Bug#24444831 MY_ERROR(ER_INNODB_ONLINE_LOG_TOO_BIG) CALLED WITH INVALID INDEX NAME

This bug was introduced in MySQL 5.6.8 with WL#6255.
When an error occurs while rebuilding a table that only has a
hidden GEN_CLUST_INDEX inside InnoDB, ha_alter_info->key_info_buffer
would be invalid and should not be dereferenced.

get_error_key_name(): Get the name of an erroneous key.
Avoid dereferencing ha_alter_info->key_info_buffer when no keys
exist in the SQL layer.

ha_innobase::inplace_alter_table(),
ha_innobase::commit_try_rebuild(): Invoke get_error_key_name()
for reporting ER_INNODB_ONLINE_LOG_TOO_BIG or ER_INDEX_CORRUPT.

RB: 13834
Reviewed-by: Jimmy Yang <jimmy.yang@oracle.com>

storage/innobase/handler/handler0alter.cc

@@ -6299,6 +6299,26 @@ alter_templ_needs_rebuild(
 	return(false);
 }
 
+/** Get the name of an erroneous key.
+@param[in]	error_key_num	InnoDB number of the erroneus key
+@param[in]	ha_alter_info	changes that were being performed
+@param[in]	table		InnoDB table
+@return	the name of the erroneous key */
+static
+const char*
+get_error_key_name(
+	ulint				error_key_num,
+	const Alter_inplace_info*	ha_alter_info,
+	const dict_table_t*		table)
+{
+	if (error_key_num == ULINT_UNDEFINED) {
+		return(FTS_DOC_ID_INDEX_NAME);
+	} else if (ha_alter_info->key_count == 0) {
+		return(dict_table_get_first_index(table)->name);
+	} else {
+		return(ha_alter_info->key_info_buffer[error_key_num].name);
+	}
+}
 
 /** Alter the table structure in-place with operations
 specified using Alter_inplace_info.
@@ -6499,17 +6519,13 @@ ha_innobase::inplace_alter_table(
 	case DB_ONLINE_LOG_TOO_BIG:
 		DBUG_ASSERT(ctx->online);
 		my_error(ER_INNODB_ONLINE_LOG_TOO_BIG, MYF(0),
-			 (m_prebuilt->trx->error_key_num == ULINT_UNDEFINED)
-			 ? FTS_DOC_ID_INDEX_NAME
-			 : ha_alter_info->key_info_buffer[
-				 m_prebuilt->trx->error_key_num].name);
+			 get_error_key_name(m_prebuilt->trx->error_key_num,
+					    ha_alter_info, m_prebuilt->table));
 		break;
 	case DB_INDEX_CORRUPT:
 		my_error(ER_INDEX_CORRUPT, MYF(0),
-			 (m_prebuilt->trx->error_key_num == ULINT_UNDEFINED)
-			 ? FTS_DOC_ID_INDEX_NAME
-			 : ha_alter_info->key_info_buffer[
-				 m_prebuilt->trx->error_key_num].name);
+			 get_error_key_name(m_prebuilt->trx->error_key_num,
+					    ha_alter_info, m_prebuilt->table));
 		break;
 	case DB_DECRYPTION_FAILED: {
 		String str;
@@ -7743,14 +7759,13 @@ commit_try_rebuild(
 			DBUG_RETURN(true);
 		case DB_ONLINE_LOG_TOO_BIG:
 			my_error(ER_INNODB_ONLINE_LOG_TOO_BIG, MYF(0),
-				 ha_alter_info->key_info_buffer[0].name);
+				 get_error_key_name(err_key, ha_alter_info,
+						    rebuilt_table));
 			DBUG_RETURN(true);
 		case DB_INDEX_CORRUPT:
 			my_error(ER_INDEX_CORRUPT, MYF(0),
-				 (err_key == ULINT_UNDEFINED)
-				 ? FTS_DOC_ID_INDEX_NAME
-				 : ha_alter_info->key_info_buffer[err_key]
-				 .name);
+				 get_error_key_name(err_key, ha_alter_info,
+						    rebuilt_table));
 			DBUG_RETURN(true);
 		default:
 			my_error_innodb(error, table_name, user_table->flags);