Re: [PATCH v3 3/3] kasan: arm64: Fix pcpu_page_first_chunk crash with KASAN_VMALLOC

[Marco Elver]

On Mon, 9 Aug 2021 at 13:10, Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
>
>
> On 2021/8/9 17:37, Kefeng Wang wrote:
> > With KASAN_VMALLOC and NEED_PER_CPU_PAGE_FIRST_CHUNK, it crashs,
> >
> > Unable to handle kernel paging request at virtual address ffff7000028f2000
> > ...
> > swapper pgtable: 64k pages, 48-bit VAs, pgdp=0000000042440000
> > [ffff7000028f2000] pgd=000000063e7c0003, p4d=000000063e7c0003, pud=000000063e7c0003, pmd=000000063e7b0003, pte=0000000000000000
> > Internal error: Oops: 96000007 [#1] PREEMPT SMP
> > Modules linked in:
> > CPU: 0 PID: 0 Comm: swapper Not tainted 5.13.0-rc4-00003-gc6e6e28f3f30-dirty #62
> > Hardware name: linux,dummy-virt (DT)
> > pstate: 200000c5 (nzCv daIF -PAN -UAO -TCO BTYPE=--)
> > pc : kasan_check_range+0x90/0x1a0
> > lr : memcpy+0x88/0xf4
> > sp : ffff80001378fe20
> > ...
> > Call trace:
> >   kasan_check_range+0x90/0x1a0
> >   pcpu_page_first_chunk+0x3f0/0x568
> >   setup_per_cpu_areas+0xb8/0x184
> >   start_kernel+0x8c/0x328
> >
> > The vm area used in vm_area_register_early() has no kasan shadow memory,
> > Let's add a new kasan_populate_early_vm_area_shadow() function to populate
> > the vm area shadow memory to fix the issue.
>
> Should add Acked-by: Marco Elver <elver@xxxxxxxxxx> [for KASAN parts] ,

My Ack is still valid, thanks for noting.

> > Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> > ---
> >   arch/arm64/mm/kasan_init.c | 16 ++++++++++++++++
> >   include/linux/kasan.h      |  6 ++++++
> >   mm/kasan/init.c            |  5 +++++
> >   mm/vmalloc.c               |  1 +
> >   4 files changed, 28 insertions(+)
> >
> > diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> > index 61b52a92b8b6..5b996ca4d996 100644
> > --- a/arch/arm64/mm/kasan_init.c
> > +++ b/arch/arm64/mm/kasan_init.c
> > @@ -287,6 +287,22 @@ static void __init kasan_init_depth(void)
> >       init_task.kasan_depth = 0;
> >   }
> >
> > +#ifdef CONFIG_KASAN_VMALLOC
> > +void __init kasan_populate_early_vm_area_shadow(void *start, unsigned long size)
> > +{
> > +     unsigned long shadow_start, shadow_end;
> > +
> > +     if (!is_vmalloc_or_module_addr(start))
> > +             return;
> > +
> > +     shadow_start = (unsigned long)kasan_mem_to_shadow(start);
> > +     shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE);
> > +     shadow_end = (unsigned long)kasan_mem_to_shadow(start + size);
> > +     shadow_end = ALIGN(shadow_end, PAGE_SIZE);
> > +     kasan_map_populate(shadow_start, shadow_end, NUMA_NO_NODE);
> > +}
> > +#endif
> > +
> >   void __init kasan_init(void)
> >   {
> >       kasan_init_shadow();
> > diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> > index dd874a1ee862..3f8c26d9ef82 100644
> > --- a/include/linux/kasan.h
> > +++ b/include/linux/kasan.h
> > @@ -133,6 +133,8 @@ struct kasan_cache {
> >       bool is_kmalloc;
> >   };
> >
> > +void kasan_populate_early_vm_area_shadow(void *start, unsigned long size);
> > +
> >   slab_flags_t __kasan_never_merge(void);
> >   static __always_inline slab_flags_t kasan_never_merge(void)
> >   {
> > @@ -303,6 +305,10 @@ void kasan_restore_multi_shot(bool enabled);
> >
> >   #else /* CONFIG_KASAN */
> >
> > +static inline void kasan_populate_early_vm_area_shadow(void *start,
> > +                                                    unsigned long size)
> > +{ }
> > +
> >   static inline slab_flags_t kasan_never_merge(void)
> >   {
> >       return 0;
> > diff --git a/mm/kasan/init.c b/mm/kasan/init.c
> > index cc64ed6858c6..d39577d088a1 100644
> > --- a/mm/kasan/init.c
> > +++ b/mm/kasan/init.c
> > @@ -279,6 +279,11 @@ int __ref kasan_populate_early_shadow(const void *shadow_start,
> >       return 0;
> >   }
> >
> > +void __init __weak kasan_populate_early_vm_area_shadow(void *start,
> > +                                                    unsigned long size)
> > +{
> > +}
> > +
> >   static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
> >   {
> >       pte_t *pte;
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index 1e8fe08725b8..66a7e1ea2561 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -2253,6 +2253,7 @@ void __init vm_area_register_early(struct vm_struct *vm, size_t align)
> >       vm->addr = (void *)addr;
> >
> >       vm_area_add_early(vm);
> > +     kasan_populate_early_vm_area_shadow(vm->addr, vm->size);
> >   }
> >
> >   static void vmap_init_free_space(void)