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

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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





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