linux-kernel - Re: [PATCH v2 3/4] selinux: use vma_is_initial_stack() and vma_is_initial

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Date:   Wed, 19 Jul 2023 11:25:12 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>,
        Christian Göttsche <cgzones@...glemail.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-perf-users@...r.kernel.org,
        selinux@...r.kernel.org,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>
Subject: Re: [PATCH v2 3/4] selinux: use vma_is_initial_stack() and vma_is_initial_heap()

On Wed, Jul 19, 2023 at 6:23 AM Kefeng Wang <wangkefeng.wang@...wei.com> wrote:
> On 2023/7/19 17:02, Christian Göttsche wrote:
> > On Wed, 19 Jul 2023 at 09:40, Kefeng Wang <wangkefeng.wang@...wei.com> wrote:
> >>
> >> Use the helpers to simplify code.
> >>
> >> Cc: Paul Moore <paul@...l-moore.com>
> >> Cc: Stephen Smalley <stephen.smalley.work@...il.com>
> >> Cc: Eric Paris <eparis@...isplace.org>
> >> Acked-by: Paul Moore <paul@...l-moore.com>
> >> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.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