From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id EB00C6B0069 for ; Mon, 31 Oct 2011 14:22:51 -0400 (EDT) Received: from hpaq12.eem.corp.google.com (hpaq12.eem.corp.google.com [172.25.149.12]) by smtp-out.google.com with ESMTP id p9VIMlIY027212 for ; Mon, 31 Oct 2011 11:22:48 -0700 Received: from pzk2 (pzk2.prod.google.com [10.243.19.130]) by hpaq12.eem.corp.google.com with ESMTP id p9VHt3HR003544 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=NOT) for ; Mon, 31 Oct 2011 11:22:46 -0700 Received: by pzk2 with SMTP id 2so22982391pzk.8 for ; Mon, 31 Oct 2011 11:22:44 -0700 (PDT) Date: Mon, 31 Oct 2011 11:22:42 -0700 (PDT) From: David Rientjes Subject: Re: [PATCH v2] oom: fix integer overflow of points in oom_badness In-Reply-To: <1320076569-23872-1-git-send-email-fhrbata@redhat.com> Message-ID: References: <1320048865-13175-1-git-send-email-fhrbata@redhat.com> <1320076569-23872-1-git-send-email-fhrbata@redhat.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Frantisek Hrbata Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , KOSAKI Motohiro , Oleg Nesterov , Minchan Kim , stable@kernel.org, eteo@redhat.com, pmatouse@redhat.com On Mon, 31 Oct 2011, 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 > This commit was introduced in 2.6.39 but also backported to stable since 2.6.36, so presumably we'd need to mark this for stable as well going back that far. > 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: David Rientjes Cc: stable@kernel.org [2.6.36+] -- 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