linux-kernel - Re: [PATCH 1/1] drm/sun4i: hdmi: Check for null pointer before cleanup

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Message-ID: <20191216161258.lmkq2ersfm746t7q@gilmour.lan>
Date:   Mon, 16 Dec 2019 17:12:58 +0100
From:   Maxime Ripard <mripard@...nel.org>
To:     Stefan Mavrodiev <stefan@...mex.com>
Cc:     Chen-Yu Tsai <wens@...e.org>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        "open list:DRM DRIVERS FOR ALLWINNER A10" 
        <dri-devel@...ts.freedesktop.org>,
        "moderated list:ARM/Allwinner sunXi SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-sunxi@...glegroups.com
Subject: Re: [PATCH 1/1] drm/sun4i: hdmi: Check for null pointer before
 cleanup

Hi,

On Mon, Dec 16, 2019 at 04:43:48PM +0200, Stefan Mavrodiev wrote:
> It's possible hdmi->connector and hdmi->encoder divices to be NULL.
> This can happen when building as kernel module and you try to remove
> the module.
>
> This patch make simple null check, before calling the cleanup functions.
>
> Signed-off-by: Stefan Mavrodiev <stefan@...mex.com>
> ---
>  drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
> index a7c4654445c7..b61e00f2ecb8 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
> @@ -685,8 +685,10 @@ static void sun4i_hdmi_unbind(struct device *dev, struct device *master,
>  	struct sun4i_hdmi *hdmi = dev_get_drvdata(dev);
>
>  	cec_unregister_adapter(hdmi->cec_adap);
> -	drm_connector_cleanup(&hdmi->connector);
> -	drm_encoder_cleanup(&hdmi->encoder);
> +	if (hdmi->connector.dev)
> +		drm_connector_cleanup(&hdmi->connector);
> +	if (hdmi->encoder.dev)
> +		drm_encoder_cleanup(&hdmi->encoder);

Hmmm, this doesn't look right. Do you have more information on how you
can reproduce it?

Maxime

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