Reland "Fix sandbox::PolicyBase leak"

sandbox/win/src/broker_services.cc

Index: sandbox/win/src/broker_services.cc
diff --git a/sandbox/win/src/broker_services.cc b/sandbox/win/src/broker_services.cc
index 096e4bb821809a92d02fec21bf7dfdf3e89a581e..bf05a8e71c54fa71664e4d3175ace97a9e0f3016 100644
--- a/sandbox/win/src/broker_services.cc
+++ b/sandbox/win/src/broker_services.cc
@@ -53,7 +53,8 @@ enum {
 // Helper structure that allows the Broker to associate a job notification
 // with a job object and with a policy.
 struct JobTracker {
-  JobTracker(base::win::ScopedHandle job, sandbox::PolicyBase* policy)
+  JobTracker(base::win::ScopedHandle job,
+             scoped_refptr<sandbox::PolicyBase> policy)
       : job(std::move(job)), policy(policy) {}
   ~JobTracker() {
     FreeResources();
@@ -64,7 +65,7 @@ struct JobTracker {
   void FreeResources();
 
   base::win::ScopedHandle job;
-  sandbox::PolicyBase* policy;
+  scoped_refptr<sandbox::PolicyBase> policy;
 };
 
 void JobTracker::FreeResources() {
@@ -78,8 +79,7 @@ void JobTracker::FreeResources() {
 
     // In OnJobEmpty() we don't actually use the job handle directly.
     policy->OnJobEmpty(stale_job_handle);
-    policy->Release();
-    policy = NULL;
+    policy = nullptr;
   }
 }
 
@@ -140,10 +140,13 @@ BrokerServicesBase::~BrokerServicesBase() {
   ::DeleteCriticalSection(&lock_);
 }
 
-TargetPolicy* BrokerServicesBase::CreatePolicy() {
+scoped_refptr<TargetPolicy> BrokerServicesBase::CreatePolicy() {
   // If you change the type of the object being created here you must also
   // change the downcast to it in SpawnTarget().
-  return new PolicyBase;
+  scoped_refptr<TargetPolicy> policy(new PolicyBase);
+  // PolicyBase starts with refcount 1.
+  policy->Release();
+  return policy;
 }
 
 // The worker thread stays in a loop waiting for asynchronous notifications
@@ -266,7 +269,7 @@ DWORD WINAPI BrokerServicesBase::TargetEventsThread(PVOID param) {
 // process inside the sandbox.
 ResultCode BrokerServicesBase::SpawnTarget(const wchar_t* exe_path,
                                            const wchar_t* command_line,
-                                           TargetPolicy* policy,
+                                           scoped_refptr<TargetPolicy> policy,
                                            ResultCode* last_warning,
                                            DWORD* last_error,
                                            PROCESS_INFORMATION* target_info) {
@@ -287,7 +290,7 @@ ResultCode BrokerServicesBase::SpawnTarget(const wchar_t* exe_path,
   AutoLock lock(&lock_);
 
   // This downcast is safe as long as we control CreatePolicy()
-  PolicyBase* policy_base = static_cast<PolicyBase*>(policy);
+  scoped_refptr<PolicyBase> policy_base(static_cast<PolicyBase*>(policy.get()));
 
   // Construct the tokens and the job object that we are going to associate
   // with the soon to be created target process.
@@ -439,7 +442,6 @@ ResultCode BrokerServicesBase::SpawnTarget(const wchar_t* exe_path,
 
   // We are going to keep a pointer to the policy because we'll call it when
   // the job object generates notifications using the completion port.
-  policy_base->AddRef();
   if (job.IsValid()) {
     std::unique_ptr<JobTracker> tracker =
         base::MakeUnique<JobTracker>(std::move(job), policy_base);
@@ -454,6 +456,11 @@ ResultCode BrokerServicesBase::SpawnTarget(const wchar_t* exe_path,
     tracker_list_.push_back(std::move(tracker));
     child_process_ids_.insert(process_info.process_id());
   } else {
+    // Leak policy_base. This needs to outlive the child process, but there's
+    // nothing that tracks that lifetime properly if there's no job object.
+    // TODO(wfh): Find a way to make this have the correct lifetime.
+    policy_base->AddRef();

[Will Harris, 2017/01/24 19:47:32]

note: new change

+
     // We have to signal the event once here because the completion port will
     // never get a message that this target is being terminated thus we should
     // not block WaitForAllTargets until we have at least one target with job.