[PATCH v3] phy: apple: atc: Fix typec switch/mux leak on unbind

[David Carlier]

atcphy_probe_switch() and atcphy_probe_mux() discard the pointers
returned by typec_switch_register() and typec_mux_register(). The
platform driver has no .remove callback, so when the driver unbinds
(e.g. via sysfs unbind) neither typec_switch_unregister() nor
typec_mux_unregister() is called. The framework reference taken in
typec_switch_register() (device_initialize() + device_add() in
drivers/usb/typec/mux.c) is therefore never dropped and the
typec_switch_dev / typec_mux_dev objects stay live forever, with
their sysfs entries under the typec_mux class also left behind. A
subsequent rebind cannot recreate them with the same fwnode-derived
name.

Save the registered handles and unregister them through
devm_add_action_or_reset() so framework registration is torn down
in step with the driver's other devm-managed state. While here,
drop struct apple_atcphy::sw and ::mux: they were declared with the
consumer-side types (typec_switch *, typec_mux *) instead of the
provider-side types and were never assigned.

Scope of the fix
================
This patch fixes the registration leak only. It does not close the
use-after-free window that arises when a consumer that obtained a
reference via fwnode_typec_switch_get() / fwnode_typec_mux_get()
outlives the provider unbind: such consumers keep the underlying
typec_switch_dev / typec_mux_dev alive past device_unregister(),
and a later typec_switch_set() / typec_mux_set() still invokes the
registered atcphy_sw_set() / atcphy_mux_set(), which dereferences
the freed apple_atcphy through typec_{switch,mux}_get_drvdata().

On Apple Silicon the relevant consumers are the typec port and the
cd321x controller registered by drivers/usb/typec/tipd/core.c.
Cable plug / orientation events and alt-mode transitions trigger
the .set callbacks via:

  tps6598x_interrupt()                 drivers/usb/typec/tipd/core.c
    tps6598x_handle_plug_event()
      tps6598x_connect()/_disconnect()
        typec_set_orientation()        drivers/usb/typec/class.c
          typec_switch_set(port->sw)   drivers/usb/typec/mux.c
            atcphy_sw_set()            drivers/phy/apple/atc.c

  cd321x_update_work()                 drivers/usb/typec/tipd/core.c
    cd321x_typec_update_mode()
      typec_mux_set(cd321x->mux)       drivers/usb/typec/mux.c
        atcphy_mux_set()               drivers/phy/apple/atc.c

Closing that window requires framework support for invalidating
consumer-held references on provider unbind. The same
consumer-survives-provider pattern has been discussed for the PHY
framework [1] and is out of scope here.

[1] https://lore.kernel.org/linux-phy/aZejMSJ9qqRWb2pX@google.com/

Fixes: 8e98ca1e74db ("phy: apple: Add Apple Type-C PHY")
Signed-off-by: David Carlier <devnexen at gmail.com>
Reviewed-by: Vladimir Oltean <olteanv at gmail.com>
---
 drivers/phy/apple/atc.c | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/drivers/phy/apple/atc.c b/drivers/phy/apple/atc.c
index e9d106f135c5..4156fabad742 100644
--- a/drivers/phy/apple/atc.c
+++ b/drivers/phy/apple/atc.c
@@ -628,9 +628,6 @@ struct apple_atcphy {
 
 	struct reset_controller_dev rcdev;
 
-	struct typec_switch *sw;
-	struct typec_mux *mux;
-
 	struct mutex lock;
 };
 
@@ -2066,15 +2063,25 @@ static int atcphy_sw_set(struct typec_switch_dev *sw, enum typec_orientation ori
 	return 0;
 }
 
+static void atcphy_typec_switch_unregister(void *data)
+{
+	typec_switch_unregister(data);
+}
+
 static int atcphy_probe_switch(struct apple_atcphy *atcphy)
 {
+	struct typec_switch_dev *sw;
 	struct typec_switch_desc sw_desc = {
 		.drvdata = atcphy,
 		.fwnode = atcphy->dev->fwnode,
 		.set = atcphy_sw_set,
 	};
 
-	return PTR_ERR_OR_ZERO(typec_switch_register(atcphy->dev, &sw_desc));
+	sw = typec_switch_register(atcphy->dev, &sw_desc);
+	if (IS_ERR(sw))
+		return PTR_ERR(sw);
+
+	return devm_add_action_or_reset(atcphy->dev, atcphy_typec_switch_unregister, sw);
 }
 
 static int atcphy_mux_set(struct typec_mux_dev *mux, struct typec_mux_state *state)
@@ -2146,15 +2153,25 @@ static int atcphy_mux_set(struct typec_mux_dev *mux, struct typec_mux_state *sta
 	return atcphy_configure(atcphy, target_mode);
 }
 
+static void atcphy_typec_mux_unregister(void *data)
+{
+	typec_mux_unregister(data);
+}
+
 static int atcphy_probe_mux(struct apple_atcphy *atcphy)
 {
+	struct typec_mux_dev *mux;
 	struct typec_mux_desc mux_desc = {
 		.drvdata = atcphy,
 		.fwnode = atcphy->dev->fwnode,
 		.set = atcphy_mux_set,
 	};
 
-	return PTR_ERR_OR_ZERO(typec_mux_register(atcphy->dev, &mux_desc));
+	mux = typec_mux_register(atcphy->dev, &mux_desc);
+	if (IS_ERR(mux))
+		return PTR_ERR(mux);
+
+	return devm_add_action_or_reset(atcphy->dev, atcphy_typec_mux_unregister, mux);
 }
 
 static int atcphy_load_tunables(struct apple_atcphy *atcphy)
-- 
2.53.0