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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 39318C433E2 for ; Fri, 28 Aug 2020 07:39:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F3A0720776 for ; Fri, 28 Aug 2020 07:39:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728397AbgH1Hjb convert rfc822-to-8bit (ORCPT ); Fri, 28 Aug 2020 03:39:31 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:28996 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726500AbgH1Hj3 (ORCPT ); Fri, 28 Aug 2020 03:39:29 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-266-Gqqjngt5NDyRwtlGJI5Pew-1; Fri, 28 Aug 2020 08:39:26 +0100 X-MC-Unique: Gqqjngt5NDyRwtlGJI5Pew-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Fri, 28 Aug 2020 08:39:25 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Fri, 28 Aug 2020 08:39:25 +0100 From: David Laight To: 'Kees Cook' , Denis Efremov CC: Julia Lawall , Joe Perches , "Gustavo A. R. Silva" , Greg Kroah-Hartman , "linux-usb@vger.kernel.org" , Rasmus Villemoes , "linux-kernel@vger.kernel.org" , cocci , "accessrunner-general@lists.sourceforge.net" , Alex Dewar Subject: RE: [Cocci] [PATCH] usb: atm: don't use snprintf() for sysfs attrs Thread-Topic: [Cocci] [PATCH] usb: atm: don't use snprintf() for sysfs attrs Thread-Index: AQHWfMBUatYqQRMSW0+Lm7S5UM8VU6lNInTw Date: Fri, 28 Aug 2020 07:39:25 +0000 Message-ID: <24d45f0868b74a3ba4924f031e968c55@AcuMS.aculab.com> References: <20200824222322.22962-1-alex.dewar90@gmail.com> <48f2dc90-7852-eaf1-55d7-2c85cf954688@rasmusvillemoes.dk> <20200827071537.GA168593@kroah.com> <20200827131819.7rcl2f5js3hkoqj2@lenovo-laptop> <20200827144846.yauuttjaqtxaldxg@lenovo-laptop> <5d1dfb9b031130d4d20763ec621233a19d6a88a2.camel@perches.com> <5853c58e-7d26-2cf9-6cbf-698ecd93cbf9@linux.com> <202008271517.ECC1F1F8F@keescook> In-Reply-To: <202008271517.ECC1F1F8F@keescook> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: aculab.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kees Cook > Sent: 27 August 2020 23:21 ... > > Agreed. This just makes me cringe. If the API design declares that when > a show() callback starts, buf has been allocated with PAGE_SIZE bytes, > then that's how the logic should proceed, and it should be using > scnprintf... > > show(...) { > size_t remaining = PAGE_SIZE; > > ... > remaining -= scnprintf(buf, remaining, "fmt", var args ...); > remaining -= scnprintf(buf, remaining, "fmt", var args ...); > remaining -= scnprintf(buf, remaining, "fmt", var args ...); Not quite what you had in mind, maybe: char *end = buf + PAGE_SIZE; buf += scnprintf(buf, end - buf, ...); return PAGE_SIZE - (end - buf); David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)