1 files changed, 15 insertions, 4 deletions
diff --git a/third_party/base/allocator/partition_allocator/address_space_randomization.cc b/third_party/base/allocator/partition_allocator/address_space_randomization.cc
index fdcc5911b9..08f22be80a 100644
--- a/third_party/base/allocator/partition_allocator/address_space_randomization.cc
+++ b/third_party/base/allocator/partition_allocator/address_space_randomization.cc
@@ -15,6 +15,11 @@
 #include <unistd.h>
 #endif
 
+// VersionHelpers.h must be included after windows.h.
+#if defined(OS_WIN)
+#include <VersionHelpers.h>
+#endif
+
 namespace pdfium {
 namespace base {
 
@@ -90,11 +95,17 @@ void* GetRandomPageBase() {
 // This address mask gives a low likelihood of address space collisions. We
 // handle the situation gracefully if there is a collision.
 #if defined(OS_WIN)
-  // 64-bit Windows has a bizarrely small 8TB user address space. Allocates in
-  // the 1-5TB region. TODO(palmer): See if Windows >= 8.1 has the full 47 bits,
-  // and use it if so. crbug.com/672219
   random &= 0x3ffffffffffUL;
-  random += 0x10000000000UL;
+  // Windows >= 8.1 has the full 47 bits. Use them where available.
+  static bool windows_81 = false;
+  static bool windows_81_initialized = false;
+  if (!windows_81_initialized) {
+    windows_81 = IsWindows8Point1OrGreater();
+    windows_81_initialized = true;
+  }
+  if (!windows_81) {
+    random += 0x10000000000UL;
+  }
 #elif defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
   // This range is copied from the TSan source, but works for all tools.
   random &= 0x007fffffffffUL;