netdev - Re: [PATCH v2] kptr_restrict for hiding kernel pointers from unprivileged users

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Date:	Wed, 15 Dec 2010 12:18:12 +0800
From:	Eugene Teo <eugeneteo@...nel.org>
To:	Dan Rosenberg <drosenberg@...curity.com>
CC:	netdev@...r.kernel.org, linux-security-module@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...e.hu>,
	Kees Cook <kees.cook@...onical.com>,
	Eugene Teo <eugeneteo@...nel.org>,
	James Morris <jmorris@...ei.org>
Subject: Re: [PATCH v2] kptr_restrict for hiding kernel pointers from unprivileged
 users

On 12/15/2010 12:06 PM, Dan Rosenberg wrote:
> The below patch adds the %pK format specifier, the
> CONFIG_SECURITY_KPTR_RESTRICT configuration option, and the
> kptr_restrict sysctl.
>
> The %pK format specifier is designed to hide exposed kernel pointers
> from unprivileged users, specifically via /proc interfaces.  Its
> behavior depends on the kptr_restrict sysctl, whose default value
> depends on CONFIG_SECURITY_KPTR_RESTRICT.  If kptr_restrict is set to 0,
> no deviation from the standard %p behavior occurs.  If kptr_restrict is
> set to 1, if the current user (intended to be a reader via seq_printf(),
> etc.) does not have CAP_SYSLOG (which is currently in the LSM tree),
> kernel pointers using %pK are printed as 0's.  This was chosen over the
> default "(null)", which cannot be parsed by userland %p, which expects
> "(nil)".
>
> v2 improves checking for inappropriate context, on suggestion by Peter
> Zijlstra.  Thanks to Thomas Graf for suggesting use of a centralized
> format specifier.
>
> Signed-off-by: Dan Rosenberg <drosenberg@...curity.com>
> CC: James Morris <jmorris@...ei.org>
> CC: Eugene Teo <eugeneteo@...nel.org>
> CC: Kees Cook <kees.cook@...onical.com>
> CC: Ingo Molnar <mingo@...e.hu>
> CC: David S. Miller <davem@...emloft.net>
> CC: linux-security-module@...r.kernel.org
> CC: netdev@...r.kernel.org

Acked-by: Eugene Teo <eugeneteo@...nel.org>

Eugene
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