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From:   Daniel Vetter <daniel@ffwll.ch>
Date:   Wed, 20 Jan 2021 17:03:22 +0100
Message-ID: <CAKMK7uGGDe8bZpeTnyCkF7g_2gC1nixOzWe4FWYXPRWi-q5y7A@mail.gmail.com>
Subject: Re: [PATCH v2 1/3] drm: bridge/panel: Cleanup connector on bridge detach
To:     Paul Cercueil <paul@crapouillou.net>
Cc:     David Airlie <airlied@linux.ie>, Sam Ravnborg <sam@ravnborg.org>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        od@zcrc.me, dri-devel <dri-devel@lists.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        stable <stable@vger.kernel.org>,
        Andrzej Hajda <a.hajda@samsung.com>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Jonas Karlman <jonas@kwiboo.se>,
        Jernej Skrabec <jernej.skrabec@siol.net>
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On Wed, Jan 20, 2021 at 1:35 PM Paul Cercueil <paul@crapouillou.net> wrote:
>
> If we don't call drm_connector_cleanup() manually in
> panel_bridge_detach(), the connector will be cleaned up with the other
> DRM objects in the call to drm_mode_config_cleanup(). However, since our
> drm_connector is devm-allocated, by the time drm_mode_config_cleanup()
> will be called, our connector will be long gone. Therefore, the
> connector must be cleaned up when the bridge is detached to avoid
> use-after-free conditions.

For -fixes this sounds ok, but for -next I think switching to drmm_
would be much better.
-Daniel

> v2: Cleanup connector only if it was created
>
> Fixes: 13dfc0540a57 ("drm/bridge: Refactor out the panel wrapper from the lvds-encoder bridge.")
> Cc: <stable@vger.kernel.org> # 4.12+
> Cc: Andrzej Hajda <a.hajda@samsung.com>
> Cc: Neil Armstrong <narmstrong@baylibre.com>
> Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
> Cc: Jonas Karlman <jonas@kwiboo.se>
> Cc: Jernej Skrabec <jernej.skrabec@siol.net>
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> ---
>  drivers/gpu/drm/bridge/panel.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
> index 0ddc37551194..df86b0ee0549 100644
> --- a/drivers/gpu/drm/bridge/panel.c
> +++ b/drivers/gpu/drm/bridge/panel.c
> @@ -87,6 +87,12 @@ static int panel_bridge_attach(struct drm_bridge *bridge,
>
>  static void panel_bridge_detach(struct drm_bridge *bridge)
>  {
> +       struct panel_bridge *panel_bridge = drm_bridge_to_panel_bridge(bridge);
> +       struct drm_connector *connector = &panel_bridge->connector;
> +
> +       /* Cleanup the connector if we know it was initialized */
> +       if (!!panel_bridge->connector.dev)
> +               drm_connector_cleanup(connector);
>  }
>
>  static void panel_bridge_pre_enable(struct drm_bridge *bridge)
> --
> 2.29.2
>


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