Subject: CVE-2024-27041: drm/amd/display: fix NULL checks for adev->dm.dc in amdgpu_dm_fini()

From: Greg Kroah-Hartman <[email-masked]>

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

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

drm/amd/display: fix NULL checks for adev->dm.dc in amdgpu_dm_fini()

Since 'adev->dm.dc' in amdgpu_dm_fini() might turn out to be NULL
before the call to dc_enable_dmub_notifications(), check
beforehand to ensure there will not be a possible NULL-ptr-deref
there.

Also, since commit 1e88eb1b2c25 ("drm/amd/display: Drop
CONFIG_DRM_AMD_DC_HDCP") there are two separate checks for NULL in
'adev->dm.dc' before dc_deinit_callbacks() and dc_dmub_srv_destroy().
Clean up by combining them all under one 'if'.

Found by Linux Verification Center (linuxtesting.org) with static
analysis tool SVACE.

The Linux kernel CVE team has assigned CVE-2024-27041 to this issue.

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

	Issue introduced in 5.14 with commit 81927e2808be and fixed in 6.6.23 with commit e040f1fbe9ab
	Issue introduced in 5.14 with commit 81927e2808be and fixed in 6.7.11 with commit ca2eb375db76
	Issue introduced in 5.14 with commit 81927e2808be and fixed in 6.8.2 with commit 1c62697e4086
	Issue introduced in 5.14 with commit 81927e2808be and fixed in 6.9 with commit 2a3cfb9a24a2

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-2024-27041
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/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.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/e040f1fbe9abae91b12b074cfc3bbb5367b79811
	https://git.kernel.org/stable/c/ca2eb375db76fd50f31afdd67d6ca4f833254957
	https://git.kernel.org/stable/c/1c62697e4086de988b31124fb8c79c244ea05f2b
	https://git.kernel.org/stable/c/2a3cfb9a24a28da9cc13d2c525a76548865e182c