linux-kernel - [PATCH] drm/amd/display: Fix potential null dereference

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Date:   Mon,  3 Apr 2023 16:10:37 +0300
From:   Igor Artemiev <Igor.A.Artemiev@...t.ru>
To:     David Airlie <airlied@...il.com>
Cc:     Igor Artemiev <Igor.A.Artemiev@...t.ru>,
        Daniel Vetter <daniel@...ll.ch>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Harry Wentland <harry.wentland@....com>,
        Nicholas Kazlauskas <Nicholas.Kazlauskas@....com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: [PATCH] drm/amd/display: Fix potential null dereference

The adev->dm.dc pointer can be NULL and dereferenced in amdgpu_dm_fini()
without checking.

Add a NULL pointer check before calling dc_dmub_srv_destroy(). 

Found by Linux Verification Center (linuxtesting.org) with SVACE. 

Fixes: 9a71c7d31734 ("drm/amd/display: Register DMUB service with DC")
Signed-off-by: Igor Artemiev <Igor.A.Artemiev@...t.ru>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index a01fd41643fc..27f7a554874e 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -1854,7 +1854,8 @@ static void amdgpu_dm_fini(struct amdgpu_device *adev)
 		dc_deinit_callbacks(adev->dm.dc);
 #endif
 
-	dc_dmub_srv_destroy(&adev->dm.dc->ctx->dmub_srv);
+	if (adev->dm.dc)
+		dc_dmub_srv_destroy(&adev->dm.dc->ctx->dmub_srv);
 
 	if (dc_enable_dmub_notifications(adev->dm.dc)) {
 		kfree(adev->dm.dmub_notify);
-- 
2.30.2