Reserve the bottom of the address space to prevent predictable alocations.

sandbox/src/target_process.cc

Index: sandbox/src/target_process.cc
===================================================================
--- sandbox/src/target_process.cc	(revision 123489)
+++ sandbox/src/target_process.cc	(working copy)
@@ -39,8 +39,29 @@
   }
 }
 
+// Reserve a random range at the bottom of the address space in the target
+// process to prevent predictable alocations at low addresses.
+void PoisonLowerAddressRange(HANDLE process) {
+  unsigned int limit;
+  rand_s(&limit);
+  char* ptr = 0;
+  const size_t kMask64k = 0xFFFF;
+  // Random range (512k-4.5mb) in 64k steps.
+  const char* end = ptr + ((((limit % 4096) + 512) * 1024) & ~kMask64k);
+  while (ptr < end) {
+    MEMORY_BASIC_INFORMATION memory_info;
+    if (!::VirtualQueryEx(process, ptr, &memory_info, sizeof(memory_info)))
+      break;
+    size_t size = std::min((memory_info.RegionSize + kMask64k) & ~kMask64k,
+                           static_cast<SIZE_T>(end - ptr));
+    if (ptr && memory_info.State == MEM_FREE)
+      ::VirtualAllocEx(process, ptr, size, MEM_RESERVE, PAGE_NOACCESS);
+    ptr += size;
+  }
 }
 
+}
+
 namespace sandbox {
 
 SANDBOX_INTERCEPT HANDLE g_shared_section;
@@ -152,6 +173,8 @@
     return ::GetLastError();
   }
 
+  PoisonLowerAddressRange(process_info.hProcess);
+
   DWORD win_result = ERROR_SUCCESS;
 
   // Assign the suspended target to the windows job object