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=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 267B5C56202 for ; Tue, 24 Nov 2020 18:03:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B1532208CA for ; Tue, 24 Nov 2020 18:03:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="F3cHrruK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403966AbgKXSDJ (ORCPT ); Tue, 24 Nov 2020 13:03:09 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:57101 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2403997AbgKXSDJ (ORCPT ); Tue, 24 Nov 2020 13:03:09 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606240987; 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: in-reply-to:in-reply-to:references:references; bh=JQRdCyEjd8lB1hJnU6FBbehjJrMGCDIdPwywH5xUhec=; b=F3cHrruKqokAUNYMyINP8ywhDlYxdjZSGEK6bqix/Lkth1CVIoByODRo17H0EZB24UgieP N5LCsvSlUs6NAhejkRQDyG6X+tB2KTEgHGZJpGAiAKIQmfTCy4aVtGGyhV41+8p5oSQwJO ox0GayFsHQhi0k/dngXHfi6mECjmPRA= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-350-IEMlTEUgMoO_v_UEUqZUmA-1; Tue, 24 Nov 2020 13:03:03 -0500 X-MC-Unique: IEMlTEUgMoO_v_UEUqZUmA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5802A18C43C7; Tue, 24 Nov 2020 18:03:01 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-112-141.ams2.redhat.com [10.36.112.141]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 770F75D6AB; Tue, 24 Nov 2020 18:02:55 +0000 (UTC) From: Florian Weimer To: Jann Horn Cc: Christoph Hellwig , Kees Cook , Andy Lutomirski , Will Drewry , Mark Wielaard , Christian Brauner , Linux API , "open list:DOCUMENTATION" , kernel list , dev@opencontainers.org, Jonathan Corbet , "Carlos O'Donell" Subject: Re: [PATCH] syscalls: Document OCI seccomp filter interactions & workaround References: <87lfer2c0b.fsf@oldenburg2.str.redhat.com> <20201124122639.x4zqtxwlpnvw7ycx@wittgenstein> <878saq3ofx.fsf@oldenburg2.str.redhat.com> <20201124164546.GA14094@infradead.org> Date: Tue, 24 Nov 2020 19:02:53 +0100 In-Reply-To: (Jann Horn's message of "Tue, 24 Nov 2020 18:06:38 +0100") Message-ID: <87pn42zl82.fsf@oldenburg2.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org * Jann Horn: > +seccomp maintainers/reviewers > [thread context is at > https://lore.kernel.org/linux-api/87lfer2c0b.fsf@oldenburg2.str.redhat.com/ > ] > > On Tue, Nov 24, 2020 at 5:49 PM Christoph Hellwig wrote: >> On Tue, Nov 24, 2020 at 03:08:05PM +0100, Mark Wielaard wrote: >> > For valgrind the issue is statx which we try to use before falling back >> > to stat64, fstatat or stat (depending on architecture, not all define >> > all of these). The problem with these fallbacks is that under some >> > containers (libseccomp versions) they might return EPERM instead of >> > ENOSYS. This causes really obscure errors that are really hard to >> > diagnose. >> >> So find a way to detect these completely broken container run times >> and refuse to run under them at all. After all they've decided to >> deliberately break the syscall ABI. (and yes, we gave the the rope >> to do that with seccomp :(). > > FWIW, if the consensus is that seccomp filters that return -EPERM by > default are categorically wrong, I think it should be fairly easy to > add a check to the seccomp core that detects whether the installed > filter returns EPERM for some fixed unused syscall number and, if so, > prints a warning to dmesg or something along those lines... But that's playing Core Wars, right? Someone will write a seccomp filter trying to game that kernel check. I don't really think it solves anything until there is consensus what a system call filter should do with system calls not on the permitted list. Thanks, Florian -- Red Hat GmbH, https://de.redhat.com/ , Registered seat: Grasbrunn, Commercial register: Amtsgericht Muenchen, HRB 153243, Managing Directors: Charles Cachera, Brian Klemm, Laurie Krebs, Michael O'Neill