CVE-2024-26647: drm/amd/display: Fix late derefrence 'dsc' check in 'link_set_dsc_pps_packet()'

CVE-2024-26647: drm/amd/display: Fix late derefrence 'dsc' check in 'link_set_dsc_pps_packet()'

[Lee Jones]

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

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

drm/amd/display: Fix late derefrence 'dsc' check in 'link_set_dsc_pps_packet()'

In link_set_dsc_pps_packet(), 'struct display_stream_compressor *dsc'
was dereferenced in a DC_LOGGER_INIT(dsc->ctx->logger); before the 'dsc'
NULL pointer check.

Fixes the below:
drivers/gpu/drm/amd/amdgpu/../display/dc/link/link_dpms.c:905 link_set_dsc_pps_packet() warn: variable dereferenced before check 'dsc' (see line 903)

The Linux kernel CVE team has assigned CVE-2024-26647 to this issue.


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

	Fixed in 6.6.15 with commit 6aa5ede66651
	Fixed in 6.7.3 with commit cf656fc7276e
	Fixed in 6.8 with commit 3bb9b1f958c3

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-2024-26647
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/link/link_dpms.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/6aa5ede6665122f4c8abce3c6eba06b49e54d25c
	https://git.kernel.org/stable/c/cf656fc7276e5b3709a81bc9d9639459be2b2647
	https://git.kernel.org/stable/c/3bb9b1f958c3d986ed90a3ff009f1e77e9553207