linux-kernel - [PATCH 4.4 02/36] gpu: drm: radeon: Fix a possible null-pointer dereference in radeon_connector_set

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Message-Id: <20191006171041.813628230@linuxfoundation.org>
Date:   Sun,  6 Oct 2019 19:18:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jia-Ju Bai <baijiaju1990@...il.com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 02/36] gpu: drm: radeon: Fix a possible null-pointer dereference in radeon_connector_set_property()

From: Jia-Ju Bai <baijiaju1990@...il.com>

[ Upstream commit f3eb9b8f67bc28783eddc142ad805ebdc53d6339 ]

In radeon_connector_set_property(), there is an if statement on line 743
to check whether connector->encoder is NULL:
    if (connector->encoder)

When connector->encoder is NULL, it is used on line 755:
    if (connector->encoder->crtc)

Thus, a possible null-pointer dereference may occur.

To fix this bug, connector->encoder is checked before being used.

This bug is found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/radeon/radeon_connectors.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c b/drivers/gpu/drm/radeon/radeon_connectors.c
index c6bf378534f83..bebcef2ce6b88 100644
--- a/drivers/gpu/drm/radeon/radeon_connectors.c
+++ b/drivers/gpu/drm/radeon/radeon_connectors.c
@@ -758,7 +758,7 @@ static int radeon_connector_set_property(struct drm_connector *connector, struct
 
 		radeon_encoder->output_csc = val;
 
-		if (connector->encoder->crtc) {
+		if (connector->encoder && connector->encoder->crtc) {
 			struct drm_crtc *crtc  = connector->encoder->crtc;
 			const struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;
 			struct radeon_crtc *radeon_crtc = to_radeon_crtc(crtc);
-- 
2.20.1