Re: [libnftnl PATCH 1/2] utils: ensure \0 is in place in nft_fprintf()

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Mon, Aug 25, 2014 at 03:02:21PM +0200, Arturo Borrero Gonzalez wrote:
> We must make sure the buffer contains a \0 in the last position,
> to avoid printing trash by the last fprintf() call.

snprintf already guarantees that the string is nul-terminated if there
is enough room to add \0.

        ret = snprintf_cb(buf, bufsiz, obj, type, flags);
        if (ret < 0)
                goto out;

        if (ret >= NFT_SNPRINTF_BUFSIZ) {
                bufsiz = ret + 1;

                buf = malloc(bufsiz);
                if (buf == NULL)
                        return -1;

                ret = snprintf_cb(buf, bufsiz, obj, type, flags);
                if (ret < 0)
                        goto out;
        }

        ret = fprintf(fp, "%s", buf);

I think we have guarantees that buf is always nul-terminated after the
second try.

Patch 2/2 looks good to enough to me since it already resolves the
printed "garbage" at the end of the output issue.