as you described, the permissions of /var/log/hive are ok:
[root@sandbox ~]# ls -ladh /var/log/hive
drwxr-xr-x 2 hive hadoop 4,0K 29. Apr 06:42 /var/log/hive
Unfortunately, hiveserver2 tries to log to the root-directory “/” and reports the mentioned permission problem. The real issue is the configuration setting for the log directory.