linux-kernel - Re: [PATCH V2 1/6] namespaces: assign each namespace instance a serial number

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Message-ID: <20140513143925.GD27560@madcap2.tricolour.ca>
Date:	Tue, 13 May 2014 10:39:25 -0400
From:	Richard Guy Briggs <rgb@...hat.com>
To:	Eric Paris <eparis@...hat.com>
Cc:	linux-audit@...hat.com, linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, arozansk@...hat.com,
	serge@...lyn.com, ebiederm@...ssion.com, sgrubb@...hat.com
Subject: Re: [PATCH V2 1/6] namespaces: assign each namespace instance a
 serial number

On 14/05/10, Eric Paris wrote:
> On Fri, 2014-05-09 at 20:27 -0400, Richard Guy Briggs wrote:
> > Generate and assign a serial number per namespace instance since boot.
> > 
> > Use a serial number per namespace (unique across one boot of one kernel)
> > instead of the inode number (which is claimed to have had the right to change
> > reserved and is not necessarily unique if there is more than one proc fs) to
> > uniquely identify it per kernel boot.
> > 
> > Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> > ---
> 
> > +/**
> > + * ns_serial - compute a serial number for the namespace
> > + *
> > + * Compute a serial number for the namespace to uniquely identify it in
> > + * audit records.
> > + */
> > +unsigned long long ns_serial(void)
> > +{
> > +	static DEFINE_SPINLOCK(serial_lock);
> > +	static unsigned long long serial = 4; /* reserved for IPC, UTS, user, PID */
> > +	unsigned long flags;
> > +
> > +	spin_lock_irqsave(&serial_lock, flags);
> > +	++serial;
> > +	spin_unlock_irqrestore(&serial_lock, flags);
> > +	BUG_ON(!serial);
> > +
> > +	return serial;
> > +}
> > +
> >  static inline struct nsproxy *create_nsproxy(void)
> >  {
> >  	struct nsproxy *nsproxy;
> 
> atomic64_t instead of doing it yourself?

I'm willing to switch to atomic64_*.  Thanks for pointing out its
existence.

> and why _irqsave() ?  Can we seriously create new namespaces in irq
> context?  If you use the atomic though, you don't have to worry about
> it...

Agreed.  That is unlikely.

- RGB

--
Richard Guy Briggs <rbriggs@...hat.com>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545
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