From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A83FBC4332F for ; Sat, 15 Oct 2022 02:36:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229640AbiJOCgv (ORCPT ); Fri, 14 Oct 2022 22:36:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55132 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229542AbiJOCgt (ORCPT ); Fri, 14 Oct 2022 22:36:49 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E6CDA2B1AA; Fri, 14 Oct 2022 19:36:48 -0700 (PDT) Received: from dggpeml500026.china.huawei.com (unknown [172.30.72.53]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4Mq6j50HSmz1P7MC; Sat, 15 Oct 2022 10:32:09 +0800 (CST) Received: from [10.174.178.66] (10.174.178.66) by dggpeml500026.china.huawei.com (7.185.36.106) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Sat, 15 Oct 2022 10:36:46 +0800 Message-ID: Date: Sat, 15 Oct 2022 10:36:46 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.0.2 Subject: Re: [PATCH v4,bpf-next] bpf: Don't redirect packets with invalid pkt_len To: , Lorenz Bauer CC: Alexei Starovoitov , Daniel Borkmann , , , References: <20220715115559.139691-1-shaozhengchao@huawei.com> <20220914111936.19881-1-oss@lmb.io> <5a3c5ea9-d557-6070-d778-1092f3c51257@huawei.com> <04d2eb4a-7365-495a-ab74-704febac2789@app.fastmail.com> From: shaozhengchao In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.66] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpeml500026.china.huawei.com (7.185.36.106) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/10/15 0:55, sdf@google.com wrote: > On 10/14, Lorenz Bauer wrote: >> On Thu, 13 Oct 2022, at 11:44, shaozhengchao wrote: >> >     Sorry, I haven't fully understood your intentions yet. >> > Can you explain it more detail? > >> I'll try! Roughly, we do the following: > >> 1. Create a BPF_PROG_TYPE_SOCKET_FILTER program that just returns 0 >> 2. Load the program into the kernel >> 3. Call BPF_PROG_RUN with data_size_in == 14 > >> After your bugfix, it seems like step 3 is rejected due to >> data_size_in == 14. We had to increase data_size_in to 15 to >> avoid this, see [0]. > >> This breaks user space, so it would be great if you could fix this in >> a way that doesn't refuse BPF_PROG_RUN with > > [..] > >> data_size_in == 14. Since I don't understand the original problem very >> well I can't tell you what the best fix is however. > > The problem was that we were able to generate skb with len=0 via > BPF_PROG_RUN. Prohibiting those cases breaks backwards compatibility, so > we either have to: > > a) (preferred?) accept inputs with <14, but maybe internally pad to 14 > bytes to make the core stack happy > b) revert the patch and instead have length checks at runtime; doesn't > seem to > be worth the penalty in the forwarding path because of some corner cases > like these ? > Hi sdf: a） looks better and I'll put up a patch as soon as possible to fix it. Zhengchao Shao > >> 0: >> https://github.com/cilium/ebpf/commit/a38fb6b5a46ab3b5639ea4d421232a10013596c0 > >> Thanks >> Lorenz