linux-kernel - Re: [PATCH] drm/meson: fix potential NULL pointer exception in meson_drv

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Date:   Thu, 17 Jun 2021 16:58:20 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Jiajun Cao <jjcao20@...an.edu.cn>
Cc:     yuanxzhang@...an.edu.cn, Xin Tan <tanxin.ctf@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        dri-devel@...ts.freedesktop.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/meson: fix potential NULL pointer exception in
 meson_drv_unbind()

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@...an.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@...il.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