[PATCH] usb: typec: ucsi: fix teardown races with late notifications

["Iván Ezequiel Rodriguez" <ivanrwcm25@gmail.com>]

ucsi_acpi_remove() freed the UCSI instance before removing the ACPI
notify handler. A concurrent notify could call into ucsi_acpi_notify()
and use ua->ucsi after it was destroyed.

Clear ucsi->ntfy before disabling PPM notifications and NULL the
connector array after free so ucsi_connector_change() cannot schedule
work on a dangling connector while a backend still delivers events.

Tested: built drivers/usb/typec/ucsi/ with CONFIG_TYPEC_UCSI=m and
CONFIG_UCSI_ACPI=m via docker kbuild; checkpatch clean.

Signed-off-by: Iván Ezequiel Rodriguez <ivanrwcm25@gmail.com>
---
 drivers/usb/typec/ucsi/ucsi.c      | 11 +++++++++++
 drivers/usb/typec/ucsi/ucsi_acpi.c | 11 ++++++++---
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index bef3f9b71d71..3395614764cf 100644
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -2369,6 +2369,15 @@ void ucsi_unregister(struct ucsi *ucsi)
 
 	ucsi_debugfs_unregister(ucsi);
 
+	/*
+	 * Stop accepting connector-change events before the PPM disable
+	 * command and before freeing connectors. Backends may still deliver
+	 * a late notification (e.g. ACPI) until their own handler is removed;
+	 * with ntfy cleared, ucsi_connector_change() returns early instead of
+	 * scheduling work on a connector that is about to be freed.
+	 */
+	ucsi->ntfy = 0;
+
 	/* Disable notifications */
 	ucsi->ops->async_control(ucsi, cmd);
 
@@ -2382,6 +2391,8 @@ void ucsi_unregister(struct ucsi *ucsi)
 	}
 
 	kfree(ucsi->connector);
+	ucsi->connector = NULL;
+	memset(&ucsi->cap, 0, sizeof(ucsi->cap));
 }
 EXPORT_SYMBOL_GPL(ucsi_unregister);
 
diff --git a/drivers/usb/typec/ucsi/ucsi_acpi.c b/drivers/usb/typec/ucsi/ucsi_acpi.c
index 18286d3e9cc5..5fc485121dbb 100644
--- a/drivers/usb/typec/ucsi/ucsi_acpi.c
+++ b/drivers/usb/typec/ucsi/ucsi_acpi.c
@@ -256,11 +256,16 @@ static void ucsi_acpi_remove(struct platform_device *pdev)
 {
 	struct ucsi_acpi *ua = platform_get_drvdata(pdev);
 
-	ucsi_unregister(ua->ucsi);
-	ucsi_destroy(ua->ucsi);
-
+	/*
+	 * Drop the ACPI notify handler before tearing down the UCSI instance.
+	 * Otherwise a concurrent notify can race into ucsi_acpi_notify() and
+	 * use ua->ucsi after it has been freed.
+	 */
 	acpi_remove_notify_handler(ACPI_HANDLE(&pdev->dev), ACPI_DEVICE_NOTIFY,
 				   ucsi_acpi_notify);
+
+	ucsi_unregister(ua->ucsi);
+	ucsi_destroy(ua->ucsi);
 }
 
 static int ucsi_acpi_suspend(struct device *dev)
-- 
2.43.0