linux-kernel - [PATCH] drm/sun4i: Fix crash during suspend after component bind failure

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Date:   Wed, 15 Jun 2022 00:42:53 -0500
From:   Samuel Holland <samuel@...lland.org>
To:     Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Maxime Ripard <mripard@...nel.org>
Cc:     Samuel Holland <samuel@...lland.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Ondrej Jirman <megous@...ous.com>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...ts.linux.dev
Subject: [PATCH] drm/sun4i: Fix crash during suspend after component bind failure

If the component driver fails to bind, or is unbound, the driver data
for the top-level platform device points to a freed drm_device. If the
system is then suspended, the driver passes this dangling pointer to
drm_mode_config_helper_suspend(), which crashes.

Fix this by only setting the driver data while the platform driver holds
a reference to the drm_device.

Fixes: 624b4b48d9d8 ("drm: sun4i: Add support for suspending the display driver")
Signed-off-by: Samuel Holland <samuel@...lland.org>
---

 drivers/gpu/drm/sun4i/sun4i_drv.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/sun4i/sun4i_drv.c b/drivers/gpu/drm/sun4i/sun4i_drv.c
index 275f7e4a03ae..8841dba989ee 100644
--- a/drivers/gpu/drm/sun4i/sun4i_drv.c
+++ b/drivers/gpu/drm/sun4i/sun4i_drv.c
@@ -73,7 +73,6 @@ static int sun4i_drv_bind(struct device *dev)
 		goto free_drm;
 	}
 
-	dev_set_drvdata(dev, drm);
 	drm->dev_private = drv;
 	INIT_LIST_HEAD(&drv->frontend_list);
 	INIT_LIST_HEAD(&drv->engine_list);
@@ -114,6 +113,8 @@ static int sun4i_drv_bind(struct device *dev)
 
 	drm_fbdev_generic_setup(drm, 32);
 
+	dev_set_drvdata(dev, drm);
+
 	return 0;
 
 finish_poll:
@@ -130,6 +131,7 @@ static void sun4i_drv_unbind(struct device *dev)
 {
 	struct drm_device *drm = dev_get_drvdata(dev);
 
+	dev_set_drvdata(dev, NULL);
 	drm_dev_unregister(drm);
 	drm_kms_helper_poll_fini(drm);
 	drm_atomic_helper_shutdown(drm);
-- 
2.35.1