Messages in this thread | | | From | Andy Lutomirski <> | Date | Fri, 24 Nov 2017 08:27:09 -0800 | Subject | Re: [PATCH v3 05/19] x86/kasan/64: Teach KASAN about the cpu_entry_area |
| |
On Fri, Nov 24, 2017 at 5:16 AM, Andrey Ryabinin <aryabinin@virtuozzo.com> wrote: > > > 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.
Any chance you could send a fixup patch or a replacement patch? You obviously understand this code *way* better than I do.
Or you could do my table-based approach and fix it permanently... :)
> >> + (void *)KASAN_SHADOW_END); >> >> load_cr3(init_top_pgt); >> __flush_tlb_all(); >>
| |