linux-kernel - Re: [BUGFIX][PATCH -mmotm] memcg: avoid oom-killing innocent task in case of use

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]

Date:	Tue, 24 Nov 2009 23:00:29 +0900
From:	Daisuke Nishimura <d-nishimura@....biglobe.ne.jp>
To:	Balbir Singh <balbir@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>, stable <stable@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Subject: Re: [BUGFIX][PATCH -mmotm] memcg: avoid oom-killing innocent task
 in  case of use_hierarchy

On Tue, 24 Nov 2009 19:01:54 +0530
Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:

> On Tue, Nov 24, 2009 at 11:27 AM, Daisuke Nishimura
> <nishimura@....nes.nec.co.jp> wrote:
> > task_in_mem_cgroup(), which is called by select_bad_process() to check whether
> > a task can be a candidate for being oom-killed from memcg's limit, checks
> > "curr->use_hierarchy"("curr" is the mem_cgroup the task belongs to).
> >
> > But this check return true(it's false positive) when:
> >
> >        <some path>/00          use_hierarchy == 0      <- hitting limit
> >          <some path>/00/aa     use_hierarchy == 1      <- "curr"
> >
> > This leads to killing an innocent task in 00/aa. This patch is a fix for this
> > bug. And this patch also fixes the arg for mem_cgroup_print_oom_info(). We
> > should print information of mem_cgroup which the task being killed, not current,
> > belongs to.
> >
> 
> Quick Question: What happens if <some path>/00 has no tasks in it
> after your patches?
> 
Nothing would happen because <some path>/00 never hit its limit.

The bug that this patch fixes is:

- create a dir <some path>/00 and set some limits.
- create a sub dir <some path>/00/aa w/o any limits, and enable hierarchy.
- run some programs in both in 00 and 00/aa. programs in 00 should be
  big enough to cause oom by its limit.
- when oom happens by 00's limit, tasks in 00/aa can also be killed.


Regards,
Daisuke Nishimura.
--
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/