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 Received: from second.openwall.net (second.openwall.net [193.110.157.125]) by smtp.lore.kernel.org (Postfix) with SMTP id EA477C2BD09 for ; Tue, 9 Jul 2024 10:06:49 +0000 (UTC) Received: (qmail 7760 invoked by uid 550); 9 Jul 2024 10:06:38 -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 7735 invoked from network); 9 Jul 2024 10:06:37 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1720519588; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tjTUnc7IhcTY8yXbQZCHDpYRmcDVvOi7wtfkPwMCZy4=; b=Jmxx1qkTxK7lv9nfnILaf/LRMAbZ0ZrxJsn9+rR2fGMZ3N0JczgUYyEgq6X4gqeiXBm3SP 91Nb3Ubn7bF44Uc96BfLUZCE/1eKPCbEtPCvp2tNpx1JvyV+tlm+a8PG1EjzNF/GBQG9fE RRSVW0Pm/eGfzhoKPvOkd5n749e0TNQ= X-MC-Unique: UiV9XaiFPlaMJoCqgi_zcA-1 From: Florian Weimer To: =?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?= Cc: Jeff Xu , Al Viro , Christian Brauner , Kees Cook , Linus Torvalds , Paul Moore , Theodore Ts'o , Alejandro Colomar , Aleksa Sarai , Andrew Morton , Andy Lutomirski , Arnd Bergmann , Casey Schaufler , Christian Heimes , Dmitry Vyukov , Eric Biggers , Eric Chiang , Fan Wu , Geert Uytterhoeven , James Morris , Jan Kara , Jann Horn , Jonathan Corbet , Jordan R Abrahams , Lakshmi Ramasubramanian , Luca Boccassi , Luis Chamberlain , "Madhavan T . Venkataraman" , Matt Bobrowski , Matthew Garrett , Matthew Wilcox , Miklos Szeredi , Mimi Zohar , Nicolas Bouchinet , Scott Shell , Shuah Khan , Stephen Rothwell , Steve Dower , Steve Grubb , Thibaut Sautereau , Vincent Strubel , Xiaoming Ni , Yin Fengwei , kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org Subject: Re: [RFC PATCH v19 1/5] exec: Add a new AT_CHECK flag to execveat(2) In-Reply-To: <20240709.gae4cu4Aiv6s@digikod.net> (=?utf-8?Q?=22Micka=C3=AB?= =?utf-8?Q?l_Sala=C3=BCn=22's?= message of "Tue, 9 Jul 2024 11:18:00 +0200") References: <20240704190137.696169-1-mic@digikod.net> <20240704190137.696169-2-mic@digikod.net> <87bk3bvhr1.fsf@oldenburg.str.redhat.com> <87ed83etpk.fsf@oldenburg.str.redhat.com> <87r0c3dc1c.fsf@oldenburg.str.redhat.com> <20240709.gae4cu4Aiv6s@digikod.net> Date: Tue, 09 Jul 2024 12:05:50 +0200 Message-ID: <87ed82283l.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 * Micka=C3=ABl Sala=C3=BCn: >> > If we want to avoid that, we could have an agreed-upon error code which >> > the LSM can signal that it'll never fail AT_CHECK checks, so we only >> > have to perform the extra system call once. > > I'm not sure to follow. Either we check executable code or we don't, > but it doesn't make sense to only check some parts (except for migration > of user space code in a system, which is one purpose of the securebits > added with the next patch). > > The idea with AT_CHECK is to unconditionnaly check executable right the > same way it is checked when a file is executed. User space can decide > to check that or not according to its policy (i.e. securebits). I meant it purely as a performance optimization, to skip future system calls if we know they won't provide any useful information for this process. In the grand scheme of things, the extra system call probably does not matter because we already have to do costly things like mmap. Thanks, Florian