linux-cve-announce - CVE-2025-38682: i2c: core: Fix double-free of fwnode in i2c_unregister

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <2025090446-CVE-2025-38682-a90a@gregkh>
Date: Thu,  4 Sep 2025 17:32:47 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38682: i2c: core: Fix double-free of fwnode in i2c_unregister_device()

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

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

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

i2c: core: Fix double-free of fwnode in i2c_unregister_device()

Before commit df6d7277e552 ("i2c: core: Do not dereference fwnode in struct
device"), i2c_unregister_device() only called fwnode_handle_put() on
of_node-s in the form of calling of_node_put(client->dev.of_node).

But after this commit the i2c_client's fwnode now unconditionally gets
fwnode_handle_put() on it.

When the i2c_client has no primary (ACPI / OF) fwnode but it does have
a software fwnode, the software-node will be the primary node and
fwnode_handle_put() will put() it.

But for the software fwnode device_remove_software_node() will also put()
it leading to a double free:

[   82.665598] ------------[ cut here ]------------
[   82.665609] refcount_t: underflow; use-after-free.
[   82.665808] WARNING: CPU: 3 PID: 1502 at lib/refcount.c:28 refcount_warn_saturate+0xba/0x11
...
[   82.666830] RIP: 0010:refcount_warn_saturate+0xba/0x110
...
[   82.666962]  <TASK>
[   82.666971]  i2c_unregister_device+0x60/0x90

Fix this by not calling fwnode_handle_put() when the primary fwnode is
a software-node.

The Linux kernel CVE team has assigned CVE-2025-38682 to this issue.


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

	Issue introduced in 6.16 with commit df6d7277e5525d6cce63127dd93ebec4c6354fa0 and fixed in 6.16.2 with commit ffe02f7c4e36090154646612e67d331832f92037
	Issue introduced in 6.16 with commit df6d7277e5525d6cce63127dd93ebec4c6354fa0 and fixed in 6.17-rc1 with commit 1c24e5fc0c7096e00c202a6a3e0c342c1afb47c2

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-2025-38682
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/i2c/i2c-core-base.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/ffe02f7c4e36090154646612e67d331832f92037
	https://git.kernel.org/stable/c/1c24e5fc0c7096e00c202a6a3e0c342c1afb47c2