
CC:     "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        Gal Pressman <gal@...dia.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] vdpa/mlx5: Fix double release of debugfs entry

On Tue, 2023-08-29 at 20:40 +0300, Dragos Tatulea wrote:
> 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>

Gentle ping. Are there any comments on this patch?

Thanks,
Dragos
> ---
>  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);