Re: [PATCH v6 13/41] mm: Make pte_mkwrite() take a VMA

[Kees Cook]

On Sat, Feb 18, 2023 at 01:14:05PM -0800, Rick Edgecombe wrote:
> The x86 Control-flow Enforcement Technology (CET) feature includes a new
> type of memory called shadow stack. This shadow stack memory has some
> unusual properties, which requires some core mm changes to function
> properly.
> 
> One of these unusual properties is that shadow stack memory is writable,
> but only in limited ways. These limits are applied via a specific PTE
> bit combination. Nevertheless, the memory is writable, and core mm code
> will need to apply the writable permissions in the typical paths that
> call pte_mkwrite().
> 
> In addition to VM_WRITE, the shadow stack VMA's will have a flag denoting
> that they are special shadow stack flavor of writable memory. So make
> pte_mkwrite() take a VMA, so that the x86 implementation of it can know to
> create regular writable memory or shadow stack memory.
> 
> Apply the same changes for pmd_mkwrite() and huge_pte_mkwrite().
> 
> No functional change.
> 
> Cc: linux-doc@xxxxxxxxxxxxxxx
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> Cc: Michal Simek <monstr@xxxxxxxxx>
> Cc: Dinh Nguyen <dinguyen@xxxxxxxxxx>
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> Cc: linux-mm@xxxxxxxxx
> Tested-by: Pengfei Xu <pengfei.xu@xxxxxxxxx>
> Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>

I'm not an arch maintainer, but it looks like a correct tree-wide
refactor.

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

-- 
Kees Cook