linux-cve-announce - CVE-2022-49110: netfilter: conntrack: revisit gc autotuning

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Message-ID: <2025022602-CVE-2022-49110-5519@gregkh>
Date: Wed, 26 Feb 2025 02:55:15 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49110: netfilter: conntrack: revisit gc autotuning

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

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

netfilter: conntrack: revisit gc autotuning

as of commit 4608fdfc07e1
("netfilter: conntrack: collect all entries in one cycle")
conntrack gc was changed to run every 2 minutes.

On systems where conntrack hash table is set to large value, most evictions
happen from gc worker rather than the packet path due to hash table
distribution.

This causes netlink event overflows when events are collected.

This change collects average expiry of scanned entries and
reschedules to the average remaining value, within 1 to 60 second interval.

To avoid event overflows, reschedule after each bucket and add a
limit for both run time and number of evictions per run.

If more entries have to be evicted, reschedule and restart 1 jiffy
into the future.

The Linux kernel CVE team has assigned CVE-2022-49110 to this issue.

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

	Fixed in 5.15.34 with commit 58d52743ae85d28c9335c6034d6ce350b8689951
	Fixed in 5.16.20 with commit 7cd361d5e6d986c0d4cafb9ceaa803359048ae15
	Fixed in 5.17.3 with commit 592e57591826f3d09c28d755a39ea8e9d13705ad
	Fixed in 5.18 with commit 2cfadb761d3d0219412fd8150faea60c7e863833

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-2022-49110
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_conntrack_core.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/58d52743ae85d28c9335c6034d6ce350b8689951
	https://git.kernel.org/stable/c/7cd361d5e6d986c0d4cafb9ceaa803359048ae15
	https://git.kernel.org/stable/c/592e57591826f3d09c28d755a39ea8e9d13705ad
	https://git.kernel.org/stable/c/2cfadb761d3d0219412fd8150faea60c7e863833