Re: [PATCH v2 3/4] selinux: use vma_is_initial_stack() and vma_is_initial_heap()

[Paul Moore <paul@paul-moore.com>]

On Thu, Jul 20, 2023 at 4:28 AM Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
> On 2023/7/19 23:25, Paul Moore wrote:
> > On Wed, Jul 19, 2023 at 6:23 AM Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
> >> On 2023/7/19 17:02, Christian Göttsche wrote:
> >>> On Wed, 19 Jul 2023 at 09:40, Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
> >>>>
> >>>> Use the helpers to simplify code.
> >>>>
> >>>> Cc: Paul Moore <paul@paul-moore.com>
> >>>> Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
> >>>> Cc: Eric Paris <eparis@parisplace.org>
> >>>> Acked-by: Paul Moore <paul@paul-moore.com>
> >>>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> >>>> ---
> >>>>    security/selinux/hooks.c | 7 ++-----
> >>>>    1 file changed, 2 insertions(+), 5 deletions(-)
> >>>>
> >>>> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> >>>> index d06e350fedee..ee8575540a8e 100644
> >>>> --- a/security/selinux/hooks.c
> >>>> +++ b/security/selinux/hooks.c
> >>>> @@ -3762,13 +3762,10 @@ static int selinux_file_mprotect(struct vm_area_struct *vma,
> >>>>           if (default_noexec &&
> >>>>               (prot & PROT_EXEC) && !(vma->vm_flags & VM_EXEC)) {
> >>>>                   int rc = 0;
> >>>> -               if (vma->vm_start >= vma->vm_mm->start_brk &&
> >>>> -                   vma->vm_end <= vma->vm_mm->brk) {
> >>>> +               if (vma_is_initial_heap(vma)) {
> >>>
> >>> This seems to change the condition from
> >>>
> >>>       vma->vm_start >= vma->vm_mm->start_brk && vma->vm_end <= vma->vm_mm->brk
> >>>
> >>> to
> >>>
> >>>       vma->vm_start <= vma->vm_mm->brk && vma->vm_end >= vma->vm_mm->start_brk
> >>>
> >>> (or AND arguments swapped)
> >>>
> >>>       vma->vm_end >= vma->vm_mm->start_brk && vma->vm_start <= vma->vm_mm->brk
> >>>
> >>> Is this intended?
> >>
> >> The new condition is to check whether there is intersection between
> >> [startbrk,brk] and [vm_start,vm_end], it contains orignal check, so
> >> I think it is ok, but for selinux check, I am not sure if there is
> >> some other problem.
> >
> > This particular SELinux vma check is see if the vma falls within the
> > heap; can you confirm that this change preserves this?
>
> Yes, within is one case of new vma scope check.

Thanks for the confirmation.

-- 
paul-moore.com