innodb_log_file_size set to a lower value than the size of ib_lofile0 and iblogfile1
The InnoDB buffer pool is different from the InnoDB log file, i.e. the undo log (a.k.a. the redo log), whose size is controlled by the innodb_log_file_size and innodb_log_files_in_group variables.

The buffer pool is a cache for frequently used data and indexes, so that MariaDB doesn't have to read them from disk. On the other hand, the undo log stores old versions of data being modified by write transactions.   

If you need to change the size of the buffer pool, the variable to modify is innodb_buffer_pool_size. This is a dynamic variable starting with MariaDB 10.2, so can also be modified without restarting by executing a command like SET GLOBAL innodb_buffer_pool_size=32G;