netdev - Re: [PATCH net-next 3/7] mlx4: protect mlx4_en_start_port in mlx4_en_restart with rtnl

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Date:	Fri, 10 Jun 2016 13:55:01 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	netdev@...r.kernel.org, jesse@...nel.org,
	Eugenia Emantayev <eugenia@...lanox.com>,
	Yishai Hadas <yishaih@...lanox.com>
Subject: Re: [PATCH net-next 3/7] mlx4: protect mlx4_en_start_port in
 mlx4_en_restart with rtnl_lock

On Mon, 2016-04-18 at 21:19 +0200, Hannes Frederic Sowa wrote:
> mlx4_en_start_port requires rtnl_lock to be held.
> 
> Cc: Eugenia Emantayev <eugenia@...lanox.com>
> Cc: Yishai Hadas <yishaih@...lanox.com>
> Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
> ---
>  drivers/net/ethernet/mellanox/mlx4/en_netdev.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> index b4b258c8ca47d4..8bd143dda95d11 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> @@ -1856,6 +1856,7 @@ static void mlx4_en_restart(struct work_struct *work)
>  
>  	en_dbg(DRV, priv, "Watchdog task called for port %d\n", priv->port);
>  
> +	rtnl_lock();
>  	mutex_lock(&mdev->state_lock);
>  	if (priv->port_up) {
>  		mlx4_en_stop_port(dev, 1);
> @@ -1863,6 +1864,7 @@ static void mlx4_en_restart(struct work_struct *work)
>  			en_err(priv, "Failed restarting port %d\n", priv->port);
>  	}
>  	mutex_unlock(&mdev->state_lock);
> +	rtnl_unlock();
>  }
>  
>  static void mlx4_en_clear_stats(struct net_device *dev)

It looks that this work queue is not canceled at device dismantle.

I suspect a use after free is possible.