diff --git a/private/system_server.te b/private/system_server.te
index 750ee3e..de62eef 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -880,7 +880,8 @@
 neverallow system_server dex2oat_exec:file no_x_file_perms;
 
 # system_server should never execute or load executable shared libraries
-# in /data
+# in /data. Executable files in /data are a persistence vector.
+# https://bugs.chromium.org/p/project-zero/issues/detail?id=955 for example.
 neverallow system_server data_file_type:file no_x_file_perms;
 
 # The only block device system_server should be accessing is
@@ -889,6 +890,8 @@
 neverallow system_server { dev_type -frp_block_device }:blk_file no_rw_file_perms;
 
 # system_server should never use JIT functionality
+# See https://googleprojectzero.blogspot.com/2016/12/bitunmap-attacking-android-ashmem.html
+# in the section titled "A Short ROP Chain" for why.
 neverallow system_server self:process execmem;
 neverallow system_server ashmem_device:chr_file execute;