Re: BUG: 2.6.25-rc1: iptables postrouting setup causes oops

On Tue, 12 Feb 2008 22:46:01 +1100 Ben Nizette <bn@xxxxxxxxxxxxxxx> wrote:


On an AVR32, root over NFS, config attached, running (from a startup
script):

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

Results in (dmesg extract including a bit of context for good measure):
-------------8<----------------
VFS: Mounted root (nfs filesystem).
Freeing init memory: 72K (90000000 - 90012000)
eth0: no IPv6 routers present
warning: `dnsmasq' uses 32-bit capabilities (legacy support in use)
ip_tables: (C) 2000-2006 Netfilter Core Team
nf_conntrack version 0.5.0 (1024 buckets, 4096 max)
Unable to handle kernel paging request at virtual address d76a7138
ptbr = 91d3b000 pgd = 0000e5f3 pte = 00014370
Oops: Kernel access of bad area, sig: 11 [#1]
FRAME_POINTER chip: 0x01f:0x1e82 rev 2
Modules linked in: nf_conntrack_ipv4(+) nf_conntrack ip_tables
PC is at kmem_cache_alloc+0x2c/0x54
LR is at nf_conntrack_l4proto_register+0x34/0x9c [nf_conntrack]

I take it that the above means that the crash is in kmem_cache_alloc()?

pc : [<9004fa78>] lr : [<c08537d8>] Not tainted
sp : 91eb5e9c r12: 901cc588 r11: 000000d0
r10: 901e03a0 r9 : 00000002 r8 : 91d33800
r7 : 91eb5e9c r6 : 901d9138 r5 : 901cc588 r4 : 0007a008
r3 : 000000d0 r2 : 00400005 r1 : c085f9c0 r0 : c08c1424
Flags: qvNzc
Mode bits: hjmde....G
CPU Mode: Supervisor
Process: insmod [250] (task: 91d789c0 thread: 91eb4000)
Stack: (0x91eb5e9c to 0x91eb6000)
5e80: c08537d8
5ea0: 91eb5ec0 c085a6b4 00000000 0007a008 fffffff0 00000027 c085f9c0 c08c1424
5ec0: c0861024 91eb5ee4 00000000 c085f654 0007a008 901d31b0 00000027 c085f9c0
5ee0: c08c1424 900358d4 91eb5f94 91d6ddf0 901d31b8 0007a008 91eb5f08 0007a008
5f00: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
5f20: 0000000c 00000000 00000000 00000000 00000007 c08df440 91d1c660 c08c19ec
5f40: c08c16a4 c0881000 00000000 000000b2 000000b2 c085e17c 90022414 00000027
5f60: c08c12c3 c08c1424 c08c1a3c c08c1a14 00000027 00000025 00060000 2ab17000
5f80: 90047080 91eb5f94 91eb4000 00000000 c087ef80 90012132 00000000 00072e14
5fa0: 0000535e 0007a008 00072858 7f89ff73 80000000 91eb4000 00000001 2aae23ec
5fc0: 7f89fd98 7f89fd88 2ab17008 0005edf5 0007a008 0005edf5 00000073 7f89fedc
5fe0: 00072e14 0000535e 0007a008 00072858 7f89ff73 00000002 00059538 2ab17008
Call trace:
[<c08537d8>] nf_conntrack_l4proto_register+0x34/0x9c [nf_conntrack]
[<c0861024>] nf_conntrack_l3proto_ipv4_init+0x24/0x108 [nf_conntrack_ipv4]
[<900358d4>] sys_init_module+0xf78/0x1028
[<90012132>] syscall_return+0x0/0x12

iptable_nat: gave up waiting for init of module nf_conntrack_ipv4.
iptable_nat: Unknown symbol need_ipv4_conntrack
----------------8<---------------------------------

iptables version 1.3.8

If so, the bug could be almost anywhere - in slab, or in some random piece
of code which scribbles on slab's data structures.

Perfectly repeatable.

If my theory is correct, changing pretty much anything in the kernel config
might just make it go away. But still, it would be most valuable if you
could try running a bisection search, as described in
http://www.kernel.org/doc/local/git-quick.html, thanks.

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