USB: prevent char device open/deregister race

[sagit-ice-cold/kernel_xiaomi_msm8998.git] / drivers / usb / misc / ldusb.c

diff --git a/drivers/usb/misc/ldusb.c b/drivers/usb/misc/ldusb.c
index 7bad494..5e950b9 100644 (file)
--- a/drivers/usb/misc/ldusb.c
+++ b/drivers/usb/misc/ldusb.c
@@ -176,9 +176,6 @@ struct ld_usb {
        int                     interrupt_out_busy;
 };
 
-/* prevent races between open() and disconnect() */
-static DEFINE_MUTEX(disconnect_mutex);
-
 static struct usb_driver ld_usb_driver;
 
 /**
@@ -298,35 +295,28 @@ static int ld_usb_open(struct inode *inode, struct file *file)
 {
        struct ld_usb *dev;
        int subminor;
-       int retval = 0;
+       int retval;
        struct usb_interface *interface;
 
        nonseekable_open(inode, file);
        subminor = iminor(inode);
 
-       mutex_lock(&disconnect_mutex);
-
        interface = usb_find_interface(&ld_usb_driver, subminor);
 
        if (!interface) {
                err("%s - error, can't find device for minor %d\n",
                     __FUNCTION__, subminor);
-               retval = -ENODEV;
-               goto unlock_disconnect_exit;
+               return -ENODEV;
        }
 
        dev = usb_get_intfdata(interface);
 
-       if (!dev) {
-               retval = -ENODEV;
-               goto unlock_disconnect_exit;
-       }
+       if (!dev)
+               return -ENODEV;
 
        /* lock this device */
-       if (down_interruptible(&dev->sem)) {
-               retval = -ERESTARTSYS;
-               goto unlock_disconnect_exit;
-       }
+       if (down_interruptible(&dev->sem))
+               return -ERESTARTSYS;
 
        /* allow opening only once */
        if (dev->open_count) {
@@ -366,9 +356,6 @@ static int ld_usb_open(struct inode *inode, struct file *file)
 unlock_exit:
        up(&dev->sem);
 
-unlock_disconnect_exit:
-       mutex_unlock(&disconnect_mutex);
-
        return retval;
 }
 
@@ -766,18 +753,16 @@ static void ld_usb_disconnect(struct usb_interface *intf)
        struct ld_usb *dev;
        int minor;
 
-       mutex_lock(&disconnect_mutex);
-
        dev = usb_get_intfdata(intf);
        usb_set_intfdata(intf, NULL);
 
-       down(&dev->sem);
-
        minor = intf->minor;
 
        /* give back our minor */
        usb_deregister_dev(intf, &ld_usb_class);
 
+       down(&dev->sem);
+
        /* if the device is not opened, then we clean up right now */
        if (!dev->open_count) {
                up(&dev->sem);
@@ -787,8 +772,6 @@ static void ld_usb_disconnect(struct usb_interface *intf)
                up(&dev->sem);
        }
 
-       mutex_unlock(&disconnect_mutex);
-
        dev_info(&intf->dev, "LD USB Device #%d now disconnected\n",
                 (minor - USB_LD_MINOR_BASE));
 }