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

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Message-ID: <1e839238-c78d-71e0-28ae-7efff0e04953@huawei.com>
Date:   Thu, 20 Jul 2023 16:28:19 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Paul Moore <paul@...l-moore.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 2023/7/19 23:25, Paul Moore wrote:
> 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?

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

>