drm/amd/display: Avoid reading audio pattern past AUDIO_CHANNELS_COUNT

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>

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 c15c46b..55a5a6a 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -4464,7 +4464,7 @@ 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 ||