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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 E5A52C04AB4 for ; Fri, 17 May 2019 16:14:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C1EFA2168B for ; Fri, 17 May 2019 16:14:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729443AbfEQQOH convert rfc822-to-8bit (ORCPT ); Fri, 17 May 2019 12:14:07 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:21021 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729175AbfEQQOH (ORCPT ); Fri, 17 May 2019 12:14:07 -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-86-z4caW1bFMVyOh5eJcQm2Ag-1; Fri, 17 May 2019 17:14:04 +0100 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b::d117) by AcuMS.aculab.com (fd9f:af1c:a25b::d117) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Fri, 17 May 2019 17:14:03 +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, 17 May 2019 17:14:03 +0100 From: David Laight To: 'Kees Cook' CC: 'Jan Kara' , Dan Williams , "linux-nvdimm@lists.01.org" , "stable@vger.kernel.org" , Jeff Moyer , Ingo Molnar , Christoph Hellwig , Al Viro , Thomas Gleixner , Matthew Wilcox , Jeff Smits , "linux-fsdevel@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH] libnvdimm/pmem: Bypass CONFIG_HARDENED_USERCOPY overhead Thread-Topic: [PATCH] libnvdimm/pmem: Bypass CONFIG_HARDENED_USERCOPY overhead Thread-Index: AQHVDI00Hs6UetBw5UmdJ+47dYtmSqZvBeSAgABhswCAABTF4A== Date: Fri, 17 May 2019 16:14:03 +0000 Message-ID: References: <155805321833.867447.3864104616303535270.stgit@dwillia2-desk3.amr.corp.intel.com> <20190517084739.GB20550@quack2.suse.cz> <2d8b1ba7890940bf8a512d4eef0d99b3@AcuMS.aculab.com> <201905170845.1B4E2A03@keescook> In-Reply-To: <201905170845.1B4E2A03@keescook> 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: z4caW1bFMVyOh5eJcQm2Ag-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Kees Cook > Sent: 17 May 2019 16:54 ... > > I've changed some of our code to use __get_user() to avoid > > these stupid overheads. > > __get_user() skips even access_ok() checking too, so that doesn't seem > like a good idea. Did you run access_ok() checks separately? (This > generally isn't recommended.) Of course, I'm not THAT stupid :-) David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)