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 6613AC38A2A for ; Sun, 10 May 2020 14:34:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 45CDD20725 for ; Sun, 10 May 2020 14:34:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729113AbgEJOeI convert rfc822-to-8bit (ORCPT ); Sun, 10 May 2020 10:34:08 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:27454 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728849AbgEJOeI (ORCPT ); Sun, 10 May 2020 10:34:08 -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-46-WIrgiLb1OoGiMrDQB_cpGw-1; Sun, 10 May 2020 15:34:04 +0100 X-MC-Unique: WIrgiLb1OoGiMrDQB_cpGw-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; Sun, 10 May 2020 15:34:04 +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; Sun, 10 May 2020 15:34:04 +0100 From: David Laight To: 'Al Viro' , "linux-kernel@vger.kernel.org" CC: Linus Torvalds , "linux-fsdevel@vger.kernel.org" Subject: RE: [PATCHES] uaccess simple access_ok() removals Thread-Topic: [PATCHES] uaccess simple access_ok() removals Thread-Index: AQHWJltq6fE30OjG4EOuI+zbUBs5vKihYCkw Date: Sun, 10 May 2020 14:34:04 +0000 Message-ID: <847a5160e4e64a82962dc1531cd52e11@AcuMS.aculab.com> References: <20200509234124.GM23230@ZenIV.linux.org.uk> In-Reply-To: <20200509234124.GM23230@ZenIV.linux.org.uk> 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-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com 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: Al Viro > Sent: 10 May 2020 00:41 > > One of the uaccess-related branches; this one is just the > cases when access_ok() calls are trivially pointless - the address > in question gets fed only to primitives that do access_ok() checks > themselves. There is also the check in rw_copy_check_uvector() that should always be replicated by the copy_to/from_user() in _copy_to/from_iter(). And the strange call to rw_copy_check_uvector() in mm/process_vm_access.c which carefully avoids the access_ok() check for the target process. I did a quick look, but failed to see an obvious check further down the call path. The code is doing a read/write from another process, not sure when it is used - not by gdb. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)