Prevent non-superusers from reading pg_backend_memory_contexts, by default.

pg_backend_memory_contexts view contains some internal information of
memory contexts. Since exposing them to any users by default may cause
security issue, this commit allows only superusers to read this view,
by default, like we do for pg_shmem_allocations view.

Bump catalog version.

Author: Atsushi Torikoshi
Reviewed-by: Michael Paquier, Fujii Masao
Discussion: https://postgr.es/m/1414992.1597849297@sss.pgh.pa.us

doc/src/sgml/catalogs.sgml

@@ -9697,6 +9697,10 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
    </tgroup>
   </table>
 
+  <para>
+   By default, the <structname>pg_backend_memory_contexts</structname> view can be
+   read only by superusers.
+  </para>
  </sect1>
 
  <sect1 id="view-pg-config">

src/backend/catalog/system_views.sql

@@ -557,6 +557,9 @@ REVOKE EXECUTE ON FUNCTION pg_get_shmem_allocations() FROM PUBLIC;
 CREATE VIEW pg_backend_memory_contexts AS
     SELECT * FROM pg_get_backend_memory_contexts();
 
+REVOKE ALL ON pg_backend_memory_contexts FROM PUBLIC;
+REVOKE EXECUTE ON FUNCTION pg_get_backend_memory_contexts() FROM PUBLIC;
+
 -- Statistics views
 
 CREATE VIEW pg_stat_all_tables AS

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202008191
+#define CATALOG_VERSION_NO	202008261
 
 #endif