Re: [Xen-devel] Re: Panic in ipt_do_table with 2.6.16.13-xen

[Keir Fraser <Keir.Fraser@cl.cam.ac.uk>]

On 23 May 2006, at 22:23, Matt Ayres wrote:

>> Having looked at disassembly, the fault happens when accessing 
>> e->ip.invflags in ip_packet_match() inlined inside ipt_do_table().
>>  e = private->entries[smp_processor_id()] + 
>> private->hook_entry[NF_IP_FORWARD]
>> smp_processor_id() should be 0 (since the oops appears to occur on 
>> cpu0) and presumably all the ipt_entry structures are static once set 
>> up. Since this crash happens on a common path in ipt_do_table(), and 
>> since it happens only after the system has been up a while (I 
>> believe?), it rather looks as though something has either corrupted a 
>> pointer or unmapped memory from under iptables' feet.
>
> As the concerned user, what does this mean to me?  It will only affect 
> SMP systems?  It is a bug in Xen or netfilter?

Probably a Xen bug, but if so then it's basically a memory corruption. 
It's weird it would hit the iptables rules every time though, and not 
be a more random crash. This might well need reproducing in a developer 
test-machine environment to stand a chance of tracking down.

  -- Keir

> I'd just like to understand what is going on.