Comment 1 for bug 1505480

Root cause is calling fclose() in signal handler context.
Functions like fopen(), fclose(), malloc(), free(), etc are not allowed to call in signal handler context.

I believe following upstream commit will solve your issue.

http://git.netfilter.org/ulogd2/commit/?id=1f70d2ba45e2b067777d5386b8d3f2e09be9118b

In my environment, I applied this patch to ulogd-2.0.4 and it works well.
I cloud applied upstream patch cleanly to ulogd-2.0.4.