linux-kernel - [PATCH v5 09/10] drm/bridge: samsung-dsim: refcount the out

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Message-Id: <20241231-hotplug-drm-bridge-v5-9-173065a1ece1@bootlin.com>
Date: Tue, 31 Dec 2024 11:40:03 +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 09/10] drm/bridge: samsung-dsim: refcount the out_bridge

Refcount the out_bridge to avoid a use-after-free in case it is
hot-unplugged.

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

---

This patch was added in v5.
---
 drivers/gpu/drm/bridge/samsung-dsim.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index c4d1563fd32019efde523dfc0863be044c05a826..4d32c453265931b5aecdc125623368fecacf4be3 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -1756,6 +1756,7 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host,
 		return ret;
 	}
 
+	drm_bridge_get(out_bridge);
 	dsi->out_bridge = out_bridge;
 
 	DRM_DEV_INFO(dev, "Attached %s device (lanes:%d bpp:%d mode-flags:0x%lx)\n",
@@ -1774,13 +1775,13 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host,
 	if (!(device->mode_flags & MIPI_DSI_MODE_VIDEO)) {
 		ret = samsung_dsim_register_te_irq(dsi, &device->dev);
 		if (ret)
-			return ret;
+			goto err_put_bridge;
 	}
 
 	if (pdata->host_ops && pdata->host_ops->attach) {
 		ret = pdata->host_ops->attach(dsi, device);
 		if (ret)
-			return ret;
+			goto err_put_bridge;
 	}
 
 	dsi->lanes = device->lanes;
@@ -1788,6 +1789,10 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host,
 	dsi->mode_flags = device->mode_flags;
 
 	return 0;
+
+err_put_bridge:
+	drm_bridge_put_and_clear(dsi->out_bridge);
+	return ret;
 }
 
 static void samsung_dsim_unregister_te_irq(struct samsung_dsim *dsi)
@@ -1804,7 +1809,7 @@ static int samsung_dsim_host_detach(struct mipi_dsi_host *host,
 	struct samsung_dsim *dsi = host_to_dsi(host);
 	const struct samsung_dsim_plat_data *pdata = dsi->plat_data;
 
-	dsi->out_bridge = NULL;
+	drm_bridge_put_and_clear(dsi->out_bridge);
 
 	if (pdata->host_ops && pdata->host_ops->detach)
 		pdata->host_ops->detach(dsi, device);

-- 
2.34.1