[RFC 5/8] ethdev: avoid possible overflow in xstat names

[Stephen Hemminger <stephen@networkplumber.org>]

The compiler doesn't know that all the elements in the table
of queue stats are short enough to avoid overflowing the snprintf.
Add a condition that will not happen to warn if it ever does;
maybe some day a new long named queue stat could be added.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/ethdev/rte_ethdev.c | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c
index c6fe0d5165..5bd3fbc0bc 100644
--- a/lib/ethdev/rte_ethdev.c
+++ b/lib/ethdev/rte_ethdev.c
@@ -3501,10 +3501,16 @@ eth_basic_stats_get_names(struct rte_eth_dev *dev,
 	num_q = RTE_MIN(dev->data->nb_rx_queues, RTE_ETHDEV_QUEUE_STAT_CNTRS);
 	for (id_queue = 0; id_queue < num_q; id_queue++) {
 		for (idx = 0; idx < RTE_NB_RXQ_STATS; idx++) {
-			snprintf(xstats_names[cnt_used_entries].name,
-				sizeof(xstats_names[0].name),
-				"rx_q%u_%s",
-				id_queue, eth_dev_rxq_stats_strings[idx].name);
+			unsigned int cc;
+
+			cc = snprintf(xstats_names[cnt_used_entries].name, sizeof(xstats_names[0].name),
+				      "rx_q%u_%s",
+				      id_queue, eth_dev_rxq_stats_strings[idx].name);
+
+			/* could only happen if a long string was added to eth_dev_rxq_stats_strings */
+			if (cc >= sizeof(xstats_names[0].name))
+				RTE_ETHDEV_LOG_LINE(ERR, "truncated rxq stat string '%s'",
+						    eth_dev_rxq_stats_strings[idx].name);
 			cnt_used_entries++;
 		}
 
@@ -3512,10 +3518,15 @@ eth_basic_stats_get_names(struct rte_eth_dev *dev,
 	num_q = RTE_MIN(dev->data->nb_tx_queues, RTE_ETHDEV_QUEUE_STAT_CNTRS);
 	for (id_queue = 0; id_queue < num_q; id_queue++) {
 		for (idx = 0; idx < RTE_NB_TXQ_STATS; idx++) {
-			snprintf(xstats_names[cnt_used_entries].name,
-				sizeof(xstats_names[0].name),
-				"tx_q%u_%s",
-				id_queue, eth_dev_txq_stats_strings[idx].name);
+			unsigned int cc;
+
+			cc = snprintf(xstats_names[cnt_used_entries].name, sizeof(xstats_names[0].name),
+				      "tx_q%u_%s",
+				      id_queue, eth_dev_txq_stats_strings[idx].name);
+			/* could only happen if a long string was added to eth_dev_rxq_stats_strings */
+			if (cc >= sizeof(xstats_names[0].name))
+				RTE_ETHDEV_LOG_LINE(ERR, "truncated txq stat string '%s'",
+						    eth_dev_txq_stats_strings[idx].name);
 			cnt_used_entries++;
 		}
 	}
-- 
2.51.0