usb: typec: ucsi: Hold con->lock for the entire duration of ucsi_register_port()

Commit 081da132 ("usb: typec: ucsi: displayport: Fix a potential race
during registration") made the ucsi code hold con->lock in
ucsi_register_displayport(). But we really don't want any interactions
with the connector to run before the port-registration process is fully
complete.

This commit moves the taking of con->lock from ucsi_register_displayport()
into ucsi_register_port() to achieve this.

Cc: stable@vger.kernel.org
Fixes: 081da132 ("usb: typec: ucsi: displayport: Fix a potential race during registration")
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20200809141904.4317-5-hdegoede@redhat.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/ucsi/displayport.c

@@ -288,8 +288,6 @@ struct typec_altmode *ucsi_register_displayport(struct ucsi_connector *con,
 	struct typec_altmode *alt;
 	struct ucsi_dp *dp;
 
-	mutex_lock(&con->lock);
-
 	/* We can't rely on the firmware with the capabilities. */
 	desc->vdo |= DP_CAP_DP_SIGNALING | DP_CAP_RECEPTACLE;
 
@@ -298,15 +296,12 @@ struct typec_altmode *ucsi_register_displayport(struct ucsi_connector *con,
 	desc->vdo |= all_assignments << 16;
 
 	alt = typec_port_register_altmode(con->port, desc);
-	if (IS_ERR(alt)) {
-		mutex_unlock(&con->lock);
+	if (IS_ERR(alt))
 		return alt;
-	}
 
 	dp = devm_kzalloc(&alt->dev, sizeof(*dp), GFP_KERNEL);
 	if (!dp) {
 		typec_unregister_altmode(alt);
-		mutex_unlock(&con->lock);
 		return ERR_PTR(-ENOMEM);
 	}
 
@@ -319,7 +314,5 @@ struct typec_altmode *ucsi_register_displayport(struct ucsi_connector *con,
 	alt->ops = &ucsi_displayport_ops;
 	typec_altmode_set_drvdata(alt, dp);
 
-	mutex_unlock(&con->lock);
-
 	return alt;
 }

drivers/usb/typec/ucsi/ucsi.c

@@ -898,12 +898,15 @@ static int ucsi_register_port(struct ucsi *ucsi, int index)
 	con->num = index + 1;
 	con->ucsi = ucsi;
 
+	/* Delay other interactions with the con until registration is complete */
+	mutex_lock(&con->lock);
+
 	/* Get connector capability */
 	command = UCSI_GET_CONNECTOR_CAPABILITY;
 	command |= UCSI_CONNECTOR_NUMBER(con->num);
 	ret = ucsi_send_command(ucsi, command, &con->cap, sizeof(con->cap));
 	if (ret < 0)
-		return ret;
+		goto out;
 
 	if (con->cap.op_mode & UCSI_CONCAP_OPMODE_DRP)
 		cap->data = TYPEC_PORT_DRD;
@@ -935,26 +938,32 @@ static int ucsi_register_port(struct ucsi *ucsi, int index)
 
 	ret = ucsi_register_port_psy(con);
 	if (ret)
-		return ret;
+		goto out;
 
 	/* Register the connector */
 	con->port = typec_register_port(ucsi->dev, cap);
-	if (IS_ERR(con->port))
-		return PTR_ERR(con->port);
+	if (IS_ERR(con->port)) {
+		ret = PTR_ERR(con->port);
+		goto out;
+	}
 
 	/* Alternate modes */
 	ret = ucsi_register_altmodes(con, UCSI_RECIPIENT_CON);
-	if (ret)
+	if (ret) {
 		dev_err(ucsi->dev, "con%d: failed to register alt modes\n",
 			con->num);
+		goto out;
+	}
 
 	/* Get the status */
 	command = UCSI_GET_CONNECTOR_STATUS | UCSI_CONNECTOR_NUMBER(con->num);
 	ret = ucsi_send_command(ucsi, command, &con->status, sizeof(con->status));
 	if (ret < 0) {
 		dev_err(ucsi->dev, "con%d: failed to get status\n", con->num);
-		return 0;
+		ret = 0;
+		goto out;
 	}
+	ret = 0; /* ucsi_send_command() returns length on success */
 
 	switch (UCSI_CONSTAT_PARTNER_TYPE(con->status.flags)) {
 	case UCSI_CONSTAT_PARTNER_TYPE_UFP:
@@ -979,17 +988,21 @@ static int ucsi_register_port(struct ucsi *ucsi, int index)
 
 	if (con->partner) {
 		ret = ucsi_register_altmodes(con, UCSI_RECIPIENT_SOP);
-		if (ret)
+		if (ret) {
 			dev_err(ucsi->dev,
 				"con%d: failed to register alternate modes\n",
 				con->num);
-		else
+			ret = 0;
+		} else {
 			ucsi_altmode_update_active(con);
+		}
 	}
 
 	trace_ucsi_register_port(con->num, &con->status);
 
-	return 0;
+out:
+	mutex_unlock(&con->lock);
+	return ret;
 }
 
 /**