Re: [PATCH v3 1/4] examples/server_node_efd: fix format overflow

[Bruce Richardson <bruce.richardson@intel.com>]

On Sat, Nov 15, 2025 at 11:36:36AM -0800, Stephen Hemminger wrote:
> If format-truncation is enabled, the compiler detects a string overflow
> since the snprintf() is putting ethernet address and new line
> in buffer only sized for the address.
> 
> Since get_rx_queue_name() is used to create a ring name.
> The buffer should be sized to be a valid ring name.
> This fixes some format-overflow warnings and also corrects
> for future errors.
> 
> In file included from ../examples/server_node_efd/efd_server/main.c:31:
> In function ‘get_printable_mac_addr’,
>     inlined from ‘do_stats_display’ at ../examples/server_node_efd/efd_server/main.c:136:3:
> ../lib/net/rte_ether.h:248:36: warning: ‘snprintf’ output truncated before the last format character [-Wformat-truncation=]
>   248 | #define RTE_ETHER_ADDR_PRT_FMT     "%02X:%02X:%02X:%02X:%02X:%02X"
>       |                                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ../examples/server_node_efd/efd_server/main.c:86:33: note: in expansion of macro ‘RTE_ETHER_ADDR_PRT_FMT’
>    86 |                                 RTE_ETHER_ADDR_PRT_FMT "\n",
>       |                                 ^~~~~~~~~~~~~~~~~~~~~~
> ../examples/server_node_efd/efd_server/main.c: In function ‘do_stats_display’:
> ../examples/server_node_efd/efd_server/main.c:86:59: note: format string is defined here
>    86 |                                 RTE_ETHER_ADDR_PRT_FMT "\n",
>       |
> 
> Fixes: 39aad0e88c58 ("examples/flow_distributor: new example to demonstrate EFD")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>

> ---
>  examples/server_node_efd/efd_server/main.c | 2 +-
>  examples/server_node_efd/shared/common.h   | 3 ++-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/examples/server_node_efd/efd_server/main.c b/examples/server_node_efd/efd_server/main.c
> index 75ff0ea532..62c3f4a16d 100644
> --- a/examples/server_node_efd/efd_server/main.c
> +++ b/examples/server_node_efd/efd_server/main.c
> @@ -68,7 +68,7 @@ static const char *
>  get_printable_mac_addr(uint16_t port)
>  {
>  	static const char err_address[] = "00:00:00:00:00:00";
> -	static char addresses[RTE_MAX_ETHPORTS][sizeof(err_address)];
> +	static char addresses[RTE_MAX_ETHPORTS][RTE_ETHER_ADDR_FMT_SIZE + 1];
>  	struct rte_ether_addr mac;
>  	int ret;
>  
> diff --git a/examples/server_node_efd/shared/common.h b/examples/server_node_efd/shared/common.h
> index e1ab7e62b7..6726e2031e 100644
> --- a/examples/server_node_efd/shared/common.h
> +++ b/examples/server_node_efd/shared/common.h
> @@ -58,8 +58,9 @@ get_rx_queue_name(unsigned int id)
>  	/*
>  	 * Buffer for return value. Size calculated by %u being replaced
>  	 * by maximum 3 digits (plus an extra byte for safety)
> +	 * Used as ring name, so upper limit is ring name size.
>  	 */
> -	static char buffer[sizeof(MP_NODE_RXQ_NAME) + 2];
> +	static char buffer[RTE_RING_NAMESIZE];
>  
>  	snprintf(buffer, sizeof(buffer), MP_NODE_RXQ_NAME, id);
>  	return buffer;
> -- 
> 2.51.0
>