Merge pull request #332 from LK4D4/fix_panic_in_getpids

Reorder checks in Walk to avoid panics

libcontainer/cgroups/utils.go

@@ -329,21 +329,18 @@ func GetPids(path string) ([]int, error) {
 	var pids []int
 	// collect pids from all sub-cgroups
 	err := filepath.Walk(path, func(p string, info os.FileInfo, iErr error) error {
-		if info.IsDir() {
+		dir, file := filepath.Split(p)
+		if file != "cgroup.procs" {
 			return nil
 		}
-
-		dir, file := filepath.Split(p)
-		if file == "cgroup.procs" {
-			if iErr != nil {
-				return iErr
-			}
-			cPids, err := readProcsFile(dir)
-			if err != nil {
-				return err
-			}
-			pids = append(pids, cPids...)
+		if iErr != nil {
+			return iErr
 		}
+		cPids, err := readProcsFile(dir)
+		if err != nil {
+			return err
+		}
+		pids = append(pids, cPids...)
 		return nil
 	})
 	return pids, err

libcontainer/integration/exec_test.go

@@ -1250,3 +1250,29 @@ func TestRootfsPropagationSharedMount(t *testing.T) {
 		t.Fatalf("Mount in container on %s did not propagate to host on %s. finmnt output=%s", dir2cont, dir2host, outtrim)
 	}
 }
+
+func TestPIDHost(t *testing.T) {
+	if testing.Short() {
+		return
+	}
+
+	rootfs, err := newRootfs()
+	ok(t, err)
+	defer remove(rootfs)
+
+	l, err := os.Readlink("/proc/1/ns/pid")
+	ok(t, err)
+
+	config := newTemplateConfig(rootfs)
+	config.Namespaces.Remove(configs.NEWPID)
+	buffers, exitCode, err := runContainer(config, "", "readlink", "/proc/self/ns/pid")
+	ok(t, err)
+
+	if exitCode != 0 {
+		t.Fatalf("exit code not 0. code %d stderr %q", exitCode, buffers.Stderr)
+	}
+
+	if actual := strings.Trim(buffers.Stdout.String(), "\n"); actual != l {
+		t.Fatalf("ipc link not equal to host link %q %q", actual, l)
+	}
+}