linux-kernel - [PATCH v4 1/3] drm: bridge/panel: Cleanup connector on bridge detach

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Message-Id: <20210327115742.18986-2-paul@crapouillou.net>
Date:   Sat, 27 Mar 2021 11:57:40 +0000
From:   Paul Cercueil <paul@...pouillou.net>
To:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>
Cc:     Sam Ravnborg <sam@...nborg.org>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, od@...c.me,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-mips@...r.kernel.org, Paul Cercueil <paul@...pouillou.net>,
        stable@...r.kernel.org, Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Subject: [PATCH v4 1/3] drm: bridge/panel: Cleanup connector on bridge detach

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.

v2: Cleanup connector only if it was created

v3: Add FIXME

v4: (Use connector->dev) directly in if() block

Fixes: 13dfc0540a57 ("drm/bridge: Refactor out the panel wrapper from the lvds-encoder bridge.")
Cc: <stable@...r.kernel.org> # 4.12+
Cc: Andrzej Hajda <a.hajda@...sung.com>
Cc: Neil Armstrong <narmstrong@...libre.com>
Cc: Laurent Pinchart <Laurent.pinchart@...asonboard.com>
Cc: Jonas Karlman <jonas@...boo.se>
Cc: Jernej Skrabec <jernej.skrabec@...l.net>
Signed-off-by: Paul Cercueil <paul@...pouillou.net>
Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
---
 drivers/gpu/drm/bridge/panel.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
index 0ddc37551194..c916f4b8907e 100644
--- a/drivers/gpu/drm/bridge/panel.c
+++ b/drivers/gpu/drm/bridge/panel.c
@@ -87,6 +87,18 @@ 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.
+	 *
+	 * FIXME: This wouldn't be needed if the panel_bridge structure was
+	 * allocated with drmm_kzalloc(). This might be tricky since the
+	 * drm_device pointer can only be retrieved when the bridge is attached.
+	 */
+	if (connector->dev)
+		drm_connector_cleanup(connector);
 }
 
 static void panel_bridge_pre_enable(struct drm_bridge *bridge)
-- 
2.30.2