[RFC v2 08/14] ethdev: avoid possible overflow in xstat names

[Bruce Richardson]

On Thu, Dec 04, 2025 at 06:28:17PM -0800, Stephen Hemminger wrote:
> 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 at networkplumber.org>
> ---
>  lib/ethdev/rte_ethdev.c | 28 ++++++++++++++++++++--------
>  1 file changed, 20 insertions(+), 8 deletions(-)
Acked-by: Bruce Richardson <bruce.richardson at intel.com>

> 
> diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c
> index c6fe0d5165..20a6ce3450 100644
> --- a/lib/ethdev/rte_ethdev.c
> +++ b/lib/ethdev/rte_ethdev.c
> @@ -3501,10 +3501,17 @@ 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 */
> +			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 +3519,15 @@ 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);
> +			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
>