From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id 4A1C86B003D for ; Wed, 6 May 2009 13:53:46 -0400 (EDT) Date: Wed, 6 May 2009 18:54:22 +0100 (BST) From: Hugh Dickins Subject: Re: [PATCH 3/6] ksm: change the KSM_REMOVE_MEMORY_REGION ioctl. In-Reply-To: <20090506170917.GE15712@x200.localdomain> Message-ID: References: <1241475935-21162-1-git-send-email-ieidus@redhat.com> <1241475935-21162-2-git-send-email-ieidus@redhat.com> <1241475935-21162-3-git-send-email-ieidus@redhat.com> <1241475935-21162-4-git-send-email-ieidus@redhat.com> <4A00DF9B.1080501@redhat.com> <4A014C7B.9080702@redhat.com> <4A01AC5E.6000906@redhat.com> <20090506161424.GC15712@x200.localdomain> <20090506170917.GE15712@x200.localdomain> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Chris Wright Cc: Izik Eidus , Rik van Riel , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, aarcange@redhat.com, alan@lxorguk.ukuu.org.uk, device@lanana.org, linux-mm@kvack.org, nickpiggin@yahoo.com.au List-ID: On Wed, 6 May 2009, Chris Wright wrote: > * Hugh Dickins (hugh@veritas.com) wrote: > > > > Is the phrase "covert channel" going to come up somehow? > > There's two (still hand wavy) conerns I see there. First is the security > implication: timing writes to see cow and guess the shared data for > another apps VM_LOCKED region, Mmm, yes, there's fun to be had there; though I don't see it as having anything to do with VM_LOCKED, beyond that the paranoid have reason to place their most anxious data in VM_LOCKED areas. I'm thinking of an app which prepares pages full of scurrilous rumour, then waits around looking at its /proc/self/smaps to see if anyone else is writing stories like that! > second is just plain old complaints of > those rt latency sensitive apps that somehow have VM_LOCKED|VM_MERGE > and complain of COW fault time, probably just "don't do that". Right. There are sensitive sites which ought not to configure such merging on; but I don't think we should disallow merging locked. Hugh -- 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/ . Don't email: email@kvack.org