From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 7 Mar 2007 13:36:52 +0100 From: Nick Piggin Subject: Re: [patch 4/6] mm: merge populate and nopage into fault (fixes nonlinear) Message-ID: <20070307123652.GD18704@wotan.suse.de> References: <20070307094503.GD8609@wotan.suse.de> <20070307100430.GA5080@wotan.suse.de> <1173262002.6374.128.camel@twins> <20070307102106.GB5555@wotan.suse.de> <1173263085.6374.132.camel@twins> <20070307103842.GD5555@wotan.suse.de> <1173264462.6374.140.camel@twins> <20070307110035.GE5555@wotan.suse.de> <20070307122224.GP18774@holomorphy.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070307122224.GP18774@holomorphy.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Bill Irwin , Peter Zijlstra , Miklos Szeredi , akpm@linux-foundation.org, mingo@elte.hu, linux-mm@kvack.org, linux-kernel@vger.kernel.org, benh@kernel.crashing.org List-ID: On Wed, Mar 07, 2007 at 04:22:24AM -0800, Bill Irwin wrote: > On Wed, Mar 07, 2007 at 11:47:42AM +0100, Peter Zijlstra wrote: > >> Well, now they don't, but it could be done or even exploited as a DoS. > > On Wed, Mar 07, 2007 at 12:00:36PM +0100, Nick Piggin wrote: > > But so could nonlinear page reclaim. I think we need to restrict nonlinear > > mappings to root if we're worried about that. > > Please not root. The users really don't want to be privileged. UML > itself is at least partly for use as privilege isolation of the guest > workload. Oracle has some of the same concerns itself, which is part of > why it uses separate processes heavily, even: to isolate instances from > each other. Well non-root users could be allowed to work on mlocked regions on tmpfs/shm. That way they avoid the pathological nonlinear problems, and can work within the mlock ulimit. That is, if we are worried about such a DoS. -- 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