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 51EAFC4332F for ; Fri, 25 Nov 2022 15:27:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229606AbiKYP1O convert rfc822-to-8bit (ORCPT ); Fri, 25 Nov 2022 10:27:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49738 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229452AbiKYP1N (ORCPT ); Fri, 25 Nov 2022 10:27:13 -0500 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.85.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5534221888 for ; Fri, 25 Nov 2022 07:27:12 -0800 (PST) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-98-qxRf-fgQM2mvgZarnXUlzg-1; Fri, 25 Nov 2022 15:27:09 +0000 X-MC-Unique: qxRf-fgQM2mvgZarnXUlzg-1 Received: from AcuMS.Aculab.com (10.202.163.6) by AcuMS.aculab.com (10.202.163.6) with Microsoft SMTP Server (TLS) id 15.0.1497.42; Fri, 25 Nov 2022 15:27:07 +0000 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.044; Fri, 25 Nov 2022 15:27:07 +0000 From: David Laight To: 'Andy Shevchenko' CC: LKML , Andrew Morton , Steven Rostedt , "'Joe Perches'" , Linus Torvalds Subject: RE: [PATCH 0/1] Slightly relax the type checking done by min() and max(). Thread-Topic: [PATCH 0/1] Slightly relax the type checking done by min() and max(). Thread-Index: AdkA3hAUrkOWi1xYRg2SAA6P778SAwAA2U8AAAAaTjA= Date: Fri, 25 Nov 2022 15:27:07 +0000 Message-ID: <7e594ad64e444d448c747688b8f28249@AcuMS.aculab.com> References: In-Reply-To: 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 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andy Shevchenko > Sent: 25 November 2022 15:21 > > On Fri, Nov 25, 2022 at 03:00:40PM +0000, David Laight wrote: > > The min() and max() defines include a type check to avoid the unexpected > > behaviour when a negative value is compared against and unsigned value. > > However a lot of code hits this check and uses min_t() to avoid the error. > > Many of these are just plain wrong. > > > > Those casting to u8 or u16 are particularly suspect, eg: > > drivers/usb/misc/usb251xb.c:528: > > hub->max_current_sp = min_t(u8, property_u32 / 2000, 50); > > I don't buy this. What's exactly wrong with this code? Consider what happens if propery_u32 is 512000. The returned value is 0 not 50. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)