MDEV-30023 Revoking Privilege on the Column Yields the Error

The change from MDEV-29465 exposed a flaw in replace_column_table
where again we were not properly updating the column-level bits.

replace_table_table was changed in MDEV-29465 to properly update
grant_table->init_cols, however replace_column_table still only
modified grant_column->rights when the GRANT_COLUMN already existed.

This lead to a missmatch between GRANT_COLUMN::init_rights and
GRANT_COLUMN::rights, *if* the GRANT_COLUMN already existed.

As an example:

GRANT SELECT (col1) ...
Here:
For col1
GRANT_COLUMN::init_rights and GRANT_COLUMN::rights are set to 1 (SELECT) in
replace_column_table.

GRANT INSERT (col1) ...
Here, without this patch GRANT_COLUMN::init_rights is still 1 and
GRANT_COLUMN::rights is 3 (SELECT_PRIV | INSERT_PRIV)

Finally, if before this patch, one does:

REVOKE SELECT (col1) ...

replace_table_table will see that init_rights loses bit 1 thus it
considers there are no more rights granted on that particular table.

This prompts the whole GRANT_TABLE to be removed via the first revoke,
when the GRANT_COLUMN corresponding to it should still have init_rights == 2.

By also updating replace_column_table to keep init_rights in sync
properly, the issue is resolved.

Reviewed by <serg@mariadb.com>

mysql-test/main/grant5.result

@@ -296,4 +296,28 @@ drop database db;
 drop user foo@localhost;
 drop user bar@localhost;
 drop user buz@localhost;
+CREATE USER foo;
+CREATE DATABASE db;
+CREATE TABLE db.test_getcolpriv(col1 INT, col2 INT);
+GRANT SELECT (col1,col2) ON db.test_getcolpriv TO foo;
+GRANT INSERT (col1) ON db.test_getcolpriv TO foo;
+SHOW GRANTS FOR foo;
+Grants for foo@%
+GRANT USAGE ON *.* TO `foo`@`%`
+GRANT SELECT (col2, col1), INSERT (col1) ON `db`.`test_getcolpriv` TO `foo`@`%`
+REVOKE SELECT (col1,col2) ON db.test_getcolpriv FROM foo;
+SHOW GRANTS FOR foo;
+Grants for foo@%
+GRANT USAGE ON *.* TO `foo`@`%`
+GRANT INSERT (col1) ON `db`.`test_getcolpriv` TO `foo`@`%`
+REVOKE INSERT (col1) ON db.test_getcolpriv FROM foo;
+SHOW GRANTS FOR foo;
+Grants for foo@%
+GRANT USAGE ON *.* TO `foo`@`%`
+FLUSH PRIVILEGES;
+SHOW GRANTS FOR foo;
+Grants for foo@%
+GRANT USAGE ON *.* TO `foo`@`%`
+DROP USER foo;
+DROP DATABASE db;
 # End of 10.3 tests

mysql-test/main/grant5.test

@@ -259,4 +259,23 @@ drop user foo@localhost;
 drop user bar@localhost;
 drop user buz@localhost;
 
+CREATE USER foo;
+CREATE DATABASE db;
+CREATE TABLE db.test_getcolpriv(col1 INT, col2 INT);
+
+GRANT SELECT (col1,col2) ON db.test_getcolpriv TO foo;
+GRANT INSERT (col1) ON db.test_getcolpriv TO foo;
+
+SHOW GRANTS FOR foo;
+REVOKE SELECT (col1,col2) ON db.test_getcolpriv FROM foo;
+SHOW GRANTS FOR foo;
+REVOKE INSERT (col1) ON db.test_getcolpriv FROM foo;
+
+SHOW GRANTS FOR foo;
+FLUSH PRIVILEGES;
+SHOW GRANTS FOR foo;
+
+DROP USER foo;
+DROP DATABASE db;
+
 --echo # End of 10.3 tests

sql/sql_acl.cc

@@ -5149,7 +5149,10 @@ static int replace_column_table(GRANT_TABLE *g_t,
       grant_column= column_hash_search(g_t, column->column.ptr(),
                                        column->column.length());
       if (grant_column)  // Should always be true
+      {
         grant_column->rights= privileges;	// Update hash
+        grant_column->init_rights= privileges;
+      }
     }
     else					// new grant
     {