[PATCH 6.1] drm/amd/display: Fix out-of-bounds read in dp_get_eq_aux_rd_interval()

[Roman Demidov]

From: Harry Wentland <harry.wentland@xxxxxxx>

commit e8b4d37eba05141ee01794fc6b7f2da808cee83b upstream.

[Why & How]
The aux_rd_interval array in struct dc_lttpr_caps is declared with
MAX_REPEATER_CNT - 1 (7) elements, indexed 0..6. However, the offset
parameter passed to dp_get_eq_aux_rd_interval() can be as large as
MAX_REPEATER_CNT (8) when a sink reports 8 LTTPR repeaters via DPCD.
This leads to an out-of-bounds read of aux_rd_interval[7] when offset
is 8.

Fix this by growing aux_rd_interval to MAX_REPEATER_CNT elements to
accommodate the full range of valid repeater counts defined by the DP
spec.

Assisted-by: GitHub Copilot:Claude claude-4-opus
Signed-off-by: Harry Wentland <harry.wentland@xxxxxxx>
Signed-off-by: Ray Wu <ray.wu@xxxxxxx>
Tested-by: Daniel Wheeler <daniel.wheeler@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
(cherry picked from commit a55a458a8df37a65ffda5cf721d554a8f74f6b04)
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Roman Demidov <roman.demidov.nn@xxxxxxxxx>
---
Backport fix for CVE-2026-53330

 drivers/gpu/drm/amd/display/dc/dc_types.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dc_types.h b/drivers/gpu/drm/amd/display/dc/dc_types.h
index 6050a3469a57..579a38478d0f 100644
--- a/drivers/gpu/drm/amd/display/dc/dc_types.h
+++ b/drivers/gpu/drm/amd/display/dc/dc_types.h
@@ -403,7 +403,7 @@ struct dc_lttpr_caps {
 	uint8_t max_ext_timeout;
 	union dp_main_link_channel_coding_lttpr_cap main_link_channel_coding;
 	union dp_128b_132b_supported_lttpr_link_rates supported_128b_132b_rates;
-	uint8_t aux_rd_interval[MAX_REPEATER_CNT - 1];
+	uint8_t aux_rd_interval[MAX_REPEATER_CNT];
 };
 
 struct dc_dongle_dfp_cap_ext {
-- 
2.53.0