linux-kernel - Re: [PATCH v2 2/3] drm/ingenic: Register devm action to cleanup encoders

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Date:   Wed, 20 Jan 2021 14:01:26 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     David Airlie <airlied@...ux.ie>, Sam Ravnborg <sam@...nborg.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        od@...c.me, dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] drm/ingenic: Register devm action to cleanup encoders

On Wed, Jan 20, 2021 at 1:36 PM Paul Cercueil <paul@...pouillou.net> 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
>
> Fixes: c369cb27c267 ("drm/ingenic: Support multiple panels/bridges")
> Cc: <stable@...r.kernel.org> # 5.8+
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
>
> Notes:
>     Use the V1 of this patch to fix v5.11 and older kernels. This V2 only
>     applies on the current drm-misc-next branch.
>
>  drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 16 +++++++---------
>  1 file changed, 7 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..158433b4c084 100644
> --- a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> +++ b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> @@ -1014,20 +1014,18 @@ 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_simple_encoder_alloc(drm, sizeof(*encoder), 0,

Please don't use the __ prefixed functions, those are the internal
ones. The official one comes with type checking and all that included.
Otherwise lgtm.
-Daniel

> +                                                     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");
> --
> 2.29.2
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch