Re: [PATCH v3 4/4] mm: perform VMA allocation, freeing, duplication in mm

[Kees Cook <kees@kernel.org>]

On Mon, Apr 28, 2025 at 04:28:17PM +0100, Lorenzo Stoakes wrote:
> Right now these are performed in kernel/fork.c which is odd and a violation
> of separation of concerns, as well as preventing us from integrating this
> and related logic into userland VMA testing going forward, and perhaps more
> importantly - enabling us to, in a subsequent commit, make VMA
> allocation/freeing a purely internal mm operation.
> 
> There is a fly in the ointment - nommu - mmap.c is not compiled if
> CONFIG_MMU not set, and neither is vma.c.
> 
> To square the circle, let's add a new file - vma_init.c. This will be
> compiled for both CONFIG_MMU and nommu builds, and will also form part of
> the VMA userland testing.
> 
> This allows us to de-duplicate code, while maintaining separation of
> concerns and the ability for us to userland test this logic.
> 
> Update the VMA userland tests accordingly, additionally adding a
> detach_free_vma() helper function to correctly detach VMAs before freeing
> them in test code, as this change was triggering the assert for this.
> 
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

Reviewed-by: Kees Cook <kees@kernel.org>

-- 
Kees Cook