netfilter: conntrack: fix wrong ct->timeout value

In the Linux kernel, the following vulnerability has been resolved:

netfilter: conntrack: fix wrong ct->timeout value

(struct nf_conn)->timeout is an interval before the conntrack confirmed. After confirmed, it becomes a timestamp.

It is observed that timeout of an unconfirmed conntrack: - Set by calling ctnetlink_change_timeout(). As a result, nfct_time_stamp was wrongly added to ct->timeout twice. - Get by calling ctnetlink_dump_timeout(). As a result, nfct_time_stamp was wrongly subtracted.

Call Trace:

dump_stack_lvl ctnetlink_dump_timeout __ctnetlink_glue_build ctnetlink_glue_build __nfqnl_enqueue_packet nf_queue nf_hook_slow ip_mc_output ? __pfx_ip_finish_output ip_send_skb ? __pfx_dst_output udp_send_skb udp_sendmsg ? __pfx_ip_generic_getfrag sock_sendmsg

Separate the 2 cases in: - Setting ct->timeout in __nf_ct_set_timeout(). - Getting ct->timeout in ctnetlink_dump_timeout().

Pablo appends:

Update ctnetlink to set up the timeout _after_ the IPS_CONFIRMED flag is set on, otherwise conntrack creation via ctnetlink breaks.

Note that the problem described in this patch occurs since the introduction of the nfnetlink_queue conntrack support, select a sufficiently old Fixes: tag for -stable kernel to pick up this fix.