Re: [PATCH v26 29/30] mm: Update arch_validate_flags() to test vma anonymous

From: Kirill A. Shutemov
Date: Tue May 11 2021 - 07:35:43 EST

On Tue, Apr 27, 2021 at 01:43:14PM -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 <yu-cheng.yu@xxxxxxxxx>

Reviewed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>

Kirill A. Shutemov