Merge pull request #1561 from zhangningdlut:chris_tty

PiperOrigin-RevId: 291821850

pkg/sentry/kernel/tty.go

@@ -33,6 +33,8 @@ type TTY struct {
 // TTY returns the thread group's controlling terminal. If nil, there is no
 // controlling terminal.
 func (tg *ThreadGroup) TTY() *TTY {
+	tg.pidns.owner.mu.RLock()
+	defer tg.pidns.owner.mu.RUnlock()
 	tg.signalHandlers.mu.Lock()
 	defer tg.signalHandlers.mu.Unlock()
 	return tg.tty