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Subject: Re: [PATCH] drm/meson: fix shutdown crash when component not probed
To:     dri-devel@lists.freedesktop.org
Cc:     linux-amlogic@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Stefan Agner <stefan@agner.ch>
References: <20210430082744.3638743-1-narmstrong@baylibre.com>
From:   Neil Armstrong <narmstrong@baylibre.com>
Organization: Baylibre
Message-ID: <0359d826-49d5-d724-b38e-012e3389ae43@baylibre.com>
Date:   Tue, 25 May 2021 09:27:11 +0200
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On 30/04/2021 10:27, Neil Armstrong wrote:
> 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)
> 

Applied to drm-misc-fixes

Neil