linux-kernel - [PATCH 6.1.y] drm/amd/display: Don't refer to dc_sink in is_dsc_need_re

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Message-ID: <20241211101544.2121147-1-jianqi.ren.cn@windriver.com>
Date: Wed, 11 Dec 2024 18:15:44 +0800
From: <jianqi.ren.cn@...driver.com>
To: <wayne.lin@....com>, <gregkh@...uxfoundation.org>
CC: <patches@...ts.linux.dev>, <jerry.zuo@....com>, <zaeem.mohamed@....com>,
        <daniel.wheeler@....com>, <alexander.deucher@....com>,
        <stable@...r.kernel.org>, <harry.wentland@....com>,
        <sunpeng.li@....com>, <Rodrigo.Siqueira@....com>,
        <christian.koenig@....com>, <airlied@...il.com>, <daniel@...ll.ch>,
        <Jerry.Zuo@....com>, <amd-gfx@...ts.freedesktop.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH 6.1.y] drm/amd/display: Don't refer to dc_sink in is_dsc_need_re_compute

From: Wayne Lin <wayne.lin@....com>

[ Upstream commit fcf6a49d79923a234844b8efe830a61f3f0584e4 ]

[Why]
When unplug one of monitors connected after mst hub, encounter null pointer dereference.

It's due to dc_sink get released immediately in early_unregister() or detect_ctx(). When
commit new state which directly referring to info stored in dc_sink will cause null pointer
dereference.

[how]
Remove redundant checking condition. Relevant condition should already be covered by checking
if dsc_aux is null or not. Also reset dsc_aux to NULL when the connector is disconnected.

Reviewed-by: Jerry Zuo <jerry.zuo@....com>
Acked-by: Zaeem Mohamed <zaeem.mohamed@....com>
Signed-off-by: Wayne Lin <wayne.lin@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Jianqi Ren <jianqi.ren.cn@...driver.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
index 1acef5f3838f..a1619f4569cf 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
@@ -183,6 +183,8 @@ amdgpu_dm_mst_connector_early_unregister(struct drm_connector *connector)
 		dc_sink_release(dc_sink);
 		aconnector->dc_sink = NULL;
 		aconnector->edid = NULL;
+		aconnector->dsc_aux = NULL;
+		port->passthrough_aux = NULL;
 	}
 
 	aconnector->mst_status = MST_STATUS_DEFAULT;
@@ -487,6 +489,8 @@ dm_dp_mst_detect(struct drm_connector *connector,
 		dc_sink_release(aconnector->dc_sink);
 		aconnector->dc_sink = NULL;
 		aconnector->edid = NULL;
+		aconnector->dsc_aux = NULL;
+		port->passthrough_aux = NULL;
 
 		amdgpu_dm_set_mst_status(&aconnector->mst_status,
 			MST_REMOTE_EDID | MST_ALLOCATE_NEW_PAYLOAD | MST_CLEAR_ALLOCATED_PAYLOAD,
-- 
2.25.1