linux-kernel - [PATCH 5.15 220/846] drm/amd/display: Fix out of bounds access on DNC31 stream encoder regs

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Message-Id: <20220124184108.511512456@linuxfoundation.org>
Date:   Mon, 24 Jan 2022 19:35:37 +0100
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>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 220/846] drm/amd/display: Fix out of bounds access on DNC31 stream encoder regs

From: Nicholas Kazlauskas <nicholas.kazlauskas@....com>

[ Upstream commit d374d3b493215d637b9e7be12a93f22caf4c1f97 ]

[Why]
During dcn31_stream_encoder_create, if PHYC/D get remapped to F/G on B0
then we'll index 5 or 6 into a array of length 5 - leading to an
access violation on some configs during device creation.

[How]
Software won't be touching PHYF/PHYG directly, so just extend the
array to cover all possible engine IDs.

Even if it does by try to access one of these registers by accident
the offset will be 0 and we'll get a warning during the access.

Fixes: 2fe9a0e1173f ("drm/amd/display: Fix DCN3 B0 DP Alt Mapping")
Reviewed-by: Harry Wentland <harry.wentland@....com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/dc/dcn31/dcn31_resource.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn31/dcn31_resource.c b/drivers/gpu/drm/amd/display/dc/dcn31/dcn31_resource.c
index 0fe570717ba01..d4fe5352421fc 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn31/dcn31_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn31/dcn31_resource.c
@@ -470,7 +470,8 @@ static const struct dcn30_afmt_mask afmt_mask = {
 	SE_DCN3_REG_LIST(id)\
 }
 
-static const struct dcn10_stream_enc_registers stream_enc_regs[] = {
+/* Some encoders won't be initialized here - but they're logical, not physical. */
+static const struct dcn10_stream_enc_registers stream_enc_regs[ENGINE_ID_COUNT] = {
 	stream_enc_regs(0),
 	stream_enc_regs(1),
 	stream_enc_regs(2),
-- 
2.34.1