Patch "drm/amd/display: fix NULL checks for adev->dm.dc in amdgpu_dm_fini()" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    drm/amd/display: fix NULL checks for adev->dm.dc in amdgpu_dm_fini()

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-amd-display-fix-null-checks-for-adev-dm.dc-in-am.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 537a9b10b2fc74b3404e628ea064411f054da7a4
Author: Nikita Zhandarovich <n.zhandarovich@xxxxxxxxxx>
Date:   Tue Feb 6 08:50:56 2024 -0800

    drm/amd/display: fix NULL checks for adev->dm.dc in amdgpu_dm_fini()
    
    [ Upstream commit 2a3cfb9a24a28da9cc13d2c525a76548865e182c ]
    
    Since 'adev->dm.dc' in amdgpu_dm_fini() might turn out to be NULL
    before the call to dc_enable_dmub_notifications(), check
    beforehand to ensure there will not be a possible NULL-ptr-deref
    there.
    
    Also, since commit 1e88eb1b2c25 ("drm/amd/display: Drop
    CONFIG_DRM_AMD_DC_HDCP") there are two separate checks for NULL in
    'adev->dm.dc' before dc_deinit_callbacks() and dc_dmub_srv_destroy().
    Clean up by combining them all under one 'if'.
    
    Found by Linux Verification Center (linuxtesting.org) with static
    analysis tool SVACE.
    
    Fixes: 81927e2808be ("drm/amd/display: Support for DMUB AUX")
    Signed-off-by: Nikita Zhandarovich <n.zhandarovich@xxxxxxxxxx>
    Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

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 50444ab7b3cc0..53c05c41341fe 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -1902,17 +1902,15 @@ static void amdgpu_dm_fini(struct amdgpu_device *adev)
 		adev->dm.hdcp_workqueue = NULL;
 	}
 
-	if (adev->dm.dc)
+	if (adev->dm.dc) {
 		dc_deinit_callbacks(adev->dm.dc);
-
-	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);
-		adev->dm.dmub_notify = NULL;
-		destroy_workqueue(adev->dm.delayed_hpd_wq);
-		adev->dm.delayed_hpd_wq = NULL;
+		if (dc_enable_dmub_notifications(adev->dm.dc)) {
+			kfree(adev->dm.dmub_notify);
+			adev->dm.dmub_notify = NULL;
+			destroy_workqueue(adev->dm.delayed_hpd_wq);
+			adev->dm.delayed_hpd_wq = NULL;
+		}
 	}
 
 	if (adev->dm.dmub_bo)