Re: [PATCH nf 1/1] netfilter: h323,sip: Fix possible dead loop in nat_rtp_rtcp and nf_nat_sdp_media

Hi Liping,

On Thu, Mar 2, 2017 at 7:18 PM, Liping Zhang [off-list ref] wrote:

Hi,
2017-03-02 18:18 GMT+08:00 Gao Feng [off-list ref]:
[...]

quoted

The expect class is NF_CT_EXPECT_CLASS_DEFAULT, and proto is
IPPROTO_UDP at the function "expect_rtp_rtcp",
And it makes sure the port is even number.

But look at the process_gcf, the port is got from the packet data at
function get_h225_addr.
So it may be odd number.
It also would add one expect node whose class is
NF_CT_EXPECT_CLASS_DEFAULT, and proto is IPPROTO_UDP.

The nat_rtp_rtcp() is only invoked by expect_rtp_rtcp, and nf_nat_sdp_media()
is only invoked by set_expected_rtp_rtcp. So the RTP port is ensured to be
even, as well as the rtp_exp->tuple.dst.u.udp.port.

Note: the rtp_exp is alloced by nf_ct_expect_alloc, and initialized by
nf_ct_expect_init, then passed to nat_rtp_rtcp or nf_nat_sdp_media.

So I cannot figure out why process_gcf will affect this? Or I missed something?

I was lost in codes and forgot to check the caller of nat_rtp_rtcp.
Thanks your explanations.

There is no any issue in current codes indeed.

Best Regards
Feng