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=-0.8 required=3.0 tests=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 831D0C352AA for ; Tue, 1 Oct 2019 14:36:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5661120842 for ; Tue, 1 Oct 2019 14:36:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389056AbfJAOgW convert rfc822-to-8bit (ORCPT ); Tue, 1 Oct 2019 10:36:22 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([146.101.78.151]:37232 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727143AbfJAOgW (ORCPT ); Tue, 1 Oct 2019 10:36:22 -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-217-OO_eyhEkOW2W7nALFS7WXw-1; Tue, 01 Oct 2019 15:36:10 +0100 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; Tue, 1 Oct 2019 15:36:09 +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; Tue, 1 Oct 2019 15:36:09 +0100 From: David Laight To: 'Dan Carpenter' , Denis Efremov CC: "devel@driverdev.osuosl.org" , Jes Sorensen , Greg Kroah-Hartman , "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" , Hans de Goede , Bastien Nocera , Dmitry Vyukov , Larry Finger Subject: RE: [PATCH] staging: rtl8723bs: hal: Fix memcpy calls Thread-Topic: [PATCH] staging: rtl8723bs: hal: Fix memcpy calls Thread-Index: AQHVd36LU5ikVLKK6EuvH5wLNYQtMKdEMyLwgAGeKE+AAAh2kA== Date: Tue, 1 Oct 2019 14:36:09 +0000 Message-ID: <8d2e8196cae74ec4ae20e9c23e898207@AcuMS.aculab.com> References: <20190930110141.29271-1-efremov@linux.com> <37b195b700394e95aa8329afc9f60431@AcuMS.aculab.com> <20191001135649.GH22609@kadam> In-Reply-To: <20191001135649.GH22609@kadam> Accept-Language: en-GB, en-US Content-Language: 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-MC-Unique: OO_eyhEkOW2W7nALFS7WXw-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > From: Dan Carpenter > Sent: 01 October 2019 14:57 > Subject: Re: [PATCH] staging: rtl8723bs: hal: Fix memcpy calls ... > That's true for glibc memcpy() but not for the kernel memcpy(). In the > kernel there are lots of places which do a zero size memcpy(). And probably from NULL (or even garbage) pointers. After all a pointer to the end of an array (a + ARRAY_SIZE(a)) is valid but must not be dereferenced - so memcpy() can't dereference it's source address when the length is zero. > The glibc attitude is "the standard allows us to put knives here" so > let's put knives everywhere in the path. And the GCC attitude is let's > silently remove NULL checks instead of just printing a warning that the > NULL check isn't required... It could really make someone despondent. gcc is the one that add knives... This reminds me of me of a compiler that decided to optimise away checks for function addresses being NULL. At almost exactly the same time that ELF allowed for undefined weak symbols. Checking whether a function was actually present was non-trivial. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)