Linux kernel use-after-free in Netfilter, local privilege escalation(seclists.org)

    struct foo *whatever = new_foo();
    // use 'whatever'
    free_foo(whatever);
    if (whatever->did_something) {
        log_message("The whatever did something.");
    }
    // never use 'whatever' after this point

  priv->set->use++;

  nf_tables_activate_set(ctx, priv->set);

  void nf_tables_activate_set(const struct nft_ctx *ctx, struct nft_set *set) {
    if (nft_set_is_anonymous(set))
      nft_clear(ctx->net, set);
    set->use++;
  }