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SubjectRe: [RFC][PATCH 04/10] x86/espfix: use kernel-default PTE mask
On 02/22/2018 01:27 PM, Nadav Amit wrote:
> Dave Hansen <> wrote:
>> From: Dave Hansen <>
>> In creating its page tables, the espfix code masks its PGTABLE_PROT
>> value with the supported mask: __supported_pte_mask. This ensures
>> that unsupported bits are not set in the final PTE. But, it also
>> sets _PAGE_GLOBAL which we do not want for PTE. Use
>> __default_kernel_pte_mask instead which clears _PAGE_GLOBAL for PTI.
> Can you please explain what is your concern? Exposing more gadgets for
> speculative ROP attacks?
> Or is it a general rule of not exposing any kernel code &data more than
> absolutely necessary?

I think it's good practice to just expose only the *minimal* amount of
data necessary. It's easier to audit and less likely to expose things

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