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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 2FA28C43441 for ; Thu, 22 Nov 2018 07:48:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0136620864 for ; Thu, 22 Nov 2018 07:48:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0136620864 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=hallyn.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 S2405044AbeKVS0Y (ORCPT ); Thu, 22 Nov 2018 13:26:24 -0500 Received: from mail.hallyn.com ([178.63.66.53]:57188 "EHLO mail.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729423AbeKVS0X (ORCPT ); Thu, 22 Nov 2018 13:26:23 -0500 Received: by mail.hallyn.com (Postfix, from userid 1001) id A25CAB47; Thu, 22 Nov 2018 01:48:07 -0600 (CST) Date: Thu, 22 Nov 2018 01:48:07 -0600 From: "Serge E. Hallyn" To: Tycho Andersen Cc: Christian Brauner , ebiederm@xmission.com, linux-kernel@vger.kernel.org, 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, linux-man@vger.kernel.org, Kees Cook Subject: Re: [PATCH v1 2/2] signal: add procfd_signal() syscall Message-ID: <20181122074807.GB15484@mail.hallyn.com> References: <20181119103241.5229-1-christian@brauner.io> <20181119103241.5229-3-christian@brauner.io> <20181119223954.GA4992@cisco> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181119223954.GA4992@cisco> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 19, 2018 at 03:39:54PM -0700, Tycho Andersen wrote: > On Mon, Nov 19, 2018 at 11:32:39AM +0100, Christian Brauner wrote: > > > > +/** > > + * sys_procfd_signal - send a signal to a process through a process file > > + * descriptor > > + * @fd: the file descriptor of the process > > + * @sig: signal to be sent > > + * @info: the signal info > > + * @flags: future flags to be passed > > + */ > > +SYSCALL_DEFINE4(procfd_signal, int, fd, int, sig, siginfo_t __user *, info, > > + int, flags) > > +{ > > Can I just register an objection here that I think using a syscall > just for this is silly? > > My understanding is that the concern is that some code might do: > > unknown_fd = recv_fd(); > ioctl(unknown_fd, SOME_IOCTL, NULL); // where SOME_IOCTL == PROC_FD_KILL > // whoops, unknown_fd was a procfd and we killed a task! This could just be my own mental model, but for something like "kill a task", an ioctl just seems wrong. Syscall seems more natural. I'd ack either method. -serge