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

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

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?

-- 
paul-moore.com