Kernel panic for unknown reason

I'm getting kernel panics and I don't understand why. In /var/log/messages they always occur in three's, as below:

Aug 27 13:29:37 freenas smbd[37669]: [2014/08/27 13:29:37.455656, 0] ../source3/lib/util.c:785(smb_panic_s3)
Aug 27 13:29:37 freenas smbd[37669]: PANIC (pid 37669): num_bytes too large: 4294966797
Aug 27 13:29:37 freenas kernel: pid 37669 (smbd), uid 1001: exited on signal 10

I'm running linux freenas 9.2.1.5, with 8gb of ram:
[root@freenas] ~# sysctl hw.physmem
hw.physmem:...

Kernel panic for unknown reason