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 2B4B7C433E1 for ; Wed, 15 Jul 2020 18:52:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 079A020656 for ; Wed, 15 Jul 2020 18:52:27 +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="jKgAd/6c" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726634AbgGOSw0 (ORCPT ); Wed, 15 Jul 2020 14:52:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35680 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726086AbgGOSw0 (ORCPT ); Wed, 15 Jul 2020 14:52:26 -0400 Received: from mail-lf1-x143.google.com (mail-lf1-x143.google.com [IPv6:2a00:1450:4864:20::143]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EACD5C061755 for ; Wed, 15 Jul 2020 11:52:25 -0700 (PDT) Received: by mail-lf1-x143.google.com with SMTP id i80so1641348lfi.13 for ; Wed, 15 Jul 2020 11:52:25 -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=i7YueQdqAJYT+fpCto/bvYJkJ4ybanqp43vlLg3jdqM=; b=jKgAd/6cq9sk+c8tRgWSBQAWMz1AJJMSiDNrG4d5dxjToe8kykSbqhtgpUwpxRI1m+ iSsQn0PV2UtrqemPy0N1XF1fYAZxJRiIHhLuw2yBWz2t4j09OufWP1xS5KxHW6rvxo4U wfqzThLzU9r34BZSnKiIy7BWyarcJa0gV3PGYAwi5Aniay8kaPR0k9CluieJ+uoocDhx U7t7GjNB6jIB10eRXPeh3Sy/URMpwDA8cwJ+uD2wVmyREYFnYXmdwSFp4op2f+/C08S+ cIvXv+0TGkEiVU2AZwNJfkxEyLL4j3uD2H+TxpJLA2mo2Yjau5xr5vPZk/EGI3YMLvB+ uXpQ== 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=i7YueQdqAJYT+fpCto/bvYJkJ4ybanqp43vlLg3jdqM=; b=aSRYDELjtFcHannXZYPtAYQZi4Dial+qP4FEqWaG9FK4N5uQp8UvAduMvUTQosQVM0 8sGYzp4BZ+wJ60JqtT5iXTwwIxGOnvFnyddFiQyVIGPWrP69z96Nzx4yRRuR07LWvv0v raJ/6qKqzMJBfHxL6Oo0uLTR6whkXfVXA1OSytgxms2RMWnOIiy/nq3x0X8PFDWXzuGH bX6dPAynmegC81Pogws8qeTGiARGk9G4eF5IMfVnnJjoFs+8xdjLHnu16pwW97/xNyes ASbUeqymI8PsIYdsgfoCmNTGNQu8WoKmP7bVBqeSGVU7tnAV44ZxEGCoa70AM2tn6CRD kqzQ== X-Gm-Message-State: AOAM530Nn8cZ8wr7y5G5w3+HrUqe172eDEY9JLWGFigF/wZCvJeKLmwE EdwPm5VsHIukkYFbGYTCNFKXwRaqdh8gJqIhL7IdIw== X-Google-Smtp-Source: ABdhPJwHomwN5nKmAUL3j1kSugMVN7GrSNZ5RklUqQ7rZDY7b54H8J+qTzMwYhKpuoykYK891TFSD3kiVBKHn31G5lY= X-Received: by 2002:a19:8253:: with SMTP id e80mr200821lfd.199.1594839144224; Wed, 15 Jul 2020 11:52:24 -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 14:52:12 -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 1:10 PM Mike Palmiotto wrote: > > 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. Okay, maybe not that shortly. I tried your suggestion and dbus doesn't appear to receive the netlink messages. Initially I figured it had something to do with avc_create_thread(avc_netlink_loop) call still being in avc_init_internal, so I exposed the thread pointer in avc_internal.h and moved the call into avc_netlink_open, which seemed more appropriate. Still no dice. I'm probably doing something wrong -- I'll figure it out, but it's going to take me longer than I thought to track this down. -- Mike Palmiotto https://crunchydata.com