[PATCH] telemetry: avoid truncation of strlcpy return before check

[Bruce Richardson]

On Wed, Aug 02, 2023 at 02:21:01PM -0700, Tyler Retzlaff wrote:
> strlcpy returns type size_t when directly assigning to
> struct rte_tel_data data_len field it may be truncated leading to
> compromised length check that follows
> 
> Since the limit in the check is < UINT_MAX the value returned is
> safe to be cast to unsigned int (which may be narrower than size_t)
> but only after being checked against RTE_TEL_MAX_SINGLE_STRING_LEN
> 
> Signed-off-by: Tyler Retzlaff <roretzla at linux.microsoft.com>
> ---
Acked-by: Bruce Richardson <bruce.richardson at intel.com>

This probably should be marked as a fix for backport.

>  lib/telemetry/telemetry_data.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/telemetry/telemetry_data.c b/lib/telemetry/telemetry_data.c
> index 3b1a240..52307cb 100644
> --- a/lib/telemetry/telemetry_data.c
> +++ b/lib/telemetry/telemetry_data.c
> @@ -41,12 +41,13 @@
>  int
>  rte_tel_data_string(struct rte_tel_data *d, const char *str)
>  {
> +	const size_t len = strlcpy(d->data.str, str, sizeof(d->data.str));
>  	d->type = TEL_STRING;
> -	d->data_len = strlcpy(d->data.str, str, sizeof(d->data.str));
> -	if (d->data_len >= RTE_TEL_MAX_SINGLE_STRING_LEN) {
> +	if (len >= RTE_TEL_MAX_SINGLE_STRING_LEN) {
>  		d->data_len = RTE_TEL_MAX_SINGLE_STRING_LEN - 1;
>  		return E2BIG; /* not necessarily and error, just truncation */
>  	}
> +	d->data_len = (unsigned int)len;
>  	return 0;
>  }
>  
> -- 
> 1.8.3.1
>