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=-4.0 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 26789C433E0 for ; Mon, 27 Jul 2020 04:22:10 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 7C4DC206E7 for ; Mon, 27 Jul 2020 04:22:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7C4DC206E7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-19453-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 28020 invoked by uid 550); 27 Jul 2020 04:22:02 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 27997 invoked from network); 27 Jul 2020 04:22:01 -0000 Date: Mon, 27 Jul 2020 05:21:06 +0100 From: Al Viro To: =?iso-8859-1?Q?Micka=EBl_Sala=FCn?= Cc: linux-kernel@vger.kernel.org, Aleksa Sarai , Alexei Starovoitov , Andrew Morton , Andy Lutomirski , Christian Brauner , Christian Heimes , Daniel Borkmann , Deven Bowers , Dmitry Vyukov , Eric Biggers , Eric Chiang , Florian Weimer , James Morris , Jan Kara , Jann Horn , Jonathan Corbet , Kees Cook , Lakshmi Ramasubramanian , Matthew Garrett , Matthew Wilcox , Michael Kerrisk , Mimi Zohar , Philippe =?iso-8859-1?Q?Tr=E9buchet?= , Scott Shell , Sean Christopherson , Shuah Khan , Steve Dower , Steve Grubb , Tetsuo Handa , Thibaut Sautereau , Vincent Strubel , kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org, Thibaut Sautereau Subject: Re: [PATCH v7 4/7] fs: Introduce O_MAYEXEC flag for openat2(2) Message-ID: <20200727042106.GB794331@ZenIV.linux.org.uk> References: <20200723171227.446711-1-mic@digikod.net> <20200723171227.446711-5-mic@digikod.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200723171227.446711-5-mic@digikod.net> Sender: Al Viro On Thu, Jul 23, 2020 at 07:12:24PM +0200, Mickaël Salaün wrote: > When the O_MAYEXEC flag is passed, openat2(2) may be subject to > additional restrictions depending on a security policy managed by the > kernel through a sysctl or implemented by an LSM thanks to the > inode_permission hook. This new flag is ignored by open(2) and > openat(2) because of their unspecified flags handling. When used with > openat2(2), the default behavior is only to forbid to open a directory. Correct me if I'm wrong, but it looks like you are introducing a magical flag that would mean "let the Linux S&M take an extra special whip for this open()". Why is it done during open? If the caller is passing it deliberately, why not have an explicit request to apply given torture device to an already opened file? Why not sys_masochism(int fd, char *hurt_flavour), for that matter?