linux-kernel - [PATCH AUTOSEL 5.19 058/105] drm/amd/display: Guard against ddc

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Date:   Thu, 11 Aug 2022 11:27:42 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
        Michael Strauss <Michael.Strauss@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Daniel Wheeler <daniel.wheeler@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>, harry.wentland@....com,
        sunpeng.li@....com, christian.koenig@....com, Xinhui.Pan@....com,
        airlied@...ux.ie, daniel@...ll.ch, wyatt.wood@....com,
        aric.cyr@....com, arnd@...db.de,
        meenakshikumar.somasundaram@....com, Jing.Zhou@....com,
        baihaowen@...zu.com, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.19 058/105] drm/amd/display: Guard against ddc_pin being NULL for AUX

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

[ 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@....com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@....com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 9e39cd7b203e..49d3145ae8fb 100644
--- a/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
+++ b/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
@@ -572,6 +572,11 @@ int dce_aux_transfer_raw(struct ddc_service *ddc,
 
 	memset(&aux_req, 0, sizeof(aux_req));
 
+	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