Re: [BUG] ipt_SAME rule can't be deleted

[Pablo Neira <pablo@eurodev.net>]

Henrik Nordstrom wrote:

> On Sat, 4 Dec 2004, Fang Han wrote:
>
>> Kernel 2.6.9 ac2
>>
>> Using the next test command:
>>
>> /sbin/iptables  -t nat -I POSTROUTING -s 192.168.100.23 -o eth0 -j 
>> SAME --to 192.168.1.60
>> /sbin/iptables  -t nat -D POSTROUTING -s 192.168.100.23 -o eth0 -j 
>> SAME --to 192.168.1.60
>>
>> generate error:
>> iptables: Bad rule (does a matching rule exist in that chain?)
>
>
> This is quite likely due to that kernel land pointer within the target 
> info...
>
>         u_int32_t *iparray;
>
> If I am right the same problem applies to -m limit and any other 
> extension storing private kernel side stuff within it's info data..


Right, we bite the dust when having pointers within the target private 
info... If we try to remove a rule, it won't match the existing because 
in user space that pointer is set to NULL, but in kernel space is set to 
whatever kmalloc reserved the space for us.

In iptables, target_difference() complains because, in the case of 
ipt_same, iparray isn't NULL. Same thing with iplimit. I think that in 
pkttables we need a private info part for match/targets which is not 
shared with user space.

--
Pablo