Subject: CVE-2024-49920: drm/amd/display: Check null pointers before multiple uses

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

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

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

drm/amd/display: Check null pointers before multiple uses

[WHAT & HOW]
Poniters, such as stream_enc and dc->bw_vbios, are null checked previously
in the same function, so Coverity warns "implies that stream_enc and
dc->bw_vbios might be null". They are used multiple times in the
subsequent code and need to be checked.

This fixes 10 FORWARD_NULL issues reported by Coverity.

The Linux kernel CVE team has assigned CVE-2024-49920 to this issue.

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

	Fixed in 6.11.3 with commit 26787fb6c2b2
	Fixed in 6.12-rc1 with commit fdd5ecbbff75

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-2024-49920
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/dc/core/dc_hw_sequencer.c
	drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c
	drivers/gpu/drm/amd/display/dc/link/accessories/link_dp_cts.c
	drivers/gpu/drm/amd/display/dc/link/hwss/link_hwss_dio.c
	drivers/gpu/drm/amd/display/dc/resource/dce112/dce112_resource.c
	drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
	drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource_helpers.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/26787fb6c2b2ee0d1a7e1574b36f4711ae40fe27
	https://git.kernel.org/stable/c/fdd5ecbbff751c3b9061d8ebb08e5c96119915b4