"Memory modified after free" - by whom?

    I noticed this while checking the logs on one of my test boxes
after restarting the network. Any idea where I should start looking
into this (has IPv6 enabled but wasn't using it, em/cxgbe/ixgbe
interfaces with the ixgbe interfaces lagged previously, but now not)?
It looks suspiciously like the same size as a jumbo frame, but I'm not
100% sure if that's the real problem.
Thanks,
-Garrett

Dec 10 14:03:12 wf158 kernel: em0: link state changed to DOWN
Dec 10 14:03:13 wf158 kernel: ix0: link state changed to DOWN
Dec 10 14:03:13 wf158 kernel: ix0: link state changed to UP
Dec 10 14:03:13 wf158 kernel: ix1: link state changed to DOWN
Dec 10 14:03:13 wf158 kernel: ix1: link state changed to UP
Dec 10 14:03:13 wf158 kernel: ix0: link state changed to DOWN
Dec 10 14:03:13 wf158 kernel: ix0: link state changed to UP
Dec 10 14:03:15 wf158 kernel: em0: link state changed to UP
Dec 10 14:03:15 wf158 dhclient: New IP Address (em0): 10.7.169.89
Dec 10 14:03:15 wf158 dhclient: New Subnet Mask (em0): 255.255.240.0
Dec 10 14:03:15 wf158 dhclient: New Broadcast Address (em0): 10.7.175.255
Dec 10 14:03:15 wf158 dhclient: New Routers (em0): 10.7.160.1
Dec 10 14:03:16 wf158 kernel: ix0: link state changed to DOWN
Dec 10 14:03:16 wf158 kernel: ix0: link state changed to UP
Dec 10 14:03:31 wf158 kernel: in6_purgeaddr: err=65, destination
address delete failed
Dec 10 14:03:31 wf158 dhclient[4539]: My address (10.7.169.89) was
deleted, dhclient exiting
Dec 10 14:03:32 wf158 dhclient[4521]: short write: wanted 20 got 0 bytes
Dec 10 14:03:32 wf158 dhclient[4521]: exiting.
Dec 10 14:03:33 wf158 kernel: em0: link state changed to DOWN
Dec 10 14:03:33 wf158 kernel: ix1: link state changed to DOWN
Dec 10 14:03:34 wf158 kernel: ix1: link state changed to UP
Dec 10 14:03:34 wf158 kernel: ix1: link state changed to DOWN
Dec 10 14:03:34 wf158 kernel: ix1: link state changed to UP
Dec 10 14:03:34 wf158 kernel: ix0: link state changed to DOWN
Dec 10 14:03:34 wf158 kernel: ix0: link state changed to UP
Dec 10 14:03:34 wf158 kernel: ix1: link state changed to DOWN
Dec 10 14:03:34 wf158 kernel: ix1: link state changed to UP
Dec 10 14:03:36 wf158 kernel: em0: link state changed to UP
Dec 10 14:03:36 wf158 dhclient: New IP Address (em0): 10.7.169.89
Dec 10 14:03:36 wf158 dhclient: New Subnet Mask (em0): 255.255.240.0
Dec 10 14:03:36 wf158 dhclient: New Broadcast Address (em0): 10.7.175.255
Dec 10 14:03:36 wf158 dhclient: New Routers (em0): 10.7.160.1
Dec 10 14:05:34 wf158 kernel: Memory modified after free
0xffffff81c016d000(9216) val=ffffffff _at_ 0xffffff81c016d000
Dec 10 14:05:35 wf158 kernel: Memory modified after free
0xffffff81b5cdc000(9216) val=ffffffff _at_ 0xffffff81b5cdc000

# uname -a
FreeBSD wf158.west.isilon.com 10.0-CURRENT FreeBSD 10.0-CURRENT #1
r+2760369-dirty: Mon Dec 10 08:04:46 PST 2012
root_at_wf158.west.isilon.com:/usr/obj/usr/src/sys/ISI-GENERIC  amd64