CVE-2026-93200: i3c: master: Fix use-after-free of master->this

CVE-2026-93200: i3c: master: Fix use-after-free of master->this

[Greg Kroah-Hartman]

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

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

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

i3c: master: Fix use-after-free of master->this

sysfs attribute callbacks for the master controller device dereference
master->this.  However, master->this is freed in
i3c_master_detach_free_devs() before the master device itself is
released.

As a result, sysfs accesses can dereference a freed master->this
pointer, leading to a use-after-free.

Keep master->this alive until i3c_masterdev_release(), which is called
after the master device and its sysfs state are being torn down. Do not
free master->this as part of the normal device detach path.

On the error path in i3c_master_set_info(), reset master->this and
bus.cur_master to NULL before freeing the allocated device.

The Linux kernel CVE team has assigned CVE-2026-93200 to this issue.


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

	Issue introduced in 5.0 with commit 3a379bbcea0af6280e1ca0d1edfcf4e68cde6ee0 and fixed in 6.18.52 with commit 4f3145db05fede36b35f8249b8acde5bd5d54864
	Issue introduced in 5.0 with commit 3a379bbcea0af6280e1ca0d1edfcf4e68cde6ee0 and fixed in 7.2.6 with commit 50034d8d0f797c3a7a599f750a7d3e792e80dea5
	Issue introduced in 5.0 with commit 3a379bbcea0af6280e1ca0d1edfcf4e68cde6ee0 and fixed in 7.3-rc1 with commit feb0ed76601f3c2f91f08688c5a7d8b9d382f720

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-2026-93200
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/i3c/master.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/4f3145db05fede36b35f8249b8acde5bd5d54864
	https://git.kernel.org/stable/c/50034d8d0f797c3a7a599f750a7d3e792e80dea5
	https://git.kernel.org/stable/c/feb0ed76601f3c2f91f08688c5a7d8b9d382f720