linux-kernel - [PATCH 1/3] usb: ucsi: Add missing ppm

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Date: Tue, 16 Jan 2024 23:40:39 +0100
From: "Christian A. Ehrhardt" <lk@...e.de>
To: Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	linux-usb@...r.kernel.org
Cc: "Christian A. Ehrhardt" <lk@...e.de>,
	Dell.Client.Kernel@...l.com,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Hans de Goede <hdegoede@...hat.com>,
	Jack Pham <quic_jackp@...cinc.com>,
	Fabrice Gasnier <fabrice.gasnier@...s.st.com>,
	Samuel Čavoj <samuel@...oj.net>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] usb: ucsi: Add missing ppm_lock

Calling ->sync_write must be done while holding the PPM lock as the
mailbox logic does not support concurrent commands.

Thus protect the only call to ucsi_acknowledge_connector_change
with the PPM lock as it calls ->sync_write. All other calls to
->sync_write already happen under the PPM lock.

Signed-off-by: Christian A. Ehrhardt <lk@...e.de>
---
NOTE: This is not a theoretical issue. I've seen problems resulting
from the missing lock on real hardware.

 drivers/usb/typec/ucsi/ucsi.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index 61b64558f96c..8f9dff993b3d 100644
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -935,7 +935,9 @@ static void ucsi_handle_connector_change(struct work_struct *work)
 
 	clear_bit(EVENT_PENDING, &con->ucsi->flags);
 
+	mutex_lock(&ucsi->ppm_lock);
 	ret = ucsi_acknowledge_connector_change(ucsi);
+	mutex_unlock(&ucsi->ppm_lock);
 	if (ret)
 		dev_err(ucsi->dev, "%s: ACK failed (%d)", __func__, ret);
 
-- 
2.40.1