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 68BA4C43441 for ; Mon, 19 Nov 2018 14:15:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 38C612089F for ; Mon, 19 Nov 2018 14:15:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 38C612089F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ACULAB.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 S1729483AbeKTAjN convert rfc822-to-8bit (ORCPT ); Mon, 19 Nov 2018 19:39:13 -0500 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:20423 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728252AbeKTAjM (ORCPT ); Mon, 19 Nov 2018 19:39:12 -0500 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-112-1WagJuYKPWyp2NEK7jIZzg-1; Mon, 19 Nov 2018 14:15:25 +0000 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b::d117) by AcuMS.aculab.com (fd9f:af1c:a25b::d117) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Mon, 19 Nov 2018 14:15:31 +0000 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Mon, 19 Nov 2018 14:15:31 +0000 From: David Laight To: 'Christian Brauner' , "ebiederm@xmission.com" , "linux-kernel@vger.kernel.org" CC: "serge@hallyn.com" , "jannh@google.com" , "luto@kernel.org" , "akpm@linux-foundation.org" , "oleg@redhat.com" , "cyphar@cyphar.com" , "viro@zeniv.linux.org.uk" , "linux-fsdevel@vger.kernel.org" , "linux-api@vger.kernel.org" , "dancol@google.com" , "timmurray@google.com" , Kees Cook Subject: RE: [PATCH] proc: allow killing processes via file descriptors Thread-Topic: [PATCH] proc: allow killing processes via file descriptors Thread-Index: AQHUfzCMPJnedN49+EaYHywV7sQfyKVXJFlw Date: Mon, 19 Nov 2018 14:15:31 +0000 Message-ID: <9a269517770e4881b92756d47f17a5fd@AcuMS.aculab.com> References: <20181118111751.6142-1-christian@brauner.io> In-Reply-To: <20181118111751.6142-1-christian@brauner.io> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-MC-Unique: 1WagJuYKPWyp2NEK7jIZzg-1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: > Christian Brauner > Sent: 18 November 2018 11:18 > > With this patch an open() call on /proc/ will give userspace a handle > to struct pid of the process associated with /proc/. This allows to > maintain a stable handle on a process. My 3c... You need to add a version of fork() that returns an open fd to /proc/pid to the parent. Is it possible to overload fcntl() rather than ioctl() ? More interestingly what about a 'unique pid' (eg the pid extended to (say) 128 bits with a use count) that can be safely put into a /var/run/pid file for a daemon and used later in a 'kill' that will only ever reference the correct process. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)