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Date: Fri, 10 Feb 2017 20:52:40 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: "Roberts, William C" <william.c.roberts@...el.com>
Cc: "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
Kees Cook <keescook@...omium.org>
Subject: Re: %pK continuation
On Fri, Feb 10, 2017 at 07:02:42PM +0000, Roberts, William C wrote:
> I haven't had time to really work on the continuation of:
> http://www.openwall.com/lists/kernel-hardening/2016/10/07/1
>
> I think the simple approach of killing %p based on kptr_restrict remains the simplest, IMHO best way to achieve a better level of
> preventing leaks of kernel addresses. In example of %pK going wrong can be found here:
> https://googleprojectzero.blogspot.com/2017/02/lifting-hyper-visor-bypassing-samsungs.html.
>
> Granted, the exploit author would have found another way to defeat KASL, I'd like to force their hand.
>
> In a nut shell, the driver use %pk instead of %pK (capitalization of K matters). This would actually be a
> good checkpatch.pl check. I grep'd the kernel for %pk (lower case k) and found no usages!
%pk is not a valid kernel printk() modifier at all, so I sure hope you
%would not find any usages :)
Documentation/printk-formats.txt is a good thing to check.
thanks,
greg k-h
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