linux-kernel - Re: System freeze on reboot

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Date:	Wed, 2 Sep 2009 23:45:03 +0200
From:	Zdenek Kabelac <zdenek.kabelac@...il.com>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Robin Holt <holt@....com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Jesper Dangaard Brouer <hawk@...x.dk>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Netfilter Developers <netfilter-devel@...r.kernel.org>
Subject: Re: System freeze on reboot - general protection fault

2009/8/17 Patrick McHardy <kaber@...sh.net>:
> Eric Dumazet wrote:
>> Zdenek Kabelac a écrit :
>>>  [<ffffffffa02c502f>] nf_conntrack_ftp_fini+0x2f/0x70 [nf_conntrack_ftp]
>>>  [<ffffffff8027bcc5>] sys_delete_module+0x1a5/0x270
>>>  [<ffffffff8020d329>] ? retint_swapgs+0xe/0x13
>>>  [<ffffffff80271bf2>] ? trace_hardirqs_on_caller+0x162/0x1b0
>>>  [<ffffffff80292121>] ? audit_syscall_entry+0x191/0x1c0
>>>  [<ffffffff80526dae>] ? trace_hardirqs_on_thunk+0x3a/0x3f
>>>  [<ffffffff8020c84b>] system_call_fastpath+0x16/0x1b
>>> Code: c6 00 00 0f 82 66 ff ff ff 49 8b 9e d8 05 00 00 48 85 db 75 16
>>> e9 8e 00 00 00 0f 1f 44 00 00 48 85 c0 0f 84 80 00 00 00 48 89 c3 <0f>
>>> b6 4b 37 48 8b 03 48 8d 14 cd 00 00 00 00 0f 18 08 48 29 ca
>>> RIP  [<ffffffffa02b2c2c>] nf_conntrack_helper_unregister+0x16c/0x320
>>> [nf_conntrack]
>>>  RSP <ffff88013982fe68>
>>> CR2: 0000000000000038
>>> ---[ end trace bc3a0ede3d0084db ]---
>>>
>> I am currently traveling and wont be able to help you before next week.
>>
>> I added netdev, Patrick, and netfilter-devel in CC so that more eyes can take a look.
>
> Thanks for the report, I'll have a look at this. Zdenek, please
> send me the nf_conntrack.ko file used in the above oops. Thanks.
>

Ok

I've found the solution for my problem.

http://thread.gmane.org/gmane.comp.security.firewalls.netfilter.devel/30483

I've made this small fix from this thread:

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core
index b5869b9..68488f8 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1108,6 +1108,7 @@ static void nf_conntrack_cleanup_init_net(void)
 {
        nf_conntrack_helper_fini();
        nf_conntrack_proto_fini();
+       rcu_barrier();
        kmem_cache_destroy(nf_conntrack_cachep);
 }

@@ -1266,7 +1267,7 @@ static int nf_conntrack_init_init_net(void)

        nf_conntrack_cachep = kmem_cache_create("nf_conntrack",
                                                sizeof(struct nf_conn),
-                                               0, SLAB_DESTROY_BY_RCU, NULL);
+                                               0, 0, NULL);
        if (!nf_conntrack_cachep) {
                printk(KERN_ERR "Unable to create nf_conn slab cache\n");
                ret = -ENOMEM;


As the thread nf_conntrack: Use rcu_barrier() and fix kmem_cache_create flags
seems to be samewhat 'unfinished'  and already a bit old and I've no
idea whether it actually fixes problem completely or just hides it in
my case - I'm leaving it to some RCU gurus to fix this issue.

All I could say is - this this extra rcu_barrier() and removal of
SLAB_DESTROY removes my GPF on reboot.

Zdenek
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