From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pablo Neira Ayuso Subject: Re: [PATCH nf 1/2] netfilter: nft_set_bitmap: fetch the element key based on the set->klen Date: Mon, 6 Mar 2017 13:01:19 +0100 Message-ID: <20170306120119.GA3461@salvia> References: <1488729773-48343-1-git-send-email-zlpnobody@163.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netfilter-devel@vger.kernel.org, Liping Zhang To: Liping Zhang Return-path: Received: from mail.us.es ([193.147.175.20]:46646 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753200AbdCFMBf (ORCPT ); Mon, 6 Mar 2017 07:01:35 -0500 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id 4A7CF19833F for ; Mon, 6 Mar 2017 13:01:31 +0100 (CET) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 386E2DA817 for ; Mon, 6 Mar 2017 13:01:31 +0100 (CET) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 640DDDA81F for ; Mon, 6 Mar 2017 13:01:27 +0100 (CET) Content-Disposition: inline In-Reply-To: <1488729773-48343-1-git-send-email-zlpnobody@163.com> Sender: netfilter-devel-owner@vger.kernel.org List-ID: On Mon, Mar 06, 2017 at 12:02:52AM +0800, Liping Zhang wrote: > From: Liping Zhang > > Currently we just assume the element key as a u32 integer, regardless of > the set key length. > > This is incorrect, for example, the tcp port number is only 16 bits. > So when we use the nft_payload expr to get the tcp dport and store > it to dreg, the dport will be stored at 0~15 bits, and 16~31 bits > will be padded with zero. > > So the reg->data[dreg] will be looked like as below: > 0 15 31 > +-+-+-+-+-+-+-+-+-+-+-+-+ > | tcp dport | 0 | > +-+-+-+-+-+-+-+-+-+-+-+-+ > But for these big-endian systems, if we treate this register as a u32 > integer, the element key will be larger than 65535, so the following > lookup in bitmap set will cause out of bound access. > > Another issue is that if we add element with comments in bitmap > set(although the comments will be ignored eventually), the element will > vanish strangely. Because we treate the element key as a u32 integer, so > the comments will become the part of the element key, then the element > key will also be larger than 65535 and out of bound access will happen: > # nft add element t s { 1 comment test } Right, the userdata case is not handled properly. And in this case we have no specific flag at set creation, so element comments may come without previous notice via set flags. I think we have to keep a list of dummy nft_set_ext that is only used in the dump path, we can simplify this logic at the cost of increasing memory consumption. Another alternative is to keep around a structure to store only the set element userdata that we need for comments. Let me think. Your patches look good to me. Probably we can skip 2/2 if we introduce the dummy nft_set_ext list, and remove the ->flush field for nft_set_iter. Thanks.