Re: [BUG]: mm/vmalloc: uninitialized variable access in pcpu_get_vm_areas

[Roman Penyaev]

On 2019-06-17 16:04, Arnd Bergmann wrote:
> On Mon, Jun 17, 2019 at 3:49 PM Roman Penyaev <rpenyaev@xxxxxxx> wrote:
> > >               augment_tree_propagate_from(va);
> > >
> > > -             if (type == NE_FIT_TYPE)
> > > -                     insert_vmap_area_augment(lva, &va->rb_node,
> > > -                             &free_vmap_area_root, &free_vmap_area_list);
> > > -     }
> > > -
> > >       return 0;
> > >  }
> >
> >
> > Hi Arnd,
> >
> > Seems the proper fix is just setting lva to NULL.  The only place
> > where lva is allocated and then used is when type == NE_FIT_TYPE,
> > so according to my shallow understanding of the code everything
> > should be fine.
>
> I don't see how NULL could work here. insert_vmap_area_augment()
> passes the va pointer into find_va_links() and link_va(), both of
> which dereference the pointer, see

Exactly, but insert_vmap_area_augement() accepts 'va', not 'lva',
but in your variant 'va' is already freed (see type == FL_FIT_TYPE
branch, on top of that function).  So that should be use-after-free.

--
Roman