Re: [PATCH v3 1/2] tools/libs/stat: use memcpy instead of strncpy in getBridge

[Bertrand Marquis <Bertrand.Marquis@arm.com>]

Hi,

Could this be reviewed so that gcc10 issues are fixed ?

Thanks
Bertrand

> On 7 Oct 2020, at 14:57, Bertrand Marquis <bertrand.marquis@arm.com> 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>
> ---
> Changes in v3:
> Do a memset 0 on destination buffer and use MIN between string length
> and resultLen - 1.
> Changes in v2:
> Use MIN between string length of de->d_name and resultLen to copy only
> the minimum size required and prevent crossing to from an unallocated
> space.
> ---
> tools/libs/stat/xenstat_linux.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/libs/stat/xenstat_linux.c b/tools/libs/stat/xenstat_linux.c
> index d2ee6fda64..e0d242e1bc 100644
> --- a/tools/libs/stat/xenstat_linux.c
> +++ b/tools/libs/stat/xenstat_linux.c
> @@ -29,6 +29,7 @@
> #include <string.h>
> #include <unistd.h>
> #include <regex.h>
> +#include <xen-tools/libs.h>
> 
> #include "xenstat_priv.h"
> 
> @@ -78,8 +79,14 @@ 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);
> -					result[resultLen - 1] = 0;
> +					/*
> +					 * Do not use strncpy to prevent compiler warning with
> +					 * gcc >= 10.0
> +					 * If de->d_name is longer then resultLen we truncate it
> +					 */
> +					memset(result, 0, resultLen);
> +					memcpy(result, de->d_name, MIN(strnlen(de->d_name,
> +									NAME_MAX),resultLen - 1));
> 				}
> 		}
> 	}
> @@ -264,7 +271,7 @@ 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
> 
>