Subject: CVE-2022-48976: netfilter: flowtable_offload: fix using __this_cpu_add in preemptible

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

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

netfilter: flowtable_offload: fix using __this_cpu_add in preemptible

flow_offload_queue_work() can be called in workqueue without
bh disabled, like the call trace showed in my act_ct testing,
calling NF_FLOW_TABLE_STAT_INC() there would cause a call
trace:

  BUG: using __this_cpu_add() in preemptible [00000000] code: kworker/u4:0/138560
  caller is flow_offload_queue_work+0xec/0x1b0 [nf_flow_table]
  Workqueue: act_ct_workqueue tcf_ct_flow_table_cleanup_work [act_ct]
  Call Trace:
   <TASK>
   dump_stack_lvl+0x33/0x46
   check_preemption_disabled+0xc3/0xf0
   flow_offload_queue_work+0xec/0x1b0 [nf_flow_table]
   nf_flow_table_iterate+0x138/0x170 [nf_flow_table]
   nf_flow_table_free+0x140/0x1a0 [nf_flow_table]
   tcf_ct_flow_table_cleanup_work+0x2f/0x2b0 [act_ct]
   process_one_work+0x6a3/0x1030
   worker_thread+0x8a/0xdf0

This patch fixes it by using NF_FLOW_TABLE_STAT_INC_ATOMIC()
instead in flow_offload_queue_work().

Note that for FLOW_CLS_REPLACE branch in flow_offload_queue_work(),
it may not be called in preemptible path, but it's good to use
NF_FLOW_TABLE_STAT_INC_ATOMIC() for all cases in
flow_offload_queue_work().

The Linux kernel CVE team has assigned CVE-2022-48976 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 6.0 with commit b038177636f8 and fixed in 6.0.13 with commit a220a11fda01
	Issue introduced in 6.0 with commit b038177636f8 and fixed in 6.1 with commit a81047154e7c
	Issue introduced in 5.15.157 with commit 5345d78ae64d

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2022-48976
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	net/netfilter/nf_flow_table_offload.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/a220a11fda012fba506b35929672374c2723ae6d
	https://git.kernel.org/stable/c/a81047154e7ce4eb8769d5d21adcbc9693542a79