Messages in this thread | | | Subject | Re: [PATCH v3 05/19] x86/kasan/64: Teach KASAN about the cpu_entry_area | From | Andrey Ryabinin <> | Date | Fri, 24 Nov 2017 16:16:18 +0300 |
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On 11/24/2017 07:32 AM, Andy Lutomirski wrote: > The cpu_entry_area will contain stacks. Make sure that KASAN has > appropriate shadow mappings for them. > > Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> > Cc: Alexander Potapenko <glider@google.com> > Cc: Dmitry Vyukov <dvyukov@google.com> > Cc: kasan-dev@googlegroups.com > Signed-off-by: Andy Lutomirski <luto@kernel.org> > --- > arch/x86/mm/kasan_init_64.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c > index 99dfed6dfef8..54561dce742e 100644 > --- a/arch/x86/mm/kasan_init_64.c > +++ b/arch/x86/mm/kasan_init_64.c > @@ -277,6 +277,7 @@ void __init kasan_early_init(void) > void __init kasan_init(void) > { > int i; > + void *cpu_entry_area_begin, *cpu_entry_area_end; > > #ifdef CONFIG_KASAN_INLINE > register_die_notifier(&kasan_die_notifier); > @@ -329,8 +330,18 @@ void __init kasan_init(void) > (unsigned long)kasan_mem_to_shadow(_end), > early_pfn_to_nid(__pa(_stext))); > > + cpu_entry_area_begin = (void *)(__fix_to_virt(FIX_CPU_ENTRY_AREA_BOTTOM)); > + cpu_entry_area_end = (void *)(__fix_to_virt(FIX_CPU_ENTRY_AREA_TOP) + PAGE_SIZE); > + > kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END), > - (void *)KASAN_SHADOW_END); > + kasan_mem_to_shadow(cpu_entry_area_begin)); > + > + kasan_populate_shadow((unsigned long)kasan_mem_to_shadow(cpu_entry_area_begin), > + (unsigned long)kasan_mem_to_shadow(cpu_entry_area_end), > + 0); > + > + kasan_populate_zero_shadow(kasan_mem_to_shadow(cpu_entry_area_end),
Seems we need to round_up kasan_mem_to_shadow(cpu_entry_area_end) to the next page (or alternatively - round_up(cpu_entry_area_end, KASAN_SHADOW_SCALE_SIZE*PAGE_SIZE)). Otherwise, kasan_populate_zero_shadow() will overpopulate the last shadow page of cpu_entry area with kasan_zero_page.
We don't necessarily need to round_down(kasan_mem_to_shadow(cpu_entry_area_begin), PAGE_SIZE) because kasan_populate_zero_shadow() will not populate the last 'incomplete' page and kasan_populate_shadow() does round_down() internally, which is exactly what we want here. But it might be better to round_down() explicitly anyway, to avoid relying on such subtle implementation details.
> + (void *)KASAN_SHADOW_END); > > load_cr3(init_top_pgt); > __flush_tlb_all(); >
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