[PATCH] USB: error handling of open of acm driver

this adds error handling to the open method of the cdc acm driver.
The change set is relative to my last patch rewriting probe.
  - add error handling to open method
Signed-off-by: Oliver Neukum <oliver@neukum.name>
Signed-off-by: Vojtech Pavlik <vojtech@suse.cz>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/usb/class/cdc-acm.c

@@ -27,6 +27,7 @@
  *	v0.22 - probe only the control interface. if usbcore doesn't choose the
  *		config we want, sysadmin changes bConfigurationValue in sysfs.
  *	v0.23 - use softirq for rx processing, as needed by tty layer
+ *	v0.24 - change probe method to evaluate CDC union descriptor
  */
 
 /*
@@ -73,6 +74,8 @@ static struct usb_driver acm_driver;
 static struct tty_driver *acm_tty_driver;
 static struct acm *acm_table[ACM_TTY_MINORS];
 
+static DECLARE_MUTEX(open_sem);
+
 #define ACM_READY(acm)	(acm && acm->dev && acm->used)
 
 /*
@@ -256,22 +259,23 @@ static int acm_tty_open(struct tty_struct *tty, struct file *filp)
 	tty->driver_data = acm;
 	acm->tty = tty;
 
-        lock_kernel();
+        down(&open_sem);
 
-	if (acm->used++) {
-                unlock_kernel();
-                return 0;
+	if (acm->used) {
+		goto done;
         }
 
-        unlock_kernel();
-
 	acm->ctrlurb->dev = acm->dev;
-	if (usb_submit_urb(acm->ctrlurb, GFP_KERNEL))
+	if (usb_submit_urb(acm->ctrlurb, GFP_KERNEL)) {
 		dbg("usb_submit_urb(ctrl irq) failed");
+		goto bail_out;
+	}
 
 	acm->readurb->dev = acm->dev;
-	if (usb_submit_urb(acm->readurb, GFP_KERNEL))
+	if (usb_submit_urb(acm->readurb, GFP_KERNEL)) {
 		dbg("usb_submit_urb(read bulk) failed");
+		goto bail_out_and_unlink;
+	}
 
 	acm_set_control(acm, acm->ctrlout = ACM_CTRL_DTR | ACM_CTRL_RTS);
 
@@ -279,7 +283,16 @@ static int acm_tty_open(struct tty_struct *tty, struct file *filp)
 	   otherwise it is scheduled, and with high data rates data can get lost. */
 	tty->low_latency = 1;
 
+done:
+	acm->used++;
+	up(&open_sem);
 	return 0;
+
+bail_out_and_unlink:
+	usb_unlink_urb(acm->ctrlurb);
+bail_out:
+	up(&open_sem);
+	return -EIO;
 }
 
 static void acm_tty_close(struct tty_struct *tty, struct file *filp)
@@ -289,6 +302,7 @@ static void acm_tty_close(struct tty_struct *tty, struct file *filp)
 	if (!acm || !acm->used)
 		return;
 
+	down(&open_sem);
 	if (!--acm->used) {
 		if (acm->dev) {
 			acm_set_control(acm, acm->ctrlout = 0);
@@ -304,6 +318,7 @@ static void acm_tty_close(struct tty_struct *tty, struct file *filp)
 			kfree(acm);
 		}
 	}
+	up(&open_sem);
 }
 
 static int acm_tty_write(struct tty_struct *tty, int from_user, const unsigned char *buf, int count)