Re: [RFC][PATCH 04/10] x86/espfix: use kernel-default PTE mask

Nadav Amit
2018-02-22T21:27:36Z

Dave Hansen <dave.hansen@linux.intel.com> wrote:

>
> From: Dave Hansen <dave.hansen@linux.intel.com>
>
> 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?