linux-kernel - [PATCH 5.17 018/140] drm/amd/display: Avoid reading audio pattern past AUDIO_CHANNELS

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Date:   Tue, 10 May 2022 15:06:48 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Harry Wentland <harry.wentland@....com>,
        Alex Deucher <alexander.deucher@....com>
Subject: [PATCH 5.17 018/140] drm/amd/display: Avoid reading audio pattern past AUDIO_CHANNELS_COUNT

From: Harry Wentland <harry.wentland@....com>

commit 3dfe85fa87b2a26bdbd292b66653bba065cf9941 upstream.

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@....com>
Reviewed-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Cc: stable@...r.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -4634,7 +4634,7 @@ static void dp_test_get_audio_test_data(
 		&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 ||