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 X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 58F61C742C8 for ; Fri, 12 Jul 2019 15:15:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3C4A4206B8 for ; Fri, 12 Jul 2019 15:15:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727186AbfGLPPM (ORCPT ); Fri, 12 Jul 2019 11:15:12 -0400 Received: from www62.your-server.de ([213.133.104.62]:45880 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726266AbfGLPPM (ORCPT ); Fri, 12 Jul 2019 11:15:12 -0400 Received: from [78.46.172.3] (helo=sslproxy06.your-server.de) by www62.your-server.de with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89_1) (envelope-from ) id 1hlxGJ-0007bi-K7; Fri, 12 Jul 2019 17:15:03 +0200 Received: from [2a02:1205:5069:fce0:c5f9:cd68:79d4:446d] (helo=linux.home) by sslproxy06.your-server.de with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1hlxGJ-000X25-CS; Fri, 12 Jul 2019 17:15:03 +0200 Subject: Re: [PATCH 0/2] Fold checksum at the end of bpf_csum_diff and fix To: Andrii Nakryiko , Paolo Pisati Cc: 20190710231439.GD32439@tassilo.jf.intel.com, Alexei Starovoitov , Martin KaFai Lau , Song Liu , Yonghong Song , "David S . Miller" , Shuah Khan , Jakub Kicinski , Jiong Wang , Networking , bpf , "open list:KERNEL SELFTEST FRAMEWORK" , open list References: <1562837513-745-1-git-send-email-p.pisati@gmail.com> From: Daniel Borkmann Message-ID: <8bd99845-4d59-f0a4-3b50-ab6d539b36bc@iogearbox.net> Date: Fri, 12 Jul 2019 17:15:02 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.100.3/25508/Fri Jul 12 10:10:04 2019) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 07/12/2019 01:50 AM, Andrii Nakryiko wrote: > On Thu, Jul 11, 2019 at 2:32 AM Paolo Pisati wrote: >> From: Paolo Pisati >> >> After applying patch 0001, all checksum implementations i could test (x86-64, arm64 and >> arm), now agree on the return value. >> >> Patch 0002 fix the expected return value for test #13: i did the calculation manually, >> and it correspond. >> >> Unfortunately, after applying patch 0001, other test cases now fail in >> test_verifier: Thanks for catching, sigh. :/ >> $ sudo ./tools/testing/selftests/bpf/test_verifier >> ... >> #417/p helper access to variable memory: size = 0 allowed on NULL (ARG_PTR_TO_MEM_OR_NULL) FAIL retval 65535 != 0 >> #419/p helper access to variable memory: size = 0 allowed on != NULL stack pointer (ARG_PTR_TO_MEM_OR_NULL) FAIL retval 65535 != 0 >> #423/p helper access to variable memory: size possible = 0 allowed on != NULL packet pointer (ARG_PTR_TO_MEM_OR_NULL) FAIL retval 65535 != 0 > > I'm not entirely sure this fix is correct, given these failures, to be honest. > > Let's wait for someone who understands intended semantics for > bpf_csum_diff, before changing returned value so drastically. > > But in any case, fixes for these test failures should be in your patch > series as well. Your change would actually break applications. The bpf_csum_diff() helper is heavily used with cascading so one result can be fed into another bpf_csum_diff() call as seed. Quick test on x86-64: static int __init foo(void) { u8 data[32 * sizeof(u32)]; u32 res1, res2, res3; int i; prandom_bytes(data, sizeof(data)); res1 = csum_fold(csum_partial(data, sizeof(data), 0)); for (i = sizeof(u32); i < sizeof(data); i += sizeof(u32)) { res2 = csum_fold(csum_partial(data, i, 0)); res2 = csum_fold(csum_partial(data+i, sizeof(data)-i, res2)); res3 = csum_partial(data, i, 0); res3 = csum_fold(csum_partial(data+i, sizeof(data)-i, res3)); printk("%8d: [%4x (reference), %4x (unfolded), %4x (folded)]\n", i, res1, res3, res2); } return -1; } Gives for all three: [19113.233942] 4: [6b70 (reference), 6b70 (unfolded), 223d (folded)] [19113.233943] 8: [6b70 (reference), 6b70 (unfolded), a812 (folded)] [19113.233943] 12: [6b70 (reference), 6b70 (unfolded), 1c26 (folded)] [19113.233944] 16: [6b70 (reference), 6b70 (unfolded), 4f76 (folded)] [19113.233944] 20: [6b70 (reference), 6b70 (unfolded), 2801 (folded)] [19113.233945] 24: [6b70 (reference), 6b70 (unfolded), b63 (folded)] [19113.233945] 28: [6b70 (reference), 6b70 (unfolded), 2fe0 (folded)] [19113.233946] 32: [6b70 (reference), 6b70 (unfolded), 18a2 (folded)] [19113.233946] 36: [6b70 (reference), 6b70 (unfolded), 2597 (folded)] [19113.233947] 40: [6b70 (reference), 6b70 (unfolded), 2f8e (folded)] [19113.233947] 44: [6b70 (reference), 6b70 (unfolded), b8af (folded)] [19113.233948] 48: [6b70 (reference), 6b70 (unfolded), fb8b (folded)] [19113.233948] 52: [6b70 (reference), 6b70 (unfolded), e9c0 (folded)] [19113.233949] 56: [6b70 (reference), 6b70 (unfolded), 6af1 (folded)] [19113.233949] 60: [6b70 (reference), 6b70 (unfolded), d7f4 (folded)] [19113.233949] 64: [6b70 (reference), 6b70 (unfolded), 8bc6 (folded)] [19113.233950] 68: [6b70 (reference), 6b70 (unfolded), 8718 (folded)] [19113.233950] 72: [6b70 (reference), 6b70 (unfolded), 27d8 (folded)] [19113.233951] 76: [6b70 (reference), 6b70 (unfolded), a2db (folded)] [19113.233952] 80: [6b70 (reference), 6b70 (unfolded), 3fd (folded)] [19113.233952] 84: [6b70 (reference), 6b70 (unfolded), 4be5 (folded)] [19113.233952] 88: [6b70 (reference), 6b70 (unfolded), 41ad (folded)] [19113.233953] 92: [6b70 (reference), 6b70 (unfolded), ca9b (folded)] [19113.233953] 96: [6b70 (reference), 6b70 (unfolded), f8ec (folded)] [19113.233954] 100: [6b70 (reference), 6b70 (unfolded), 5451 (folded)] [19113.233954] 104: [6b70 (reference), 6b70 (unfolded), 763 (folded)] [19113.233955] 108: [6b70 (reference), 6b70 (unfolded), e37c (folded)] [19113.233955] 112: [6b70 (reference), 6b70 (unfolded), 4ee6 (folded)] [19113.233956] 116: [6b70 (reference), 6b70 (unfolded), 4f73 (folded)] [19113.233956] 120: [6b70 (reference), 6b70 (unfolded), 1cfd (folded)] [19113.233957] 124: [6b70 (reference), 6b70 (unfolded), 7d1a (folded)] I'll take a look next week wrt fixing this uniformly for all archs. Thanks, Daniel