Re: [PATCH] iproute_lwtunnel: Add check for result of get_u32 function

[Stephen Hemminger <stephen@networkplumber.org>]

On Sun,  7 Jul 2024 18:49:28 +0300
Maks Mishin <maks.mishinfz@gmail.com> wrote:

> Signed-off-by: Maks Mishin <maks.mishinFZ@gmail.com>
> ---
>  ip/iproute_lwtunnel.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/ip/iproute_lwtunnel.c b/ip/iproute_lwtunnel.c
> index b4df4348..2946fa4d 100644
> --- a/ip/iproute_lwtunnel.c
> +++ b/ip/iproute_lwtunnel.c
> @@ -1484,7 +1484,8 @@ static int parse_encap_seg6local(struct rtattr *rta, size_t len, int *argcp,
>  				NEXT_ARG();
>  				if (hmac_ok++)
>  					duparg2("hmac", *argv);
> -				get_u32(&hmac, *argv, 0);
> +				if (get_u32(&hmac, *argv, 0) || hmac == 0)
> +					invarg("\"hmac\" value is invalid\n", *argv);
>  			} else {
>  				continue;
>  			}

There is another unchecked call to get_u32() in the same file.
Please fix all of them and add more detail in commit message.

If the get_XXX functions are modified to force checks on return value get:

iproute_lwtunnel.c: In function ‘parse_encap_seg6’:
iproute_lwtunnel.c:972:25: warning: ignoring return value of ‘get_u32’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
  972 |                         get_u32(&hmac, *argv, 0);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~
iproute_lwtunnel.c: In function ‘parse_encap_seg6local’:
iproute_lwtunnel.c:1487:33: warning: ignoring return value of ‘get_u32’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
 1487 |                                 get_u32(&hmac, *argv, 0);
      |                                 ^~~~~~~~~~~~~~~~~~~~~~~~