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

[Kefeng Wang <wangkefeng.wang@huawei.com>]

On 2023/7/19 23:25, Paul Moore wrote:
> 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?

Yes, within is one case of new vma scope check.

>