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=-10.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 A7749C433E0 for ; Mon, 1 Mar 2021 16:07:43 +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 4AC5364E2E for ; Mon, 1 Mar 2021 16:07:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4AC5364E2E 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]:58688 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lGl5C-0005ov-9l for qemu-devel@archiver.kernel.org; Mon, 01 Mar 2021 11:07:42 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:42588) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lGl4b-0005M0-Hs for qemu-devel@nongnu.org; Mon, 01 Mar 2021 11:07:05 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:28737) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lGl4Y-0001ps-Gc for qemu-devel@nongnu.org; Mon, 01 Mar 2021 11:07:05 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614614821; h=from:from:reply-to: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=pbyFDJEDdQ/7KjVU6x/2FKWXcstShEThs+7DuTD1W9s=; b=bViX4PJNsqhBaoquYaqlVTkLCD6e+e3EocXcRvkqKvFMNGYdfGcCaV2CoIyi9JZqwMJaGl wBO3gaERcgc4hswiWJH6i3UAh8nfBheoc+qmkhtNHET20jAJ1SYKWf62Rp9eMdxFevfEDQ k+5RjAfxqaeagZkfWJTSztgBnP5r/lA= 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-528-XI13_YTPOZ67mk5VRZ81Fw-1; Mon, 01 Mar 2021 11:06:58 -0500 X-MC-Unique: XI13_YTPOZ67mk5VRZ81Fw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 28819107ACE3; Mon, 1 Mar 2021 16:06:57 +0000 (UTC) Received: from redhat.com (ovpn-113-132.ams2.redhat.com [10.36.113.132]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 248B810013D7; Mon, 1 Mar 2021 16:06:50 +0000 (UTC) Date: Mon, 1 Mar 2021 16:06:47 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Eric Blake Subject: Re: [PATCH] docs: show how to spawn qemu-storage-daemon with fd passing Message-ID: References: <20210301153159.35660-1-stefanha@redhat.com> <5b86b310-8e3b-8bb6-365c-a73b0f2843be@redhat.com> MIME-Version: 1.0 In-Reply-To: <5b86b310-8e3b-8bb6-365c-a73b0f2843be@redhat.com> User-Agent: Mutt/2.0.5 (2021-01-21) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Kevin Wolf , qemu-block@nongnu.org, qemu-devel@nongnu.org, Stefan Hajnoczi Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Mar 01, 2021 at 09:49:21AM -0600, Eric Blake wrote: > On 3/1/21 9:41 AM, Daniel P. Berrangé wrote: > > On Mon, Mar 01, 2021 at 03:31:59PM +0000, Stefan Hajnoczi wrote: > >> The QMP monitor, NBD server, and vhost-user-blk export all support file > >> descriptor passing. This is a useful technique because it allows the > >> parent process to spawn and wait for qemu-storage-daemon without busy > >> waiting, which may delay startup due to arbitrary sleep() calls. > >> > >> This Python example is inspired by the test case written for libnbd by > >> Richard W.M. Jones : > >> https://gitlab.com/nbdkit/libnbd/-/commit/89113f484effb0e6c322314ba75c1cbe07a04543 > >> > >> Thanks to Daniel P. Berrangé for suggestions on > >> how to get this working. Now let's document it! > >> > > >> + sock_path = '/tmp/qmp-{}.sock'.format(os.getpid()) > > > > Example code inevitably gets cut+paste into real world apps, and this > > example is a tmpfile CVE flaw. At least put it in $CWD instead. > > Except $CWD may be too long for a sock file name to be created. > Creating the sock in a securely-created subdirectory of /tmp is more > reliable. $XDG_RUNTIME_DIR then, which is /run/user/$UID, so safely per user on all modern OS. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|