Re: [dpdk-dev] [PATCH] net/mlx5: fix possible endless loop when clearing flow flags

["Nélio Laranjeiro" <nelio.laranjeiro@6wind.com>]

On Mon, Jul 23, 2018 at 11:27:44AM -0700, Yongseok Koh wrote:
> If one of (*priv->rxqs)[] is null, the for loop can iterate infinitely as
> idx can't be increased.
> 
> Fixes: cd24d526395e ("net/mlx5: add mark/flag flow action")
> Cc: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
> 
> Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
> ---
>  drivers/net/mlx5/mlx5_flow.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/mlx5/mlx5_flow.c b/drivers/net/mlx5/mlx5_flow.c
> index 32854198b..c156f01eb 100644
> --- a/drivers/net/mlx5/mlx5_flow.c
> +++ b/drivers/net/mlx5/mlx5_flow.c
> @@ -2762,22 +2762,20 @@ mlx5_flow_rxq_flags_clear(struct rte_eth_dev *dev)
>  {
>  	struct priv *priv = dev->data->dev_private;
>  	unsigned int i;
> -	unsigned int idx;
>  
> -	for (idx = 0, i = 0; idx != priv->rxqs_n; ++i) {
> +	for (i = 0; i != priv->rxqs_n; ++i) {
>  		struct mlx5_rxq_ctrl *rxq_ctrl;
>  		unsigned int j;
>  
> -		if (!(*priv->rxqs)[idx])
> +		if (!(*priv->rxqs)[i])
>  			continue;
> -		rxq_ctrl = container_of((*priv->rxqs)[idx],
> +		rxq_ctrl = container_of((*priv->rxqs)[i],
>  					struct mlx5_rxq_ctrl, rxq);
>  		rxq_ctrl->flow_mark_n = 0;
>  		rxq_ctrl->rxq.mark = 0;
>  		for (j = 0; j != MLX5_FLOW_TUNNEL; ++j)
>  			rxq_ctrl->flow_tunnels_n[j] = 0;
>  		rxq_ctrl->rxq.tunnel = 0;
> -		++idx;
>  	}
>  }
>  
> -- 
> 2.11.0
 
This patch is wrong, (*priv->rxqs)[i] may un-initialised by the
application, the number of queues says how are in used, it does not mean
they are contiguous in the rxqs arrays and this due to the DPDK API
which configure the number of queues with rte_eth_dev_configure()
whereas queues are instantiated with rte_eth_rx_queue_setup() which
takes an position in the array as parameter.

Indeed this code is wrong, idx should always increase whereas i should
only increase if the (*priv->rxqs)[idx] is non null.

-- 
Nélio Laranjeiro
6WIND