USB: serial: fix port attribute-creation race

Fix attribute-creation race with userspace by using the port device
groups field to create the port attributes.

Also use %u when printing the port number, which is unsigned, even
though we do not currently support more than 128 ports per device.

Reported-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Greg Kroah-Hartman <greg@kroah.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index 19842370a07f..529066bbc7e8 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -687,6 +687,21 @@ static void serial_port_dtr_rts(struct tty_port *port, int on)
                 drv->dtr_rts(p, on);
 }
 
+static ssize_t port_number_show(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        struct usb_serial_port *port = to_usb_serial_port(dev);
+
+        return sprintf(buf, "%u\n", port->port_number);
+}
+static DEVICE_ATTR_RO(port_number);
+
+static struct attribute *usb_serial_port_attrs[] = {
+        &dev_attr_port_number.attr,
+        NULL
+};
+ATTRIBUTE_GROUPS(usb_serial_port);
+
 static const struct tty_port_operations serial_port_ops = {
         .carrier_raised         = serial_port_carrier_raised,
         .dtr_rts                = serial_port_dtr_rts,
@@ -902,6 +917,7 @@ static int usb_serial_probe(struct usb_interface *interface,
                 port->dev.driver = NULL;
                 port->dev.bus = &usb_serial_bus_type;
                 port->dev.release = &usb_serial_port_release;
+                port->dev.groups = usb_serial_port_groups;
                 device_initialize(&port->dev);
         }