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

[Kefeng Wang]

On 2023/7/19 17:02, Christian Göttsche wrote:
> On Wed, 19 Jul 2023 at 09:40, Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
> > Use the helpers to simplify code.
> >
> > Cc: Paul Moore <paul@xxxxxxxxxxxxxx>
> > Cc: Stephen Smalley <stephen.smalley.work@xxxxxxxxx>
> > Cc: Eric Paris <eparis@xxxxxxxxxxxxxx>
> > Acked-by: Paul Moore <paul@xxxxxxxxxxxxxx>
> > Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> > ---
> >   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.

> >                          rc = avc_has_perm(sid, sid, SECCLASS_PROCESS,
> >                                            PROCESS__EXECHEAP, NULL);
> > -               } else if (!vma->vm_file &&
> > -                          ((vma->vm_start <= vma->vm_mm->start_stack &&
> > -                            vma->vm_end >= vma->vm_mm->start_stack) ||
> > +               } else if (!vma->vm_file && (vma_is_initial_stack(vma) ||
> >                              vma_is_stack_for_current(vma))) {
> >                          rc = avc_has_perm(sid, sid, SECCLASS_PROCESS,
> >                                            PROCESS__EXECSTACK, NULL);
> > --
> > 2.27.0