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SubjectRe: [BUG] panic 2.6.20-rc3 in nf_conntrack
On Tue, 2 Jan 2007, Chuck Ebbert wrote:

> > [ 336.476284] EIP is at device_cmp+0x1b/0x2e [ipt_MASQUERADE]
> > [ 336.476344] eax: de6d4000 ebx: 00000000 ecx: d944b7a0 edx: dd664d48
> > [ 336.476404] esi: 00000004 edi: 00001f58 ebp: 000003eb esp: de6d4e90
> > [ 336.476464] ds: 007b es: 007b ss: 0068
> > [ 336.476520] Process pppd (pid: 3846, ti=de6d4000 task=deda4a90 task.ti=de6d4000)
> > [ 336.476580] Stack: dd664c7c dd664c84 dfe8990d 00000004 dff16044 00000000 dff16b18 c164b000
> > [ 336.477024] 00000002 dff16041 c011c79f c164b000 000010d0 00001091 00000000 c01ea41a
> > [ 336.477527] c164b000 c01e99d5 d98b49e0 00000000 d98b4a0c ddc100c0 c022200b c164b000
> > [ 336.478030] Call Trace:
> > [ 336.478132] [<dfe8990d>] nf_ct_iterate_cleanup+0x62/0xda [nf_conntrack]
> > [ 336.478259] [<dff16044>] device_cmp+0x0/0x2e [ipt_MASQUERADE]
> > [ 336.478366] [<dff16041>] masq_device_event+0x12/0x15 [ipt_MASQUERADE]
> > [ 336.478468] [<c011c79f>] notifier_call_chain+0x19/0x29
> > [ 336.478576] [<c01ea41a>] dev_close+0x5c/0x60
>
> AFAICT 'nat' is zero here because bit 2 of i->features is zero:
>
> static inline int
> device_cmp(struct ip_conntrack *i, void *ifindex)
> {
> #ifdef CONFIG_NF_NAT_NEEDED
> struct nf_conn_nat *nat = nfct_nat(i);
> #endif
> int ret;
>
> read_lock_bh(&masq_lock);
> #ifdef CONFIG_NF_NAT_NEEDED
> ret = (nat->masq_index == (int)(long)ifindex); <===============
> #else
> ret = (i->nat.masq_index == (int)(long)ifindex);
> #endif
> read_unlock_bh(&masq_lock);
>
> return ret;
> }

I saw your (correct) analysis after having made the patch below, it has
been tested successfully by Bernhard Schmidt. (Netfilter bugzilla #528)

Check the return value of nfct_nat() in device_cmp(), we might very well
have non NAT conntrack entries as well.

Signed-off-by: Martin Josefsson <gandalf@wlug.westbo.se>

--- linux-2.6.20-rc3/net/ipv4/netfilter/ipt_MASQUERADE.c.orig 2007-01-02 22:47:14.000000000 +0100
+++ linux-2.6.20-rc3/net/ipv4/netfilter/ipt_MASQUERADE.c 2007-01-02 22:57:11.000000000 +0100
@@ -127,10 +127,13 @@
static inline int
device_cmp(struct ip_conntrack *i, void *ifindex)
{
+ int ret;
#ifdef CONFIG_NF_NAT_NEEDED
struct nf_conn_nat *nat = nfct_nat(i);
+
+ if (!nat)
+ return 0;
#endif
- int ret;

read_lock_bh(&masq_lock);
#ifdef CONFIG_NF_NAT_NEEDED
-
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