MDEV-13655: Set role does not properly grant privileges.

When granting a role to another role, DB privileges get propagated. If
the grantee had no previous DB privileges, an extra ACL_DB entry is created to
house those "indirectly received" privileges. If, afterwards, DB
privileges are granted to the grantee directly, we must make sure to not
create a duplicate ACL_DB entry.

mysql-test/suite/roles/set_role-13655.result

+#
+# MDEV-13655: SET ROLE does not properly grant privileges.
+#
+# We must test that if aditional db privileges get granted to a role
+# which previously inherited privileges from another granted role
+# keep the internal memory structures intact.
+#
+create role simple;
+#
+# First we create an entry with privileges for databases for the simple role.
+#
+grant select, insert, update, delete, lock tables, execute on t.* to simple;
+create role admin;
+#
+# Now we grant the simple role to admin. This means that db privileges
+# should propagate to admin.
+#
+grant simple to admin;
+show grants for admin;
+Grants for admin
+GRANT simple TO 'admin'
+GRANT USAGE ON *.* TO 'admin'
+GRANT USAGE ON *.* TO 'simple'
+GRANT SELECT, INSERT, UPDATE, DELETE, LOCK TABLES, EXECUTE ON `t`.* TO 'simple'
+#
+# Finally, we give the admin all the available privileges for the db.
+#
+grant all on t.* to admin;
+#
+# Create a user to test out the new roles;
+#
+create user foo;
+grant admin to foo;
+create database t;
+ERROR 42000: Access denied for user 'foo'@'%' to database 't'
+set role admin;
+show grants;
+Grants for foo@%
+GRANT admin TO 'foo'@'%'
+GRANT USAGE ON *.* TO 'foo'@'%'
+GRANT simple TO 'admin'
+GRANT USAGE ON *.* TO 'admin'
+GRANT ALL PRIVILEGES ON `t`.* TO 'admin'
+GRANT USAGE ON *.* TO 'simple'
+GRANT SELECT, INSERT, UPDATE, DELETE, LOCK TABLES, EXECUTE ON `t`.* TO 'simple'
+create database t;
+drop database t;
+drop role simple;
+drop role admin;
+drop user foo;

mysql-test/suite/roles/set_role-13655.test

+source include/not_embedded.inc;
+
+--echo #
+--echo # MDEV-13655: SET ROLE does not properly grant privileges.
+--echo #
+--echo # We must test that if aditional db privileges get granted to a role
+--echo # which previously inherited privileges from another granted role
+--echo # keep the internal memory structures intact.
+--echo #
+
+create role simple;
+
+--echo #
+--echo # First we create an entry with privileges for databases for the simple role.
+--echo #
+grant select, insert, update, delete, lock tables, execute on t.* to simple;
+create role admin;
+
+--echo #
+--echo # Now we grant the simple role to admin. This means that db privileges
+--echo # should propagate to admin.
+--echo #
+grant simple to admin;
+show grants for admin;
+
+--echo #
+--echo # Finally, we give the admin all the available privileges for the db.
+--echo #
+grant all on t.* to admin;
+
+--echo #
+--echo # Create a user to test out the new roles;
+--echo #
+create user foo;
+grant admin to foo;
+
+connect (foo,localhost,foo,,,,,);
+--error ER_DBACCESS_DENIED_ERROR
+create database t;
+set role admin;
+show grants;
+create database t;
+drop database t;
+
+connection default;
+
+drop role simple;
+drop role admin;
+drop user foo;

sql/sql_acl.cc

@@ -2129,37 +2129,42 @@ static void acl_insert_user(const char *user, const char *host,
 }
 
 
-static void acl_update_db(const char *user, const char *host, const char *db,
+static bool acl_update_db(const char *user, const char *host, const char *db,
                           ulong privileges)
 {
   mysql_mutex_assert_owner(&acl_cache->lock);
 
+  bool updated= false;
+
   for (uint i=0 ; i < acl_dbs.elements ; i++)
   {
     ACL_DB *acl_db=dynamic_element(&acl_dbs,i,ACL_DB*);
     if ((!acl_db->user && !user[0]) ||
-	(acl_db->user &&
-	!strcmp(user,acl_db->user)))
+        (acl_db->user &&
+         !strcmp(user,acl_db->user)))
     {
       if ((!acl_db->host.hostname && !host[0]) ||
-	  (acl_db->host.hostname &&
-	   !strcmp(host, acl_db->host.hostname)))
+          (acl_db->host.hostname &&
+           !strcmp(host, acl_db->host.hostname)))
       {
-	if ((!acl_db->db && !db[0]) ||
-	    (acl_db->db && !strcmp(db,acl_db->db)))
+        if ((!acl_db->db && !db[0]) ||
+            (acl_db->db && !strcmp(db,acl_db->db)))
 
-	{
-	  if (privileges)
+        {
+          if (privileges)
           {
             acl_db->access= privileges;
             acl_db->initial_access= acl_db->access;
           }
-	  else
-	    delete_dynamic_element(&acl_dbs,i);
-	}
+          else
+            delete_dynamic_element(&acl_dbs,i);
+          updated= true;
+        }
       }
     }
   }
+
+  return updated;
 }
 
 
@@ -3428,9 +3433,21 @@ static int replace_db_table(TABLE *table, const char *db,
   acl_cache->clear(1);				// Clear privilege cache
   if (old_row_exists)
     acl_update_db(combo.user.str,combo.host.str,db,rights);
-  else
-  if (rights)
-    acl_insert_db(combo.user.str,combo.host.str,db,rights);
+  else if (rights)
+  {
+    /*
+       If we did not have an already existing row, for users, we must always
+       insert an ACL_DB entry. For roles however, it is possible that one was
+       already created when DB privileges were propagated from other granted
+       roles onto the current role. For this case, first try to update the
+       existing entry, otherwise insert a new one.
+    */
+    if (!combo.is_role() ||
+        !acl_update_db(combo.user.str, combo.host.str, db, rights))
+    {
+      acl_insert_db(combo.user.str,combo.host.str,db,rights);
+    }
+  }
   DBUG_RETURN(0);
 
   /* This could only happen if the grant tables got corrupted */

sql/structs.h

@@ -191,7 +191,7 @@ typedef int *(*update_var)(THD *, struct st_mysql_show_var *);
 
 typedef struct	st_lex_user {
   LEX_STRING user, host, password, plugin, auth;
-  bool is_role() { return user.str[0] && !host.str[0]; }
+  bool is_role() const { return user.str[0] && !host.str[0]; }
   void set_lex_string(LEX_STRING *l, char *buf)
   {
     if (is_role())