[PATCH 5.4 071/177] drm/meson: fix shutdown crash when component not probed

[Greg Kroah-Hartman]

From: Neil Armstrong <narmstrong@xxxxxxxxxxxx>

commit 7cfc4ea78fc103ea51ecbacd9236abb5b1c490d2 upstream.

When main component is not probed, by example when the dw-hdmi module is
not loaded yet or in probe defer, the following crash appears on shutdown:

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000038
...
pc : meson_drv_shutdown+0x24/0x50
lr : platform_drv_shutdown+0x20/0x30
...
Call trace:
meson_drv_shutdown+0x24/0x50
platform_drv_shutdown+0x20/0x30
device_shutdown+0x158/0x360
kernel_restart_prepare+0x38/0x48
kernel_restart+0x18/0x68
__do_sys_reboot+0x224/0x250
__arm64_sys_reboot+0x24/0x30
...

Simply check if the priv struct has been allocated before using it.

Fixes: fa0c16caf3d7 ("drm: meson_drv add shutdown function")
Reported-by: Stefan Agner <stefan@xxxxxxxx>
Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
Tested-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20210430082744.3638743-1-narmstrong@xxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/meson/meson_drv.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/meson/meson_drv.c
+++ b/drivers/gpu/drm/meson/meson_drv.c
@@ -423,11 +423,12 @@ static int meson_probe_remote(struct pla
 static void meson_drv_shutdown(struct platform_device *pdev)
 {
 	struct meson_drm *priv = dev_get_drvdata(&pdev->dev);
-	struct drm_device *drm = priv->drm;
 
-	DRM_DEBUG_DRIVER("\n");
-	drm_kms_helper_poll_fini(drm);
-	drm_atomic_helper_shutdown(drm);
+	if (!priv)
+		return;
+
+	drm_kms_helper_poll_fini(priv->drm);
+	drm_atomic_helper_shutdown(priv->drm);
 }
 
 static int meson_drv_probe(struct platform_device *pdev)