From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751978Ab1LBTAq (ORCPT ); Fri, 2 Dec 2011 14:00:46 -0500 Received: from cantor2.suse.de ([195.135.220.15]:41988 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751174Ab1LBTAo (ORCPT ); Fri, 2 Dec 2011 14:00:44 -0500 Date: Fri, 2 Dec 2011 11:00:19 -0800 From: Greg KH To: Frantisek Hrbata Cc: rientjes@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, kosaki.motohiro@jp.fujitsu.com, oleg@redhat.com, minchan.kim@gmail.com, stable@kernel.org, eteo@redhat.com, pmatouse@redhat.com Subject: Re: [PATCH v2 RESEND] oom: fix integer overflow of points in oom_badness Message-ID: <20111202190019.GA13283@suse.de> References: <1320048865-13175-1-git-send-email-fhrbata@redhat.com> <20111202174526.GA11483@dhcp-26-164.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111202174526.GA11483@dhcp-26-164.brq.redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 02, 2011 at 06:45:27PM +0100, Frantisek Hrbata wrote: > An integer overflow will happen on 64bit archs if task's sum of rss, swapents > and nr_ptes exceeds (2^31)/1000 value. This was introduced by commit > > f755a04 oom: use pte pages in OOM score > > where the oom score computation was divided into several steps and it's no > longer computed as one expression in unsigned long(rss, swapents, nr_pte are > unsigned long), where the result value assigned to points(int) is in > range(1..1000). So there could be an int overflow while computing > > 176 points *= 1000; > > and points may have negative value. Meaning the oom score for a mem hog task > will be one. > > 196 if (points <= 0) > 197 return 1; > > For example: > [ 3366] 0 3366 35390480 24303939 5 0 0 oom01 > Out of memory: Kill process 3366 (oom01) score 1 or sacrifice child > > Here the oom1 process consumes more than 24303939(rss)*4096~=92GB physical > memory, but it's oom score is one. > > In this situation the mem hog task is skipped and oom killer kills another and > most probably innocent task with oom score greater than one. > > The points variable should be of type long instead of int to prevent the int > overflow. > > Signed-off-by: Frantisek Hrbata > Acked-by: KOSAKI Motohiro > Acked-by: Oleg Nesterov > Acked-by: David Rientjes > Cc: stable@kernel.org [2.6.36+] For what it's worth, the stable address has changed to stable@vger.kernel.org so you might want to fix that up in future submissions. I still catch patches that are tagged with this marking, but you will not end up posting stuff to the list this way :) thanks, greg k-h