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=-5.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MSGID_FROM_MTA_HEADER,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,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 4FD81C48BC2 for ; Fri, 25 Jun 2021 06:26:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2A26761404 for ; Fri, 25 Jun 2021 06:26:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233193AbhFYG2l (ORCPT ); Fri, 25 Jun 2021 02:28:41 -0400 Received: from mx0a-0064b401.pphosted.com ([205.220.166.238]:4114 "EHLO mx0a-0064b401.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230097AbhFYG2c (ORCPT ); Fri, 25 Jun 2021 02:28:32 -0400 Received: from pps.filterd (m0250810.ppops.net [127.0.0.1]) by mx0a-0064b401.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 15P6E20k024402; Thu, 24 Jun 2021 23:25:32 -0700 Received: from nam02-bn1-obe.outbound.protection.outlook.com (mail-bn1nam07lp2047.outbound.protection.outlook.com [104.47.51.47]) by mx0a-0064b401.pphosted.com with ESMTP id 39d22wran7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 24 Jun 2021 23:25:31 -0700 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=T1RhacBmFyuEwdARuRjhbDLI9PNCoAfr6cEg8S/I577y2KIfXrm+9FPLnYPSYPjTNtGWrMWFS9uXqxp1FU4djACmltzb3neKoMl2Y8xvVyHod2K+QCCJ5yxWThke+nfhCUOON2zQQoFJnmTprd/aEFZys9o/P2Sfu39dhqEbcXzyhHKIoXAX5emnniQp1bLdKbZRnw5Zza0oloCrJ75V9TxH/nFOm++yvE6wtQJgoo1qjnfHpiwopSMDKy7QR2cEq44/cqkNgr9eZxPdHBk7LkxKyBj7tkei2XgWIUnoVF/RVecVEFWEyMwDavL2JLYKIIwW1wumVNIqw61NydEgQA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=CFeU7A34Sfx5wy9feIjs0v7/tUWwRnXEZtvqxqdxXqQ=; b=n+o/YoX+L8/eKXVh+Ql/D5yucmCDAdXnlnFKKVguDS7H3boSD/csaE6kes+9SSZYeJFyzJ5ByN5Cwjf7fy42sBK1oVTBxyLIyNQ205ibtNzgVitDObMTIuJzMhfIvLKB9vHDOGhbSGJUIOgUViwsQlYaOObGDi0zaabLEQAOhHu2kEf5hLI75gE7H8OMW/6wkf7QsHZWQR4j3vZG69Il779cDfhI0CQpsfH8JrJMzN9vIFgl7CYjUjxV/p48Tzhpj6wgdJDj6eyqQVwZQLMG+47JX7IFTd2B1w4+XW7PnYYpH+4BUdxBtMruFcRtj8mIfpCEzW1qZrMAgIMuTmYReg== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=windriver.com; dmarc=pass action=none header.from=windriver.com; dkim=pass header.d=windriver.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=windriversystems.onmicrosoft.com; s=selector2-windriversystems-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=CFeU7A34Sfx5wy9feIjs0v7/tUWwRnXEZtvqxqdxXqQ=; b=LKYbbYWE14WSYd/36BvdchnGMZhLizI/HWU8ePD4aP03oWHhRRI3FMbOT3BuI1vK7OeENg7PTznvOx6q+lH5fs6g23RABO01wGKC3+SA9x5AK0kvNB67ex5X2Md2L9aA3QJMO7ubLVS+u5qQKgxfBKuW4G+L/V1X9ArJHzdz6mA= Authentication-Results: windriver.com; dkim=none (message not signed) header.d=none;windriver.com; dmarc=none action=none header.from=windriver.com; Received: from SN6PR11MB3008.namprd11.prod.outlook.com (2603:10b6:805:cf::18) by SN6PR11MB2592.namprd11.prod.outlook.com (2603:10b6:805:57::25) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4264.23; Fri, 25 Jun 2021 06:25:27 +0000 Received: from SN6PR11MB3008.namprd11.prod.outlook.com ([fe80::d5d8:17f2:f40:2bf2]) by SN6PR11MB3008.namprd11.prod.outlook.com ([fe80::d5d8:17f2:f40:2bf2%4]) with mapi id 15.20.4264.020; Fri, 25 Jun 2021 06:25:27 +0000 Subject: Re: [PATCH] seq_buf: let seq_buf_putmem_hex support len larger than 8 To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, ying.xue@windriver.com, "Li, Zhiquan" References: <20210624131646.17878-1-yun.zhou@windriver.com> <20210624105422.5c8aaf4d@oasis.local.home> <32276a16-b893-bdbb-e552-7f5ecaaec5f1@windriver.com> <20210625000854.36ed6f2d@gandalf.local.home> From: Yun Zhou Message-ID: <133301fa-634b-e9b6-578e-08c16026f754@windriver.com> Date: Fri, 25 Jun 2021 14:25:19 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 In-Reply-To: <20210625000854.36ed6f2d@gandalf.local.home> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [60.247.85.82] X-ClientProxiedBy: HKAPR03CA0022.apcprd03.prod.outlook.com (2603:1096:203:c9::9) To SN6PR11MB3008.namprd11.prod.outlook.com (2603:10b6:805:cf::18) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [128.224.155.46] (60.247.85.82) by HKAPR03CA0022.apcprd03.prod.outlook.com (2603:1096:203:c9::9) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4287.12 via Frontend Transport; Fri, 25 Jun 2021 06:25:25 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 98038a04-c0fb-4bc4-7603-08d937a205e9 X-MS-TrafficTypeDiagnostic: SN6PR11MB2592: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:10000; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:SN6PR11MB3008.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(346002)(366004)(376002)(39840400004)(136003)(396003)(31696002)(44832011)(107886003)(31686004)(2906002)(86362001)(36756003)(4326008)(2616005)(38350700002)(38100700002)(316002)(956004)(478600001)(6706004)(5660300002)(66946007)(66476007)(16576012)(66556008)(83380400001)(52116002)(53546011)(8676002)(8936002)(6486002)(6916009)(16526019)(186003)(6666004)(26005)(78286007)(43740500002)(45980500001);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?MmdMZmc0cExQS3RkZ2s1L282cy94VmNqU3V3ZStBblJnRmlIcGpNM1FPM2Vo?= =?utf-8?B?UHhFNW5UOTduTGpsaG82TndVNUJQaWV0VGs2K3BtdHprLzR2OXN5UVlkZmRI?= =?utf-8?B?OWtFRUNra3B3QWFZOSt2LzNYeHlaYlFKUDJ0eHl3TDFtdnRmS1J6NUNVMmRS?= =?utf-8?B?dUxTT2E1T3c5MXBoMUZhU2ZSNFloamg1NmVsQnBjbHo1YjhSUnpLNTJTd0gx?= =?utf-8?B?WGYydWdlbkRRWkhUbkNyc1ZKNExTRk0xVnMrKzloR1lKSnAvcjYvUzd3eUcr?= =?utf-8?B?NFY0djVJeDZGWG9BRVNzK1ZtNzIxNEJjZm1YZDI2ck1zc2JXb25neE8xeXFC?= =?utf-8?B?d0hxM1RqdUtXYnNlUUh5dGlwTkZHZFZLR3FFSEVPcE90akdFb04rYWpZb3FP?= =?utf-8?B?NXBsWnRLajhSNWNjR2ZFeG1OeTA1WHVtOGlFNld6MXJDNnpOdjN5cGE4SExw?= =?utf-8?B?YUxjU25WS0t6cnh1QXRIb2pCUXlFYUFnbllCYXI4dUlrSmlHajJHZzhYbjFU?= =?utf-8?B?WjVUbWRYYlBqN21PSGMwRmlNbkgrMy9kN1l0NHJZd0dvQW1hUWc4VTVJM3Zv?= =?utf-8?B?QmtGVWZGT1M0Rk9ka2R0cDVRM1Q5eko4dkl6YkEySWFyVTh6U0JvZ1djallD?= =?utf-8?B?REZQQlF6S1ZUbUlVTW5pM1VBNVoxR1M1V0tSV0ptMjBNcXlJa3p3U0NpbmlD?= =?utf-8?B?Q2luZFMyeno2VW1TdVZwVklLU2NTOHkzamdoYkgwTVFZckRPTjkyeElSLzRN?= =?utf-8?B?Y3ZsQS8zaThWUVRHcmpXZzZnSXRTbWszTXhQRWFteGtIanJRTVdqRm5XMjdY?= =?utf-8?B?MXgyaDNMUXRkZG9ONWpoZWtTMCtyQkZ0cmVnS2xva2xjTG9aK3JlUVhEcGRk?= =?utf-8?B?SHlTYlNFMFZXZWkvUHdRS0JnWEduYjQ2anJKdVV6WGRWRlk1UGxrM0IvR3Zn?= =?utf-8?B?amJsUE5WRTBEQ2ZUQnpseE05M01xbWl4VWwyajAxN05vSnJMWlNhSUROd0lS?= =?utf-8?B?Q2VybHJxUnkrUWhsL2lBZnA5MzVtUmVneEZmcHFZR21WS1doeElPcWpvaG5i?= =?utf-8?B?WWNIaWRjSzZyU1M2YVRlTWw1dUdUcEZZcVp2cVNsQ1FDVmExWE5zUm84Ylpu?= =?utf-8?B?cU1yMUgzRHVQeEljREpLY0hGMlFBZ09qanZ5VFlMTHVSK0VsWDFncUgwMXJw?= =?utf-8?B?c2dvS2tYTUUvbFlDelRqSHo2YW9rOEZIZk53Qld2L2ZwVUxkVDFWV1MvRTFE?= =?utf-8?B?VElSVXpYbWFONmhpUlBmQ0hzalhhQmRzYnpKUG5UNjZydml0SzE0WHptdTlQ?= =?utf-8?B?RndhdWxEQU5NY3R2Nk9KVHNWcHo2bkR4aEw1Q2NlRldNeEk1VW43R1o0bTNm?= =?utf-8?B?S0hza1RJQ1RxcUVGbHpmeEJrK2lmWWVwSU5PSFFPS1p5bHZoL05lTDU2OXdq?= =?utf-8?B?a3ZMVWc1ajAxalh3NncrWnNqV2hkWEdVN1Z2V3lpTWVsOFFtYlJPN1VPclNY?= =?utf-8?B?TExtd3R1T2d4eW5LOWc1c1dOdm1weGRNYmN0OU9VYWkrTzlkSmRObHpoUmlL?= =?utf-8?B?RG5QVTZRR0M2clI4U1ZmUVBLaVh6dUdGL2VrTXdINEpVTmVuY1RJZ2tDZjFL?= =?utf-8?B?dGIxeHBjdm5rOUxjVURBazA0TGNxQTZ5RVc3eVhtVk53bkdGdklUS0tzUmpU?= =?utf-8?B?SzhudkVxL2xCV0NNWU1ia1RjTFVvZnhGMURoL3FXbXY1ZXhxMXVtZGIyVkxZ?= =?utf-8?Q?yZrVLFuQF+pplT6kcTzJ8MxOd5h0/rGIu6QygWH?= X-OriginatorOrg: windriver.com X-MS-Exchange-CrossTenant-Network-Message-Id: 98038a04-c0fb-4bc4-7603-08d937a205e9 X-MS-Exchange-CrossTenant-AuthSource: SN6PR11MB3008.