Add sepolicy for gsid properties, and allow system_server to read them.

Bug: 123777418
Test: manual test
Change-Id: I9f8c721dfd074e638573d85cf1d8045a69c3854e
diff --git a/private/gsid.te b/private/gsid.te
index 0c2e50c..62ac06b 100644
--- a/private/gsid.te
+++ b/private/gsid.te
@@ -9,6 +9,7 @@
 binder_use(gsid)
 binder_service(gsid)
 add_service(gsid, gsi_service)
+set_prop(gsid, gsid_prop)
 
 # Needed to create/delete device-mapper nodes, and read/write to them.
 allow gsid dm_device:chr_file rw_file_perms;
@@ -33,6 +34,8 @@
 # gsi_tool passes the system image over the adb connection, via stdin.
 allow gsid adbd:fd use;
 
+neverallow { domain -gsid -init } gsid_prop:property_service set;
+
 # gsid needs to store images on /data, but cannot use file I/O. If it did, the
 # underlying blocks would be encrypted, and we couldn't mount the GSI image in
 # first-stage init. So instead of directly writing to /data, we: