Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Neil Armstrong <narmstrong@baylibre.com>
To:     dri-devel@lists.freedesktop.org
Cc:     linux-amlogic@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Neil Armstrong <narmstrong@baylibre.com>,
        Stefan Agner <stefan@agner.ch>
Subject: [PATCH] drm/meson: fix shutdown crash when component not probed
Date:   Fri, 30 Apr 2021 10:27:44 +0200
Message-Id: <20210430082744.3638743-1-narmstrong@baylibre.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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@agner.ch>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
---
 drivers/gpu/drm/meson/meson_drv.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/meson/meson_drv.c b/drivers/gpu/drm/meson/meson_drv.c
index 453d8b4c5763..07fcd12dca16 100644
--- a/drivers/gpu/drm/meson/meson_drv.c
+++ b/drivers/gpu/drm/meson/meson_drv.c
@@ -485,11 +485,12 @@ static int meson_probe_remote(struct platform_device *pdev,
 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)
-- 
2.25.1