USB: prevent char device open/deregister race

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

diff --git a/drivers/usb/misc/usblcd.c b/drivers/usb/misc/usblcd.c
index 12bad8a..6e093c2 100644 (file)
--- a/drivers/usb/misc/usblcd.c
+++ b/drivers/usb/misc/usblcd.c
@@ -51,7 +51,6 @@ struct usb_lcd {
 #define USB_LCD_CONCURRENT_WRITES      5
 
 static struct usb_driver lcd_driver;
-static DEFINE_MUTEX(usb_lcd_open_mutex);
 
 
 static void lcd_delete(struct kref *kref)
@@ -69,24 +68,19 @@ static int lcd_open(struct inode *inode, struct file *file)
        struct usb_lcd *dev;
        struct usb_interface *interface;
        int subminor;
-       int retval = 0;
 
        subminor = iminor(inode);
 
-       mutex_lock(&usb_lcd_open_mutex);
        interface = usb_find_interface(&lcd_driver, subminor);
        if (!interface) {
                err ("USBLCD: %s - error, can't find device for minor %d",
                     __FUNCTION__, subminor);
-               retval = -ENODEV;
-               goto exit;
+               return -ENODEV;
        }
 
        dev = usb_get_intfdata(interface);
-       if (!dev) {
-               retval = -ENODEV;
-               goto exit;
-       }
+       if (!dev)
+               return -ENODEV;
 
        /* increment our usage count for the device */
        kref_get(&dev->kref);
@@ -94,9 +88,7 @@ static int lcd_open(struct inode *inode, struct file *file)
        /* save our object in the file's private structure */
        file->private_data = dev;
 
-exit:
-       mutex_unlock(&usb_lcd_open_mutex);
-       return retval;
+       return 0;
 }
 
 static int lcd_release(struct inode *inode, struct file *file)
@@ -363,17 +355,12 @@ static void lcd_disconnect(struct usb_interface *interface)
        struct usb_lcd *dev;
         int minor = interface->minor;
 
-        /* prevent skel_open() from racing skel_disconnect() */
-        mutex_lock(&usb_lcd_open_mutex);
-
         dev = usb_get_intfdata(interface);
         usb_set_intfdata(interface, NULL);
 
         /* give back our minor */
         usb_deregister_dev(interface, &lcd_class);
  
-       mutex_unlock(&usb_lcd_open_mutex);
-
        /* decrement our usage count */
        kref_put(&dev->kref, lcd_delete);