arm64/kasan: don't allocate extra shadow memory

We used to read several bytes of the shadow memory in advance.
Therefore additional shadow memory mapped to prevent crash if
speculative load would happen near the end of the mapped shadow memory.

Now we don't have such speculative loads, so we no longer need to map
additional shadow memory.

Link: http://lkml.kernel.org/r/20170601162338.23540-3-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 687a358a37337af9cf7a0d50c27b0176cfbd2012..81f03959a4ab2f1729718fa6a528d751d0495482 100644 (file)
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -191,14 +191,8 @@ void __init kasan_init(void)
                if (start >= end)
                        break;
 
-               /*
-                * end + 1 here is intentional. We check several shadow bytes in
-                * advance to slightly speed up fastpath. In some rare cases
-                * we could cross boundary of mapped shadow, so we just map
-                * some more here.
-                */
                vmemmap_populate((unsigned long)kasan_mem_to_shadow(start),
-                               (unsigned long)kasan_mem_to_shadow(end) + 1,
+                               (unsigned long)kasan_mem_to_shadow(end),
                                pfn_to_nid(virt_to_pfn(start)));
        }