netdev - Re: [patch 1/1] net: convert %p usage to %pK

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Message-Id: <20110524.011330.1077020828173889583.davem@davemloft.net>
Date:	Tue, 24 May 2011 01:13:30 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	akpm@...ux-foundation.org
Cc:	netdev@...r.kernel.org, drosenberg@...curity.com,
	a.p.zijlstra@...llo.nl, eparis@...isplace.org,
	eric.dumazet@...il.com, eugeneteo@...nel.org, jmorris@...ei.org,
	kees.cook@...onical.com, mingo@...e.hu, tgraf@...radead.org
Subject: Re: [patch 1/1] net: convert %p usage to %pK

From: akpm@...ux-foundation.org
Date: Mon, 23 May 2011 15:17:35 -0700

> From: Dan Rosenberg <drosenberg@...curity.com>
> 
> The %pK format specifier is designed to hide exposed kernel pointers,
> specifically via /proc interfaces.  Exposing these pointers provides an
> easy target for kernel write vulnerabilities, since they reveal the
> locations of writable structures containing easily triggerable function
> pointers.  The behavior of %pK depends on the kptr_restrict sysctl.
> 
> If kptr_restrict is set to 0, no deviation from the standard %p behavior
> occurs.  If kptr_restrict is set to 1, the default, if the current user
> (intended to be a reader via seq_printf(), etc.) does not have CAP_SYSLOG
> (currently in the LSM tree), kernel pointers using %pK are printed as 0's.
>  If kptr_restrict is set to 2, kernel pointers using %pK are printed as
> 0's regardless of privileges.  Replacing with 0's was chosen over the
> default "(null)", which cannot be parsed by userland %p, which expects
> "(nil)".
> 
> The supporting code for kptr_restrict and %pK are currently in the -mm
> tree.  This patch converts users of %p in net/ to %pK.  Cases of printing
> pointers to the syslog are not covered, since this would eliminate useful
> information for postmortem debugging and the reading of the syslog is
> already optionally protected by the dmesg_restrict sysctl.
> 
> Signed-off-by: Dan Rosenberg <drosenberg@...curity.com>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>

Applied.
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