[移动开发]Android 8.1 如何动态修改devnull权限组

现象：在系统上面，点击应用会退出的问题。报如下错误：Failed to open /dev/null
原因：/dev/null权限组导致的
代码路径：
frameworks/base/core/jni/com_android_internal_os_Zygote.cpp
在com_android_internal_os_Zygote.cpp文件中DetachDescriptors方法中修改/dev/null权限

static void DetachDescriptors(JNIEnv* env, jintArray fdsToClose) {
  if (!fdsToClose) {
    return;
  }
  jsize count = env->GetArrayLength(fdsToClose);
  ScopedIntArrayRO ar(env, fdsToClose);
  if (ar.get() == NULL) {
      RuntimeAbort(env, __LINE__, "Bad fd array");
  }
  jsize i;
  int devnull;
  for (i = 0; i < count; i++) {
+	chmod("/dev/null", 0666);
+	chown("/dev/null", AID_ROOT, AID_ROOT);
+	//ALOGW("chmod /dev/null: %d", rec);
    devnull = open("/dev/null", O_RDWR);
    if (devnull < 0) {
      ALOGE("Failed to open /dev/null: %s", strerror(errno));
      RuntimeAbort(env, __LINE__, "Failed to open /dev/null");
      continue;
    }
    ALOGV("Switching descriptor %d to /dev/null: %s", ar[i], strerror(errno));
    if (dup2(devnull, ar[i]) < 0) {
      ALOGE("Failed dup2() on descriptor %d: %s", ar[i], strerror(errno));
      RuntimeAbort(env, __LINE__, "Failed dup2()");
    }
    close(devnull);
  }
}