linux-kernel - Re: [PATCH 2/3] drm/ingenic: Register devm action to cleanup encoders

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Date:   Mon, 18 Jan 2021 11:43:47 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org, od@...c.me,
        dri-devel@...ts.freedesktop.org, Sam Ravnborg <sam@...nborg.org>
Subject: Re: [PATCH 2/3] drm/ingenic: Register devm action to cleanup encoders

Hi Paul,

Thank you for the patch.

On Sun, Jan 17, 2021 at 11:26:45AM +0000, Paul Cercueil wrote:
> Since the encoders have been devm-allocated, they will be freed way
> before drm_mode_config_cleanup() is called. To avoid use-after-free
> conditions, we then must ensure that drm_encoder_cleanup() is called
> before the encoders are freed.

How about allocating the encoder with drmm_encoder_alloc() instead ?

> Fixes: c369cb27c267 ("drm/ingenic: Support multiple panels/bridges")
> Cc: <stable@...r.kernel.org> # 5.8+
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
>  drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> index 368bfef8b340..d23a3292a0e0 100644
> --- a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> +++ b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> @@ -803,6 +803,11 @@ static void __maybe_unused ingenic_drm_release_rmem(void *d)
>  	of_reserved_mem_device_release(d);
>  }
>  
> +static void ingenic_drm_encoder_cleanup(void *encoder)
> +{
> +	drm_encoder_cleanup(encoder);
> +}
> +
>  static int ingenic_drm_bind(struct device *dev, bool has_components)
>  {
>  	struct platform_device *pdev = to_platform_device(dev);
> @@ -1011,6 +1016,11 @@ static int ingenic_drm_bind(struct device *dev, bool has_components)
>  			return ret;
>  		}
>  
> +		ret = devm_add_action_or_reset(dev, ingenic_drm_encoder_cleanup,
> +					       encoder);
> +		if (ret)
> +			return ret;
> +
>  		ret = drm_bridge_attach(encoder, bridge, NULL, 0);
>  		if (ret) {
>  			dev_err(dev, "Unable to attach bridge\n");

-- 
Regards,

Laurent Pinchart