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

Bruce Richardson
2025-12-05T08:34:28Z

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@networkplumber.org>
> ---
> lib/ethdev/rte_ethdev.c | 28 ++++++++++++++++++++--------
> 1 file changed, 20 insertions(+), 8 deletions(-)
Acked-by: Bruce Richardson <bruce.richardson@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
>