net/mlx5: fix xstats reset reinitialization

[ upstream commit 42dcd45 ]

The mlx5_xstats_reset clears the device extended statistics.
In this function the driver may reinitialize the structures
that are used to read device counters.

In case of reinitialization, the number of counters may
change, which wouldn't be taken into account by the
reset API callback and can cause a segmentation fault.

This issue is fixed by allocating the counters size after
the reinitialization.

Fixes: a4193ae ("net/mlx5: support extended statistics")

Reported-by: Ralf Hoffmann <ralf.hoffmann@allegro-packets.com>
Signed-off-by: Shiri Kuzin <shirik@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>

drivers/net/mlx5/mlx5_stats.c

@@ -536,8 +536,7 @@ mlx5_xstats_reset(struct rte_eth_dev *dev)
 	struct mlx5_xstats_ctrl *xstats_ctrl = &priv->xstats_ctrl;
 	int stats_n;
 	unsigned int i;
-	unsigned int n = xstats_ctrl->mlx5_stats_n;
-	uint64_t counters[n];
+	uint64_t *counters;
 	int ret;
 
 	stats_n = mlx5_ethtool_get_stats_n(dev);
@@ -548,17 +547,26 @@ mlx5_xstats_reset(struct rte_eth_dev *dev)
 	}
 	if (xstats_ctrl->stats_n != stats_n)
 		mlx5_stats_init(dev);
+	counters =  malloc(sizeof(*counters) * xstats_ctrl->mlx5_stats_n);
+	if (!counters) {
+		DRV_LOG(WARNING, "port %u unable to allocate memory for xstats "
+				"counters",
+		     dev->data->port_id);
+		rte_errno = ENOMEM;
+		return -rte_errno;
+	}
 	ret = mlx5_read_dev_counters(dev, counters);
 	if (ret) {
 		DRV_LOG(ERR, "port %u cannot read device counters: %s",
 			dev->data->port_id, strerror(rte_errno));
+		free(counters);
 		return ret;
 	}
-	for (i = 0; i != n; ++i) {
+	for (i = 0; i != xstats_ctrl->mlx5_stats_n; ++i) {
 		xstats_ctrl->base[i] = counters[i];
 		xstats_ctrl->hw_stats[i] = 0;
 	}
-
+	free(counters);
 	return 0;
 }