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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 393A7C43461 for ; Mon, 7 Sep 2020 10:35:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 074EC20768 for ; Mon, 7 Sep 2020 10:35:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728186AbgIGKfj (ORCPT ); Mon, 7 Sep 2020 06:35:39 -0400 Received: from foss.arm.com ([217.140.110.172]:60366 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728637AbgIGKfU (ORCPT ); Mon, 7 Sep 2020 06:35:20 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2B137106F; Mon, 7 Sep 2020 03:35:20 -0700 (PDT) Received: from arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CCDF53F66E; Mon, 7 Sep 2020 03:35:18 -0700 (PDT) Date: Mon, 7 Sep 2020 11:35:16 +0100 From: Dave Martin To: Boyan Karatotev Cc: Shuah Khan , boian4o1@gmail.com, Catalin Marinas , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, amit.kachhap@arm.com, vincenzo.frascino@arm.com, Will Deacon , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 3/4] kselftests/arm64: add PAuth test for whether exec() changes keys Message-ID: <20200907103516.GO6642@arm.com> References: <20200831110450.30188-1-boyan.karatotev@arm.com> <20200831110450.30188-4-boyan.karatotev@arm.com> <20200902170854.GK6642@arm.com> <926691e4-1990-207e-bcb9-40ab6d3b0fa0@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <926691e4-1990-207e-bcb9-40ab6d3b0fa0@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Thu, Sep 03, 2020 at 11:48:37AM +0100, Boyan Karatotev wrote: > On 02/09/2020 18:08, Dave Martin wrote: > > On Mon, Aug 31, 2020 at 12:04:49PM +0100, Boyan Karatotev wrote: > >> +/* > >> + * fork() does not change keys. Only exec() does so call a worker program. > >> + * Its only job is to sign a value and report back the resutls > >> + */ > >> +TEST(exec_unique_keys) > >> +{ > > > > The kernel doesn't guarantee that keys are unique. > > > > Can we present all the "unique keys" wording differently, say > > > > exec_key_collision_likely() > > I agree that this test's name is a bit out of place. I would rather have > it named "exec_changed_keys" though. > > > Otherwise people might infer from this test code that the keys are > > supposed to be truly unique and start reporting bugs on the kernel. > > > > I can't see an obvious security argument for unique keys (rather, the > > keys just need to be "unique enough". That's the job of > > get_random_bytes().) > > The "exec_unique_keys" test only checks that the keys changed after an > exec() which I think the name change would reflect. > > The thing with the "single_thread_unique_keys" test is that the kernel > says the the keys will be random. Yes, there is no uniqueness guarantee > but I'm not sure how to phrase it differently. There is some minuscule > chance that the keys end up the same, but for this test I pretend this > will not happen. Would changing up the comments and the failure message > communicate this? Maybe substitute "unique" for "different" and say how > many keys clashed? Yes, something like that seems reasonable. Cheers ---Dave