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 B4E66C432C0 for ; Fri, 29 Nov 2019 18:24:50 +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 7E89D21736 for ; Fri, 29 Nov 2019 18:24:50 +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="cVEfI9ky" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7E89D21736 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]:33468 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iakwi-0003dR-MX for qemu-devel@archiver.kernel.org; Fri, 29 Nov 2019 13:24:49 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:34203) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iaksg-0002j0-AA for qemu-devel@nongnu.org; Fri, 29 Nov 2019 13:20:39 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iaksX-00027u-W9 for qemu-devel@nongnu.org; Fri, 29 Nov 2019 13:20:31 -0500 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:49923) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iaksX-000233-R3 for qemu-devel@nongnu.org; Fri, 29 Nov 2019 13:20:29 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1575051628; 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=7f76va/W8GqafPCpbkjbcbHwllHVm+aQ8mBHggg2PrA=; b=cVEfI9kyV8nIYxAeoLUvctOyqBesizyfFwZFhkDv5EGFiAk2gKusVogc8tj8Dg4mEi8/rz QPxDHokQ5D/igo216BqY960vAxdWsfIJt+6DI2z14KFMXpPfl8hYG5Cbi01Z1yFGMgjFE+ r/6vYZKeg01ItzaRHmjmY70YD5igRKg= 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-10-nxrqzeumPzazHXFyFpTvxg-1; Fri, 29 Nov 2019 13:20:25 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D81EF10054E3 for ; Fri, 29 Nov 2019 18:20:24 +0000 (UTC) Received: from work-vm (ovpn-117-253.ams2.redhat.com [10.36.117.253]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 997E75D9C9; Fri, 29 Nov 2019 18:20:23 +0000 (UTC) Date: Fri, 29 Nov 2019 18:20:21 +0000 From: "Dr. David Alan Gilbert" To: Paolo Bonzini Subject: Re: libcap vs libcap-ng mess Message-ID: <20191129182021.GD2837@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> MIME-Version: 1.0 In-Reply-To: <1e59f880-1a62-3230-c56a-533f2b797525@redhat.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-MC-Unique: nxrqzeumPzazHXFyFpTvxg-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: 205.139.110.61 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: thuth@redhat.com, Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , 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: > On 29/11/19 19:01, Dr. David Alan Gilbert wrote: > >> It's not entirely trivial because fsdev-proxy-helper wants to keep the > >> effective set and clear the permitted set; in libcap-ng you can only > ^^^^^ >=20 > (Wrong, this is "modify" the permitted set. The permitted set is > already cleared by setresuid/setresgid). >=20 > >> apply both sets at once, and you cannot choose only one of them in > >> capng_clear/capng_get_caps_process. But it's doable, I'll take a look= . > > I'm having some difficulties making the same conversion for virtiofsd; > > all it wants to do is drop (and later recover) CAP_FSETID > > from it's effective set; so I'm calling capng_get_caps_process > > (it used to be cap_get_proc). While libcap survives just using the > > capget syscall, libcap-ng wants to read /proc//status - and > > that's a problem because we're in a sandbox without /proc mounted > > at that point. >=20 > The state of libcap-ng persists after capng_apply. So you can just call > capng_update({CAP_ADD,CAP_DROP}) followed by capng_apply. But the internal state needs initialising doesn't it? So that when you capng_update it tweaks a set that was originally read from somewhere? (and that's per-thread?) > Does virtiofsd have to do uid/gid dances like virtfs-proxy-helper? It looks like it; I can see setresuid calls to save and restore euid/egid. Dave > Thanks, >=20 > Paolo >=20 -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK