Re: [PATCH 1/5] mm: Introduce OOM kill timeout.

[Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>]

Michal Hocko wrote:
> On Mon 24-11-14 14:29:00, David Rientjes wrote:
> > On Mon, 24 Nov 2014, Michal Hocko wrote:
> > 
> > > > The problem described above is one of phenomena which is triggered by
> > > > a vulnerability which exists since (if I didn't miss something)
> > > > Linux 2.0 (18 years ago). However, it is too difficult to backport
> > > > patches which fix the vulnerability.
> > > 
> > > What is the vulnerability?
> > > 
> > 
> > There have historically been issues when oom killed processes fail to 
> > exit, so this is probably trying to address one of those issues.

Exactly.

> 
> Let me clarify. The patch is sold as a security fix. In that context
> vulnerability means a behavior which might be abused by a user. I was
> merely interested whether there are some known scenarios which would
> turn a potential OOM killer deadlock into an exploitable bug. The
> changelog was rather unclear about it and rather strong in claims that
> any user might trigger OOM deadlock.

Well, both of you are in the CC: list of my mail which includes a reproducer
program which I sent on Thu, 26 Jun 2014 21:02:36 +0900.

Please prepare two VMs, one with XFS and one without XFS. Compile and run
the reproducer program as a local unpriviledged user and see what happens.
You will see stalled traces as with cited in this patchset.

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