linux-kernel - [PATCH 6.6 426/638] drm/amd/display: Add 'replay' NULL check in 'edp_set_replay_allow

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Date: Sun, 24 Mar 2024 18:57:43 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Srinivasan Shanmugam <srinivasan.shanmugam@....com>,
	Bhawanpreet Lakha <Bhawanpreet.Lakha@....com>,
	Roman Li <roman.li@....com>,
	Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
	Aurabindo Pillai <aurabindo.pillai@....com>,
	Tom Chung <chiahsuan.chung@....com>,
	Alex Deucher <alexander.deucher@....com>,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH 6.6 426/638] drm/amd/display: Add 'replay' NULL check in 'edp_set_replay_allow_active()'

From: Srinivasan Shanmugam <srinivasan.shanmugam@....com>

[ Upstream commit f6aed043ee5d75b3d1bfc452b1a9584b63c8f76b ]

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)

Fixes: c7ddc0a800bc ("drm/amd/display: Add Functions to enable Freesync Panel Replay")
Cc: Bhawanpreet Lakha <Bhawanpreet.Lakha@....com>
Cc: Roman Li <roman.li@....com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@....com>
Cc: Aurabindo Pillai <aurabindo.pillai@....com>
Cc: Tom Chung <chiahsuan.chung@....com>
Suggested-by: Tom Chung <chiahsuan.chung@....com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@....com>
Reviewed-by: Tom Chung <chiahsuan.chung@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 .../drm/amd/display/dc/link/protocols/link_edp_panel_control.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c b/drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c
index 6f64aab18f07b..13104d000b9e0 100644
--- a/drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c
+++ b/drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c
@@ -882,7 +882,8 @@ bool edp_set_replay_allow_active(struct dc_link *link, const bool *allow_active,
 
 	/* Set power optimization flag */
 	if (power_opts && link->replay_settings.replay_power_opt_active != *power_opts) {
-		if (link->replay_settings.replay_feature_enabled && replay->funcs->replay_set_power_opt) {
+		if (replay != NULL && 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;
 		}
-- 
2.43.0