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Date: Mon, 4 Jul 2011 20:06:20 +0400
From: Vasiliy Kulikov <segoon@openwall.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: kernel-hardening@lists.openwall.com, Randy Dunlap <rdunlap@xenotime.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
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        Ingo Molnar <mingo@elte.hu>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org
Subject: Re: [RFC] ipc: introduce shm_rmid_forced sysctl
Message-ID: <20110704160620.GA28320@albatros>
References: <20110622152514.GA9521@albatros>
 <20110704150859.GB6893@redhat.com>
 <20110704153644.GB21350@albatros>
 <20110704154405.GA9544@redhat.com>
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On Mon, Jul 04, 2011 at 17:44 +0200, Oleg Nesterov wrote:
> On 07/04, Vasiliy Kulikov wrote:
> >
> > On Mon, Jul 04, 2011 at 17:08 +0200, Oleg Nesterov wrote:
> > > On 06/22, Vasiliy Kulikov wrote:
> > > >
> > > > +void exit_shm(struct task_struct *task)
> > > > +{
> > > > +	struct nsproxy *nsp = task->nsproxy;
> > > > +	struct ipc_namespace *ns;
> > > > +
> > > > +	if (!nsp)
> > > > +		return;
> > > > +	ns = nsp->ipc_ns;
> > > > +	if (!ns || !ns->shm_rmid_forced)
> > >
> > > This looks confusing, imho. How it is possible that ->nsproxy or
> > > ->ipc_ns is NULL?
> >
> > I spotted the same checking logic in other places.  I don't know whether
> > it is redundant, I guess it can happen when the namespace is dying.
> > Probably it cannot happed inside of task do_exit(), only for extern
> > observers.
> 
> No, afaics it can't happen in do_exit() until we call exit_notify().
> Otherwise, for example, any dying child will OOPS in do_notify_parent().
> Or please look at exit_sem()->sem_lock_check(tsk->nsproxy->ipc_ns).

Looks you're still right :)

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