From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758708AbZBTP4i (ORCPT ); Fri, 20 Feb 2009 10:56:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753249AbZBTP4a (ORCPT ); Fri, 20 Feb 2009 10:56:30 -0500 Received: from e4.ny.us.ibm.com ([32.97.182.144]:41818 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753856AbZBTP43 (ORCPT ); Fri, 20 Feb 2009 10:56:29 -0500 Date: Fri, 20 Feb 2009 07:56:27 -0800 From: "Paul E. McKenney" To: Ingo Molnar Cc: Vegard Nossum , stable@kernel.org, Andrew Morton , Nick Piggin , Pekka Enberg , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: fix lazy vmap purging (use-after-free error) Message-ID: <20090220155626.GA8404@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20090220134121.GA19575@damson.getinternet.no> <20090220135000.GA9616@elte.hu> <20090220140157.GA12799@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090220140157.GA12799@elte.hu> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 20, 2009 at 03:01:57PM +0100, Ingo Molnar wrote: > > * Ingo Molnar wrote: > > > ah, indeed: > > > > list_del_rcu(&va->list); > > > > i suspect it could be hit big time in a workload that opens > > more than 512 files, as expand_files() uses a > > vmalloc()+vfree() pair in that case. > > hm, perhaps it's not a problem after all. The freeing is done > via rcu, and list_del_rcu() leaves the forward pointer intact. > > So how did it happen that the entry got kfree()d before the loop > was done? We are in a spinlocked section so the CPU should not > have entered rcu processing. Good point -- is the .config file available? Thanx, Paul