From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx191.postini.com [74.125.245.191]) by kanga.kvack.org (Postfix) with SMTP id 2D8F06B007E for ; Thu, 23 Feb 2012 02:45:32 -0500 (EST) Received: by qadz32 with SMTP id z32so7240746qad.14 for ; Wed, 22 Feb 2012 23:45:31 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <1326912662-18805-1-git-send-email-asharma@fb.com> References: <1326912662-18805-1-git-send-email-asharma@fb.com> Date: Thu, 23 Feb 2012 13:15:30 +0530 Message-ID: Subject: Re: [PATCH] mm: Enable MAP_UNINITIALIZED for archs with mmu From: Balbir Singh Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Arun Sharma Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, KAMEZAWA Hiroyuki , akpm@linux-foundation.org On Thu, Jan 19, 2012 at 12:21 AM, Arun Sharma wrote: > > This enables malloc optimizations where we might > madvise(..,MADV_DONTNEED) a page only to fault it > back at a different virtual address. > > To ensure that we don't leak sensitive data to > unprivileged processes, we enable this optimization > only for pages that are reused within a memory > cgroup. > So the assumption is that only apps that have access to each others VMA's will run in this cgroup? > The idea is to make this opt-in both at the mmap() > level and cgroup level so the default behavior is > unchanged after the patch. > 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? So I am going to NACK this. Balbir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org