[PATCH AUTOSEL 4.19 14/26] drm/amd/display: Guard against NULL pointer deref when get_i2c_info fails

From: Sasha Levin
Date: Wed Feb 24 2021 - 09:06:37 EST


From: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx>

[ 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@xxxxxxx>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx>
Reviewed-by: Eric Yang <eric.yang2@xxxxxxx>
Acked-by: Anson Jacob <anson.jacob@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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