linux-kernel - [PATCH AUTOSEL 4.19 14/26] drm/amd/display: Guard against NULL pointer deref when get_i2c

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Message-Id: <20210224125435.483539-14-sashal@kernel.org>
Date:   Wed, 24 Feb 2021 07:54:22 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
        Daniel Wheeler <daniel.wheeler@....com>,
        Eric Yang <eric.yang2@....com>,
        Anson Jacob <anson.jacob@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 4.19 14/26] drm/amd/display: Guard against NULL pointer deref when get_i2c_info fails

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

[ Upstream commit 44a09e3d95bd2b7b0c224100f78f335859c4e193 ]

[Why]
If the BIOS table is invalid or corrupt then get_i2c_info can fail
and we dereference a NULL pointer.

[How]
Check that ddc_pin is not NULL before using it and log an error if it
is because this is unexpected.

Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@....com>
Reviewed-by: Eric Yang <eric.yang2@....com>
Acked-by: Anson Jacob <anson.jacob@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
index fa0e6c8e2447c..e3bedf4cc9c03 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -1124,6 +1124,11 @@ static bool construct(
 		goto ddc_create_fail;
 	}
 
+	if (!link->ddc->ddc_pin) {
+		DC_ERROR("Failed to get I2C info for connector!\n");
+		goto ddc_create_fail;
+	}
+
 	link->ddc_hw_inst =
 		dal_ddc_get_line(
 			dal_ddc_service_get_ddc_pin(link->ddc));
-- 
2.27.0