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Subject: Re: [PATCH 24/30] x86, kaiser: disable native VSYSCALL
To: Andy Lutomirski <luto@kernel.org>
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From: Dave Hansen <dave.hansen@linux.intel.com>
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Date: Thu, 9 Nov 2017 16:57:45 -0800
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On 11/09/2017 04:53 PM, Andy Lutomirski wrote:
>> The KAISER code attempts to "poison" the user portion of the kernel page
>> tables.  It detects the entries pages that it wants that it wants to
>> poison in two ways:
>>  * Looking for addresses >= PAGE_OFFSET
>>  * Looking for entries without _PAGE_USER set
> What do you mean "poison"?

I meant the _PAGE_NX magic that we do in here:

https://git.kernel.org/pub/scm/linux/kernel/git/daveh/x86-kaiser.git/commit/?h=kaiser-414rc7-20171108&id=c4f7d0819170761f092fcf2327b85b082368e73a

to ensure that userspace is unable to run on the kernel PGD.