Re: [PATCH] Revert "selinux: use vma_is_initial_stack() and vma_is_initial_heap()"

[Paul Moore <paul@paul-moore.com>]

On Thu, Aug 8, 2024 at 9:40 AM Stephen Smalley
<stephen.smalley.work@gmail.com> wrote:
>
> On Thu, Aug 8, 2024 at 9:09 AM Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
> >
> > This reverts commit 68df1baf158fddc07b6f0333e4c81fe1ccecd6ff.
> >
> > The selinux only want to check whether the VMA range is within the heap
> > range or not, but vma_is_initial_heap() helper will check the intersection
> > between the two ranges, which leads to some issue, let's turn back to the
> > original validation.
> >
> > Reported-by: Marc Reisner <reisner.marc@gmail.com>
> > Closes: https://lore.kernel.org/all/ZrPmoLKJEf1wiFmM@marcreisner.com/
> > Fixes: 68df1baf158f ("selinux: use vma_is_initial_stack() and vma_is_initial_heap()")
> > Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>
> I was only going to recommend reverting the change to the heap check
> but in case Paul is fine with a straight revert,
> Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>

I was hoping that the mm folks would put together a quick patch to fix
what looks like a problem with the helper, but I'm not sure when that
is going to happen and with other callers I don't want to change the
helper and break a different part of the kernel.  Unfortunately that
leaves us with needing a revert, but like Stephen said, I think
reverting just the heap helper is the right thing to do right now; I
also want to put a comment in there for the next time someone tries to
re-add the vma_is_initial_heap().  Give me some time, I'll have a
patch out for this later today.

> > ---
> >  security/selinux/hooks.c | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> > index 81fbfa5b80d4..f5805d4b0aec 100644
> > --- a/security/selinux/hooks.c
> > +++ b/security/selinux/hooks.c
> > @@ -3845,10 +3845,13 @@ 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_is_initial_heap(vma)) {
> > +               if (vma->vm_start >= vma->vm_mm->start_brk &&
> > +                   vma->vm_end <= vma->vm_mm->brk) {
> >                         rc = avc_has_perm(sid, sid, SECCLASS_PROCESS,
> >                                           PROCESS__EXECHEAP, NULL);
> > -               } else if (!vma->vm_file && (vma_is_initial_stack(vma) ||
> > +               } else if (!vma->vm_file &&
> > +                          ((vma->vm_start <= vma->vm_mm->start_stack &&
> > +                            vma->vm_end >= vma->vm_mm->start_stack) ||
> >                             vma_is_stack_for_current(vma))) {
> >                         rc = avc_has_perm(sid, sid, SECCLASS_PROCESS,
> >                                           PROCESS__EXECSTACK, NULL);
> > --
> > 2.41.0

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