netdev - Re: [PATCH net v2 1/1] mlxbf_gige: Fix kernel panic at shutdown

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Date: Sun, 11 Jun 2023 21:11:25 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Asmaa Mnebhi <asmaa@...dia.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, netdev@...r.kernel.org, cai.huoqing@...ux.dev,
	brgl@...ev.pl, chenhao288@...ilicon.com, huangguangbin2@...wei.com,
	David Thompson <davthompson@...dia.com>
Subject: Re: [PATCH net v2 1/1] mlxbf_gige: Fix kernel panic at shutdown

On Wed, Jun 07, 2023 at 10:03:35AM -0400, Asmaa Mnebhi wrote:
> There is a race condition happening during shutdown due to pending napi transactions.
> Since mlxbf_gige_poll is still running, it tries to access a NULL pointer and as a
> result causes a kernel panic.
> To fix this during shutdown, invoke mlxbf_gige_remove to disable and dequeue napi.
> 
> Fixes: f92e1869d74e ("Add Mellanox BlueField Gigabit Ethernet driver")
> Signed-off-by: Asmaa Mnebhi <asmaa@...dia.com>
> ---
>  .../net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c    | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c b/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c
> index 694de9513b9f..609d038b034e 100644
> --- a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c
> +++ b/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c
> @@ -475,6 +475,9 @@ static int mlxbf_gige_remove(struct platform_device *pdev)
>  {
>  	struct mlxbf_gige *priv = platform_get_drvdata(pdev);
>  
> +	if (!priv)
> +		return 0;
> +

How can this check be correct? You are removing mlxbf_gige driver, priv
should be always exist here.

>  	unregister_netdev(priv->netdev);
>  	phy_disconnect(priv->netdev->phydev);
>  	mlxbf_gige_mdio_remove(priv);
> @@ -485,10 +488,7 @@ static int mlxbf_gige_remove(struct platform_device *pdev)
>  
>  static void mlxbf_gige_shutdown(struct platform_device *pdev)
>  {
> -	struct mlxbf_gige *priv = platform_get_drvdata(pdev);
> -
> -	writeq(0, priv->base + MLXBF_GIGE_INT_EN);
> -	mlxbf_gige_clean_port(priv);
> +	mlxbf_gige_remove(pdev);
>  }
>  
>  static const struct acpi_device_id __maybe_unused mlxbf_gige_acpi_match[] = {
> -- 
> 2.30.1
> 
>