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

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Date:	Mon, 23 May 2011 23:33:13 -0700
From:	Joe Perches <joe@...ches.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, akpm@...ux-foundation.org,
	netdev@...r.kernel.org, drosenberg@...curity.com,
	a.p.zijlstra@...llo.nl, eparis@...isplace.org,
	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

On Tue, 2011-05-24 at 08:17 +0200, Eric Dumazet wrote:
> We probably need to extend this to inet_diag as well.
> Provide a mayber_hide_ptr() helper and use it in inet_diag to not
> disclose kernel pointers to user, with kptr_restrict logic :
> kptr_restrict = 0 : kernel pointers are not mangled
> kptr_restrict = 1 : if the current user does not have CAP_SYSLOG,
> kernel pointers are replaced by 0
> kptr_restrict = 2 : kernel pointers are replaced by 0
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
[]
> +void *maybe_hide_ptr(void *ptr)
> +{
> +	if (!((kptr_restrict == 0) ||
> +	      (kptr_restrict == 1 &&
> +	       has_capability_noaudit(current, CAP_SYSLOG))))
> +		ptr = NULL;
> +	return ptr;
> +}
> +EXPORT_SYMBOL(maybe_hide_ptr);

Makes sense to me.

Maybe for clarity it'd be better to use a switch/case
or something like:

	if (kptr_restrict == 0)
		return ptr;
	if (ptr_restrict == 1 &&
	    has_capability_noaudit(current, CAP_SYSLOG))
		return ptr;
	return NULL;


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