linux-kernel - Re: [RFC][PATCH] Randomize kernel base address on boot

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Message-ID: <20110526203502.GK29496@redhat.com>
Date:	Thu, 26 May 2011 16:35:02 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Dan Rosenberg <rosenberg@...curity.com>
Cc:	Dan Rosenberg <drosenberg@...curity.com>,
	Tony Luck <tony.luck@...il.com>, linux-kernel@...r.kernel.org,
	davej@...hat.com, kees.cook@...onical.com, davem@...emloft.net,
	eranian@...gle.com, torvalds@...ux-foundation.org,
	adobriyan@...il.com, penberg@...nel.org, hpa@...or.com,
	Arjan van de Ven <arjan@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Valdis.Kletnieks@...edu, Ingo Molnar <mingo@...e.hu>,
	pageexec@...email.hu
Subject: Re: [RFC][PATCH] Randomize kernel base address on boot

On Tue, May 24, 2011 at 04:31:45PM -0400, Dan Rosenberg wrote:
> This introduces CONFIG_RANDOMIZE_BASE, which randomizes the address at
> which the kernel is decompressed at boot as a security feature that
> deters exploit attempts relying on knowledge of the location of kernel
> internals.  The default values of the kptr_restrict and dmesg_restrict
> sysctls are set to (1) when this is enabled, since hiding kernel
> pointers is necessary to preserve the secrecy of the randomized base
> address.

What happens to /proc/iomem interface which gives us the physical memory
location where kernel is loaded. kexec-tools relies on that interface
heavily so we can not take it away. And if we can not take it away then
I think somebody should be easibly be able to calculate this randomized
base address.

Thanks
Vivek
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