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Jun 2021 06:25:27.5510 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ddb2873-a1ad-4a18-ae4e-4644631433be X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: B83Qw5+F7i8PB2/FkXZbxFem7+nzbAsF+PheBNB0yL75BE/6E1S4yfsiBSMJP3/wCCOQRnxp4As5Z7as0OAe9Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN6PR11MB2592 X-Proofpoint-ORIG-GUID: Qi3iWl_8zISEViGH9HFDGNvVGaxzw8wM X-Proofpoint-GUID: Qi3iWl_8zISEViGH9HFDGNvVGaxzw8wM X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-06-25_02:2021-06-24,2021-06-25 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=999 impostorscore=0 phishscore=0 lowpriorityscore=0 spamscore=0 clxscore=1015 mlxscore=0 malwarescore=0 adultscore=0 bulkscore=0 priorityscore=1501 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106250035 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Steve, I think my patch is the simplest way and has the least impact on original code. If now we let it only support single word, there will be much modification, e.g. 1. The 'while' loop will have no longer meaning to exist. The following lines also     need to be removed. 244         /* j increments twice per loop */ 245         len -= j / 2; 246         hex[j++] = ' '; 2. We need to comment on both seq_buf_putmem_hex() and trace_seq_putmem_hex(),     to prompt the caller not use more than 8 bytes of     data. Please consider my solution carefully. Or, I will develop a new patch to request review. Regards, Yun On 6/25/21 12:08 PM, Steven Rostedt wrote: > [Please note: This e-mail is from an EXTERNAL e-mail address] > > On Fri, 25 Jun 2021 11:41:35 +0800 > Yun Zhou wrote: > >> Hi Steve, >> >> Thanks very much for your friendly and clear feedback. >> >> Although in current kernel trace_seq_putmem_hex() is only used for >> single word, >> >> I think it should/need support longer data. These are my arguments: >> >> 1. The design of double loop is used to process more data. If only >> supports single word, >> >> the inner loop is enough, and the outer loop and the following >> lines are no longer needed. >> >> len -= j / 2; >> >> hex[j++] = ' '; >> >> 2. The last line above try to split two words/dwords with space. If only >> supports single word, >> >> this strange behavior is hard to understand. >> >> 3. If it only supports single word, I think parameter 'len' is redundant. > Not really, we have to differentiate char, short, int and long long. > >> 4. The comments of both seq_buf_putmem_hex() and trace_seq_putmem_hex() >> have not >> >> indicated the scope of 'len'. >> >> 5. If it only supports single word, we need to design a new function to >> support bigger block of data. >> >> I think it is redundant since the current function can perfectly >> deal with. >> >> 6. If follow my patch, it can support any length of data, including the >> single word. >> >> How do you think? > First, since you found a real bug, we need to just fix that first (single > word as is done currently). Because this needs to go to stable, and what > you are explaining above is an enhancement, and not something that needs to > be backported. > > Second, is there a use case? Honestly, I never use the "hex" version of the > output. That was only pulled in because it was implemented in the original > code that was in the rt patch. I wish we could just get rid of it. > > Thus, if there's a use case for handling more than one word, then I'm fine > with adding that enhancement. But if it is being done just because it can > be, then I don't think we should bother. > > What use case do you have in mind? > > Anyway, please send just a fix patch, and then we can discuss the merits of > this update later. I'd like the fix to be in ASAP. > > Thanks! > > -- Steve