Re: [PATCH v3 2/4] mm: abstract initial stack setup to mm subsystem

[Kees Cook <kees@kernel.org>]

On Mon, Apr 28, 2025 at 04:28:15PM +0100, Lorenzo Stoakes wrote:
> There are peculiarities within the kernel where what is very clearly mm
> code is performed elsewhere arbitrarily.
> 
> This violates separation of concerns and makes it harder to refactor code
> to make changes to how fundamental initialisation and operation of mm logic
> is performed.
> 
> One such case is the creation of the VMA containing the initial stack upon
> execve()'ing a new process. This is currently performed in __bprm_mm_init()
> in fs/exec.c.
> 
> Abstract this operation to create_init_stack_vma(). This allows us to limit
> use of vma allocation and free code to fork and mm only.
> 
> We previously did the same for the step at which we relocate the initial
> stack VMA downwards via relocate_vma_down(), now we move the initial VMA
> establishment too.
> 
> Take the opportunity to also move insert_vm_struct() to mm/vma.c as it's no
> longer needed anywhere outside of mm.
> 
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

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

-- 
Kees Cook