Updating ExploitabilityLinux to check memory mapping names against a prefix

instead of a specific name.

This will prevent false positives on systems which use a format such as
“[stack:69616]” for stack memory mapping names.

Change-Id: I51aeda2fe856c1f37f0d18ac06cce69fec2fffa2
Reviewed-on: https://chromium-review.googlesource.com/377086
Reviewed-by: Mike Frysinger <vapier@chromium.org>

src/processor/exploitability_linux.cc

@@ -54,14 +54,18 @@
 
 namespace {
 
+// Prefixes for memory mapping names.
+constexpr char kHeapPrefix[] = "[heap";
+constexpr char kStackPrefix[] =  "[stack";
+
 // This function in libc is called if the program was compiled with
 // -fstack-protector and a function's stack canary changes.
-const char kStackCheckFailureFunction[] = "__stack_chk_fail";
+constexpr char kStackCheckFailureFunction[] = "__stack_chk_fail";
 
 // This function in libc is called if the program was compiled with
 // -D_FORTIFY_SOURCE=2, a function like strcpy() is called, and the runtime
 // can determine that the call would overflow the target buffer.
-const char kBoundsCheckFailureFunction[] = "__chk_fail";
+constexpr char kBoundsCheckFailureFunction[] = "__chk_fail";
 
 #ifndef _WIN32
 const unsigned int MAX_INSTRUCTION_LEN = 15;
@@ -539,9 +543,9 @@ bool ExploitabilityLinux::StackPointerOffStack(uint64_t 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]"));
+  return !linux_maps || (linux_maps->GetPathname().compare("") &&
+                         linux_maps->GetPathname().compare(
+                             0, strlen(kStackPrefix), kStackPrefix));
 }
 
 bool ExploitabilityLinux::ExecutableStackOrHeap() {
@@ -551,9 +555,10 @@ bool ExploitabilityLinux::ExecutableStackOrHeap() {
       const MinidumpLinuxMaps *linux_maps =
           linux_maps_list->GetLinuxMapsAtIndex(i);
       // Check for executable stack or heap for each mapping.
-      if (linux_maps &&
-          (!linux_maps->GetPathname().compare("[stack]") ||
-           !linux_maps->GetPathname().compare("[heap]")) &&
+      if (linux_maps && (!linux_maps->GetPathname().compare(
+                             0, strlen(kStackPrefix), kStackPrefix) ||
+                         !linux_maps->GetPathname().compare(
+                             0, strlen(kHeapPrefix), kHeapPrefix)) &&
           linux_maps->IsExecutable()) {
         return true;
       }

src/processor/exploitability_unittest.cc

@@ -161,6 +161,8 @@ TEST(ExploitabilityTest, TestLinuxEngine) {
             ExploitabilityFor("linux_inside_module_exe_region2.dmp"));
   ASSERT_EQ(google_breakpad::EXPLOITABILITY_INTERESTING,
             ExploitabilityFor("linux_stack_pointer_in_stack.dmp"));
+  ASSERT_EQ(google_breakpad::EXPLOITABILITY_INTERESTING,
+            ExploitabilityFor("linux_stack_pointer_in_stack_alt_name.dmp"));
   ASSERT_EQ(google_breakpad::EXPLOITABILITY_HIGH,
             ExploitabilityFor("linux_stack_pointer_in_module.dmp"));
   ASSERT_EQ(google_breakpad::EXPLOITABILITY_HIGH,