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 A4C62C433EF for ; Sat, 11 Dec 2021 17:53:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230412AbhLKRxw convert rfc822-to-8bit (ORCPT ); Sat, 11 Dec 2021 12:53:52 -0500 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.85.151]:23078 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230363AbhLKRxu (ORCPT ); Sat, 11 Dec 2021 12:53:50 -0500 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-14-gpculCQTMuGutzfqbGQ0WA-1; Sat, 11 Dec 2021 17:53:47 +0000 X-MC-Unique: gpculCQTMuGutzfqbGQ0WA-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.26; Sat, 11 Dec 2021 17:53:46 +0000 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.026; Sat, 11 Dec 2021 17:53:46 +0000 From: David Laight To: 'Tiezhu Yang' , Dave Young , Baoquan He , Vivek Goyal , Andrew Morton CC: "linux-arm-kernel@lists.infradead.org" , "linux-ia64@vger.kernel.org" , "linux-mips@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-riscv@lists.infradead.org" , "linux-sh@vger.kernel.org" , "x86@kernel.org" , "linux-fsdevel@vger.kernel.org" , "kexec@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Xuefeng Li Subject: RE: [PATCH v2 0/2] kdump: simplify code Thread-Topic: [PATCH v2 0/2] kdump: simplify code Thread-Index: AQHX7j/jzYqw5kMpA0qY43nH0kUm2Kwtku5w Date: Sat, 11 Dec 2021 17:53:46 +0000 Message-ID: <0c5cb37139af4f3e85cc2c5115d7d006@AcuMS.aculab.com> References: <1639193588-7027-1-git-send-email-yangtiezhu@loongson.cn> In-Reply-To: <1639193588-7027-1-git-send-email-yangtiezhu@loongson.cn> 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 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: Tiezhu Yang > Sent: 11 December 2021 03:33 > > v2: > -- add copy_to_user_or_kernel() in lib/usercopy.c > -- define userbuf as bool type Instead of having a flag to indicate whether the buffer is user or kernel, would it be better to have two separate buffer pointers. One for a user space buffer, the other for a kernel space buffer. Exactly one of the buffers should always be NULL. That way the flag is never incorrectly set. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)