Also similar bug with unloading kernel on 2.6.30-2 (Debian)
ipt_netflow from CVS trunk.

Nov 23 14:58:37 sp0 kernel: [ 6847.555933] ipt_netflow unloading..
Nov 23 14:58:37 sp0 kernel: [ 6847.568051] netflow: remove destination 127.0.0.1
:3050 (f0f03100)
Nov 23 14:58:37 sp0 kernel: [ 6847.568167] ipt_netflow unloaded.
Nov 23 14:58:37 sp0 kernel: [ 6847.568705] ------------[ cut here ]------------
Nov 23 14:58:37 sp0 kernel: [ 6847.568733] kernel BUG at /home/ad/ipt_netflow-1.
6/linux-2.6-2.6.30/debian/build/source_i386_none/mm/slab.c:600!
Nov 23 14:58:37 sp0 kernel: [ 6847.568778] invalid opcode: 0000 [#1] SMP
Nov 23 14:58:37 sp0 kernel: [ 6847.568803] last sysfs file: /sys/module/ip_table
s/initstate
Nov 23 14:58:37 sp0 kernel: [ 6847.568827] Modules linked in: ppp_deflate zlib_d
eflate bsd_comp battery speedstep_lib cpufreq_userspace cpufreq_powersave cpufre
q_conservative cpufreq_stats ppp_async crc_ccitt cls_fw cls_u32 sch_sfq sch_htb
ipt_REJECT xt_TCPMSS ipt_ULOG xt_multiport iptable_filter xt_tcpudp iptable_nat
nf_nat nf_conntrack_ipv4 nf_conntrack nf_defrag_ipv4 xt_MARK iptable_mangle ip_t
ables x_tables 8021q garp stp pppoe pppox ppp_generic slhc loop snd_pcsp snd_pcm
_oss snd_mixer_oss snd_pcm snd_timer snd soundcore i2c_piix4 snd_page_alloc evde
v serio_raw i2c_core psmouse processor button ext3 jbd mbcache sg sd_mod crc_t10
dif ide_cd_mod cdrom ide_pci_generic ata_generic libata ohci_hcd ehci_hcd mptspi
serverworks mptscsih mptbase scsi_transport_spi tg3 usbcore libphy ide_core scs
i_mod sworks_agp agpgart floppy thermal fan thermal_sys [last unloaded: ipt_NETFLOW]
Nov 23 14:58:37 sp0 kernel: [ 6847.569218]
Nov 23 14:58:37 sp0 kernel: [ 6847.569236] Pid: 10354, comm: rmmod Not tainted (2.6.30-2-686 #1) eserver xSeries 335 -[8676G1X]-
Nov 23 14:58:37 sp0 kernel: [ 6847.569275] EIP: 0060:[<c0189a15>] EFLAGS: 00010046 CPU: 0
Nov 23 14:58:37 sp0 kernel: [ 6847.569301] EIP is at kfree+0x66/0x9b
Nov 23 14:58:37 sp0 kernel: [ 6847.569321] EAX: c1706240 EBX: f8310a3c ECX: f7017080 EDX: 00000008
Nov 23 14:58:37 sp0 kernel: [ 6847.569344] ESI: f83125c8 EDI: 00000286 EBP: 00000880 ESP: eefe7f2c
Nov 23 14:58:37 sp0 kernel: [ 6847.569368] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
Nov 23 14:58:37 sp0 kernel: [ 6847.569391] Process rmmod (pid: 10354, ti=eefe6000 task=eb9cd8a0 task.ti=eefe6000)
Nov 23 14:58:37 sp0 kernel: [ 6847.569428] Stack:
Nov 23 14:58:37 sp0 kernel: [ 6847.569445] f8310a3c 00000007 00000008 c013565f f83129b0 bfa4acb0 00000000 c0145b5e
Nov 23 14:58:37 sp0 kernel: [ 6847.569594] Call Trace:
Nov 23 14:58:37 sp0 kernel: [ 6847.569614] [<c013565f>] ? destroy_params+0x1b/0x27
Nov 23 14:58:37 sp0 kernel: [ 6847.569642] [<c0145b5e>] ? free_module+0x92/0xd6
Nov 23 14:58:37 sp0 kernel: [ 6847.569669] [<c0145db0>] ? sys_delete_module+0x1c7/0x1e7
Nov 23 14:58:37 sp0 kernel: [ 6847.569694] [<c017e590>] ? remove_vma+0x3e/0x43
Nov 23 14:58:37 sp0 kernel: [ 6847.569720] [<c0102ff4>] ? sysenter_do_call+0x12/0x28
Nov 23 14:58:37 sp0 kernel: [ 6847.569746] Code: 26 00 8d 86 00 00 00 40 c1 e8 0c c1 e0 05 03 05 80 fe 52 c0 66 83 38 00 79 03 8b 40 0c 66 83 38 00 79 03 8b 40 0c 80 38 00 78 04 <0f> 0b eb fe 8b 48 18 64 a1 80 f4 48 c0 8b 1c 81 8b 03 3b 43 04
Nov 23 14:58:37 sp0 kernel: [ 6847.569935] EIP: [<c0189a15>] kfree+0x66/0x9b SS:ESP 0068:eefe7f2c
Nov 23 14:58:37 sp0 kernel: [ 6847.570238] ---[ end trace 4c7be61c60bba0b6 ]---