Patch for Bug#57952 (privilege change is not taken into account by EXECUTE).

The user-visible problem was that changes to column-level privileges,
happened in between of PREPARE and EXECUTE of a prepared statement, were
neglected. I.e. a prepared statement could be executed with the
column-level privileges as of PREPARE-time. The problem existed for
column-level privileges only.

A similar problem existed for stored programs: the changes between
executions didn't have an effect.

Technically the thing is that table references are cached in
Prepared_statement::prepare() call. In subsequent
Prepared_statement::execute() calls those cached values are used.
There are two functions to get a field by name: find_field_in_table() and
find_field_in_table_ref(). On prepare-phase find_field_in_table_ref() is
called, on execute-phase -- find_field_in_table() because the table is
cached. find_field_in_table() does not check column-level privileges and
expects the caller to do that. The problem was that this check was
forgotten.

The fix is to check them there as it happens in find_field_in_table_ref().

1 files changed, 12 insertions, 0 deletions

diff --git a/sql/sql_base.cc b/sql/sql_base.cc
index 88d1e8879d1..669229a8404 100644
--- a/sql/sql_base.cc
+++ b/sql/sql_base.cc
@@ -3657,6 +3657,8 @@ find_field_in_natural_join(THD *thd, TABLE_LIST *table_ref, const char *name,
 /*
   Find field by name in a base table or a view with temp table algorithm.
 
+  The caller is expected to check column-level privileges.
+
   SYNOPSIS
     find_field_in_table()
     thd				thread handler
@@ -3753,6 +3755,8 @@ find_field_in_table(THD *thd, TABLE *table, const char *name, uint length,
     This procedure detects the type of the table reference 'table_list'
     and calls the corresponding search routine.
 
+    The routine checks column-level privieleges for the found field.
+
   RETURN
     0			field is not found
     view_ref_found	found value in VIEW (real result is in *ref)
@@ -3944,8 +3948,16 @@ find_field_in_tables(THD *thd, Item_ident *item,
       when table_ref->field_translation != NULL.
       */
     if (table_ref->table && !table_ref->view)
+    {
       found= find_field_in_table(thd, table_ref->table, name, length,
                                  TRUE, &(item->cached_field_index));
+#ifndef NO_EMBEDDED_ACCESS_CHECKS
+      /* Check if there are sufficient access rights to the found field. */
+      if (found && check_privileges &&
+          check_column_grant_in_table_ref(thd, table_ref, name, length))
+        found= WRONG_GRANT;
+#endif
+    }
     else
       found= find_field_in_table_ref(thd, table_ref, name, length, item->name,
                                      NULL, NULL, ref, check_privileges,