Validate no-cross-domain /proc/PID access

am: 7a463809

Change-Id: Iba80938afccd21f0c3b69626223b35c672358e77

private/app.te

@@ -402,8 +402,10 @@ neverallow appdomain zygote_socket:sock_file write;
 # ptrace access to non-app domains.
 neverallow appdomain { domain -appdomain }:process ptrace;
 
-# Write access to /proc/pid entries for any non-app domain.
-neverallow appdomain { domain -appdomain }:file write;
+# Read or write access to /proc/pid entries for any non-app domain.
+# A different form of hidepid=2 like protections
+neverallow appdomain { domain -appdomain }:file no_w_file_perms;
+neverallow { appdomain -shell } { domain -appdomain }:file no_rw_file_perms;
 
 # signal access to non-app domains.
 # sigchld allowed for parent death notification.

public/te_macros

@@ -172,6 +172,8 @@ typeattribute $1 appdomain;
 tmpfs_domain($1)
 # Map with PROT_EXEC.
 allow $1 $1_tmpfs:file execute;
+neverallow { $1 -shell } { domain -$1 }:file no_rw_file_perms;
+neverallow { appdomain -shell -$1 } $1:file no_rw_file_perms;
 ')
 
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