linux-cve-announce - CVE-2024-54683: netfilter: IDLETIMER: Fix for possible ABBA deadlock

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Message-ID: <2025011159-CVE-2024-54683-042e@gregkh>
Date: Sat, 11 Jan 2025 13:30:03 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-54683: netfilter: IDLETIMER: Fix for possible ABBA deadlock

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

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

netfilter: IDLETIMER: Fix for possible ABBA deadlock

Deletion of the last rule referencing a given idletimer may happen at
the same time as a read of its file in sysfs:

| ======================================================
| WARNING: possible circular locking dependency detected
| 6.12.0-rc7-01692-g5e9a28f41134-dirty #594 Not tainted
| ------------------------------------------------------
| iptables/3303 is trying to acquire lock:
| ffff8881057e04b8 (kn->active#48){++++}-{0:0}, at: __kernfs_remove+0x20
|
| but task is already holding lock:
| ffffffffa0249068 (list_mutex){+.+.}-{3:3}, at: idletimer_tg_destroy_v]
|
| which lock already depends on the new lock.

A simple reproducer is:

| #!/bin/bash
|
| while true; do
|         iptables -A INPUT -i foo -j IDLETIMER --timeout 10 --label "testme"
|         iptables -D INPUT -i foo -j IDLETIMER --timeout 10 --label "testme"
| done &
| while true; do
|         cat /sys/class/xt_idletimer/timers/testme >/dev/null
| done

Avoid this by freeing list_mutex right after deleting the element from
the list, then continuing with the teardown.

The Linux kernel CVE team has assigned CVE-2024-54683 to this issue.


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

	Issue introduced in 2.6.36 with commit 0902b469bd25065aa0688c3cee6f11744c817e7c and fixed in 6.6.67 with commit 8c2c8445cda8f59c38dec7dc10509bcb23ae26a0
	Issue introduced in 2.6.36 with commit 0902b469bd25065aa0688c3cee6f11744c817e7c and fixed in 6.12.6 with commit 45fe76573a2557f632e248cc141342233f422b9a
	Issue introduced in 2.6.36 with commit 0902b469bd25065aa0688c3cee6f11744c817e7c and fixed in 6.13-rc3 with commit f36b01994d68ffc253c8296e2228dfe6e6431c03

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-2024-54683
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/xt_IDLETIMER.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/8c2c8445cda8f59c38dec7dc10509bcb23ae26a0
	https://git.kernel.org/stable/c/45fe76573a2557f632e248cc141342233f422b9a
	https://git.kernel.org/stable/c/f36b01994d68ffc253c8296e2228dfe6e6431c03