linux-kernel - [PATCH v5 07/10] drm/bridge: panel: use dynamic lifetime management

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Message-Id: <20241231-hotplug-drm-bridge-v5-7-173065a1ece1@bootlin.com>
Date: Tue, 31 Dec 2024 11:40:01 +0100
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: Simona Vetter <simona@...ll.ch>, Inki Dae <inki.dae@...sung.com>, 
 Jagan Teki <jagan@...rulasolutions.com>, 
 Marek Szyprowski <m.szyprowski@...sung.com>, 
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
 Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>, Daniel Thompson <danielt@...nel.org>, 
 Andrzej Hajda <andrzej.hajda@...el.com>, Jonathan Corbet <corbet@....net>
Cc: Paul Kocialkowski <contact@...lk.fr>, 
 Maxime Ripard <mripard@...nel.org>, 
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, 
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
 Hervé Codina <herve.codina@...tlin.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
 linux-doc@...r.kernel.org, 
 Paul Kocialkowski <paul.kocialkowski@...tlin.com>, 
 Luca Ceresoli <luca.ceresoli@...tlin.com>
Subject: [PATCH v5 07/10] drm/bridge: panel: use dynamic lifetime
 management

Enable lifetime management of panel-bridge, so that other modules taking a
pointer to a panel bridge can refcount it and avoid use-after-free in case
the panel bridge is hot-unplugged.

Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>

---

This patch was added in v5.
---
 drivers/gpu/drm/bridge/panel.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
index 6e88339dec0f5faee690b7c53e8dcd0f1ee2281c..805809778f79f4519d9e31214cc5407357264da3 100644
--- a/drivers/gpu/drm/bridge/panel.c
+++ b/drivers/gpu/drm/bridge/panel.c
@@ -108,6 +108,11 @@ static void panel_bridge_detach(struct drm_bridge *bridge)
 		drm_connector_cleanup(connector);
 }
 
+static void panel_bridge_destroy(struct drm_bridge *bridge)
+{
+	kfree(drm_bridge_to_panel_bridge(bridge));
+}
+
 static void panel_bridge_atomic_pre_enable(struct drm_bridge *bridge,
 				struct drm_bridge_state *old_bridge_state)
 {
@@ -210,6 +215,7 @@ static void panel_bridge_debugfs_init(struct drm_bridge *bridge,
 static const struct drm_bridge_funcs panel_bridge_bridge_funcs = {
 	.attach = panel_bridge_attach,
 	.detach = panel_bridge_detach,
+	.destroy = panel_bridge_destroy,
 	.atomic_pre_enable = panel_bridge_atomic_pre_enable,
 	.atomic_enable = panel_bridge_atomic_enable,
 	.atomic_disable = panel_bridge_atomic_disable,
@@ -286,19 +292,22 @@ struct drm_bridge *drm_panel_bridge_add_typed(struct drm_panel *panel,
 					      u32 connector_type)
 {
 	struct panel_bridge *panel_bridge;
+	int err;
 
 	if (!panel)
 		return ERR_PTR(-EINVAL);
 
-	panel_bridge = devm_kzalloc(panel->dev, sizeof(*panel_bridge),
-				    GFP_KERNEL);
+	panel_bridge = kzalloc(sizeof(*panel_bridge), GFP_KERNEL);
 	if (!panel_bridge)
 		return ERR_PTR(-ENOMEM);
 
+	err = drm_bridge_init(panel->dev, &panel_bridge->bridge, &panel_bridge_bridge_funcs);
+	if (err)
+		return ERR_PTR(err);
+
 	panel_bridge->connector_type = connector_type;
 	panel_bridge->panel = panel;
 
-	panel_bridge->bridge.funcs = &panel_bridge_bridge_funcs;
 	panel_bridge->bridge.of_node = panel->dev->of_node;
 	panel_bridge->bridge.ops = DRM_BRIDGE_OP_MODES;
 	panel_bridge->bridge.type = connector_type;
@@ -317,18 +326,13 @@ EXPORT_SYMBOL(drm_panel_bridge_add_typed);
  */
 void drm_panel_bridge_remove(struct drm_bridge *bridge)
 {
-	struct panel_bridge *panel_bridge;
-
 	if (!bridge)
 		return;
 
 	if (bridge->funcs != &panel_bridge_bridge_funcs)
 		return;
 
-	panel_bridge = drm_bridge_to_panel_bridge(bridge);
-
 	drm_bridge_remove(bridge);
-	devm_kfree(panel_bridge->panel->dev, bridge);
 }
 EXPORT_SYMBOL(drm_panel_bridge_remove);
 

-- 
2.34.1