[PATCH 5.4 45/72] drm/amd/display: Guard against NULL pointer deref when get_i2c_info fails

From: Nicholas Kazlauskas <redacted>

[ 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 <redacted>
Signed-off-by: Nicholas Kazlauskas <redacted>
Reviewed-by: Eric Yang <redacted>
Acked-by: Anson Jacob <redacted>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.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 fa92b88bc5a1..40041c61a100 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c

@@ -1303,6 +1303,11 @@ 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));

-- 
2.30.1