linux-kernel - Re: [PATCH v3 3/4] drm/ingenic: Register devm action to cleanup encoders

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Date:   Wed, 24 Mar 2021 04:27:11 +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-mips@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, od@...c.me, stable@...r.kernel.org,
        Sam Ravnborg <sam@...nborg.org>
Subject: Re: [PATCH v3 3/4] drm/ingenic: Register devm action to cleanup
 encoders

Hi Paul,

Thank you for the patch.

On Sun, Jan 24, 2021 at 08:55:51AM +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.
> 
> v2: Use the new __drmm_simple_encoder_alloc() function
> 
> v3: Use the new drmm_plain_simple_encoder_alloc() macro
> 
> Fixes: c369cb27c267 ("drm/ingenic: Support multiple panels/bridges")
> Cc: <stable@...r.kernel.org> # 5.8+
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> ---
> 
> Notes:
>     Use the V1 of this patch to fix v5.11 and older kernels. This V3 only
>     applies on the current drm-misc-next branch.
> 
>  drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 15 ++++++---------
>  1 file changed, 6 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> index 7bb31fbee29d..b23011c1c5d9 100644
> --- a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> +++ b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> @@ -1014,20 +1014,17 @@ static int ingenic_drm_bind(struct device *dev, bool has_components)
>  			bridge = devm_drm_panel_bridge_add_typed(dev, panel,
>  								 DRM_MODE_CONNECTOR_DPI);
>  
> -		encoder = devm_kzalloc(dev, sizeof(*encoder), GFP_KERNEL);
> -		if (!encoder)
> -			return -ENOMEM;
> +		encoder = drmm_plain_simple_encoder_alloc(drm, DRM_MODE_ENCODER_DPI);
> +		if (IS_ERR(encoder)) {
> +			ret = PTR_ERR(encoder);
> +			dev_err(dev, "Failed to init encoder: %d\n", ret);
> +			return ret;
> +		}
>  
>  		encoder->possible_crtcs = 1;
>  
>  		drm_encoder_helper_add(encoder, &ingenic_drm_encoder_helper_funcs);
>  
> -		ret = drm_simple_encoder_init(drm, encoder, DRM_MODE_ENCODER_DPI);
> -		if (ret) {
> -			dev_err(dev, "Failed to init encoder: %d\n", ret);
> -			return ret;
> -		}
> -
>  		ret = drm_bridge_attach(encoder, bridge, NULL, 0);
>  		if (ret) {
>  			dev_err(dev, "Unable to attach bridge\n");

-- 
Regards,

Laurent Pinchart