USB: Push BKL on open down into the drivers

Straightforward push into the drivers to allow
auditing individual drivers separately

Signed-off-by: Oliver Neukum <oliver@neukum.org>
Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

20 files changed, 99 insertions, 15 deletions

diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
index 867e08433e4..433602aed46 100644
--- a/drivers/hid/usbhid/hiddev.c
+++ b/drivers/hid/usbhid/hiddev.c
@@ -265,9 +265,10 @@ static int hiddev_release(struct inode * inode, struct file * file)
 static int hiddev_open(struct inode *inode, struct file *file)
 {
 	struct hiddev_list *list;
-	int res;
+	int res, i;
 
-	int i = iminor(inode) - HIDDEV_MINOR_BASE;
+	lock_kernel();
+	i = iminor(inode) - HIDDEV_MINOR_BASE;
 
 	if (i >= HIDDEV_MINORS || i < 0 || !hiddev_table[i])
 		return -ENODEV;
@@ -313,10 +314,12 @@ static int hiddev_open(struct inode *inode, struct file *file)
 			usbhid_open(hid);
 		}
 
+	unlock_kernel();
 	return 0;
 bail:
 	file->private_data = NULL;
 	kfree(list);
+	unlock_kernel();
 	return res;
 }
 
diff --git a/drivers/media/video/dabusb.c b/drivers/media/video/dabusb.c
index 9b413a35e04..0f505086774 100644
--- a/drivers/media/video/dabusb.c
+++ b/drivers/media/video/dabusb.c
@@ -616,10 +616,12 @@ static int dabusb_open (struct inode *inode, struct file *file)
 {
 	int devnum = iminor(inode);
 	pdabusb_t s;
+	int r;
 
 	if (devnum < DABUSB_MINOR || devnum >= (DABUSB_MINOR + NRDABUSB))
 		return -EIO;
 
+	lock_kernel();
 	s = &dabusb[devnum - DABUSB_MINOR];
 
 	dbg("dabusb_open");
@@ -634,6 +636,7 @@ static int dabusb_open (struct inode *inode, struct file *file)
 		msleep_interruptible(500);
 
 		if (signal_pending (current)) {
+			unlock_kernel();
 			return -EAGAIN;
 		}
 		mutex_lock(&s->mutex);
@@ -641,6 +644,7 @@ static int dabusb_open (struct inode *inode, struct file *file)
 	if (usb_set_interface (s->usbdev, _DABUSB_IF, 1) < 0) {
 		mutex_unlock(&s->mutex);
 		dev_err(&s->usbdev->dev, "set_interface failed\n");
+		unlock_kernel();
 		return -EINVAL;
 	}
 	s->opened = 1;
@@ -649,7 +653,9 @@ static int dabusb_open (struct inode *inode, struct file *file)
 	file->f_pos = 0;
 	file->private_data = s;
 
-	return nonseekable_open(inode, file);
+	r = nonseekable_open(inode, file);
+	unlock_kernel();
+	return r;
 }
 
 static int dabusb_release (struct inode *inode, struct file *file)
diff --git a/drivers/staging/frontier/alphatrack.c b/drivers/staging/frontier/alphatrack.c
index 15aed87fe1b..e2f82f0dbad 100644
--- a/drivers/staging/frontier/alphatrack.c
+++ b/drivers/staging/frontier/alphatrack.c
@@ -41,6 +41,7 @@
 #include <linux/mutex.h>
 
 #include <linux/uaccess.h>
+#include <linux/smp_lock.h>
 #include <linux/input.h>
 #include <linux/usb.h>
 #include <linux/poll.h>
@@ -325,6 +326,7 @@ static int usb_alphatrack_open(struct inode *inode, struct file *file)
 	int retval = 0;
 	struct usb_interface *interface;
 
+	lock_kernel();
 	nonseekable_open(inode, file);
 	subminor = iminor(inode);
 
@@ -394,6 +396,7 @@ unlock_exit:
 
 unlock_disconnect_exit:
 	mutex_unlock(&disconnect_mutex);
+	unlock_kernel();
 
 	return retval;
 }
diff --git a/drivers/staging/frontier/tranzport.c b/drivers/staging/frontier/tranzport.c
index ef8fcc8c67b..1d3f7dc90f4 100644
--- a/drivers/staging/frontier/tranzport.c
+++ b/drivers/staging/frontier/tranzport.c
@@ -40,6 +40,7 @@
 #include <linux/mutex.h>
 
 #include <linux/uaccess.h>
+#include <linux/smp_lock.h>
 #include <linux/input.h>
 #include <linux/usb.h>
 #include <linux/poll.h>
@@ -343,6 +344,7 @@ static int usb_tranzport_open(struct inode *inode, struct file *file)
 	int retval = 0;
 	struct usb_interface *interface;
 
+	lock_kernel();
 	nonseekable_open(inode, file);
 	subminor = iminor(inode);
 
@@ -413,6 +415,7 @@ unlock_exit:
 
 unlock_disconnect_exit:
 	mutex_unlock(&disconnect_mutex);
+	unlock_kernel();
 
 	return retval;
 }
diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 18aafcb08fc..b75a3d8bb02 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -19,6 +19,7 @@
 #include <linux/uaccess.h>
 #include <linux/bitops.h>
 #include <linux/poll.h>
+#include <linux/smp_lock.h>
 #include <linux/usb.h>
 #include <linux/usb/cdc.h>
 #include <asm/byteorder.h>
@@ -516,6 +517,7 @@ static int wdm_open(struct inode *inode, struct file *file)
 	struct usb_interface *intf;
 	struct wdm_device *desc;
 
+	lock_kernel();
 	mutex_lock(&wdm_mutex);
 	intf = usb_find_interface(&wdm_driver, minor);
 	if (!intf)
@@ -548,6 +550,7 @@ static int wdm_open(struct inode *inode, struct file *file)
 	usb_autopm_put_interface(desc->intf);
 out:
 	mutex_unlock(&wdm_mutex);
+	unlock_kernel();
 	return rv;
 }
 
diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
index 93b5f85d7ce..d53f9499f93 100644
--- a/drivers/usb/class/usblp.c
+++ b/drivers/usb/class/usblp.c
@@ -56,6 +56,7 @@
 #include <linux/slab.h>
 #include <linux/lp.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 #undef DEBUG
 #include <linux/usb.h>
 
@@ -395,6 +396,7 @@ static int usblp_open(struct inode *inode, struct file *file)
 	if (minor < 0)
 		return -ENODEV;
 
+	lock_kernel();
 	mutex_lock (&usblp_mutex);
 
 	retval = -ENODEV;
@@ -434,6 +436,7 @@ static int usblp_open(struct inode *inode, struct file *file)
 	}
 out:
 	mutex_unlock (&usblp_mutex);
+	unlock_kernel();
 	return retval;
 }
 
diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index 8588c0937a8..426bfc72b9b 100644
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -26,6 +26,7 @@
 #include <linux/uaccess.h>
 #include <linux/kref.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 #include <linux/usb.h>
 #include <linux/usb/tmc.h>
 
@@ -113,6 +114,7 @@ static int usbtmc_open(struct inode *inode, struct file *filp)
 	struct usbtmc_device_data *data;
 	int retval = 0;
 
+	lock_kernel();
 	intf = usb_find_interface(&usbtmc_driver, iminor(inode));
 	if (!intf) {
 		printk(KERN_ERR KBUILD_MODNAME
@@ -128,6 +130,7 @@ static int usbtmc_open(struct inode *inode, struct file *filp)
 	filp->private_data = data;
 
 exit:
+	unlock_kernel();
 	return retval;
 }
 
diff --git a/drivers/usb/core/file.c b/drivers/usb/core/file.c
index bfc6c2eea64..c3536f151f0 100644
--- a/drivers/usb/core/file.c
+++ b/drivers/usb/core/file.c
@@ -34,7 +34,6 @@ static int usb_open(struct inode * inode, struct file * file)
 	int err = -ENODEV;
 	const struct file_operations *old_fops, *new_fops = NULL;
 
-	lock_kernel();
 	down_read(&minor_rwsem);
 	c = usb_minors[minor];
 
