[v2,3/4] examples/mp_server: fix snprintf overflow
diff mbox series

Message ID 20200821171017.50531-4-bruce.richardson@intel.com
State Superseded
Delegated to: Thomas Monjalon
Headers show
Series
  • fixes for example app builds
Related show

Checks

Context Check Description
ci/checkpatch warning coding style issues

Commit Message

Bruce Richardson Aug. 21, 2020, 5:10 p.m. UTC
When producing a printable mac address the buffer was appropriately sized
for holding the mac address exactly, but the actual snprintf included a
'\n' character at the end, which means that the snprintf technically is
getting truncated i.e. the \n would not be added due to lack of space.
This gets flagged as a problem by modern versions of gcc, e.g. on Ubuntu
20.04.

main.c:77:37: warning: ‘__builtin___snprintf_chk’ output truncated before the last format character [-Wformat-truncation=]
   77 |     "%02x:%02x:%02x:%02x:%02x:%02x\n",
      |                                     ^

Since the \n is getting stripped anyway, we can fix the issue by just
removing it. In the process we can switch to using the standard ethernet
address formating function from rte_ether.h.

Fixes: af75078fece3 ("first public release")
Cc: stable@dpdk.org
Cc: Stephen Hemminger <stephen@networkplumber.org>

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>

---
V2: switched code to use standard formatting function
---
 .../client_server_mp/mp_server/main.c           | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

Comments

Nicolau, Radu Oct. 9, 2020, 11:22 a.m. UTC | #1
On 8/21/2020 6:10 PM, Bruce Richardson wrote:
> When producing a printable mac address the buffer was appropriately sized
> for holding the mac address exactly, but the actual snprintf included a
> '\n' character at the end, which means that the snprintf technically is
> getting truncated i.e. the \n would not be added due to lack of space.
> This gets flagged as a problem by modern versions of gcc, e.g. on Ubuntu
> 20.04.
>
> main.c:77:37: warning: ‘__builtin___snprintf_chk’ output truncated before the last format character [-Wformat-truncation=]
>     77 |     "%02x:%02x:%02x:%02x:%02x:%02x\n",
>        |                                     ^
>
> Since the \n is getting stripped anyway, we can fix the issue by just
> removing it. In the process we can switch to using the standard ethernet
> address formating function from rte_ether.h.
>
> Fixes: af75078fece3 ("first public release")
> Cc: stable@dpdk.org
> Cc: Stephen Hemminger <stephen@networkplumber.org>
>
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
>
> ---
> V2: switched code to use standard formatting function
> ---

Acked-by: Radu Nicolau <radu.nicolau@intel.com>

Patch
diff mbox series

diff --git a/examples/multi_process/client_server_mp/mp_server/main.c b/examples/multi_process/client_server_mp/mp_server/main.c
index 280dab8672..fb2aa49678 100644
--- a/examples/multi_process/client_server_mp/mp_server/main.c
+++ b/examples/multi_process/client_server_mp/mp_server/main.c
@@ -59,12 +59,17 @@  static struct client_rx_buf *cl_rx_buf;
 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 const struct rte_ether_addr null_mac; /* static defaults to 0 */
+	static char err_address[32];
+	static char addresses[RTE_MAX_ETHPORTS][32];
 	int ret;
 
-	if (unlikely(port >= RTE_MAX_ETHPORTS))
+	if (unlikely(port >= RTE_MAX_ETHPORTS)) {
+		if (err_address[0] == '\0')
+			rte_ether_format_addr(err_address,
+					sizeof(err_address), &null_mac);
 		return err_address;
+	}
 	if (unlikely(addresses[port][0]=='\0')){
 		struct rte_ether_addr mac;
 		ret = rte_eth_macaddr_get(port, &mac);
@@ -73,10 +78,8 @@  get_printable_mac_addr(uint16_t port)
 			       port, rte_strerror(-ret));
 			return err_address;
 		}
-		snprintf(addresses[port], sizeof(addresses[port]),
-				"%02x:%02x:%02x:%02x:%02x:%02x\n",
-				mac.addr_bytes[0], mac.addr_bytes[1], mac.addr_bytes[2],
-				mac.addr_bytes[3], mac.addr_bytes[4], mac.addr_bytes[5]);
+		rte_ether_format_addr(addresses[port],
+				sizeof(addresses[port]), &mac);
 	}
 	return addresses[port];
 }