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,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 16553ECE560 for ; Mon, 17 Sep 2018 15:24:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BFA98206B8 for ; Mon, 17 Sep 2018 15:24:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BFA98206B8 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 S1728907AbeIQUwR (ORCPT ); Mon, 17 Sep 2018 16:52:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58846 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726885AbeIQUwR (ORCPT ); Mon, 17 Sep 2018 16:52:17 -0400 Received: from smtp.corp.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.27]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 32BAF80461; Mon, 17 Sep 2018 15:24:28 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.34.27.30]) by smtp.corp.redhat.com (Postfix) with SMTP id A419C60900; Mon, 17 Sep 2018 15:24:25 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 17 Sep 2018 17:24:27 +0200 (CEST) Date: Mon, 17 Sep 2018 17:24:24 +0200 From: Oleg Nesterov To: "Eric W. Biederman" Cc: Jeff Layton , viro@zeniv.linux.org.uk, berrange@redhat.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [PATCH v3 1/3] exec: separate thread_count for files_struct Message-ID: <20180917152424.GA25173@redhat.com> References: <20180914105310.6454-1-jlayton@kernel.org> <20180914105310.6454-2-jlayton@kernel.org> <20180915160423.GA31461@redhat.com> <87o9cxv2wh.fsf@xmission.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87o9cxv2wh.fsf@xmission.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.27 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Mon, 17 Sep 2018 15:24:28 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/16, Eric W. Biederman wrote: > > Oleg Nesterov writes: > > > As for binder.c, in this case we probably actually want to unshare ->files > > on exec so we can ignore it? > > Looking at the binder case it only captures ->files on mmap. Exec > ditches the mmap. So if the order of operations are correct than > the dropping of the old mm will also drop the count on files_struct > held by binder. > > So semantically binder should not effect locks on exec, Agreed, but it does. Before your "[PATCH 0/3] exec: Moving unshare_files_struct" unshare_files() is called before exec_mmap(). And even with this series we can have another CLONE_VM process. Howver, I think this doesn't really matter. binder does __fd_install(files), so if it actually has a reference to execing_task->files, I think it should be unshared anyway. > In short as long as we get the oder of operations correct we should be > able to safely ignore binder, and not have binder affect the results of > this code. Agreed. Oleg.