1.无法读取U盘，

v_sys/system/sepolicy/private/system_app.te

+allow system_app mnt_media_rw_file:dir { search getattr open read };
+allow system_app mnt_media_rw_file:file { getattr open read map };

2.无法OTA升级U盘文件的修改！

v_sys/system/update_engine/update_engine.rc

• group root system wakelock inet cache media_rw

• group root system wakelock inet cache media_rw external_storage sdcard_rw
  
  v_sys/device/mediatek/sepolicy/base/private/update_engine.te

+# = Error 9 修复补丁 =
+# 允许 update_engine 读取 vfat (FAT32 U盘)
+allow update_engine vfat:dir { search getattr open read };
+allow update_engine vfat:file { getattr open read map ioctl };

+# 允许 update_engine 读取 exfat (大容量U盘/SD卡)
+allow update_engine exfat:dir { search getattr open read };
+allow update_engine exfat:file { getattr open read map ioctl };

+# 确保能读取挂载点
+allow update_engine mnt_media_rw_file:dir { search getattr open read };
+
+# 允许 update_engine 使用 App 传递过来的文件句柄 (FD)
+allow update_engine system_app:fd use;