Re: [PATCH v25 29/30] mm: Update arch_validate_flags() to include vma anonymous

From: Kirill A. Shutemov
Date: Mon Apr 26 2021 - 02:41:07 EST

On Thu, Apr 15, 2021 at 03:14:18PM -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 vma_is_anonymous() to arch_validate_flags().
> To prepare the introduction of PROT_SHSTK, which creates a shadow stack
> mapping and can only be applied to an anonymous VMA, update arch_validate_
> flags() to include anonymous VMA information.

I would rather pass down whole vma. Who knows what else
arch_validate_flags() would need to know about the VMA tomorrow:

arch_validate_flags(vma, newflags);

should do the trick.

Kirill A. Shutemov