From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <shemming@brocade.com>
Subject: Re: [iproute2 PATCH] utils: fix hex digits parsing in
 hexstring_a2n()
Date: Tue, 14 Jun 2016 14:25:50 -0700
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Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>
To: Beniamino Galvani <bgalvani@redhat.com>
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On Tue, 14 Jun 2016 20:55:17 +0000
Beniamino Galvani <bgalvani@redhat.com> wrote:

> strtoul() only modifies errno on overflow, so if errno is not zero
> before calling the function its value is preserved and makes the
> function fail for valid inputs; initialize it.
> 
> Signed-off-by: Beniamino Galvani <bgalvani@redhat.com>
> ---
>  lib/utils.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/lib/utils.c b/lib/utils.c
> index 70e85b7..7dceeb5 100644
> --- a/lib/utils.c
> +++ b/lib/utils.c
> @@ -924,6 +924,7 @@ __u8 *hexstring_a2n(const char *str, __u8 *buf, int blen, unsigned int *len)
>  
>  		strncpy(tmpstr, str, 2);
>  		tmpstr[2] = '\0';
> +		errno = 0;
>  		tmp = strtoul(tmpstr, &endptr, 16);
>  		if (errno != 0 || tmp > 0xFF || *endptr != '\0')
>  			return NULL;

Applied.
The code here is doing things in a manner much harder than necessary...