linux-kernel - Re: [PATCH v2] taskstats: don't allow duplicate entries in listener mode

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] [day] [month] [year] [list]

Date:	Wed, 22 Jun 2011 10:54:06 +0400
From:	Vasiliy Kulikov <segoon@...nwall.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Balbir Singh <bsingharora@...il.com>
Subject: Re: [PATCH v2] taskstats: don't allow duplicate entries in
 listener mode

On Tue, Jun 21, 2011 at 15:49 -0700, Andrew Morton wrote:
> On Thu, 16 Jun 2011 19:55:59 +0400
> Vasiliy Kulikov <segoon@...nwall.com> wrote:
> 
> > Currently a single process may register exit handlers unlimited times.
> > It may lead to a bloated listeners chain and very slow process terminations.
> > E.g. after 10KK sent TASKSTATS_CMD_ATTR_REGISTER_CPUMASKs ~300 Mb of
> > kernel memory is stolen for the handlers chain and "time id" shows 2-7
> > seconds instead of normal 0.003.  It makes it possible to exhaust all
> > kernel memory and to eat much of CPU time by triggerring numerous exits
> > on a single CPU.
> > 
> > The patch limits the number of times a single process may register
> > itself on a single CPU to one.
> > 
> > One little issue is kept unfixed - as taskstats_exit() is called before
> > exit_files() in do_exit(), the orphaned listener entry (if it was not
> > explicitly deregistered) is kept until the next someone's exit() and
> > implicit deregistration in send_cpu_listeners().  So, if a process
> > registered itself as a listener exits and the next spawned process gets
> > the same pid, it would inherit taskstats attributes.
> 
> ow. That's an unprivileged operation, isn't it?

Yes.


Thanks,

-- 
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
--
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/