linux-kernel - Re: [PATCH] oom killer: break from infinite loop

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20100331095714.9137caab.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Wed, 31 Mar 2010 09:57:14 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	anfei <anfei.zhou@...il.com>, Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	nishimura@....nes.nec.co.jp, Mel Gorman <mel@....ul.ie>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] oom killer: break from infinite loop

On Tue, 30 Mar 2010 13:29:29 -0700 (PDT)
David Rientjes <rientjes@...gle.com> wrote:

> > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > index 0cb1ca4..9e89a29 100644
> > --- a/mm/oom_kill.c
> > +++ b/mm/oom_kill.c
> > @@ -510,8 +510,10 @@ retry:
> >  	if (PTR_ERR(p) == -1UL)
> >  		goto out;
> >  
> > -	if (!p)
> > -		p = current;
> > +	if (!p) {
> > +		read_unlock(&tasklist_lock);
> > +		panic("Out of memory and no killable processes...\n");
> > +	}
> >  
> >  	if (oom_kill_process(p, gfp_mask, 0, points, limit, mem,
> >  				"Memory cgroup out of memory"))
> > 
> 
> This actually does appear to be necessary but for a different reason: if 
> current is unkillable because it has OOM_DISABLE, for example, then 
> oom_kill_process() will repeatedly fail and mem_cgroup_out_of_memory() 
> will infinitely loop.
> 
> Kame-san?
> 

When a memcg goes into OOM and it only has unkillable processes (OOM_DISABLE),
we can do nothing. (we can't panic because container's death != system death.)

Because memcg itself has mutex+waitqueue for mutual execusion of OOM killer, 
I think infinite-loop will not be critical probelm for the whole system.

And, now, memcg has oom-kill-disable + oom-kill-notifier features.
So, If a memcg goes into OOM and there is no killable process, but oom-kill is
not disabled by memcg.....it means system admin's mis-configuraton.

He can stop inifite loop by hand, anyway.
# echo 1 > ..../group_A/memory.oom_control

Thanks,
-Kame


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/