Subject: CVE-2024-38602: ax25: Fix reference count leak issues of ax25_dev

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

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

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

ax25: Fix reference count leak issues of ax25_dev

The ax25_addr_ax25dev() and ax25_dev_device_down() exist a reference
count leak issue of the object "ax25_dev".

Memory leak issue in ax25_addr_ax25dev():

The reference count of the object "ax25_dev" can be increased multiple
times in ax25_addr_ax25dev(). This will cause a memory leak.

Memory leak issues in ax25_dev_device_down():

The reference count of ax25_dev is set to 1 in ax25_dev_device_up() and
then increase the reference count when ax25_dev is added to ax25_dev_list.
As a result, the reference count of ax25_dev is 2. But when the device is
shutting down. The ax25_dev_device_down() drops the reference count once
or twice depending on if we goto unlock_put or not, which will cause
memory leak.

As for the issue of ax25_addr_ax25dev(), it is impossible for one pointer
to be on a list twice. So add a break in ax25_addr_ax25dev(). As for the
issue of ax25_dev_device_down(), increase the reference count of ax25_dev
once in ax25_dev_device_up() and decrease the reference count of ax25_dev
after it is removed from the ax25_dev_list.

The Linux kernel CVE team has assigned CVE-2024-38602 to this issue.

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

	Issue introduced in 5.17 with commit d01ffb9eee4a and fixed in 6.1.93 with commit ae467750a376
	Issue introduced in 5.17 with commit d01ffb9eee4a and fixed in 6.6.33 with commit 38eb01edfdaa
	Issue introduced in 5.17 with commit d01ffb9eee4a and fixed in 6.8.12 with commit 81d8240b0a24
	Issue introduced in 5.17 with commit d01ffb9eee4a and fixed in 6.9.3 with commit 1ea02699c755
	Issue introduced in 5.17 with commit d01ffb9eee4a and fixed in 6.10 with commit b505e0319852
	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-2024-38602
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/ae467750a3765dd1092eb29f58247950a2f9b60c
	https://git.kernel.org/stable/c/38eb01edfdaa1562fa00429be2e33f45383b1b3a
	https://git.kernel.org/stable/c/81d8240b0a243b3ddd8fa8aa172f1acc2f7cc8f3
	https://git.kernel.org/stable/c/1ea02699c7557eeb35ccff2bd822de1b3e09d868
	https://git.kernel.org/stable/c/b505e0319852b08a3a716b64620168eab21f4ced