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

Kees Cook
2023-02-19T20:40:54Z

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@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-alpha@vger.kernel.org
> Cc: linux-snps-arc@lists.infradead.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-csky@vger.kernel.org
> Cc: linux-hexagon@vger.kernel.org
> Cc: linux-ia64@vger.kernel.org
> Cc: loongarch@lists.linux.dev
> Cc: linux-m68k@lists.linux-m68k.org
> Cc: Michal Simek <monstr@monstr.eu>
> Cc: Dinh Nguyen <dinguyen@kernel.org>
> Cc: linux-mips@vger.kernel.org
> Cc: openrisc@lists.librecores.org
> Cc: linux-parisc@vger.kernel.org
> Cc: linuxppc-dev@lists.ozlabs.org
> Cc: linux-riscv@lists.infradead.org
> Cc: linux-s390@vger.kernel.org
> Cc: linux-sh@vger.kernel.org
> Cc: sparclinux@vger.kernel.org
> Cc: linux-um@lists.infradead.org
> Cc: xen-devel@lists.xenproject.org
> Cc: linux-arch@vger.kernel.org
> Cc: linux-mm@kvack.org
> Tested-by: Pengfei Xu <pengfei.xu@intel.com>
> Suggested-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>

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

Reviewed-by: Kees Cook <keescook@chromium.org>

--
Kees Cook