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

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

On Tue, Jul 24, 2018 at 09:47:19PM +0000, Yongseok Koh wrote:
> 
> > On Jul 23, 2018, at 11:57 PM, Nélio Laranjeiro <nelio.laranjeiro@6wind.com> wrote:
> > 
> > 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.
> 
> I don't understand what you mean. In rte_eth_rx_queue_setup(), rx_queue_id is
> checked against dev->data->nb_rx_queues.
> 
>         if (rx_queue_id >= dev->data->nb_rx_queues) {
>                 RTE_ETHDEV_LOG(ERR, "Invalid RX queue_id=%u\n", rx_queue_id);
>                 return -EINVAL;
>         }
> 
> This means the index should be [0, priv->rxqs_n) anyway. There is the same check
> in mlx5_rx_queue_setup(). If user mistakenly doesn't configure some of queues,
> then the corresponding slots could be null but indexes are still within the
> range.
> 
> Then, what's your point of having both i and idx?

I remember I've face some issue while I've re-write the PMD to work on
top of flow API.  That's why I've introduce such logic, but it seems not
necessary as it comply with the documentation of the function and the
code itself.

Acked-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>

-- 
Nélio Laranjeiro
6WIND