Re: [PATCH 1/2] tools: use memcpy instead of strncpy in getBridge

[Wei Liu <wl@xen.org>]

On Mon, Oct 05, 2020 at 05:02:48PM +0100, Bertrand Marquis wrote:
> Use memcpy in getBridge to prevent gcc warnings about truncated
> strings. We know that we might truncate it, so the gcc warning
> here is wrong.
> Revert previous change changing buffer sizes as bigger buffers
> are not needed.
> 
> Signed-off-by: Bertrand Marquis <bertrand.marquis@arm.com>

Juergen, are you happy with this change? I have not followed closely the
discussion on #xendevel.

> ---
>  tools/libs/stat/xenstat_linux.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/libs/stat/xenstat_linux.c b/tools/libs/stat/xenstat_linux.c
> index d2ee6fda64..1db35c604c 100644
> --- a/tools/libs/stat/xenstat_linux.c
> +++ b/tools/libs/stat/xenstat_linux.c
> @@ -78,7 +78,12 @@ static void getBridge(char *excludeName, char *result, size_t resultLen)
>  				sprintf(tmp, "/sys/class/net/%s/bridge", de->d_name);
>  
>  				if (access(tmp, F_OK) == 0) {
> -					strncpy(result, de->d_name, resultLen);
> +					/*
> +					 * Do not use strncpy to prevent compiler warning with
> +					 * gcc >= 10.0
> +					 * If de->d_name is longer then resultLen we truncate it
> +					 */
> +					memcpy(result, de->d_name, resultLen - 1);
>  					result[resultLen - 1] = 0;
>  				}
>  		}
> @@ -264,7 +269,7 @@ int xenstat_collect_networks(xenstat_node * node)
>  {
>  	/* Helper variables for parseNetDevLine() function defined above */
>  	int i;
> -	char line[512] = { 0 }, iface[16] = { 0 }, devBridge[256] = { 0 }, devNoBridge[257] = { 0 };
> +	char line[512] = { 0 }, iface[16] = { 0 }, devBridge[16] = { 0 }, devNoBridge[17] = { 0 };
>  	unsigned long long rxBytes, rxPackets, rxErrs, rxDrops, txBytes, txPackets, txErrs, txDrops;
>  
>  	struct priv_data *priv = get_priv_data(node->handle);
> -- 
> 2.17.1
>