Add persist.vendor.overlay. to properties

Allow the system_server to change. Allow the zygote to read it as well.

Test: Have system_server set a property
Change-Id: Ie90eec8b733fa7193861026a3a6e0fb0ba5d5318

private/property_contexts

@@ -56,6 +56,8 @@ persist.sys.audit_safemode      u:object_r:safemode_prop:s0
 persist.service.        u:object_r:system_prop:s0
 persist.service.bdroid. u:object_r:bluetooth_prop:s0
 persist.security.       u:object_r:system_prop:s0
+persist.vendor.overlay.  u:object_r:overlay_prop:s0
+ro.boot.vendor.overlay.  u:object_r:overlay_prop:s0
 
 # Boolean property set by system server upon boot indicating
 # if device owner is provisioned.

public/property.te

@@ -41,5 +41,6 @@ type config_prop, property_type, core_property_type;
 type device_logging_prop, property_type;
 type safemode_prop, property_type;
 type hwservicemanager_prop, property_type;
+type overlay_prop, property_type;
 
 allow property_type tmpfs:filesystem associate;

public/system_server.te

@@ -357,6 +357,7 @@ set_prop(system_server, fingerprint_prop)
 set_prop(system_server, device_logging_prop)
 set_prop(system_server, wifi_prop)
 set_prop(system_server, dumpstate_options_prop)
+set_prop(system_server, overlay_prop)
 userdebug_or_eng(`set_prop(system_server, wifi_log_prop)')
 
 # ctl interface

public/zygote.te

@@ -88,6 +88,9 @@ userdebug_or_eng(`
 allow zygote ion_device:chr_file r_file_perms;
 allow zygote tmpfs:dir r_dir_perms;
 
+# Let the zygote access overlays so it can initialize the AssetManager
+get_prop(zygote, overlay_prop)
+
 ###
 ### neverallow rules
 ###