Subject: CVE-2024-38554: ax25: Fix reference count leak issue of net_device

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

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

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

ax25: Fix reference count leak issue of net_device

There is a reference count leak issue of the object "net_device" in
ax25_dev_device_down(). When the ax25 device is shutting down, the
ax25_dev_device_down() drops the reference count of net_device one
or zero times depending on if we goto unlock_put or not, which will
cause memory leak.

In order to solve the above issue, decrease the reference count of
net_device after dev->ax25_ptr is set to null.

The Linux kernel CVE team has assigned CVE-2024-38554 to this issue.

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

	Issue introduced in 5.17 with commit d01ffb9eee4a and fixed in 6.1.93 with commit 3ec437f9bbae
	Issue introduced in 5.17 with commit d01ffb9eee4a and fixed in 6.6.33 with commit 965d940fb741
	Issue introduced in 5.17 with commit d01ffb9eee4a and fixed in 6.8.12 with commit 8bad3a20a27b
	Issue introduced in 5.17 with commit d01ffb9eee4a and fixed in 6.9.3 with commit eef95df9b752
	Issue introduced in 5.17 with commit d01ffb9eee4a and fixed in 6.10 with commit 36e56b1b002b
	Issue introduced in 4.14.277 with commit ef0a2a056572
	Issue introduced in 4.19.240 with commit e2b558fe507a
	Issue introduced in 5.4.190 with commit 418993bbaafb
	Issue introduced in 5.10.112 with commit 5ea00fc60676
	Issue introduced in 5.15.35 with commit 9af0fd5c4453

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-2024-38554
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/ax25/ax25_dev.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/3ec437f9bbae68e9b38115c4c91de995f73f6bad
	https://git.kernel.org/stable/c/965d940fb7414b310a22666503d2af69459c981b
	https://git.kernel.org/stable/c/8bad3a20a27be8d935f2aae08d3c6e743754944a
	https://git.kernel.org/stable/c/eef95df9b752699bddecefa851f64858247246e9
	https://git.kernel.org/stable/c/36e56b1b002bb26440403053f19f9e1a8bc075b2