linux-cve-announce - CVE-2025-39873: can: xilinx_can: xcan_write_frame(): fix use-after-free of transmitted SKB

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Message-ID: <2025092300-CVE-2025-39873-94d3@gregkh>
Date: Tue, 23 Sep 2025 08:01:04 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-39873: can: xilinx_can: xcan_write_frame(): fix use-after-free of transmitted SKB

From: Greg Kroah-Hartman <gregkh@...nel.org>

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

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

can: xilinx_can: xcan_write_frame(): fix use-after-free of transmitted SKB

can_put_echo_skb() takes ownership of the SKB and it may be freed
during or after the call.

However, xilinx_can xcan_write_frame() keeps using SKB after the call.

Fix that by only calling can_put_echo_skb() after the code is done
touching the SKB.

The tx_lock is held for the entire xcan_write_frame() execution and
also on the can_get_echo_skb() side so the order of operations does not
matter.

An earlier fix commit 3d3c817c3a40 ("can: xilinx_can: Fix usage of skb
memory") did not move the can_put_echo_skb() call far enough.

[mkl: add "commit" in front of sha1 in patch description]
[mkl: fix indention]

The Linux kernel CVE team has assigned CVE-2025-39873 to this issue.


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

	Issue introduced in 4.19 with commit 1598efe57b3e768056e4ca56cb9cf33111e68d1c and fixed in 6.1.153 with commit 1139321161a3ba5e45e61e0738b37f42f20bc57a
	Issue introduced in 4.19 with commit 1598efe57b3e768056e4ca56cb9cf33111e68d1c and fixed in 6.6.107 with commit 94b050726288a56a6b8ff55aa641f2fedbd3b44c
	Issue introduced in 4.19 with commit 1598efe57b3e768056e4ca56cb9cf33111e68d1c and fixed in 6.12.48 with commit 725b33deebd6e4c96fe7893f384510a54258f28f
	Issue introduced in 4.19 with commit 1598efe57b3e768056e4ca56cb9cf33111e68d1c and fixed in 6.16.8 with commit 668cc1e3bb21101d074e430de1b7ba8fd10189e7
	Issue introduced in 4.19 with commit 1598efe57b3e768056e4ca56cb9cf33111e68d1c and fixed in 6.17-rc6 with commit ef79f00be72bd81d2e1e6f060d83cf7e425deee4

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-2025-39873
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:
	drivers/net/can/xilinx_can.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/1139321161a3ba5e45e61e0738b37f42f20bc57a
	https://git.kernel.org/stable/c/94b050726288a56a6b8ff55aa641f2fedbd3b44c
	https://git.kernel.org/stable/c/725b33deebd6e4c96fe7893f384510a54258f28f
	https://git.kernel.org/stable/c/668cc1e3bb21101d074e430de1b7ba8fd10189e7
	https://git.kernel.org/stable/c/ef79f00be72bd81d2e1e6f060d83cf7e425deee4