@@ -53,7 +52,6 @@ static int usb_open(struct inode * inode, struct file * file)
 	fops_put(old_fops);
  done:
 	up_read(&minor_rwsem);
-	unlock_kernel();
 	return err;
 }
 
diff --git a/drivers/usb/image/mdc800.c b/drivers/usb/image/mdc800.c
index e192e8f7c56..dce4f7b69ac 100644
--- a/drivers/usb/image/mdc800.c
+++ b/drivers/usb/image/mdc800.c
@@ -96,6 +96,7 @@
 #include <linux/module.h>
 #include <linux/wait.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 
 #include <linux/usb.h>
 #include <linux/fs.h>
@@ -622,6 +623,7 @@ static int mdc800_device_open (struct inode* inode, struct file *file)
 	int retval=0;
 	int errn=0;
 
+	lock_kernel();
 	mutex_lock(&mdc800->io_lock);
 	
 	if (mdc800->state == NOT_CONNECTED)
@@ -660,6 +662,7 @@ static int mdc800_device_open (struct inode* inode, struct file *file)
 
 error_out:
 	mutex_unlock(&mdc800->io_lock);
+	unlock_kernel();
 	return errn;
 }
 
diff --git a/drivers/usb/misc/adutux.c b/drivers/usb/misc/adutux.c
index 306e97825b3..ac8ad91c2da 100644
--- a/drivers/usb/misc/adutux.c
+++ b/drivers/usb/misc/adutux.c
@@ -25,6 +25,7 @@
 #include <linux/module.h>
 #include <linux/usb.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 #include <asm/uaccess.h>
 
 #ifdef CONFIG_USB_DEBUG
@@ -274,6 +275,7 @@ static int adu_open(struct inode *inode, struct file *file)
 
 	dbg(2,"%s : enter", __func__);
 
+	lock_kernel();
 	subminor = iminor(inode);
 
 	if ((retval = mutex_lock_interruptible(&adutux_mutex))) {
@@ -332,6 +334,7 @@ static int adu_open(struct inode *inode, struct file *file)
 exit_no_device:
 	mutex_unlock(&adutux_mutex);
 exit_no_lock:
+	unlock_kernel();
 	dbg(2,"%s : leave, return value %d ", __func__, retval);
 	return retval;
 }
diff --git a/drivers/usb/misc/ftdi-elan.c b/drivers/usb/misc/ftdi-elan.c
index f21bf5160f8..32c47fbee28 100644
--- a/drivers/usb/misc/ftdi-elan.c
+++ b/drivers/usb/misc/ftdi-elan.c
@@ -45,6 +45,7 @@
 #include <linux/module.h>
 #include <linux/kref.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 #include <asm/uaccess.h>
 #include <linux/usb.h>
 #include <linux/workqueue.h>
@@ -623,22 +624,30 @@ static void ftdi_elan_status_work(struct work_struct *work)
 */
 static int ftdi_elan_open(struct inode *inode, struct file *file)
 {
-        int subminor = iminor(inode);
-        struct usb_interface *interface = usb_find_interface(&ftdi_elan_driver,
-                subminor);
+	int subminor;
+	struct usb_interface *interface;
+
+	lock_kernel();
+        subminor = iminor(inode);
+        interface = usb_find_interface(&ftdi_elan_driver, subminor);
+
         if (!interface) {
+		unlock_kernel();
                 printk(KERN_ERR "can't find device for minor %d\n", subminor);
                 return -ENODEV;
         } else {
                 struct usb_ftdi *ftdi = usb_get_intfdata(interface);
                 if (!ftdi) {
+			unlock_kernel();
                         return -ENODEV;
                 } else {
                         if (down_interruptible(&ftdi->sw_lock)) {
+				unlock_kernel();
                                 return -EINTR;
                         } else {
                                 ftdi_elan_get_kref(ftdi);
                                 file->private_data = ftdi;
+				unlock_kernel();
                                 return 0;
                         }
                 }
diff --git a/drivers/usb/misc/idmouse.c b/drivers/usb/misc/idmouse.c
index a54c3cb804c..68df9ac7669 100644
--- a/drivers/usb/misc/idmouse.c
+++ b/drivers/usb/misc/idmouse.c
@@ -24,6 +24,7 @@
 #include <linux/module.h>
 #include <linux/completion.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 #include <asm/uaccess.h>
 #include <linux/usb.h>
 
