usb: core: stop USB enumeration if too many retries

When a broken USB accessory connects to a USB host, usbcore might
keep doing enumeration retries. If the host has a watchdog mechanism,
the kernel panic will happen on the host.

This patch provides an attribute early_stop to limit the numbers of retries
for each port of a hub. If a port was marked with early_stop attribute,
unsuccessful connection attempts will fail quickly. In addition, if an
early_stop port has failed to initialize, it will ignore all future
connection events until early_stop attribute is clear.

Signed-off-by: Ray Chi <raychi@google.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20221107072754.3336357-1-raychi@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 60 insertions, 0 deletions

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index bbab424b0d55..77e73fc8d673 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -3081,6 +3081,48 @@ done:
 	return status;
 }
 
+/*
+ * hub_port_stop_enumerate - stop USB enumeration or ignore port events
+ * @hub: target hub
+ * @port1: port num of the port
+ * @retries: port retries number of hub_port_init()
+ *
+ * Return:
+ *    true: ignore port actions/events or give up connection attempts.
+ *    false: keep original behavior.
+ *
+ * This function will be based on retries to check whether the port which is
+ * marked with early_stop attribute would stop enumeration or ignore events.
+ *
+ * Note:
+ * This function didn't change anything if early_stop is not set, and it will
+ * prevent all connection attempts when early_stop is set and the attempts of
+ * the port are more than 1.
+ */
+static bool hub_port_stop_enumerate(struct usb_hub *hub, int port1, int retries)
+{
+	struct usb_port *port_dev = hub->ports[port1 - 1];
+
+	if (port_dev->early_stop) {
+		if (port_dev->ignore_event)
+			return true;
+
+		/*
+		 * We want unsuccessful attempts to fail quickly.
+		 * Since some devices may need one failure during
+		 * port initialization, we allow two tries but no
+		 * more.
+		 */
+		if (retries < 2)
+			return false;
+
+		port_dev->ignore_event = 1;
+	} else
+		port_dev->ignore_event = 0;
+
+	return port_dev->ignore_event;
+}
+
 /* Check if a port is power on */
 int usb_port_is_power_on(struct usb_hub *hub, unsigned int portstatus)
 {
@@ -4796,6 +4838,11 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
 	do_new_scheme = use_new_scheme(udev, retry_counter, port_dev);
 
 	for (retries = 0; retries < GET_DESCRIPTOR_TRIES; (++retries, msleep(100))) {
+		if (hub_port_stop_enumerate(hub, port1, retries)) {
+			retval = -ENODEV;
+			break;
+		}
+
 		if (do_new_scheme) {
 			struct usb_device_descriptor *buf;
 			int r = 0;
@@ -5246,6 +5293,11 @@ static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,
 	status = 0;
 
 	for (i = 0; i < PORT_INIT_TRIES; i++) {
+		if (hub_port_stop_enumerate(hub, port1, i)) {
+			status = -ENODEV;
+			break;
+		}
+
 		usb_lock_port(port_dev);
 		mutex_lock(hcd->address0_mutex);
 		retry_locked = true;
@@ -5614,6 +5666,10 @@ static void port_event(struct usb_hub *hub, int port1)
 	if (!pm_runtime_active(&port_dev->dev))
 		return;
 
+	/* skip port actions if ignore_event and early_stop are true */
+	if (port_dev->ignore_event && port_dev->early_stop)
+		return;
+
 	if (hub_handle_remote_wakeup(hub, port1, portstatus, portchange))
 		connect_change = 1;
 
@@ -5927,6 +5983,10 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
 	mutex_lock(hcd->address0_mutex);
 
 	for (i = 0; i < PORT_INIT_TRIES; ++i) {
+		if (hub_port_stop_enumerate(parent_hub, port1, i)) {
+			ret = -ENODEV;
+			break;
+		}
 
 		/* ep0 maxpacket size may change; let the HCD know about it.
 		 * Other endpoints will be handled by re-enumeration. */