From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx180.postini.com [74.125.245.180]) by kanga.kvack.org (Postfix) with SMTP id 452B76B005C for ; Wed, 7 Dec 2011 22:45:02 -0500 (EST) Received: by ggni2 with SMTP id i2so1692444ggn.14 for ; Wed, 07 Dec 2011 19:45:01 -0800 (PST) Date: Wed, 7 Dec 2011 19:44:57 -0800 (PST) From: David Rientjes Subject: Re: [PATCH v2 RESEND] oom: fix integer overflow of points in oom_badness In-Reply-To: <20111202174526.GA11483@dhcp-26-164.brq.redhat.com> Message-ID: 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 Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Frantisek Hrbata Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kosaki.motohiro@jp.fujitsu.com, oleg@redhat.com, minchan.kim@gmail.com, stable@kernel.org, eteo@redhat.com, pmatouse@redhat.com, Greg Kroah-Hartman On Fri, 2 Dec 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 > > 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+] Andrew, this looks like 3.2-rc5 material. > --- > mm/oom_kill.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 626303b..e9a1785 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -162,7 +162,7 @@ static bool oom_unkillable_task(struct task_struct *p, > unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem, > const nodemask_t *nodemask, unsigned long totalpages) > { > - int points; > + long points; > > if (oom_unkillable_task(p, mem, nodemask)) > return 0; -- 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