linux-kernel - [PATCH] drm/exynos: dp: Fix NULL pointer dereference due uninitialized connector

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Date:	Wed,  8 Jun 2016 10:13:27 -0400
From:	Javier Martinez Canillas <javier@....samsung.com>
To:	linux-kernel@...r.kernel.org
Cc:	Marc Zyngier <marc.zyngier@....com>,
	Yakir Yang <ykk@...k-chips.com>,
	Javier Martinez Canillas <javier@....samsung.com>,
	Kukjin Kim <kgene@...nel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Seung-Woo Kim <sw0312.kim@...sung.com>,
	dri-devel@...ts.freedesktop.org, Inki Dae <inki.dae@...sung.com>,
	linux-samsung-soc@...r.kernel.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Jingoo Han <jingoohan1@...il.com>,
	David Airlie <airlied@...ux.ie>,
	Joonyoung Shim <jy0922.shim@...sung.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: [PATCH] drm/exynos: dp: Fix NULL pointer dereference due uninitialized connector

From: Yakir Yang <ykk@...k-chips.com>

Commit 3424e3a4f844 ("drm: bridge: analogix/dp: split exynos dp driver to
bridge directory") split the Exynos DP core driver into a core driver and
a bridge driver for the Analogix chip since that is also used by Rockchip.

But the change introduced a regression causing a NULL pointer dereference
when trying to access an uninitialized connector in the driver .get_modes:

Fix this by instead of having a connector struct for both the Exynos and
Analogix drivers, just use the connector initialized in the bridge driver.

Fixes: 3424e3a4f844 ("drm: bridge: analogix/dp: split exynos dp driver to bridge directory")
Reported-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Yakir Yang <ykk@...k-chips.com>
[javier: wrote commit message]
Signed-off-by: Javier Martinez Canillas <javier@....samsung.com>
Tested-by: Marc Zyngier <marc.zyngier@....com>

---
Hello Inki,

This is a regression introduced in v4.7-rc1, so $SUBJECT is -rc material.

Best regards,
Javier

 drivers/gpu/drm/exynos/exynos_dp.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_dp.c b/drivers/gpu/drm/exynos/exynos_dp.c
index 468498e3fec1..4c1fb3f8b5a6 100644
--- a/drivers/gpu/drm/exynos/exynos_dp.c
+++ b/drivers/gpu/drm/exynos/exynos_dp.c
@@ -34,7 +34,7 @@
 
 struct exynos_dp_device {
 	struct drm_encoder         encoder;
-	struct drm_connector       connector;
+	struct drm_connector       *connector;
 	struct drm_bridge          *ptn_bridge;
 	struct drm_device          *drm_dev;
 	struct device              *dev;
@@ -70,7 +70,7 @@ static int exynos_dp_poweroff(struct analogix_dp_plat_data *plat_data)
 static int exynos_dp_get_modes(struct analogix_dp_plat_data *plat_data)
 {
 	struct exynos_dp_device *dp = to_dp(plat_data);
-	struct drm_connector *connector = &dp->connector;
+	struct drm_connector *connector = dp->connector;
 	struct drm_display_mode *mode;
 	int num_modes = 0;
 
@@ -103,6 +103,7 @@ static int exynos_dp_bridge_attach(struct analogix_dp_plat_data *plat_data,
 	int ret;
 
 	drm_connector_register(connector);
+	dp->connector = connector;
 
 	/* Pre-empt DP connector creation if there's a bridge */
 	if (dp->ptn_bridge) {
-- 
2.5.5