Re: [PATCH v2 1/3] drm: bridge/panel: Cleanup connector on bridge detach

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Le mer. 20 janv. 2021 à 17:03, Daniel Vetter <daniel@xxxxxxxx> a écrit :
On Wed, Jan 20, 2021 at 1:35 PM Paul Cercueil <paul@xxxxxxxxxxxxxxx> 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.

The API would need to change to have access to the drm_device struct, though. That would be quite a big patch, there are a few dozens source files that use this API already.

Cheers,
-Paul


 v2: Cleanup connector only if it was created

Fixes: 13dfc0540a57 ("drm/bridge: Refactor out the panel wrapper from the lvds-encoder bridge.")
 Cc: <stable@xxxxxxxxxxxxxxx> # 4.12+
 Cc: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
 Cc: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
 Cc: Laurent Pinchart <Laurent.pinchart@xxxxxxxxxxxxxxxx>
 Cc: Jonas Karlman <jonas@xxxxxxxxx>
 Cc: Jernej Skrabec <jernej.skrabec@xxxxxxxx>
 Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
 ---
  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


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