linux-kernel - [PATCH] drm/amd/display: invalid parameter check in dmub_hpd

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Message-Id: <20220109184245.124850-1-jose.exposito89@gmail.com>
Date:   Sun,  9 Jan 2022 19:42:45 +0100
From:   José Expósito <jose.exposito89@...il.com>
To:     shenshih@....com
Cc:     harry.wentland@....com, sunpeng.li@....com,
        Rodrigo.Siqueira@....com, alexander.deucher@....com,
        christian.koenig@....com, Xinhui.Pan@....com, airlied@...ux.ie,
        daniel@...ll.ch, nicholas.kazlauskas@....com, Anson.Jacob@....com,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        José Expósito <jose.exposito89@...il.com>
Subject: [PATCH] drm/amd/display: invalid parameter check in dmub_hpd_callback

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")
Signed-off-by: José Expósito <jose.exposito89@...il.com>
---
 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 e727f1dd2a9a..7fbded7a6d9c 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) {
-- 
2.25.1