[PATCH v4 2/3] usb: ucsi: Fix ucsi->connector race

[Hans de Goede <hdegoede@xxxxxxxxxx>]

ucsi_init() which runs from a workqueue sets ucsi->connector and
on an error will clear it again.

ucsi->connector gets dereferenced by ucsi_resume(), this checks for
ucsi->connector being NULL in case ucsi_init() has not finished yet;
or in case ucsi_init() has failed.

ucsi_init() setting ucsi->connector and then clearing it again on
an error creates a race where the check in ucsi_resume() may pass,
only to have ucsi->connector free-ed underneath it when ucsi_init()
hits an error.

Fix this race by making ucsi_init() store the connector array in
a local variable and only assign it to ucsi->connector on success.

Fixes: bdc62f2bae8f ("usb: typec: ucsi: Simplified registration and I/O API")
Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
---
Changes in v4:
- Rebase on top of v6.3-rc1

Changes in v3:
- Assign connector[i].index before calling ucsi_register_port() instead of
  passing i to ucsi_register_port()
---
 drivers/usb/typec/ucsi/ucsi.c | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index 0623861c597b..8d1baf28df55 100644
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -1125,12 +1125,11 @@ static struct fwnode_handle *ucsi_find_fwnode(struct ucsi_connector *con)
 	return NULL;
 }
 
-static int ucsi_register_port(struct ucsi *ucsi, int index)
+static int ucsi_register_port(struct ucsi *ucsi, struct ucsi_connector *con)
 {
 	struct usb_power_delivery_desc desc = { ucsi->cap.pd_version};
 	struct usb_power_delivery_capabilities_desc pd_caps;
 	struct usb_power_delivery_capabilities *pd_cap;
-	struct ucsi_connector *con = &ucsi->connector[index];
 	struct typec_capability *cap = &con->typec_cap;
 	enum typec_accessory *accessory = cap->accessory;
 	enum usb_role u_role = USB_ROLE_NONE;
@@ -1151,7 +1150,6 @@ static int ucsi_register_port(struct ucsi *ucsi, int index)
 	init_completion(&con->complete);
 	mutex_init(&con->lock);
 	INIT_LIST_HEAD(&con->partner_tasks);
-	con->num = index + 1;
 	con->ucsi = ucsi;
 
 	cap->fwnode = ucsi_find_fwnode(con);
@@ -1328,7 +1326,7 @@ static int ucsi_register_port(struct ucsi *ucsi, int index)
  */
 static int ucsi_init(struct ucsi *ucsi)
 {
-	struct ucsi_connector *con;
+	struct ucsi_connector *con, *connector;
 	u64 command, ntfy;
 	int ret;
 	int i;
@@ -1359,16 +1357,16 @@ static int ucsi_init(struct ucsi *ucsi)
 	}
 
 	/* Allocate the connectors. Released in ucsi_unregister() */
-	ucsi->connector = kcalloc(ucsi->cap.num_connectors + 1,
-				  sizeof(*ucsi->connector), GFP_KERNEL);
-	if (!ucsi->connector) {
+	connector = kcalloc(ucsi->cap.num_connectors + 1, sizeof(*connector), GFP_KERNEL);
+	if (!connector) {
 		ret = -ENOMEM;
 		goto err_reset;
 	}
 
 	/* Register all connectors */
 	for (i = 0; i < ucsi->cap.num_connectors; i++) {
-		ret = ucsi_register_port(ucsi, i);
+		connector[i].num = i + 1;
+		ret = ucsi_register_port(ucsi, &connector[i]);
 		if (ret)
 			goto err_unregister;
 	}
@@ -1380,11 +1378,12 @@ static int ucsi_init(struct ucsi *ucsi)
 	if (ret < 0)
 		goto err_unregister;
 
+	ucsi->connector = connector;
 	ucsi->ntfy = ntfy;
 	return 0;
 
 err_unregister:
-	for (con = ucsi->connector; con->port; con++) {
+	for (con = connector; con->port; con++) {
 		ucsi_unregister_partner(con);
 		ucsi_unregister_altmodes(con, UCSI_RECIPIENT_CON);
 		ucsi_unregister_port_psy(con);
@@ -1400,10 +1399,7 @@ static int ucsi_init(struct ucsi *ucsi)
 		typec_unregister_port(con->port);
 		con->port = NULL;
 	}
-
-	kfree(ucsi->connector);
-	ucsi->connector = NULL;
-
+	kfree(connector);
 err_reset:
 	memset(&ucsi->cap, 0, sizeof(ucsi->cap));
 	ucsi_reset_ppm(ucsi);
-- 
2.39.1