fix(handler): introduce upper size limit for s_log_block_size

The maximum block size limit on a 64bit system is 65536
When creating a fake filesystem with `mkfs.ext4` and setting the block
size to -b 65536, the maximum value that s_log_block_size will reach is six.

Author: nyuware

unblob/handlers/filesystem/extfs.py

@@ -84,6 +84,9 @@ def valid_header(self, header) -> bool:
                 "ExtFS header major version too high", rev_level=header.s_rev_level
             )
             return False
+        if header.s_log_block_size > 6:
+            logger.debug("ExtFS header s_log_block_size is too large", s_log_block_size=header.s_log_block_size)
+            return False
         return True
 
     def calculate_chunk(self, file: File, start_offset: int) -> Optional[ValidChunk]: