CVE-2023-53635

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:

<TASK>

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.