@@ -226,16 +227,20 @@ static int idmouse_open(struct inode *inode, struct file *file)
 	struct usb_interface *interface;
 	int result;
 
+	lock_kernel();
 	/* get the interface from minor number and driver information */
 	interface = usb_find_interface (&idmouse_driver, iminor (inode));
-	if (!interface)
+	if (!interface) {
+		unlock_kernel();
 		return -ENODEV;
+	}
 
 	mutex_lock(&open_disc_mutex);
 	/* get the device information block from the interface */
 	dev = usb_get_intfdata(interface);
 	if (!dev) {
 		mutex_unlock(&open_disc_mutex);
+		unlock_kernel();
 		return -ENODEV;
 	}
 
@@ -272,6 +277,7 @@ error:
 
 	/* unlock this device */
 	mutex_unlock(&dev->lock);
+	unlock_kernel();
 	return result;
 }
 
diff --git a/drivers/usb/misc/iowarrior.c b/drivers/usb/misc/iowarrior.c
index 5206423211f..d3c85236388 100644
--- a/drivers/usb/misc/iowarrior.c
+++ b/drivers/usb/misc/iowarrior.c
@@ -602,10 +602,12 @@ static int iowarrior_open(struct inode *inode, struct file *file)
 
 	dbg("%s", __func__);
 
+	lock_kernel();
 	subminor = iminor(inode);
 
 	interface = usb_find_interface(&iowarrior_driver, subminor);
 	if (!interface) {
+		unlock_kernel();
 		err("%s - error, can't find device for minor %d", __func__,
 		    subminor);
 		return -ENODEV;
@@ -615,6 +617,7 @@ static int iowarrior_open(struct inode *inode, struct file *file)
 	dev = usb_get_intfdata(interface);
 	if (!dev) {
 		mutex_unlock(&iowarrior_open_disc_lock);
+		unlock_kernel();
 		return -ENODEV;
 	}
 
@@ -641,6 +644,7 @@ static int iowarrior_open(struct inode *inode, struct file *file)
 
 out:
 	mutex_unlock(&dev->mutex);
+	unlock_kernel();
 	return retval;
 }
 
diff --git a/drivers/usb/misc/ldusb.c b/drivers/usb/misc/ldusb.c
index 7c0bd13eccb..8de32df5978 100644
--- a/drivers/usb/misc/ldusb.c
+++ b/drivers/usb/misc/ldusb.c
@@ -33,6 +33,7 @@
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 
 #include <asm/uaccess.h>
 #include <linux/input.h>
@@ -296,12 +297,14 @@ static int ld_usb_open(struct inode *inode, struct file *file)
 	int retval;
 	struct usb_interface *interface;
 
+	lock_kernel();
 	nonseekable_open(inode, file);
 	subminor = iminor(inode);
 
 	interface = usb_find_interface(&ld_usb_driver, subminor);
 
 	if (!interface) {
+		unlock_kernel();
 		err("%s - error, can't find device for minor %d\n",
 		     __func__, subminor);
 		return -ENODEV;
@@ -309,12 +312,16 @@ static int ld_usb_open(struct inode *inode, struct file *file)
 
 	dev = usb_get_intfdata(interface);
 
-	if (!dev)
+	if (!dev) {
+		unlock_kernel();
 		return -ENODEV;
+	}
 
 	/* lock this device */
-	if (mutex_lock_interruptible(&dev->mutex))
+	if (mutex_lock_interruptible(&dev->mutex)) {
+		unlock_kernel();
 		return -ERESTARTSYS;
+	}
 
