netdev - Re: [PATCH net] net/mlx4: prevent potential use after free in mlx4_en_do_uc

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Message-ID: <8b34f81e-86a3-4412-828f-39f0419b98c9@gmail.com>
Date: Tue, 30 Sep 2025 20:57:17 +0300
From: Tariq Toukan <ttoukan.linux@...il.com>
To: Dan Carpenter <dan.carpenter@...aro.org>, Yan Burman <yanb@...lanox.com>
Cc: Tariq Toukan <tariqt@...dia.com>, Andrew Lunn <andrew+netdev@...n.ch>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Amir Vadai <amirv@...lanox.com>, netdev@...r.kernel.org,
 linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
 kernel-janitors@...r.kernel.org
Subject: Re: [PATCH net] net/mlx4: prevent potential use after free in
 mlx4_en_do_uc_filter()

On 30/09/2025 15:25, Dan Carpenter wrote:
> Print "entry->mac" before freeing "entry".  The "entry" pointer is
> freed with kfree_rcu() so it's unlikely that we would trigger this
> in real life, but it's safer to re-order it.
> 
> Fixes: cc5387f7346a ("net/mlx4_en: Add unicast MAC filtering")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
>   drivers/net/ethernet/mellanox/mlx4/en_netdev.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> index d2071aff7b8f..308b4458e0d4 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> @@ -1180,9 +1180,9 @@ static void mlx4_en_do_uc_filter(struct mlx4_en_priv *priv,
>   				mlx4_unregister_mac(mdev->dev, priv->port, mac);
>   
>   				hlist_del_rcu(&entry->hlist);
> -				kfree_rcu(entry, rcu);
>   				en_dbg(DRV, priv, "Removed MAC %pM on port:%d\n",
>   				       entry->mac, priv->port);
> +				kfree_rcu(entry, rcu);
>   				++removed;
>   			}
>   		}

Reviewed-by: Tariq Toukan <tariqt@...dia.com>

Thanks for your patch.