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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,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 8E0E1C3279B for ; Wed, 11 Jul 2018 01:15:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 42362208AD for ; Wed, 11 Jul 2018 01:15:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 42362208AD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ZenIV.linux.org.uk 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 S1732389AbeGKBRI (ORCPT ); Tue, 10 Jul 2018 21:17:08 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:44278 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732278AbeGKBRI (ORCPT ); Tue, 10 Jul 2018 21:17:08 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.87 #1 (Red Hat Linux)) id 1fd3iy-00023i-ED; Wed, 11 Jul 2018 01:15:20 +0000 Date: Wed, 11 Jul 2018 02:15:20 +0100 From: Al Viro To: Linus Torvalds Cc: Andy Lutomirski , David Howells , Linux API , linux-fsdevel , Linux Kernel Mailing List , Jann Horn Subject: Re: [PATCH 24/32] vfs: syscall: Add fsopen() to prepare for superblock creation [ver #9] Message-ID: <20180711011520.GL30522@ZenIV.linux.org.uk> References: <153126248868.14533.9751473662727327569.stgit@warthog.procyon.org.uk> <153126264966.14533.3388004240803696769.stgit@warthog.procyon.org.uk> <686E805C-81F3-43D0-A096-50C644C57EE3@amacapital.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 10, 2018 at 06:05:49PM -0700, Linus Torvalds wrote: > Yeah, Andy is right that we should *not* make "write()" have side effects. > > Use it to queue things by all means, but not "do" things. Not unless > there's a very sane security model. > > On Tue, Jul 10, 2018 at 4:59 PM Andy Lutomirski wrote: > > > > I think the right solution is one of: > > > > (a) Pass a netlink-formatted blob to fsopen() and do the whole thing in one syscall. I don’t mean using netlink sockets — just the nlattr format. Or you could use a different format. The part that matters is using just one syscall to do the whole thing. > > Please no. Not another nasty marshalling thing. > > > (b) Keep the current structure but use a new syscall instead of write(). > > > > (c) Keep using write() but literally just buffer the data. Then have a new syscall to commit it. In other words, replace “x” with a syscall and call all the fs_context_operations helpers in that context instead of from write(). > > But yeah, b-or-c sounds fine. Umm... How about "use credentials of opener for everything"?