CVE-2023-52473: thermal: core: Fix NULL pointer dereference in zone registration error path

CVE-2023-52473: thermal: core: Fix NULL pointer dereference in zone registration error path

[Greg Kroah-Hartman]

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

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

thermal: core: Fix NULL pointer dereference in zone registration error path

If device_register() in thermal_zone_device_register_with_trips()
returns an error, the tz variable is set to NULL and subsequently
dereferenced in kfree(tz->tzp).

Commit adc8749b150c ("thermal/drivers/core: Use put_device() if
device_register() fails") added the tz = NULL assignment in question to
avoid a possible double-free after dropping the reference to the zone
device.  However, after commit 4649620d9404 ("thermal: core: Make
thermal_zone_device_unregister() return after freeing the zone"), that
assignment has become redundant, because dropping the reference to the
zone device does not cause the zone object to be freed any more.

Drop it to address the NULL pointer dereference.

The Linux kernel CVE team has assigned CVE-2023-52473 to this issue.


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

	Issue introduced in 6.4 with commit 3d439b1a2ad3 and fixed in 6.6.14 with commit 335176dd8eba
	Issue introduced in 6.4 with commit 3d439b1a2ad3 and fixed in 6.7.2 with commit 02871710b930
	Issue introduced in 6.4 with commit 3d439b1a2ad3 and fixed in 6.8-rc1 with commit 04e6ccfc93c5

Please see https://www.kernel.org or 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-2023-52473
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/thermal/thermal_core.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/335176dd8ebaca6493807dceea33c478305667fa
	https://git.kernel.org/stable/c/02871710b93058eb1249d5847c0b2d1c2c3c98ae
	https://git.kernel.org/stable/c/04e6ccfc93c5a1aa1d75a537cf27e418895e20ea