Subject: CVE-2024-49916: drm/amd/display: Add NULL check for clk_mgr and clk_mgr->funcs in dcn401_init_hw

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

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

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

drm/amd/display: Add NULL check for clk_mgr and clk_mgr->funcs in dcn401_init_hw

This commit addresses a potential null pointer dereference issue in the
`dcn401_init_hw` function. The issue could occur when `dc->clk_mgr` or
`dc->clk_mgr->funcs` is null.

The fix adds a check to ensure `dc->clk_mgr` and `dc->clk_mgr->funcs` is
not null before accessing its functions. This prevents a potential null
pointer dereference.

Reported by smatch:
drivers/gpu/drm/amd/amdgpu/../display/dc/hwss/dcn401/dcn401_hwseq.c:416 dcn401_init_hw() error: we previously assumed 'dc->clk_mgr' could be null (see line 225)

The Linux kernel CVE team has assigned CVE-2024-49916 to this issue.

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

	Fixed in 6.11.3 with commit ac1c41e31807
	Fixed in 6.12-rc1 with commit 4b6377f0e960

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-2024-49916
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/hwss/dcn401/dcn401_hwseq.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/ac1c41e318074d8a9ea925787e366be15d7645e8
	https://git.kernel.org/stable/c/4b6377f0e96085cbec96eb7f0b282430ccdd3d75