Allow installd to delete files via sdcardfs.

When installd clears cached files on external storage, the sdcardfs
kernel filesystem needs to be kept in the loop to release any cached
dentries that it's holding onto.  (Otherwise the underlying disk
space isn't actually released.)

installd can already delete the underlying files directly (via the
media_rw_data_file rules), so this technically isn't expanding its
capabilities.

avc: granted { search } for name="/" dev="tmpfs" ino=6897 scontext=u:r:installd:s0 tcontext=u:object_r:tmpfs:s0 tclass=dir
avc: denied { open } for path="/mnt/runtime/default/emulated/0/Android/data" dev="sdcardfs" ino=589830 scontext=u:r:installd:s0 tcontext=u:object_r:sdcardfs:s0 tclass=dir permissive=1
avc: denied { write } for name="com.google.android.inputmethod.japanese" dev="sdcardfs" ino=590040 scontext=u:r:installd:s0 tcontext=u:object_r:sdcardfs:s0 tclass=dir permissive=0
avc: denied { remove_name } for name="cache_r.m" dev="sdcardfs" ino=589868 scontext=u:r:installd:s0 tcontext=u:object_r:sdcardfs:s0 tclass=dir permissive=0
avc: denied { getattr } for path="/mnt/runtime/default/emulated/0/Android/data/.nomedia" dev="sdcardfs" ino=589831 scontext=u:r:installd:s0 tcontext=u:object_r:sdcardfs:s0 tclass=file permissive=1

Test: cts-tradefed run commandAndExit cts-dev -m CtsAppSecurityHostTestCases -t android.appsecurity.cts.StorageHostTest
Bug: 37486230
Change-Id: Icfd00a9ba379b1f50c48fe85849304cf9859bcb2

public/domain_deprecated.te

 # rules removed from the domain attribute
 
 # Search /storage/emulated tmpfs mount.
-allow domain_deprecated tmpfs:dir r_dir_perms;
+allow { domain_deprecated -installd } tmpfs:dir r_dir_perms;
 userdebug_or_eng(`
 auditallow {
   domain_deprecated
   -appdomain
+  -installd
   -sdcardd
   -surfaceflinger
   -system_server

public/installd.te

@@ -54,6 +54,12 @@ allow installd media_rw_data_file:file { getattr unlink };
 allow installd system_data_file:dir relabelfrom;
 allow installd media_rw_data_file:dir relabelto;
 
+# Delete /data/media files through sdcardfs, instead of going behind its back
+allow installd tmpfs:dir r_dir_perms;
+allow installd storage_file:dir search;
+allow installd sdcardfs:dir { search open read write remove_name getattr rmdir };
+allow installd sdcardfs:file { getattr unlink };
+
 # Upgrade /data/misc/keychain for multi-user if necessary.
 allow installd misc_user_data_file:dir create_dir_perms;
 allow installd misc_user_data_file:file create_file_perms;