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 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.

> 
>>                          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
>>