 	/* allow opening only once */
 	if (dev->open_count) {
@@ -353,6 +360,7 @@ static int ld_usb_open(struct inode *inode, struct file *file)
 
 unlock_exit:
 	mutex_unlock(&dev->mutex);
+	unlock_kernel();
 
 	return retval;
 }
diff --git a/drivers/usb/misc/legousbtower.c b/drivers/usb/misc/legousbtower.c
index 3d4378fb441..94e1b84134d 100644
--- a/drivers/usb/misc/legousbtower.c
+++ b/drivers/usb/misc/legousbtower.c
@@ -82,6 +82,7 @@
 #include <linux/module.h>
 #include <linux/completion.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 #include <asm/uaccess.h>
 #include <linux/usb.h>
 #include <linux/poll.h>
@@ -345,6 +346,7 @@ static int tower_open (struct inode *inode, struct file *file)
 
 	dbg(2, "%s: enter", __func__);
 
+	lock_kernel();
 	nonseekable_open(inode, file);
 	subminor = iminor(inode);
 
@@ -430,6 +432,7 @@ unlock_exit:
 	mutex_unlock(&dev->lock);
 
 exit:
+	unlock_kernel();
 	dbg(2, "%s: leave, return value %d ", __func__, retval);
 
 	return retval;
diff --git a/drivers/usb/misc/rio500.c b/drivers/usb/misc/rio500.c
index 17e4eecaee7..47ce46bb5b0 100644
--- a/drivers/usb/misc/rio500.c
+++ b/drivers/usb/misc/rio500.c
@@ -77,7 +77,7 @@ static struct rio_usb_data rio_instance;
 static int open_rio(struct inode *inode, struct file *file)
 {
 	struct rio_usb_data *rio = &rio_instance;
-
+	lock_kernel();
 	mutex_lock(&(rio->lock));
 
 	if (rio->isopen || !rio->present) {
@@ -91,6 +91,7 @@ static int open_rio(struct inode *inode, struct file *file)
 	mutex_unlock(&(rio->lock));
 
 	dev_info(&rio->rio_dev->dev, "Rio opened.\n");
+	unlock_kernel();
 
 	return 0;
 }
diff --git a/drivers/usb/misc/sisusbvga/sisusb.c b/drivers/usb/misc/sisusbvga/sisusb.c
index bb0b315b521..3991655f8f0 100644
--- a/drivers/usb/misc/sisusbvga/sisusb.c
+++ b/drivers/usb/misc/sisusbvga/sisusb.c
@@ -2416,21 +2416,28 @@ sisusb_open(struct inode *inode, struct file *file)
 	struct usb_interface *interface;
 	int subminor = iminor(inode);
 
-	if (!(interface = usb_find_interface(&sisusb_driver, subminor)))
+	lock_kernel();
+	if (!(interface = usb_find_interface(&sisusb_driver, subminor))) {
+		unlock_kernel();
 		return -ENODEV;
+	}
 
-	if (!(sisusb = usb_get_intfdata(interface)))
+	if (!(sisusb = usb_get_intfdata(interface))) {
+		unlock_kernel();
 		return -ENODEV;
+	}
 
 	mutex_lock(&sisusb->lock);
 
 	if (!sisusb->present || !sisusb->ready) {
 		mutex_unlock(&sisusb->lock);
+		unlock_kernel();
 		return -ENODEV;
 	}
 
 	if (sisusb->isopen) {
 		mutex_unlock(&sisusb->lock);
+		unlock_kernel();
 		return -EBUSY;
 	}
 
@@ -2439,11 +2446,13 @@ sisusb_open(struct inode *inode, struct file *file)
 			if (sisusb_init_gfxdevice(sisusb, 0)) {
 				mutex_unlock(&sisusb->lock);
 				dev_err(&sisusb->sisusb_dev->dev, "Failed to initialize device\n");
+				unlock_kernel();
 				return -EIO;
 			}
 		} else {
 			mutex_unlock(&sisusb->lock);
 			dev_err(&sisusb->sisusb_dev->dev, "Device not attached to USB 2.0 hub\n");
+			unlock_kernel();
 			return -EIO;
 		}
 	}
@@ -2456,6 +2465,7 @@ sisusb_open(struct inode *inode, struct file *file)
 	file->private_data = sisusb;
 
 	mutex_unlock(&sisusb->lock);
+	unlock_kernel();
 
 	return 0;
 }
diff --git a/drivers/usb/misc/usblcd.c b/drivers/usb/misc/usblcd.c
index 499d7508be9..90aede90553 100644
--- a/drivers/usb/misc/usblcd.c
+++ b/drivers/usb/misc/usblcd.c
@@ -74,10 +74,12 @@ static int lcd_open(struct inode *inode, struct file *file)
 	struct usb_interface *interface;
 	int subminor, r;
 
