Bug #50276: Security flaw in INFORMATION_SCHEMA.TABLES

check_access() returning false for a database does not
guarantee that the access is granted to it.
This wrong condition in filling the INFORMATION_SCHEMA
tables causes extra tables to be returned to the user
even if he has no rights to see them.
Fixed by correcting the condition.

mysql-test/r/information_schema.result

@@ -1725,4 +1725,26 @@ SELECT 'OK' AS TEST_RESULT FROM INFORMATION_SCHEMA.PROCESSLIST WHERE time < 0;
 TEST_RESULT
 OK
 SET TIMESTAMP=DEFAULT;
+#
+# Bug #50276: Security flaw in INFORMATION_SCHEMA.TABLES
+#
+CREATE DATABASE db1;
+USE db1;
+CREATE TABLE t1 (id INT);
+CREATE USER nonpriv;
+USE test;
+# connected as nonpriv
+# Should return 0
+SELECT COUNT(*) FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME='t1';
+COUNT(*)
+0
+USE INFORMATION_SCHEMA;
+# Should return 0
+SELECT COUNT(*) FROM TABLES WHERE TABLE_NAME='t1';
+COUNT(*)
+0
+# connected as root
+DROP USER nonpriv;
+DROP TABLE db1.t1;
+DROP DATABASE db1;
 End of 5.1 tests.

mysql-test/t/information_schema.test

@@ -1419,6 +1419,33 @@ SET TIMESTAMP=@@TIMESTAMP + 10000000;
 SELECT 'OK' AS TEST_RESULT FROM INFORMATION_SCHEMA.PROCESSLIST WHERE time < 0;
 SET TIMESTAMP=DEFAULT;
 
+
+--echo #
+--echo # Bug #50276: Security flaw in INFORMATION_SCHEMA.TABLES
+--echo #
+CREATE DATABASE db1;
+USE db1;
+CREATE TABLE t1 (id INT);
+CREATE USER nonpriv;
+USE test;
+
+connect (nonpriv_con, localhost, nonpriv,,);
+connection nonpriv_con;
+--echo # connected as nonpriv
+--echo # Should return 0
+SELECT COUNT(*) FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME='t1';
+USE INFORMATION_SCHEMA;
+--echo # Should return 0
+SELECT COUNT(*) FROM TABLES WHERE TABLE_NAME='t1';
+
+connection default;
+--echo # connected as root
+disconnect nonpriv_con;
+DROP USER nonpriv;
+DROP TABLE db1.t1;
+DROP DATABASE db1;
+
+
 --echo End of 5.1 tests.
 
 # Wait till all disconnects are completed

sql/sql_show.cc

@@ -3367,11 +3367,11 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
   while ((db_name= it++))
   {
 #ifndef NO_EMBEDDED_ACCESS_CHECKS
-    if (!check_access(thd,SELECT_ACL, db_name->str, 
-                      &thd->col_access, 0, 1, with_i_schema) ||
+    if (!(check_access(thd,SELECT_ACL, db_name->str, 
+                       &thd->col_access, 0, 1, with_i_schema) ||
+          (!thd->col_access && check_grant_db(thd, db_name->str))) ||
         sctx->master_access & (DB_ACLS | SHOW_DB_ACL) ||
-	acl_get(sctx->host, sctx->ip, sctx->priv_user, db_name->str, 0) ||
-	!check_grant_db(thd, db_name->str))
+        acl_get(sctx->host, sctx->ip, sctx->priv_user, db_name->str, 0))
 #endif
     {
       thd->no_warnings_for_error= 1;