linux-kernel - [PATCH v2] drm/meson: fix potential NULL pointer exception in meson_drv

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Date:   Fri, 18 Jun 2021 13:28:00 +0800
From:   Jiajun Cao <jjcao20@...an.edu.cn>
To:     unlisted-recipients:; (no To-header on input)
Cc:     yuanxzhang@...an.edu.cn, Jiajun Cao <jjcao20@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        dri-devel@...ts.freedesktop.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] drm/meson: fix potential NULL pointer exception in meson_drv_unbind()

Fix a potential NULL pointer exception when meson_drv_unbind()
attempts to operate on the driver_data priv which may be NULL.
Add a null pointer check on the priv struct to avoid the NULL
pointer dereference after calling dev_get_drvdata(), just like
the null pointer checks done on the struct priv in the function
meson_drv_shutdown(), meson_drv_pm_suspend() and meson_drv_pm_resume().

Signed-off-by: Jiajun Cao <jjcao20@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
---
 drivers/gpu/drm/meson/meson_drv.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/meson/meson_drv.c b/drivers/gpu/drm/meson/meson_drv.c
index 07fcd12dca16..f544fba8c44e 100644
--- a/drivers/gpu/drm/meson/meson_drv.c
+++ b/drivers/gpu/drm/meson/meson_drv.c
@@ -380,7 +380,10 @@ static int meson_drv_bind(struct device *dev)
 static void meson_drv_unbind(struct device *dev)
 {
 	struct meson_drm *priv = dev_get_drvdata(dev);
-	struct drm_device *drm = priv->drm;
+	struct drm_device *drm;
+
+	if (!priv)
+		return;
 
 	if (priv->canvas) {
 		meson_canvas_free(priv->canvas, priv->canvas_id_osd1);
@@ -389,6 +392,7 @@ static void meson_drv_unbind(struct device *dev)
 		meson_canvas_free(priv->canvas, priv->canvas_id_vd1_2);
 	}
 
+	drm = priv->drm;
 	drm_dev_unregister(drm);
 	drm_kms_helper_poll_fini(drm);
 	drm_atomic_helper_shutdown(drm);
-- 
2.17.1