From 44a09e3d95bd2b7b0c224100f78f335859c4e193 Mon Sep 17 00:00:00 2001
From: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Date: Fri, 18 Dec 2020 12:14:00 -0500
Subject: [PATCH] drm/amd/display: Guard against NULL pointer deref when get_i2c_info fails
Git-commit: 44a09e3d95bd2b7b0c224100f78f335859c4e193
Patch-mainline: v5.12-rc1
References: git-fixes

[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@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Eric Yang <eric.yang2@amd.com>
Acked-by: Anson Jacob <anson.jacob@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/amd/display/dc/core/dc_link.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -1454,6 +1454,11 @@ static bool dc_link_construct(struct dc_
 		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));