runsc: fix panic for runsc wait on stopped container.

PiperOrigin-RevId: 203016694

Author: Random-Liu

runsc/container/container.go

@@ -352,20 +352,29 @@ func (c *Container) Pid() int {
 // Wait waits for the container to exit, and returns its WaitStatus.
 func (c *Container) Wait() (syscall.WaitStatus, error) {
 	log.Debugf("Wait on container %q", c.ID)
+	if c.Status == Stopped {
+		return 0, fmt.Errorf("container is stopped")
+	}
 	return c.Sandbox.Wait(c.ID)
 }
 
 // WaitRootPID waits for process 'pid' in the sandbox's PID namespace and
 // returns its WaitStatus.
 func (c *Container) WaitRootPID(pid int32) (syscall.WaitStatus, error) {
 	log.Debugf("Wait on pid %d in sandbox %q", pid, c.Sandbox.ID)
+	if c.Status == Stopped {
+		return 0, fmt.Errorf("container is stopped")
+	}
 	return c.Sandbox.WaitPID(pid, c.Sandbox.ID)
 }
 
 // WaitPID waits for process 'pid' in the container's PID namespace and returns
 // its WaitStatus.
 func (c *Container) WaitPID(pid int32) (syscall.WaitStatus, error) {
 	log.Debugf("Wait on pid %d in container %q", pid, c.ID)
+	if c.Status == Stopped {
+		return 0, fmt.Errorf("container is stopped")
+	}
 	return c.Sandbox.WaitPID(pid, c.ID)
 }
 

runsc/container/container_test.go

@@ -1211,6 +1211,9 @@ func TestMultiContainerWait(t *testing.T) {
 			} else if es := ws.ExitStatus(); es != 0 {
 				t.Errorf("process %q exited with non-zero status %d", strings.Join(containers[1].Spec.Process.Args, " "), es)
 			}
+			if _, err := containers[1].Wait(); err == nil {
+				t.Errorf("wait for stopped process %q should fail", strings.Join(containers[1].Spec.Process.Args, " "))
+			}
 
 			// After Wait returns, ensure that the root container is running and
 			// the child has finished.
@@ -1231,6 +1234,9 @@ func TestMultiContainerWait(t *testing.T) {
 			} else if es := ws.ExitStatus(); es != 0 {
 				t.Errorf("PID %d exited with non-zero status %d", pid, es)
 			}
+			if _, err := containers[0].WaitPID(pid); err == nil {
+				t.Errorf("wait for stopped PID %d should fail", pid)
+			}
 		}()
 	}