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=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 06F6CC433ED for ; Wed, 15 Jul 2020 19:46:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CC37C20657 for ; Wed, 15 Jul 2020 19:46:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="uktTQeyy" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727819AbgGOTq4 (ORCPT ); Wed, 15 Jul 2020 15:46:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727813AbgGOTqz (ORCPT ); Wed, 15 Jul 2020 15:46:55 -0400 Received: from mail-oi1-x243.google.com (mail-oi1-x243.google.com [IPv6:2607:f8b0:4864:20::243]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C0309C061755 for ; Wed, 15 Jul 2020 12:46:55 -0700 (PDT) Received: by mail-oi1-x243.google.com with SMTP id j11so3140370oiw.12 for ; Wed, 15 Jul 2020 12:46:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=8s8DIxqCX1taMIxf+QVjIHqK8ir6JsrYpcjoKFdZtfo=; b=uktTQeyys1mhqwk8tvnsJ5n8vB+2wOUAsFBO00ycRflNQnZ8AdTvE7j/Nwj9zg7Gmf 2cHFTqKjsJWcHHwkK1Z8ujJTw/iB3KPGOMFBOQgM0PkzM7hhPu2m3ftPkcLYfljg0Tfk HJX4ySrFhrfQp0V6T70LJ0IUsXFQ57RkaJYrqjcJuqr7JmJ1vB3ArtWkK3cVCF2QSqst HFRGWEKeDSkzUGOOd4LkwRVs3x9eamdccBPhdZC9Zeu84a/T3yBw3ZkbP465imG1dGdG w6pySoFQNvA4edC6V8fHaFeW2KgfC1Dih1sEzLC0WtUNr/AElLvquB4Wl7WTn1ZU/eak UZGg== 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=8s8DIxqCX1taMIxf+QVjIHqK8ir6JsrYpcjoKFdZtfo=; b=X34XABkvPJbmtQV8rIU5VHvRH7xyTVA795aNsz5DA25RteMwBVFvt9r4EvIfaEVggg K5BWGkTS8izgehsuUjwio/BnXsr28Vn+qYZA8sKNeK8hiSxx1FAG8K9PZ82oPE+C07wc s9gsQYWhmDhetLIS5XKt62rY4cQVhtXDr9GHpzC6Ry6d3XGKBtMQWEq7+WQt4U+QSxPx r6a1bfChv6GPJQuEX0NpS+qWf8ArM9H0wQnWC0n4wnbKg6pCdKkTZBOzB3MPgi7d6uG3 5wleXTrh+TX64lDFQAbGIKMcO7Uj5mIVE2ADLNT3QiPxV/OTjP44bBj8K09Q2kJKTNy4 hkPw== X-Gm-Message-State: AOAM531cbu/LFsN6G0WYvpDPgGjyLhQKHecqCgtxAhdqswpnTb3gUj5b lvDMUb95HiB2U38IgcJ4Td5nJFh9bYFsrWrKNMM= X-Google-Smtp-Source: ABdhPJxv9kuSjgLLmWhB4S8Pt+KxiXznJ2PAww83lPqSdJ4fLMCzO4tw5paIimbu/SoJ3Q+j+uEyLI775QczS9Eeg8g= X-Received: by 2002:aca:ecc7:: with SMTP id k190mr1122219oih.92.1594842415202; Wed, 15 Jul 2020 12:46:55 -0700 (PDT) MIME-Version: 1.0 References: <20200714202934.42424-1-mike.palmiotto@crunchydata.com> In-Reply-To: From: Stephen Smalley Date: Wed, 15 Jul 2020 15:49:11 -0400 Message-ID: Subject: Re: [PATCH] libselinux: Use sestatus if open To: Mike Palmiotto 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 2:52 PM Mike Palmiotto wrote: > > 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. Recommend writing a little test program to exercise it first without bringing in all of the dbus baggage. Don't think Fedora is even using dbusd anymore, just dbus-broker. If you get stuck, feel free to send your patch and I can take a look too.