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 8EC2DC432C0 for ; Fri, 29 Nov 2019 18:18:00 +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 5921A2158A for ; Fri, 29 Nov 2019 18:18:00 +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="TuiiJtdV" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5921A2158A 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]:33432 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iakq7-0001Ty-Je for qemu-devel@archiver.kernel.org; Fri, 29 Nov 2019 13:17:59 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:47382) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iakkk-0007tM-UI for qemu-devel@nongnu.org; Fri, 29 Nov 2019 13:12:28 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iakke-0006av-MA for qemu-devel@nongnu.org; Fri, 29 Nov 2019 13:12:21 -0500 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:60758 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iakke-0006XY-9W for qemu-devel@nongnu.org; Fri, 29 Nov 2019 13:12:20 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1575051139; 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=dwg2Z5Y02hhVxGbPEesgaw/C+JhjkJ4a8QmxgSQLLOs=; b=TuiiJtdVFiaHL9XJibEoVVw0RxYkDhdwupuFBLcadiRTy9jQGePNO8fWVl9FlyohQCvgHl q4ejnK78AYPbsWDQhmMgeyfm4lkfUS85gCLaj1biEaeu/9iKz81W5wcgFNLFnreuLV0CUj 4UCDfuNwu6fsGz+5a1xaFVxo/b8GIgs= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-239-ySvN6yQXObCWg3EZWVa9fg-1; Fri, 29 Nov 2019 13:12:17 -0500 Received: by mail-wm1-f69.google.com with SMTP id l11so4824012wmi.0 for ; Fri, 29 Nov 2019 10:12:17 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=dwg2Z5Y02hhVxGbPEesgaw/C+JhjkJ4a8QmxgSQLLOs=; b=ClsYrG39MlJT3PyPWsA6H/ddNE6R9AOtzhGmBkwoWqxQzy+mYANScZ6vSBLkxRiyfC cMdLbbXIkZ5hSTklkWS6T4wtyUCOMr5tCbr51hKvV6TXofMZOhKnN7fmmNxJ4dqbNndC u3q7pbFJVf7U56S6Uf0bCoGJjXwXYHJvHxcQUI0ImI5/RUPSJtUCpDDkOTN5/z37El+Y a0eyYrv4GgleF14N51hPIViuWZVzpQ1pjfmALaSlwQPwTpqaFik5JdF79KDfE7somMP1 sHP4Jujk/wadlG97cw/BNiFZS9l6pfaCLl9x6Ivo9eoWAbrWQ2UKCmVPANYQxNgIcdse i+pA== X-Gm-Message-State: APjAAAUjSR5QLBjO5lYXlT90Rq62qo8b5gccNcWOcCacASSj51Opvbzy 0HQTyQsqvdQDuIXc6Tv4dHdLY1QZMeI6ull+La+pOo9LAeWYujURd8o2vZGLWr5Co9+2CPRqkA2 w5cu9aqiaQL3cIJI= X-Received: by 2002:adf:fe8c:: with SMTP id l12mr8204877wrr.215.1575051136735; Fri, 29 Nov 2019 10:12:16 -0800 (PST) X-Google-Smtp-Source: APXvYqx6t5o2r4dvDEZl4JeqFvCM6ebxnwpn+2cHrpGTHXg+pBhwLiH9heGod4/GXWLpn/QBKpvgAA== X-Received: by 2002:adf:fe8c:: with SMTP id l12mr8204846wrr.215.1575051136462; Fri, 29 Nov 2019 10:12:16 -0800 (PST) Received: from ?IPv6:2001:b07:6468:f312:56e1:adff:fed9:caf0? ([2001:b07:6468:f312:56e1:adff:fed9:caf0]) by smtp.gmail.com with ESMTPSA id i71sm31111832wri.68.2019.11.29.10.12.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 29 Nov 2019 10:12:15 -0800 (PST) Subject: Re: libcap vs libcap-ng mess To: "Dr. David Alan Gilbert" References: <20191128190408.GC3294@work-vm> <20191129093409.GB2260471@redhat.com> <98520a07-cf5d-a2a9-cfa4-944839b94c7c@redhat.com> <20191129180103.GA2840@work-vm> From: Paolo Bonzini Message-ID: <1e59f880-1a62-3230-c56a-533f2b797525@redhat.com> Date: Fri, 29 Nov 2019 19:12:14 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20191129180103.GA2840@work-vm> Content-Language: en-US X-MC-Unique: ySvN6yQXObCWg3EZWVa9fg-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 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, =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , qemu-devel@nongnu.org, vgoyal@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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 ^^^^^ (Wrong, this is "modify" the permitted set. The permitted set is already cleared by setresuid/setresgid). >> 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. The state of libcap-ng persists after capng_apply. So you can just call capng_update({CAP_ADD,CAP_DROP}) followed by capng_apply. Does virtiofsd have to do uid/gid dances like virtfs-proxy-helper? Thanks, Paolo