[Users] syslog "kernel: BUG: unable to handle kernel NULL pointer dereference"

[Stuart MacIntosh]

My OVZ server printed an EIP late last night when I ran my ip6tables
script. I'm no kernel hacker but thought someone on this list may want
to know.
My ip6tables command on both the HN and VE stopped working at the same
time. for example 'ip6tables -P INPUT DROP' just hangs but iptables
(IPv4) still works. Havn't rebooted yet in case I can help debug something.

baikonour:/etc/init.d# uname -a
Linux baikonour 2.6.18-028test010.1-ovz-smp #1 SMP Fri Jan 12 22:20:35
CET 2007 i686 GNU/Linux
baikonour:~# ip6tables -V
ip6tables v1.3.6
baikonour:~# cat /proc/version
Linux version 2.6.18-028test010.1-ovz-smp (root at build32.sarge.systs.org)
(gcc version 3.3.5 (Debian 1:3.3.5-13)) #1 SMP Fri Jan 12 22:20:35 CET 2007
baikonour:~# vzctl --version
vzctl version 3.0.14-1dso31.2


--- syslog messages follow ---
Mar 11 02:49:58 baikonour kernel: BUG: unable to handle kernel NULL
pointer dereference at virtual address 00000000
Mar 11 02:49:58 baikonour kernel:  printing eip:
Mar 11 02:49:58 baikonour kernel: e0b2abe3
Mar 11 02:49:58 baikonour kernel: *pde = 00000000
Mar 11 02:49:58 baikonour kernel: Oops: 0000 [#1]
Mar 11 02:49:58 baikonour kernel: SMP
Mar 11 02:49:58 baikonour kernel: Modules linked in: ip6t_LOG
ip6table_filter ip6_tables bridge llc xt_mac ipt_LOG xt_state
iptable_nat nfs lockd sunrpc simfs vznetdev vzethdev vzrst ip_nat vzcpt
ip_conntrack vzdquota vzmon vzdev xt_tcpudp xt_length ipt_ttl xt_tcpmss
ipt_TCPMSS iptable_mangle iptable_filter xt_multiport xt_limit ipt_tos
ipt_REJECT ip_tables x_tables af_packet i2c_piix4 i2c_core shpchp
uhci_hcd usbcore 3c59x mii ide_cd cdrom
Mar 11 02:49:58 baikonour kernel: CPU:    1, VCPU: 101.0
Mar 11 02:49:58 baikonour kernel: EIP:    0060:[<e0b2abe3>]    Not
tainted VLI
Mar 11 02:49:58 baikonour kernel: EFLAGS: 00010286  
(2.6.18-028test010.1-ovz-smp #1)
Mar 11 02:49:58 baikonour kernel: EIP is at xt_find_table_lock+0x43/0xe0
[x_tables]
Mar 11 02:49:58 baikonour kernel: eax: c5fae800   ebx: 0000000a   ecx:
00000000   edx: dca9b000
Mar 11 02:49:58 baikonour kernel: esi: 00000050   edi: 00000040   ebp:
bf940260   esp: cbb91dac
Mar 11 02:49:58 baikonour kernel: ds: 007b   es: 007b   ss: 0068
Mar 11 02:49:58 baikonour kernel: Process ip6tables (pid: 31695, veid:
101, ti=cbb90000 task=c5fae800 task.ti=cbb90000)
Mar 11 02:49:58 baikonour kernel: Stack: bf940260 cbb91f1c 00000040
00000040 bf940260 e0c21b85 0000000a cbb91e94
Mar 11 02:49:58 baikonour kernel:        00000020 c0198c0d cbb91de4
00000000 dcc5ae44 b7f91000 b7f91000 c0164f02
Mar 11 02:49:58 baikonour kernel:        dcc5ae40 00000007 00000000
c140bcb4 00000000 00000000 c9a1f600 b7f91000
Mar 11 02:49:58 baikonour kernel:  Call Trace:
Mar 11 02:49:58 baikonour kernel:  [<e0c21b85>]
do_ip6t_get_ctl+0x135/0x310 [ip6_tables]
Mar 11 02:49:58 baikonour kernel:  [<c0198c0d>] touch_atime+0x7d/0xe0
Mar 11 02:49:58 baikonour kernel:  [<c0164f02>] zap_pte_range+0x102/0x300
Mar 11 02:49:58 baikonour kernel:  [<c02b3373>] prio_tree_remove+0x83/0x100
Mar 11 02:49:58 baikonour kernel:  [<c015b632>] prep_new_page+0x112/0x1d0
Mar 11 02:49:58 baikonour kernel:  [<c01414d8>]
change_slab_charged+0x108/0x130
Mar 11 02:49:58 baikonour kernel:  [<c0492479>] nf_sockopt+0xc9/0x140
Mar 11 02:49:58 baikonour kernel:  [<c0492568>] nf_getsockopt+0x38/0x40
Mar 11 02:49:58 baikonour kernel:  [<c04eee18>] ipv6_getsockopt+0xe8/0x110
Mar 11 02:49:58 baikonour kernel:  [<c04724a3>]
sock_common_getsockopt+0x33/0x40
Mar 11 02:49:58 baikonour kernel:  [<c046fa59>] sys_getsockopt+0x69/0xc0
Mar 11 02:49:58 baikonour kernel:  [<c0470159>] sys_socketcall+0x229/0x260
Mar 11 02:49:58 baikonour kernel:  [<c01158a0>] do_page_fault+0x0/0x510
Mar 11 02:49:58 baikonour kernel:  [<c010311f>] syscall_call+0x7/0xb
Mar 11 02:49:58 baikonour kernel: Code: 89 f0 29 d8 8d 04 c2 e8 5c 08 9e
df 85 c0 ba fc ff ff ff 75 69 89 e0 25 00 e0 ff ff 8b 00 8b
90 8c 05 00 00 8b 8c da f8 08 00 00 <8b> 01 8d 74 26 00 8d 94 16 f8 08
00 00 39 d1 74 6d 89 34 24 89
Mar 11 02:49:58 baikonour kernel: EIP: [<e0b2abe3>]
xt_find_table_lock+0x43/0xe0 [x_tables] SS:ESP 0068:cbb91dac
--- end of relevant syslog entries ---


If I can provide you with any more relevant information to help let me know.
Or if I'm just retarded and broke it myself by setting the wrong limits
(quite possible) sorry!
-Stuart

-- 
Stuart MacIntosh
IT Consultancy & Technical Services
Phone: +64 21 2259576
Email: stuart at linuxsecurity.co.nz