linux-kernel - Re: [PATCH v5] kptr_restrict for hiding kernel pointers

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Message-ID: <20101222171307.GA25611@elte.hu>
Date:	Wed, 22 Dec 2010 18:13:07 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Dan Rosenberg <drosenberg@...curity.com>
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, davem@...emloft.net,
	a.p.zijlstra@...llo.nl, akpm@...ux-foundation.org,
	eparis@...isplace.org
Subject: Re: [PATCH v5] kptr_restrict for hiding kernel pointers

* Dan Rosenberg <drosenberg@...curity.com> wrote:

> +	case 'K':
> +		/*
> +		 * %pK cannot be used in IRQ context because its test
> +		 * for CAP_SYSLOG would be meaningless.
> +		 */
> +		if (in_irq() || in_serving_softirq() || in_nmi())
> +			WARN_ONCE(1, "%%pK used in interrupt context.\n");

Hm, that bit looks possibly broken - some useful warning in irq context could print 
a pointer into the syslog and this would generate a second warning? That probably 
would crash as it recurses back into the printk code?

Instead a warning could be inserted into the generated output instead, for example 
'pK-error' (carefully staying within pointer length limits).

Also, it would be nice to see a couple of actual %pK usage sites submitted as well - 
instead of this pure infrastructure patch.

	Ingo
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