# Re: \[PATCH v27 30/31\] mm: Update arch\_validate\_flags() to test vma anonymous

- From: Catalin Marinas \<catalin.marinas@arm.com\>
- Date: 2021-05-25 11:00:24 
- List: linux-doc
- Page: https://ratatoskr.run/linux-doc/2021/05/1391165
- Thread: https://ratatoskr.run/linux-doc/2021/05/1388103/t.md

```text
On Fri, May 21, 2021 at 03:12:10PM -0700, Yu-cheng Yu wrote:
> When newer VM flags are being created, such as VM_MTE, it becomes necessary
> for mmap/mprotect to verify if certain flags are being applied to an
> anonymous VMA.
> 
> To solve this, one approach is adding a VM flag to track that MAP_ANONYMOUS
> is specified [1], and then using the flag in arch_validate_flags().
> 
> Another approach is passing the VMA to arch_validate_flags(), and check
> vma_is_anonymous().
> 
> To prepare the introduction of PROT_SHADOW_STACK, which creates a shadow
> stack mapping and can be applied only to an anonymous VMA, update
> arch_validate_flags() to pass in the VMA.
> 
> [1] commit 9f3419315f3c ("arm64: mte: Add PROT_MTE support to mmap() and mprotect()"),
> 
> Signed-off-by: Yu-cheng Yu <redacted>
> Reviewed-by: Kirill A. Shutemov <redacted>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Kees Cook <redacted>
> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Cc: Will Deacon <will@kernel.org>

For arm64:

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
```