netfilter: nf_tables: add nft_set_elem_expr_destroy() and use it

This patch adds nft_set_elem_expr_destroy() to destroy stateful
expressions in set elements.

This patch also updates the commit path to call this function to invoke
expr->ops->destroy_clone when required.

This is implicitly fixing up a module reference counter leak and
a memory leak in expressions that allocated internal state, e.g.
nft_counter.

Fixes: 4094445 ("netfilter: nf_tables: add elements with stateful expressions")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -4882,6 +4882,17 @@ void *nft_set_elem_init(const struct nft_set *set,
 	return elem;
 }
 
+static void nft_set_elem_expr_destroy(const struct nft_ctx *ctx,
+				      struct nft_expr *expr)
+{
+	if (expr->ops->destroy_clone) {
+		expr->ops->destroy_clone(ctx, expr);
+		module_put(expr->ops->type->owner);
+	} else {
+		nf_tables_expr_destroy(ctx, expr);
+	}
+}
+
 void nft_set_elem_destroy(const struct nft_set *set, void *elem,
 			  bool destroy_expr)
 {
@@ -4894,16 +4905,9 @@ void nft_set_elem_destroy(const struct nft_set *set, void *elem,
 	nft_data_release(nft_set_ext_key(ext), NFT_DATA_VALUE);
 	if (nft_set_ext_exists(ext, NFT_SET_EXT_DATA))
 		nft_data_release(nft_set_ext_data(ext), set->dtype);
-	if (destroy_expr && nft_set_ext_exists(ext, NFT_SET_EXT_EXPR)) {
-		struct nft_expr *expr = nft_set_ext_expr(ext);
+	if (destroy_expr && nft_set_ext_exists(ext, NFT_SET_EXT_EXPR))
+		nft_set_elem_expr_destroy(&ctx, nft_set_ext_expr(ext));
 
-		if (expr->ops->destroy_clone) {
-			expr->ops->destroy_clone(&ctx, expr);
-			module_put(expr->ops->type->owner);
-		} else {
-			nf_tables_expr_destroy(&ctx, expr);
-		}
-	}
 	if (nft_set_ext_exists(ext, NFT_SET_EXT_OBJREF))
 		(*nft_set_ext_obj(ext))->use--;
 	kfree(elem);
@@ -4919,7 +4923,8 @@ static void nf_tables_set_elem_destroy(const struct nft_ctx *ctx,
 	struct nft_set_ext *ext = nft_set_elem_ext(set, elem);
 
 	if (nft_set_ext_exists(ext, NFT_SET_EXT_EXPR))
-		nf_tables_expr_destroy(ctx, nft_set_ext_expr(ext));
+		nft_set_elem_expr_destroy(ctx, nft_set_ext_expr(ext));
+
 	kfree(elem);
 }
 
@@ -5182,7 +5187,8 @@ static int nft_add_set_elem(struct nft_ctx *ctx, struct nft_set *set,
 err_trans:
 	if (obj)
 		obj->use--;
-	kfree(elem.priv);
+
+	nf_tables_set_elem_destroy(ctx, set, elem.priv);
 err_parse_data:
 	if (nla[NFTA_SET_ELEM_DATA] != NULL)
 		nft_data_release(&data, desc.type);