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=-3.8 required=3.0 tests=BAYES_00, 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 4850FC49EA7 for ; Thu, 24 Jun 2021 07:21:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2EA9D613EE for ; Thu, 24 Jun 2021 07:21:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231486AbhFXHXj convert rfc822-to-8bit (ORCPT ); Thu, 24 Jun 2021 03:23:39 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]:48775 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231132AbhFXHXh (ORCPT ); Thu, 24 Jun 2021 03:23:37 -0400 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mtapsc-5-gGbqqVa_MamySoR60Cs1mA-1; Thu, 24 Jun 2021 08:21:16 +0100 X-MC-Unique: gGbqqVa_MamySoR60Cs1mA-1 Received: from AcuMS.Aculab.com (10.202.163.4) by AcuMS.aculab.com (10.202.163.4) with Microsoft SMTP Server (TLS) id 15.0.1497.18; Thu, 24 Jun 2021 08:21:15 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.018; Thu, 24 Jun 2021 08:21:15 +0100 From: David Laight To: 'Kees Cook' CC: 'Guillaume Tucker' , Shuah Khan , "stable@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH v2] selftests/lkdtm: Use /bin/sh not $SHELL Thread-Topic: [PATCH v2] selftests/lkdtm: Use /bin/sh not $SHELL Thread-Index: AQHXaCznpjkpNTpwjEW+kA8o/GdKZashmKhggAAdGgCAABKuUIAAWbwAgACepjA= Date: Thu, 24 Jun 2021 07:21:15 +0000 Message-ID: References: <20210619025834.2505201-1-keescook@chromium.org> <42f26361db6f481e980ac349bf0079ef@AcuMS.aculab.com> <202106230917.FE2F587@keescook> <76a575d1364a47458d27c76c65b673b6@AcuMS.aculab.com> <202106231231.9B858B95A@keescook> In-Reply-To: <202106231231.9B858B95A@keescook> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kees Cook > Sent: 23 June 2021 23:47 > > On Wed, Jun 23, 2021 at 04:27:47PM +0000, David Laight wrote: ... > > You can probably even do: > > > > echo "$test" | /bin/sh -c cat >$TRIGGER || true > > > > (moving the redirect to the outer shell). > > Actually, it looks like the "write" is already happening in the exec'd > process, so this can just be: > > echo "$test" | cat >$TRIGGER || true > > But it still can't be: > > echo "$test" >$TRIGGER > > which is what I had over-engineered a solution to. :) That one fails because echo is the shell builtin. But: /bin/echo "$test" >$TRIGGER should be fine. Quite where the original came from I not sure I want to find out. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)