linux-kernel - Re: [PATCH v3] kptr_restrict for hiding kernel pointers

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Message-ID: <1292886088.4061.3.camel@dan>
Date:	Mon, 20 Dec 2010 18:01:28 -0500
From:	Dan Rosenberg <drosenberg@...curity.com>
To:	Valdis.Kletnieks@...edu
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	linux-security-module@...r.kernel.org, jmorris@...ei.org,
	eric.dumazet@...il.com, tgraf@...radead.org, eugeneteo@...nel.org,
	kees.cook@...onical.com, mingo@...e.hu, davem@...emloft.net,
	a.p.zijlstra@...llo.nl, akpm@...ux-foundation.org
Subject: Re: [PATCH v3] kptr_restrict for hiding kernel pointers

On Mon, 2010-12-20 at 17:26 -0500, Valdis.Kletnieks@...edu wrote:
> On Sat, 18 Dec 2010 12:20:34 EST, Dan Rosenberg said:
> 
> > @@ -1035,6 +1038,26 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
> >  		return buf + vsnprintf(buf, end - buf,
> >  				       ((struct va_format *)ptr)->fmt,
> >  				       *(((struct va_format *)ptr)->va));
> > +	case 'K':
> > +		/*
> > +		 * %pK cannot be used in IRQ context because it tests
> > +		 * CAP_SYSLOG.
> > +		 */
> > +		if (in_irq() || in_serving_softirq() || in_nmi())
> > +			WARN_ONCE(1, "%%pK used in interrupt context.\n");
> 
> Should this then continue on and test CAP_SYSLOG anyhow, or should it
> return a "" or or "<invalid>" or something?

This is a valid point.  I'll resend a new version shortly that defaults
to zeroing pointers if it's used incorrectly without relying on
capability checks.

Thanks,
Dan

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