netfilter: nf_tables: bogus EBUSY in helper removal from transaction

Proper use counter updates when activating and deactivating the object,
otherwise, this hits bogus EBUSY error.

Fixes: cd5125d8 ("netfilter: nf_tables: split set destruction in deactivate and destroy phase")
Reported-by: Laura Garcia <nevola@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nft_objref.c

@@ -65,21 +65,34 @@ static int nft_objref_dump(struct sk_buff *skb, const struct nft_expr *expr)
 	return -1;
 }
 
-static void nft_objref_destroy(const struct nft_ctx *ctx,
-			       const struct nft_expr *expr)
+static void nft_objref_deactivate(const struct nft_ctx *ctx,
+				  const struct nft_expr *expr,
+				  enum nft_trans_phase phase)
 {
 	struct nft_object *obj = nft_objref_priv(expr);
 
+	if (phase == NFT_TRANS_COMMIT)
+		return;
+
 	obj->use--;
 }
 
+static void nft_objref_activate(const struct nft_ctx *ctx,
+				const struct nft_expr *expr)
+{
+	struct nft_object *obj = nft_objref_priv(expr);
+
+	obj->use++;
+}
+
 static struct nft_expr_type nft_objref_type;
 static const struct nft_expr_ops nft_objref_ops = {
 	.type		= &nft_objref_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_object *)),
 	.eval		= nft_objref_eval,
 	.init		= nft_objref_init,
-	.destroy	= nft_objref_destroy,
+	.activate	= nft_objref_activate,
+	.deactivate	= nft_objref_deactivate,
 	.dump		= nft_objref_dump,
 };