graph: fix null dereference in stats

[ upstream commit 2d2bf7d ]

In function 'stats_mem_init', pointer 'stats' should
be confirmed not null before memset it.

Fixes: af1ae8b ("graph: implement stats")

Signed-off-by: Hongbo Zheng <zhenghongbo3@huawei.com>
Signed-off-by: Min Hu (Connor) <humin29@huawei.com>
Reviewed-by: Jerin Jacob <jerinj@marvell.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>

lib/librte_graph/graph_stats.c

@@ -119,8 +119,8 @@ stats_mem_init(struct cluster *cluster,
 	cluster_node_size = RTE_ALIGN(cluster_node_size, RTE_CACHE_LINE_SIZE);
 
 	stats = realloc(NULL, sz);
-	memset(stats, 0, sz);
 	if (stats) {
+		memset(stats, 0, sz);
 		stats->fn = fn;
 		stats->cluster_node_size = cluster_node_size;
 		stats->max_nodes = 0;