tree f4d034223be743129965153a87a92e433f52623b
parent adecd0ae753ae1f5dd7e4e807d5f831bf6376eb0
author Martijn Coenen <maco@google.com> 1576572102 +0100
committer Martijn Coenen <maco@google.com> 1576590206 +0100

Vold mkdirs should use lower filesystem.

If vold's view of /storage is FUSE, it means that creation of
directories in Android/ will go through FUSE as well. The implementation
of fs_mkdirs() tries to opendir() individual parts of the entire path;
so for a path "/storage/emulated/0/Android", it will try to opendir()
"/storage", "/storage/emulated", etc.

By default, "/storage/emulated" is created with 711 permissions; while
vold itself is root, access to /storage/emulated is routed through
MediaProvider (because of FUSE), and MediaProvider doesn't run as root,
nor does it have the capabilities to bypass the ACL. This means that
fs_mkdirs() as it is will fail, because opendir("/storage/emulated")
will fail from MediaProvider.

To prevent this, route these accesses directly to the lower filesystem
(currently, sdcardfs), by renaming the paths.

Bug: 146189163
Test: atest AdoptableHostTest
Change-Id: Idbb41b9ffad9713f3b255c51bd4de16f4d090223