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

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On 2023/7/19 23:25, Paul Moore wrote:
On Wed, Jul 19, 2023 at 6:23 AM Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
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.

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.





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