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>

2 files changed, 16 insertions, 19 deletions

diff --git a/drivers/usb/serial/bus.c b/drivers/usb/serial/bus.c
index 6f91eb9ae81a..b53a28692226 100644
--- a/drivers/usb/serial/bus.c
+++ b/drivers/usb/serial/bus.c
@@ -38,15 +38,6 @@ static int usb_serial_device_match(struct device *dev,
         return 0;
 }
 
-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, "%d\n", port->port_number);
-}
-static DEVICE_ATTR_RO(port_number);
-
 static int usb_serial_device_probe(struct device *dev)
 {
         struct usb_serial_driver *driver;
@@ -73,18 +64,10 @@ static int usb_serial_device_probe(struct device *dev)
                         goto exit_with_autopm;
         }
 
-        retval = device_create_file(dev, &dev_attr_port_number);
-        if (retval) {
-                if (driver->port_remove)
-                        driver->port_remove(port);
-                goto exit_with_autopm;
-        }
-
         minor = port->minor;
         tty_dev = tty_register_device(usb_serial_tty_driver, minor, dev);
         if (IS_ERR(tty_dev)) {
                 retval = PTR_ERR(tty_dev);
-                device_remove_file(dev, &dev_attr_port_number);
                 if (driver->port_remove)
                         driver->port_remove(port);
                 goto exit_with_autopm;
@@ -123,8 +106,6 @@ static int usb_serial_device_remove(struct device *dev)
         minor = port->minor;
         tty_unregister_device(usb_serial_tty_driver, minor);
 
-        device_remove_file(&port->dev, &dev_attr_port_number);
-
         driver = port->serial->type;
         if (driver->port_remove)
                 retval = driver->port_remove(port);
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);
         }