Wrong id and gid running /system/bin/sdcard
Edit:
The solution is here: https://source.android.com/devices/storage/config.html


  "For Android releases 4.3 and later, the various fstab files used by
  init, vold and recovery were unified in the /fstab. file. For
  external storage volumes that are managed by vold, the entries should
  have the following format:"


 &lt;src&gt; &lt;mnt_point&gt; &lt;type&gt; &lt;mnt_flags&gt; &lt;fs_mgr_flags&gt;



  "...Devices may provide external storage by emulating a
  case-insensitive, permissionless filesystem backed by internal
  storage. One possible implementation is provided by the FUSE daemon in
  system/core/sdcard, which can be added as a device-specific init.rc
  service:"


# virtual sdcard daemon running as media_rw (1023)
service sdcard /system/bin/sdcard &lt;source_path&gt; &lt;dest_path&gt; 1023 1023
    class late_start