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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 C23A0C432C0 for ; Mon, 2 Dec 2019 10:08:32 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8B9A1217D9 for ; Mon, 2 Dec 2019 10:08:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="YqdYXI51" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8B9A1217D9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:33238 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ibid5-00009o-OU for qemu-devel@archiver.kernel.org; Mon, 02 Dec 2019 05:08:31 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:59588) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ibicH-0007kA-9f for qemu-devel@nongnu.org; Mon, 02 Dec 2019 05:07:46 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ibicF-0003lf-Sc for qemu-devel@nongnu.org; Mon, 02 Dec 2019 05:07:41 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:44522 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ibicF-0003l8-Op for qemu-devel@nongnu.org; Mon, 02 Dec 2019 05:07:39 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1575281257; 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=kyI8l8wqUY7ICon+CFSZrZH3K6oRjmtumQ//+v7q3PA=; b=YqdYXI51ndmK9BjoYl24HU8AXTv3FtU5lTjxq7MEVvVEdxFh2NRbr1q76mHukqhl9OWa/M QrMFN0MPf6R4nIDt8tz/18tBQKNnNW8iwALFcsKAl7uXqOjERfXgEtAldkNKyMb7PO7OyB ZaTY13CccE+zndVlH7SM7Y11alAAjDg= 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-361-8K3rSoDvO4WijdtKjuoVhw-1; Mon, 02 Dec 2019 05:07:36 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id ED9F610054E3 for ; Mon, 2 Dec 2019 10:07:35 +0000 (UTC) Received: from work-vm (unknown [10.36.118.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C001467648; Mon, 2 Dec 2019 10:07:33 +0000 (UTC) Date: Mon, 2 Dec 2019 10:07:31 +0000 From: "Dr. David Alan Gilbert" To: Paolo Bonzini Subject: Re: libcap vs libcap-ng mess Message-ID: <20191202100731.GB2904@work-vm> References: <20191128190408.GC3294@work-vm> <20191129093409.GB2260471@redhat.com> <98520a07-cf5d-a2a9-cfa4-944839b94c7c@redhat.com> <20191129180103.GA2840@work-vm> <1e59f880-1a62-3230-c56a-533f2b797525@redhat.com> <20191129182021.GD2837@work-vm> <20191129185400.GF2837@work-vm> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-MC-Unique: 8K3rSoDvO4WijdtKjuoVhw-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Thomas Huth , "P. Berrange, Daniel" , qemu-devel@nongnu.org, vgoyal@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Paolo Bonzini (pbonzini@redhat.com) wrote: > Il ven 29 nov 2019, 19:54 Dr. David Alan Gilbert ha > scritto: >=20 > > > Yes, it's per thread. The state can be built from > > > capng_clear/capng_get_caps_process + capng_update, and left in there > > > forever. There is also capng_save_state/capng_restore_state which, a= s > > > far as I can see from the sources, can be used across threads. > > > > So, I think what you're saying is I need to: > > a) Before we sandbox do the capng_get_caps_process > > >=20 > Why not after sandboxing? Because in our sandbox we don't have /proc and capng_get_caps_process tries to read /proc/.../status and fails. The old libcap code doesn't use /proc, it just uses capget (which the new one also uses). > If the code is in any way similar to the 9p > proxy, you have two states, "sandboxed with capabilities" and "sandboxed > without capabilities". The former (permitted=3Deffective) is what you get > after setresuid/setresgid, the other can be computed after sandboxing and > saved using capng_save_state. The FSETID capability can be updated > explicitly before/after capng_apply. >=20 > b) Before we start a new thread do a capng_save_state and restore it > > in the thread > > >=20 > Or just save after (a), and restore always before capng_apply. Hmm yes, that's easier. > a) This code is very local - it does a drop FSETID, a write, restore > > FSETID > > b) I'm not sure but I suspect it's used only in the non-uid=3D0 case; > > the whole thing is just a hack to cause setuid/setgid to be dropped > > in the case where it's written by a process that doesn't have FSETID > > (hmm I guess if the guest was root but didn't have fsetid then it would > > be 0?) > > >=20 > Yes it would. For uid!=3D0 the kernel clears the effective capabilities s= o it > shouldn't need to do anything, unless virtiodsd restores capabilities aft= er > setresuid/setresgid. >=20 > But are you suggesting I need to change something other than the > > effective caps in that case? > > >=20 > No, only the effective caps. OK, thanks. Dave > Paolo -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK