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Subject: Re: [PATCH] drm/meson: fix potential NULL pointer exception in
 meson_drv_unbind()
To:     Jiajun Cao <jjcao20@fudan.edu.cn>
Cc:     yuanxzhang@fudan.edu.cn, Xin Tan <tanxin.ctf@gmail.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Kevin Hilman <khilman@baylibre.com>,
        Jerome Brunet <jbrunet@baylibre.com>,
        Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
        dri-devel@lists.freedesktop.org, linux-amlogic@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20210617070737.50171-1-jjcao20@fudan.edu.cn>
From:   Neil Armstrong <narmstrong@baylibre.com>
Organization: Baylibre
Message-ID: <0c367cae-9bad-d53a-01db-3d2dd801965b@baylibre.com>
Date:   Thu, 17 Jun 2021 16:58:20 +0200
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Hi,

On 17/06/2021 09:07, Jiajun Cao wrote:
> 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@fudan.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
> ---
>  drivers/gpu/drm/meson/meson_drv.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/meson/meson_drv.c b/drivers/gpu/drm/meson/meson_drv.c
> index 07fcd12dca16..adea6a2b28f5 100644
> --- a/drivers/gpu/drm/meson/meson_drv.c
> +++ b/drivers/gpu/drm/meson/meson_drv.c
> @@ -380,6 +380,8 @@ static int meson_drv_bind(struct device *dev)
>  static void meson_drv_unbind(struct device *dev)
>  {
>  	struct meson_drm *priv = dev_get_drvdata(dev);
> +	if (!priv)
> +		return;
>  	struct drm_device *drm = priv->drm;

Please move struct drm_device before the if like :

struct meson_drm *priv = dev_get_drvdata(dev);
struct drm_device *drm;

if (!priv)
	return;
drm = priv->drm;


>  
>  	if (priv->canvas) {
> 

Thanks,
Neil