[PATCH AUTOSEL 5.15 44/69] drm/amd/display: Guard against ddc_pin being NULL for AUX

[Sasha Levin]

From: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx>

[ Upstream commit bc19909f19fdc8253d720d11c948935786fbfa08 ]

[Why]
In the case where we don't support DMUB aux but we have DPIA links
in the configuration we might try to message AUX using the legacy
path - where DDC pin is NULL. This causes a NULL pointer dereference.

[How]
Guard against NULL DDC pin, return a failure for aux engine acquire.

Reviewed-by: Michael Strauss <Michael.Strauss@xxxxxxx>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@xxxxxxx>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx>
Tested-by: Daniel Wheeler <daniel.wheeler@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/gpu/drm/amd/display/dc/dce/dce_aux.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c b/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
index 3c3347341103..ae9c0df1a844 100644
--- a/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
+++ b/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
@@ -563,6 +563,11 @@ int dce_aux_transfer_raw(struct ddc_service *ddc,
 	memset(&aux_req, 0, sizeof(aux_req));
 	memset(&aux_rep, 0, sizeof(aux_rep));
 
+	if (ddc_pin == NULL) {
+		*operation_result = AUX_RET_ERROR_ENGINE_ACQUIRE;
+		return -1;
+	}
+
 	aux_engine = ddc->ctx->dc->res_pool->engines[ddc_pin->pin_data->en];
 	if (!acquire(aux_engine, ddc_pin)) {
 		*operation_result = AUX_RET_ERROR_ENGINE_ACQUIRE;
-- 
2.35.1