[sanitizer] fix calloc overflow in asan/tsan/msan

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@173441 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/sanitizer_common/sanitizer_allocator.cc b/lib/sanitizer_common/sanitizer_allocator.cc
index b13a7c6..26baf73 100644
--- a/lib/sanitizer_common/sanitizer_allocator.cc
+++ b/lib/sanitizer_common/sanitizer_allocator.cc
@@ -75,4 +75,9 @@
   low_level_alloc_callback = callback;
 }
 
+bool CallocShouldReturnNullDueToOverflow(uptr size, uptr n) {
+  uptr mul = size * n;
+  return mul < size || mul < n;
+}
+
 }  // namespace __sanitizer