CVE-2024-26784: pmdomain: arm: Fix NULL dereference on scmi_perf_domain removal

CVE-2024-26784: pmdomain: arm: Fix NULL dereference on scmi_perf_domain removal

[Greg Kroah-Hartman]

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

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

pmdomain: arm: Fix NULL dereference on scmi_perf_domain removal

On unloading of the scmi_perf_domain module got the below splat, when in
the DT provided to the system under test the '#power-domain-cells' property
was missing. Indeed, this particular setup causes the probe to bail out
early without giving any error, which leads to the ->remove() callback gets
to run too, but without all the expected initialized structures in place.

Add a check and bail out early on remove too.

 Call trace:
  scmi_perf_domain_remove+0x28/0x70 [scmi_perf_domain]
  scmi_dev_remove+0x28/0x40 [scmi_core]
  device_remove+0x54/0x90
  device_release_driver_internal+0x1dc/0x240
  driver_detach+0x58/0xa8
  bus_remove_driver+0x78/0x108
  driver_unregister+0x38/0x70
  scmi_driver_unregister+0x28/0x180 [scmi_core]
  scmi_perf_domain_driver_exit+0x18/0xb78 [scmi_perf_domain]
  __arm64_sys_delete_module+0x1a8/0x2c0
  invoke_syscall+0x50/0x128
  el0_svc_common.constprop.0+0x48/0xf0
  do_el0_svc+0x24/0x38
  el0_svc+0x34/0xb8
  el0t_64_sync_handler+0x100/0x130
  el0t_64_sync+0x190/0x198
 Code: a90153f3 f9403c14 f9414800 955f8a05 (b9400a80)
 ---[ end trace 0000000000000000 ]---

The Linux kernel CVE team has assigned CVE-2024-26784 to this issue.


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

	Issue introduced in 6.7 with commit 2af23ceb8624 and fixed in 6.7.9 with commit f6aaf131e4d4
	Issue introduced in 6.7 with commit 2af23ceb8624 and fixed in 6.8 with commit eb5555d422d0

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-2024-26784
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/pmdomain/arm/scmi_perf_domain.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/f6aaf131e4d4a9a26040ecc018eb70ab8b3d355d
	https://git.kernel.org/stable/c/eb5555d422d0fc325e1574a7353d3c616f82d8b5