+	lock_kernel();
 	subminor = iminor(inode);
 
 	interface = usb_find_interface(&lcd_driver, subminor);
 	if (!interface) {
+		unlock_kernel();
 		err ("USBLCD: %s - error, can't find device for minor %d",
 		     __func__, subminor);
 		return -ENODEV;
@@ -87,6 +89,7 @@ static int lcd_open(struct inode *inode, struct file *file)
 	dev = usb_get_intfdata(interface);
 	if (!dev) {
 		mutex_unlock(&open_disc_mutex);
+		unlock_kernel();
 		return -ENODEV;
 	}
 
@@ -98,11 +101,13 @@ static int lcd_open(struct inode *inode, struct file *file)
 	r = usb_autopm_get_interface(interface);
 	if (r < 0) {
 		kref_put(&dev->kref, lcd_delete);
+		unlock_kernel();
 		return r;
 	}
 
 	/* save our object in the file's private structure */
 	file->private_data = dev;
+	unlock_kernel();
 
 	return 0;
 }
diff --git a/drivers/usb/misc/vstusb.c b/drivers/usb/misc/vstusb.c
index 874c81bb27b..b787b25d4cc 100644
--- a/drivers/usb/misc/vstusb.c
+++ b/drivers/usb/misc/vstusb.c
@@ -27,6 +27,7 @@
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 #include <linux/uaccess.h>
 #include <linux/usb.h>
 
@@ -103,19 +104,23 @@ static int vstusb_open(struct inode *inode, struct file *file)
 	struct vstusb_device *vstdev;
 	struct usb_interface *interface;
 
+	lock_kernel();
 	interface = usb_find_interface(&vstusb_driver, iminor(inode));
 
 	if (!interface) {
 		printk(KERN_ERR KBUILD_MODNAME
 		       ": %s - error, can't find device for minor %d\n",
 		       __func__, iminor(inode));
+		unlock_kernel();
 		return -ENODEV;
 	}
 
 	vstdev = usb_get_intfdata(interface);
 
-	if (!vstdev)
+	if (!vstdev) {
+		unlock_kernel();
 		return -ENODEV;
+	}
 
 	/* lock this device */
 	mutex_lock(&vstdev->lock);
@@ -123,6 +128,7 @@ static int vstusb_open(struct inode *inode, struct file *file)
 	/* can only open one time */
 	if ((!vstdev->present) || (vstdev->isopen)) {
 		mutex_unlock(&vstdev->lock);
+		unlock_kernel();
 		return -EBUSY;
 	}
 
@@ -137,6 +143,7 @@ static int vstusb_open(struct inode *inode, struct file *file)
 	dev_dbg(&vstdev->usb_dev->dev, "%s: opened\n", __func__);
 
 	mutex_unlock(&vstdev->lock);
+	unlock_kernel();
 
 	return 0;
 }
diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c
index 61522787f39..e94176bfd27 100644
--- a/drivers/usb/usb-skeleton.c
+++ b/drivers/usb/usb-skeleton.c
@@ -18,6 +18,7 @@
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/kref.h>
+#include <linux/smp_lock.h>
 #include <linux/uaccess.h>
 #include <linux/usb.h>
 #include <linux/mutex.h>
@@ -90,6 +91,7 @@ static int skel_open(struct inode *inode, struct file *file)
 	int subminor;
 	int retval = 0;
 
+	lock_kernel();
 	subminor = iminor(inode);
 
 	interface = usb_find_interface(&skel_driver, subminor);
@@ -135,6 +137,7 @@ static int skel_open(struct inode *inode, struct file *file)
 	mutex_unlock(&dev->io_mutex);
 
 exit:
+	unlock_kernel();
 	return retval;
 }