Messages in this thread | | | From | Andy Lutomirski <> | Date | Thu, 23 Nov 2017 07:22:41 -0800 | Subject | Re: [PATCH v2 06/18] x86/kasan/64: Teach KASAN about the cpu_entry_area |
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On Thu, Nov 23, 2017 at 2:08 AM, Andrey Ryabinin <aryabinin@virtuozzo.com> wrote: > > > On 11/22/2017 06:22 PM, Andy Lutomirski wrote: >> On Wed, Nov 22, 2017 at 1:05 AM, Andrey Ryabinin >> <aryabinin@virtuozzo.com> wrote: >>> >>> >>> On 11/22/2017 07:44 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 | 9 ++++++++- >>>> 1 file changed, 8 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c >>>> index 99dfed6dfef8..43d376687315 100644 >>>> --- a/arch/x86/mm/kasan_init_64.c >>>> +++ b/arch/x86/mm/kasan_init_64.c >>>> @@ -330,7 +330,14 @@ void __init kasan_init(void) >>>> early_pfn_to_nid(__pa(_stext))); >>>> >>>> kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END), >>>> - (void *)KASAN_SHADOW_END); >>>> + kasan_mem_to_shadow((void *)(__fix_to_virt(FIX_CPU_ENTRY_AREA_BOTTOM)))); >>>> + >>>> + kasan_populate_shadow((unsigned long)kasan_mem_to_shadow((void *)(__fix_to_virt(FIX_CPU_ENTRY_AREA_BOTTOM))), >>>> + (unsigned long)kasan_mem_to_shadow((void *)(__fix_to_virt(FIX_CPU_ENTRY_AREA_TOP) + PAGE_SIZE)), >>> >>> What's '+ PAGE_SIZE' for? >>> >> >> __fix_to_virt(..._TOP) returns the address of the *bottom* of the last >> cpu_entry_area page. +PAGE_SIZE returns one past the end of the >> region, which I assume is the correct thing to pass. >> > > Right. > > Perhaps, it would be better to use variables, just avoid such awfully long lines, I mean like this: > fixmap_shadow_start = (void *)__fix_to_virt(FIX_CPU_ENTRY_AREA_BOTTOM); > fixmap_shadow_start = kasan_mem_to_shadow(fixmap_shadow_start); > > fixmap_shadow_end = (void *)__fix_to_virt(FIX_CPU_ENTRY_AREA_TOP) + PAGE_SIZE; > fixmap_shadow_end = kasan_mem_to_shadow(fixmap_shadow_end); > > kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END), > fixmap_shadow_start); > > kasan_populate_shadow((unsigned long)fixmap_shadow_start, > (unsigned long)fixmap_shadow_end, > 0); > > I'm also thinking that we should change kasan_populate_shadow() to take void* instead of 'unsigned long' > to avoid those casts.
I did something similar, but I left the kasan_mem_to_shadow in for consistency with the rest.
I think the real way to clean this up is like this:
struct kasan_range { void *start; void *end; };
struct kasan_range ranges[] = { { range 1 }, { range 2 }, };
sort(range, ARRAY_SIZE(ranges), sizeof(ranges[0]), ...);
last_end = PAGE_OFFSET; /* or whatever is right */
for (i = 0; i < ARRAY_SIZE(ranges); i++) [ WARN_ON(ranges[i].start < last_end);
if (ranges[i].start > last_end) kasan_populate_zero_shadow(...); kasan_populate_shadow(...); last_end = ranges[i].end; }
kasan_populate_zero_shadow(last_end, the real end);
Then the code doesn't need to duplicate each boundary or to hardcode the order in which things appear.
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