Subject: CVE-2024-27040: drm/amd/display: Add 'replay' NULL check in 'edp_set_replay_allow_active()'

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

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

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

drm/amd/display: Add 'replay' NULL check in 'edp_set_replay_allow_active()'

In the first if statement, we're checking if 'replay' is NULL. But in
the second if statement, we're not checking if 'replay' is NULL again
before calling replay->funcs->replay_set_power_opt().

if (replay == NULL && force_static)
    return false;

...

if (link->replay_settings.replay_feature_enabled &&
    replay->funcs->replay_set_power_opt) {
	replay->funcs->replay_set_power_opt(replay, *power_opts, panel_inst);
	link->replay_settings.replay_power_opt_active = *power_opts;
}

If 'replay' is NULL, this will cause a null pointer dereference.

Fixes the below found by smatch:
drivers/gpu/drm/amd/amdgpu/../display/dc/link/protocols/link_edp_panel_control.c:895 edp_set_replay_allow_active() error: we previously assumed 'replay' could be null (see line 887)

The Linux kernel CVE team has assigned CVE-2024-27040 to this issue.

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

	Issue introduced in 6.6 with commit c7ddc0a800bc and fixed in 6.6.23 with commit f610c46771ef
	Issue introduced in 6.6 with commit c7ddc0a800bc and fixed in 6.7.11 with commit e7cadd5d3a8f
	Issue introduced in 6.6 with commit c7ddc0a800bc and fixed in 6.8.2 with commit d0e94f4807ff
	Issue introduced in 6.6 with commit c7ddc0a800bc and fixed in 6.9 with commit f6aed043ee5d

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-2024-27040
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/protocols/link_edp_panel_control.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/f610c46771ef1047e46d61807aa7c69cd29e63d8
	https://git.kernel.org/stable/c/e7cadd5d3a8ffe334d0229ba9eda4290138d56e7
	https://git.kernel.org/stable/c/d0e94f4807ff0df66cf447d6b4bbb8ac830e99c3
	https://git.kernel.org/stable/c/f6aed043ee5d75b3d1bfc452b1a9584b63c8f76b