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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Harry Wentland <harry.wentland@amd.com>,
        =?UTF-8?q?Jos=C3=A9=20Exp=C3=B3sito?= <jose.exposito89@gmail.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.16 0821/1039] drm/amd/display: invalid parameter check in dmub_hpd_callback
Date:   Mon, 24 Jan 2022 19:43:30 +0100
Message-Id: <20220124184152.897816208@linuxfoundation.org>
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From: José Expósito <jose.exposito89@gmail.com>

[ Upstream commit 978ffac878fd64039f95798b15b430032d2d89d5 ]

The function performs a check on the "adev" input parameter, however, it
is used before the check.

Initialize the "dev" variable after the sanity check to avoid a possible
NULL pointer dereference.

Fixes: e27c41d5b0681 ("drm/amd/display: Support for DMUB HPD interrupt handling")
Addresses-Coverity-ID: 1493909 ("Null pointer dereference")
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 46d38d528468c..3a227e9d8dfcb 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -656,7 +656,7 @@ void dmub_hpd_callback(struct amdgpu_device *adev, struct dmub_notification *not
 	struct drm_connector_list_iter iter;
 	struct dc_link *link;
 	uint8_t link_index = 0;
-	struct drm_device *dev = adev->dm.ddev;
+	struct drm_device *dev;
 
 	if (adev == NULL)
 		return;
@@ -673,6 +673,7 @@ void dmub_hpd_callback(struct amdgpu_device *adev, struct dmub_notification *not
 
 	link_index = notify->link_index;
 	link = adev->dm.dc->links[link_index];
+	dev = adev->dm.ddev;
 
 	drm_connector_list_iter_begin(dev, &iter);
 	drm_for_each_connector_iter(connector, &iter) {
-- 
2.34.1