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.

References

• https://nvd.nist.gov/vuln/detail/CVE-2023-53635
• https://git.kernel.org/stable/c/73db1b8f2bb6725b7391e85aab41fdf592b3c0c1
• https://git.kernel.org/stable/c/80c5ba0078e20d926d11d0778f9a43902664ebf0
• https://git.kernel.org/stable/c/f612ae1ab4793701caf39386fb3b7f4b3ef44e48
• https://git.kernel.org/stable/c/ff5e4ac8dd7be7f1faba955c5779a68571eeb0f8