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Date: Mon, 4 Jul 2011 17:44:05 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Vasiliy Kulikov <segoon@...nwall.com>
Cc: kernel-hardening@...ts.openwall.com, Randy Dunlap <rdunlap@...otime.net>,
Andrew Morton <akpm@...ux-foundation.org>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
"Serge E. Hallyn" <serge.hallyn@...onical.com>,
Daniel Lezcano <daniel.lezcano@...e.fr>, Tejun Heo <tj@...nel.org>,
Ingo Molnar <mingo@...e.hu>, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [RFC] ipc: introduce shm_rmid_forced sysctl
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).
Oleg.
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