[PATCH 8/8] usb: typec: ucsi: validate connector number in ucsi_connector_change()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

The connector number in a UCSI CCI notification is a 7-bit field
supplied by the PPM.  ucsi_connector_change() uses it to index the
ucsi->connector[] array without checking it against the number of
connectors the PPM reported at init time, so a buggy or malicious PPM
(EC firmware, or an I2C-attached UCSI controller on the ccg / stm32g0 /
glink transports) can drive schedule_work() on memory past the end of
the array.

Reject connector numbers that are zero or exceed cap.num_connectors
before dereferencing the array.

Assisted-by: gkh_clanker_t1000
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: Benson Leung <bleung@chromium.org>
Cc: Jameson Thies <jthies@google.com>
Cc: Nathan Rebello <nathan.c.rebello@gmail.com>
Cc: Johan Hovold <johan@kernel.org>
Cc: Pooja Katiyar <pooja.katiyar@intel.com>
Cc: Hsin-Te Yuan <yuanhsinte@chromium.org>
Cc: Abel Vesa <abelvesa@kernel.org>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/typec/ucsi/ucsi.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index 5b7ad9e99cb9..539dc706798d 100644
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -1380,13 +1380,22 @@ static void ucsi_handle_connector_change(struct work_struct *work)
  */
 void ucsi_connector_change(struct ucsi *ucsi, u8 num)
 {
-	struct ucsi_connector *con = &ucsi->connector[num - 1];
+	struct ucsi_connector *con;
 
 	if (!(ucsi->ntfy & UCSI_ENABLE_NTFY_CONNECTOR_CHANGE)) {
 		dev_dbg(ucsi->dev, "Early connector change event\n");
 		return;
 	}
 
+	if (!num || num > ucsi->cap.num_connectors) {
+		dev_warn_ratelimited(ucsi->dev,
+				     "Bogus connector change on %u (max %u)\n",
+				     num, ucsi->cap.num_connectors);
+		return;
+	}
+
+	con = &ucsi->connector[num - 1];
+
 	if (!test_and_set_bit(EVENT_PENDING, &ucsi->flags))
 		schedule_work(&con->work);
 }
-- 
2.54.0