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,DKIM_SIGNED, DKIM_VALID,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 598A8C433E2 for ; Wed, 15 Jul 2020 17:10:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 239B02065E for ; Wed, 15 Jul 2020 17:10:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=crunchydata-com.20150623.gappssmtp.com header.i=@crunchydata-com.20150623.gappssmtp.com header.b="rrJiS0tP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725881AbgGORKs (ORCPT ); Wed, 15 Jul 2020 13:10:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48260 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725866AbgGORKs (ORCPT ); Wed, 15 Jul 2020 13:10:48 -0400 Received: from mail-lj1-x241.google.com (mail-lj1-x241.google.com [IPv6:2a00:1450:4864:20::241]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E4399C061755 for ; Wed, 15 Jul 2020 10:10:45 -0700 (PDT) Received: by mail-lj1-x241.google.com with SMTP id s9so3392261ljm.11 for ; Wed, 15 Jul 2020 10:10:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=crunchydata-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=BCSQ7RGQm/3ZIlRIJg+tpm5zgxFxA2ePOR+XjRj9POQ=; b=rrJiS0tPx2F7YsVvCv+abRo+uzri+VAK2wAzpjk1Fw2ixgLDOvGkM+uCa3swsvZbKv QhbUxLnz4wGg6JAq02/IQkgE/Q97ctq5kkbb7ci7K2naOINGF+pbCztRyvTA7guhr3tm pMaV+8A2QGoj5kfFfbTDnZK799bleCrrEna3YwHHExjVh1P56vZTljxgwkTxm6shWhCJ QRJ6yi4J/UgtsjFF0mscrp9DiLgB8zHll6+Eg/rxDDvD0RN+/fC2+uI00geU0KSAGiAo 3voY9TypfJCDpvd+irvVqXvLtn4uuS177o2t7iuaroQgSJ/CDlvknTTbAcyA9Qrkg9an S++A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=BCSQ7RGQm/3ZIlRIJg+tpm5zgxFxA2ePOR+XjRj9POQ=; b=gowxC3OVSPc2zaprP3kA8H1zrm6hKqG0QQ4oGvLdOjKCGiFL3IJwkmbPXiztmGCgnJ uWHBkP5kgmy1GC2dEuLuEl+ycZR4V4k39dujrUOfZayvj8C9H62W9+zUgIhbMRHIgu4t 1ztmbpZ8Mc+2uM8+eZSOTl9UuBRiOwy9bTMbZXSfkxvrdvYchNo60AHBZp1hAC4kvWwU 9h6EDUR8zz/Qa1jxgb4+feCR3WLiThRyheLYpeHvOekuUAkXoXh0mBjgtck49fKFAmWT GYx5s6pDpInrRSVEzKr4aM3v67zSXIMvCIAz4L9Sp2hKclZOHWwpOWLtZwQ7nVOlunfe 6KQQ== X-Gm-Message-State: AOAM530zKdrsK1PXk7PxLuT68aSFgHWqZZwaMYdff28I4NRkeK/wip60 i6Cm7rC9YC1wDIjdHbYdIMBBmSiU3I3OEZg5ce8DZQ== X-Google-Smtp-Source: ABdhPJzW8EEvBSoqWY4aSPia5Y5oASuYYtoGaOYZQXzJCFhpynazrV+mjjBWcF3PfrZOJCn1u14lGbPWVtIxqoaOO7k= X-Received: by 2002:a05:651c:106e:: with SMTP id y14mr66878ljm.49.1594833043294; Wed, 15 Jul 2020 10:10:43 -0700 (PDT) MIME-Version: 1.0 References: <20200714202934.42424-1-mike.palmiotto@crunchydata.com> In-Reply-To: From: Mike Palmiotto Date: Wed, 15 Jul 2020 13:10:31 -0400 Message-ID: Subject: Re: [PATCH] libselinux: Use sestatus if open To: Stephen Smalley Cc: SElinux list Content-Type: text/plain; charset="UTF-8" Sender: selinux-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org On Wed, Jul 15, 2020 at 12:28 PM Stephen Smalley wrote: > > On Wed, Jul 15, 2020 at 12:04 PM Mike Palmiotto > wrote: > > > > On Tue, Jul 14, 2020 at 6:42 PM Mike Palmiotto > > wrote: > > > > > > On Tue, Jul 14, 2020 at 5:35 PM Stephen Smalley > > > wrote: > > > > > > > > On Tue, Jul 14, 2020 at 5:20 PM Mike Palmiotto > > > > wrote: > > > > > > > Do you think we should go ahead and completely swap in sestatus? I was > > > > > just worried about breaking userspace object managers that are > > > > > currently using netlink threads by default, for instance > > > > > systemd-dbusd. I can spend some more time getting those to work with > > > > > the status page if you think that's worthwhile. > > > > > > > > I'd be interested in understanding the impact of such a change on > > > > existing userspace object managers. If we can switch the default > > > > behavior for applications that are not explicitly using > > > > avc_netlink_*() interfaces themselves (e.g. they are only using > > > > selinux_check_access or avc_has_perm), then that would be beneficial > > > > since I think it fully removes the need for a system call on the AVC > > > > cache-hit code path. > > > > > > I'll have to do a bit of digging to see how this will affect dbus, et > > > al. On first blush, it looks like they're just doing > > > avc_netlink_check_nb() in their watch thread. Presumably other object > > > managers are doing something similar so we would just need to make > > > sure there is a netlink fd available. > > > > So it looks like dbus (at least) is directly checking for a netlink > > socket[1], so just doing away with the avc_netlink_open call wouldn't > > work out. My thinking is we have two options: > > > > 1) Add a new seopt to use sestatus and let userspace object managers opt-in > > > > 2) Call both selinux_status_open and avc_netlink_open in > > avc_init_internal. This would satisfy the hard requirement for a > > netlink socket. Then we can default to using sestatus in all of the > > netlink processing paths, as you suggested in your last reply. We > > could > > > > Option 2 seems better from the standpoint of using sestatus by > > default, but it looks like recvfrom will never be called and the > > messages will just sit in kernel memory. > > > > I'm inclined to go with option 1 at this point. > > > > [1] https://gitlab.freedesktop.org/dbus/dbus/-/blob/master/bus/selinux.c#L269 > > Couldn't we change avc_netlink_acquire_fd() to test whether fd hasn't > yet been set (i.e. == -1) and call avc_netlink_open() in that case? > Then dbus would still gets its netlink fd as expected but we wouldn't > need to open it inside of avc_init? Much better. I'll send a new patch up shortly. -- Mike Palmiotto https://crunchydata.com