Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756630Ab2BWSmb (ORCPT ); Thu, 23 Feb 2012 13:42:31 -0500 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:37577 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752819Ab2BWSma (ORCPT ); Thu, 23 Feb 2012 13:42:30 -0500 Message-ID: <4F468888.9090702@fb.com> Date: Thu, 23 Feb 2012 10:42:16 -0800 From: Arun Sharma User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:10.0.2) Gecko/20120216 Thunderbird/10.0.2 MIME-Version: 1.0 To: Balbir Singh CC: , , KAMEZAWA Hiroyuki , Subject: Re: [PATCH] mm: Enable MAP_UNINITIALIZED for archs with mmu References: <1326912662-18805-1-git-send-email-asharma@fb.com> In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [192.168.18.252] X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.6.7498,1.0.260,0.0.0000 definitions=2012-02-23_07:2012-02-23,2012-02-23,1970-01-01 signatures=0 X-Proofpoint-Spam-Reason: safe Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1693 Lines: 45 Hi Balbir, Thanks for reviewing. Would you change your position if I limit the scope of the patch to a cgroup with a single address space? The moment the cgroup sees more than one address space (either due to tasks getting created or being added), this optimization would be turned off. More details below: On 2/22/12 11:45 PM, Balbir Singh wrote: > > So the assumption is that only apps that have access to each others > VMA's will run in this cgroup? > In a distributed computing environment, a user submits a job to the cluster job scheduler. The job might involve multiple related executables and might involve multiple address spaces. But they're performing one logical task, have a single resource limit enforced by a cgroup. They don't have access to each other's VMAs, but if "accidentally" one of them comes across an uninitialized page with data from another task, it's not a violation of the security model. > Sorry, I am not convinced we need to do this > > 1. I know that zeroing out memory is expensive, but building a > potential loop hole is not a good idea > 2. How do we ensure that tasks in a cgroup should be allowed to reuse > memory uninitialized, how does the cgroup admin know what she is > getting into? I was thinking of addressing this via documentation (as in: don't use this if you don't know what you're doing!). But limiting the scope to a single address space cgroup seems cleaner to me. -Arun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/