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SubjectRe: Oops in 2.1.129
On Tue, Nov 24, 1998 at 12:33:52PM +1130, Paul Rusty Russell wrote:
> In message <> you write:
> > 2.1.129 get a Null Pointer Dereference followed by an oops, followed by a
> > panic when I enable ip_forwarding under 2.1.129 with masquarading ipchains
> > rules present.
> >
> > My IP chains rules:
> >
> > ipchains -P forward DENY
> > ipchains -A forward -j MASQ -s -d
> >
> > Then I enable forwarding:
> >
> > echo "1" >/proc/sys/net/ipv4/ip_forward
> >
> > Then it goes boom (keyed in from my notes):
> Sorry for the delay; you should probably have sent this to the IP
> Firewalling maintainer as well; linux-kernel has too much noise about
> elevating chickens in assembler.

Whoops... Sorry.

It's been a while since I've followed the devel kernel stuff. The only
address I remembered was the Linux kernel mailing list.

> > >From my / around the value of EIP:
> >
> > c016eba0 t find_special
> > c016ecd0 t cleanup
> > c016ed40 t ip_fw_check
> > c016f2d0 t zero_fw_chain
> This trace is currupted: cleanup() is a leafnode. It's almost
> certainly the masq code barfing on a fragment. While that *shouldn't*
> happen, it doesn't surprise me since few people do this.

yes.. I noticed this later and looked up all the return addresses in the
call trace. Here's a better look:

Address closest to EIP and the addresses in the call trace (in order):
c016ecd0 t cleanup (EIP)
c016ed40 t ip_fw_check
c0170304 T ipfw_forward_check
c0149a6c T call_fw_firewall
c015819c T ip_forward
c0157538 T ip_rcv
c014c3f8 T net_bh
c0119570 T get_ioport_list
c010a560 T do_IRQ
c0108cec T ret_from_intr
c0107b7c T sys_rt_sigsuspend

And you're entirely right. It's barfing in ip_fw_check.

Unfortunately, it still barfs even with always defragment turned on. Unless
my kernel configuration is borked, there's still something that needs

Brian Ristuccia

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