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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 75C69C04EB8 for ; Fri, 30 Nov 2018 13:40:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4714A2145D for ; Fri, 30 Nov 2018 13:40:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4714A2145D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726841AbeLAAtq convert rfc822-to-8bit (ORCPT ); Fri, 30 Nov 2018 19:49:46 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53442 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726618AbeLAAtq (ORCPT ); Fri, 30 Nov 2018 19:49:46 -0500 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 mx1.redhat.com (Postfix) with ESMTPS id 64998C025011; Fri, 30 Nov 2018 13:40:26 +0000 (UTC) Received: from oldenburg.str.redhat.com (dhcp-192-212.str.redhat.com [10.33.192.212]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1CCEB1057065; Fri, 30 Nov 2018 13:40:23 +0000 (UTC) From: Florian Weimer To: =?utf-8?Q?J=C3=BCrg?= Billeter Cc: Andrew Morton , Oleg Nesterov , Thomas Gleixner , Eric Biederman , Kees Cook , Andy Lutomirski , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/1] prctl: add PR_{GET,SET}_KILL_DESCENDANTS_ON_EXIT References: <20181127225408.7553-2-j@bitron.ch> <20181130080004.23635-1-j@bitron.ch> <20181130080004.23635-2-j@bitron.ch> Date: Fri, 30 Nov 2018 14:40:14 +0100 In-Reply-To: <20181130080004.23635-2-j@bitron.ch> (=?utf-8?Q?=22J=C3=BCrg?= Billeter"'s message of "Fri, 30 Nov 2018 08:00:04 +0000") Message-ID: <87bm66u1j5.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Fri, 30 Nov 2018 13:40:26 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Jürg Billeter: > This introduces a new thread group flag that can be set by calling > > prctl(PR_SET_KILL_DESCENDANTS_ON_EXIT, 1, 0, 0, 0) > > When a thread group exits with this flag set, it will send SIGKILL to > all descendant processes. This can be used to prevent stray child > processes. > > This flag is cleared on privilege gaining execve(2) to ensure an > unprivileged process cannot get a privileged process to send SIGKILL. So this is inherited across regular execve? I'm not sure that's a good idea. > Descendants that are orphaned and reparented to an ancestor of the > current process before the current process exits, will not be killed. > PR_SET_CHILD_SUBREAPER can be used to contain orphaned processes. For double- or triple-forking daemons, the reparenting will be racy, if I understand things correctly. Thanks, Florian