linux-kernel - Re: [PATCH 1/4] Routine for generating an safe ID for kernel pointer

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Message-ID: <20111115152023.GA18919@google.com>
Date:	Tue, 15 Nov 2011 07:20:23 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Pavel Emelyanov <xemul@...allels.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Glauber Costa <glommer@...allels.com>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matt Helsley <matthltc@...ibm.com>
Subject: Re: [PATCH 1/4] Routine for generating an safe ID for kernel
 pointer

On Tue, Nov 15, 2011 at 03:36:33PM +0400, Pavel Emelyanov wrote:
> +unsigned long gen_object_id(void *ptr)
> +{
> +	if (!ptr)
> +		return 0;
> +
> +	if (unlikely(!ptr_poison)) {
> +		spin_lock(&ptr_poison_lock);
> +		if (!ptr_poison)
> +			get_random_bytes(&ptr_poison, sizeof(ptr_poison));
> +		spin_unlock(&ptr_poison_lock);
> +	}

One thing that worries me about this is that there's one ptr_poison
for all id's and any single leak of a pointer value will make all ids
vulnerable.  If we're going to do this, let's segregate different id
spaces and use different poison values for each.

Thank you.

-- 
tejun
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