linux-kernel - [PATCH] drm/display/dp_mst: Fix missing check for return value of drm_atomic_get_mst_payload

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Message-Id: <20230614160911.121716-1-cymi20@fudan.edu.cn>
Date:   Wed, 14 Jun 2023 09:09:11 -0700
From:   Chenyuan Mi <cymi20@...an.edu.cn>
To:     airlied@...il.com
Cc:     daniel@...ll.ch, lyude@...hat.com, jani.nikula@...el.com,
        Wayne.Lin@....com, imre.deak@...el.com, alexander.deucher@....com,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Chenyuan Mi <cymi20@...an.edu.cn>
Subject: [PATCH] drm/display/dp_mst: Fix missing check for return value of drm_atomic_get_mst_payload_state()

The drm_atomic_get_mst_payload_state() function may
return NULL, which may cause null pointer deference,
and most other callsites of drm_atomic_get_mst_payload_state()
do Null check. Add Null check for return value of
drm_atomic_get_mst_payload_state().

Found by our static analysis tool.

Signed-off-by: Chenyuan Mi <cymi20@...an.edu.cn>
---
 drivers/gpu/drm/display/drm_dp_mst_topology.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
index 38dab76ae69e..27f4bcf409ea 100644
--- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
@@ -4434,6 +4434,8 @@ void drm_dp_mst_atomic_wait_for_dependencies(struct drm_atomic_state *state)
 
 			new_payload = drm_atomic_get_mst_payload_state(new_mst_state,
 								       old_payload->port);
+			if (!new_payload)
+				continue;
 			new_payload->vc_start_slot = old_payload->vc_start_slot;
 		}
 	}
-- 
2.17.1