From 7d0e09998f671021c0f6c1b07c553283b5e344aa Mon Sep 17 00:00:00 2001
From: Harry Wentland <harry.wentland@amd.com>
Date: Tue, 19 Apr 2022 13:03:12 -0400
Subject: drm/amd/display: Avoid reading audio pattern past
 AUDIO_CHANNELS_COUNT
Git-commit: 3dfe85fa87b2a26bdbd292b66653bba065cf9941
Patch-mainline: v5.18-rc6
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

A faulty receiver might report an erroneous channel count. We
should guard against reading beyond AUDIO_CHANNELS_COUNT as
that would overflow the dpcd_pattern_period array.

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
index 22dabe596dfc..95b5b5bfa1ff 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -4440,7 +4440,7 @@ static void dp_test_get_audio_test_data(struct dc_link *link, bool disable_video
 		&dpcd_pattern_type.value,
 		sizeof(dpcd_pattern_type));
 
-	channel_count = dpcd_test_mode.bits.channel_count + 1;
+	channel_count = min(dpcd_test_mode.bits.channel_count + 1, AUDIO_CHANNELS_COUNT);
 
 	// read pattern periods for requested channels when sawTooth pattern is requested
 	if (dpcd_pattern_type.value == AUDIO_TEST_PATTERN_SAWTOOTH ||
-- 
2.38.1