Fix a data race

PiperOrigin-RevId: 705003451 Change-Id: I15dcab987592a1029c57fbcde687932bdea4d417
google · Dec 11, 2024 · 037c5c2 · 037c5c2
1 parent f06ee44
commit 037c5c2
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Showing 2 changed files with 8 additions and 2 deletions.
diff --git a/sandboxed_api/sandbox2/monitor_ptrace.cc b/sandboxed_api/sandbox2/monitor_ptrace.cc
@@ -206,6 +206,7 @@ void PtraceMonitor::NotifyMonitor() {
 }
 
 void PtraceMonitor::Join() {
+  absl::MutexLock lock(&thread_mutex_);
   if (thread_.IsJoinable()) {
     thread_.Join();
     CHECK(IsDone()) << "Monitor did not terminate";
@@ -215,7 +216,10 @@ void PtraceMonitor::Join() {
 }
 
 void PtraceMonitor::RunInternal() {
-  thread_ = sapi::Thread(this, &PtraceMonitor::Run, "sandbox2-Monitor");
+  {
+    absl::MutexLock lock(&thread_mutex_);
+    thread_ = sapi::Thread(this, &PtraceMonitor::Run, "sandbox2-Monitor");
+  }
 
   // Wait for the Monitor to set-up the sandboxee correctly (or fail while
   // doing that). From here on, it is safe to use the IPC object for

diff --git a/sandboxed_api/sandbox2/monitor_ptrace.h b/sandboxed_api/sandbox2/monitor_ptrace.h
@@ -158,8 +158,10 @@ class PtraceMonitor : public MonitorBase {
   // PidWaiter for waiting for sandboxee events.
   PidWaiter pid_waiter_;
 
+  // Synchronizes joining the monitor thread.
+  absl::Mutex thread_mutex_;
   // Monitor thread object.
-  sapi::Thread thread_;
+  sapi::Thread ABSL_GUARDED_BY(thread_mutex_) thread_;
 
   // Synchronizes deadline setting and notifying the monitor.
   absl::Mutex notify_mutex_;