selftests/bpf: Free strdup memory in veristat

The strdup() function returns a pointer to a new string which is a
duplicate of the string "input". Memory for the new string is obtained
with malloc(), and need to be freed with free().

This patch adds these missing "free(input)" in parse_stats() to avoid
memory leak in veristat.c.
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/ded44f8865cd7f337f52fc5fb0a5fbed7d6bd641.1714374022.git.tanggeliang@kylinos.cn

tools/testing/selftests/bpf/veristat.c

@@ -792,10 +792,13 @@ static int parse_stats(const char *stats_str, struct stat_specs *specs)
 
 	while ((next = strtok_r(state ? NULL : input, ",", &state))) {
 		err = parse_stat(next, specs);
-		if (err)
+		if (err) {
+			free(input);
 			return err;
+		}
 	}
 
+	free(input);
 	return 0;
 }