diff --git a/lib/asan/asan_allocator2.cc b/lib/asan/asan_allocator2.cc
index c768698..6dc7753 100644
--- a/lib/asan/asan_allocator2.cc
+++ b/lib/asan/asan_allocator2.cc
@@ -18,6 +18,7 @@
 #include "asan_allocator.h"
 #if ASAN_ALLOCATOR_VERSION == 2
 
+#include "asan_mapping.h"
 #include "asan_thread.h"
 #include "asan_thread_registry.h"
 #include "sanitizer/asan_interface.h"
@@ -26,19 +27,28 @@
 
 namespace __asan {
 
+struct AsanMapUnmapCallback {
+  void OnMap(uptr p, uptr size) const {
+    PoisonShadow(p, size, kAsanHeapLeftRedzoneMagic);
+  }
+  void OnUnmap(uptr p, uptr size) const {
+    PoisonShadow(p, size, 0);
+  }
+};
+
 #if SANITIZER_WORDSIZE == 64
 const uptr kAllocatorSpace = 0x600000000000ULL;
 const uptr kAllocatorSize  =  0x10000000000ULL;  // 1T.
 typedef SizeClassAllocator64<kAllocatorSpace, kAllocatorSize, 0 /*metadata*/,
-    DefaultSizeClassMap> PrimaryAllocator;
+    DefaultSizeClassMap, AsanMapUnmapCallback> PrimaryAllocator;
 #elif SANITIZER_WORDSIZE == 32
 static const u64 kAddressSpaceSize = 1ULL << 32;
-typedef SizeClassAllocator32<
-  0, kAddressSpaceSize, 16, CompactSizeClassMap> PrimaryAllocator;
+typedef SizeClassAllocator32<0, kAddressSpaceSize, 16,
+  CompactSizeClassMap, AsanMapUnmapCallback> PrimaryAllocator;
 #endif
 
 typedef SizeClassAllocatorLocalCache<PrimaryAllocator> AllocatorCache;
-typedef LargeMmapAllocator<> SecondaryAllocator;
+typedef LargeMmapAllocator<AsanMapUnmapCallback> SecondaryAllocator;
 typedef CombinedAllocator<PrimaryAllocator, AllocatorCache,
     SecondaryAllocator> Allocator;
 
@@ -177,6 +187,16 @@
   m->from_memalign = user_beg != beg_plus_redzone;
   m->user_requested_size = size;
 
+  uptr size_rounded_down_to_granularity = RoundDownTo(size, SHADOW_GRANULARITY);
+  // Unpoison the bulk of the memory region.
+  if (size_rounded_down_to_granularity)
+    PoisonShadow(user_beg, size_rounded_down_to_granularity, 0);
+  // Deal with the end of the region if size is not aligned to granularity.
+  if (size != size_rounded_down_to_granularity) {
+    u8 *shadow = (u8*)MemToShadow(user_beg + size_rounded_down_to_granularity);
+    *shadow = size & (SHADOW_GRANULARITY - 1);
+  }
+
   void *res = reinterpret_cast<void *>(user_beg);
   ASAN_MALLOC_HOOK(res, size);
   return res;
@@ -190,6 +210,9 @@
   uptr alloc_beg = p - ComputeRZSize(m->user_requested_size);
   if (m->from_memalign)
     alloc_beg = reinterpret_cast<uptr>(allocator.GetBlockBegin(ptr));
+  // Poison the region.
+  PoisonShadow(m->Beg(), RoundUpTo(m->user_requested_size, SHADOW_GRANULARITY),
+               kAsanHeapFreeMagic);
   ASAN_FREE_HOOK(ptr);
   allocator.Deallocate(&cache, reinterpret_cast<void *>(alloc_beg));
 }
diff --git a/lib/asan/asan_poisoning.cc b/lib/asan/asan_poisoning.cc
index dcdc7f8..3da9671 100644
--- a/lib/asan/asan_poisoning.cc
+++ b/lib/asan/asan_poisoning.cc
@@ -168,7 +168,7 @@
     // If possible, mark all the bytes mapping to last shadow byte as
     // unaddressable.
     if (end_value > 0 && end_value <= end_offset)
-      *shadow_end = kAsanStackUseAfterScopeMagic;
+      *shadow_end = (s8)kAsanStackUseAfterScopeMagic;
   } else {
     // If necessary, mark few first bytes mapping to last shadow byte
     // as addressable
diff --git a/lib/sanitizer_common/sanitizer_common.h b/lib/sanitizer_common/sanitizer_common.h
index 1f15005..74962b4 100644
--- a/lib/sanitizer_common/sanitizer_common.h
+++ b/lib/sanitizer_common/sanitizer_common.h
@@ -161,6 +161,9 @@
   CHECK(IsPowerOfTwo(boundary));
   return (size + boundary - 1) & ~(boundary - 1);
 }
+INLINE uptr RoundDownTo(uptr x, uptr boundary) {
+  return x & ~(boundary - 1);
+}
 INLINE bool IsAligned(uptr a, uptr alignment) {
   return (a & (alignment - 1)) == 0;
 }