Add check to see if stack pointer is off the stack according to the memory

src/processor/exploitability_linux.cc

Index: src/processor/exploitability_linux.cc
===================================================================
--- src/processor/exploitability_linux.cc	(revision 1481)
+++ src/processor/exploitability_linux.cc	(working copy)
@@ -102,6 +102,7 @@
   // Check if the instruction pointer is in a valid instruction region
   // by finding if it maps to an executable part of memory.
   uint64_t instruction_ptr = 0;
+  uint64_t stack_ptr = 0;
 
   const MinidumpContext *context = exception->GetContext();
   if (context == NULL) {
@@ -115,8 +116,15 @@
     return EXPLOITABILITY_ERR_PROCESSING;
   }
 
+  // Getting the stack pointer.
+  if (!context->GetStackPointer(&stack_ptr)) {
+    BPLOG(INFO) << "Failed to retrieve stack pointer.";
+    return EXPLOITABILITY_ERR_PROCESSING;
+  }
+
   // Checking for the instruction pointer in a valid instruction region.
-  if (!this->InstructionPointerInCode(instruction_ptr)) {
+  if (!this->InstructionPointerInCode(instruction_ptr) ||
+       this->StackPointerOffStack(stack_ptr)) {
     return EXPLOITABILITY_HIGH;
   }
 
@@ -125,6 +133,22 @@
   return EXPLOITABILITY_INTERESTING;
 }
 
+bool ExploitabilityLinux::StackPointerOffStack(uint64_t stack_ptr) {
+  MinidumpLinuxMapsList *linux_maps_list = dump_->GetLinuxMapsList();
+  // Inconclusive if there are no mappings available.
+  if (!linux_maps_list) {
+    return false;
+  }
+  const MinidumpLinuxMaps *linux_maps =
+      linux_maps_list->GetLinuxMapsForAddress(stack_ptr);
+  // Checks if the stack pointer maps to a valid mapping and if the mapping
+  // is not the stack. If the mapping has no name, it is inconclusive whether
+  // it is off the stack.
+  return !linux_maps ||
+         (linux_maps->GetPathname().compare("") &&
+          linux_maps->GetPathname().compare("[stack]"));
+}
+
 bool ExploitabilityLinux::InstructionPointerInCode(uint64_t instruction_ptr) {
   // Get Linux memory mapping from /proc/self/maps. Checking whether the
   // region the instruction pointer is in has executable permission can tell