Subject: CVE-2024-44955: drm/amd/display: Don't refer to dc_sink in is_dsc_need_re_compute

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

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

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

drm/amd/display: Don't refer to dc_sink in is_dsc_need_re_compute

[Why]
When unplug one of monitors connected after mst hub, encounter null pointer dereference.

It's due to dc_sink get released immediately in early_unregister() or detect_ctx(). When
commit new state which directly referring to info stored in dc_sink will cause null pointer
dereference.

[how]
Remove redundant checking condition. Relevant condition should already be covered by checking
if dsc_aux is null or not. Also reset dsc_aux to NULL when the connector is disconnected.

The Linux kernel CVE team has assigned CVE-2024-44955 to this issue.

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

	Fixed in 6.10.5 with commit 39b217193729
	Fixed in 6.11 with commit fcf6a49d7992

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-2024-44955
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_mst_types.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/39b217193729aa45eded8de24d9245468a0c0263
	https://git.kernel.org/stable/c/fcf6a49d79923a234844b8efe830a61f3f0584e4