Fix oops in pwc v4l driver

The pwc driver is defficient in locking, which can trigger an oops
when disconnecting.

Adrian Bunk:
Backported to 2.6.16.
Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Adrian Bunk <bunk@kernel.org>

drivers/usb/media/pwc/pwc-if.c

@@ -914,29 +914,49 @@ static int pwc_isoc_init(struct pwc_device *pdev)
 	return 0;
 }
 
-static void pwc_isoc_cleanup(struct pwc_device *pdev)
+static void pwc_iso_stop(struct pwc_device *pdev)
 {
 	int i;
 
-	Trace(TRACE_OPEN, ">> pwc_isoc_cleanup()\n");
-	if (pdev == NULL)
-		return;
-
 	/* Unlinking ISOC buffers one by one */
 	for (i = 0; i < MAX_ISO_BUFS; i++) {
 		struct urb *urb;
 
 		urb = pdev->sbuf[i].urb;
 		if (urb != 0) {
-			if (pdev->iso_init) {
-				Trace(TRACE_MEMORY, "Unlinking URB %p\n", urb);
-				usb_kill_urb(urb);
-			}
+			Trace(TRACE_MEMORY, "Unlinking URB %p\n", urb);
+			usb_kill_urb(urb);
+		}
+	}
+}
+
+static void pwc_iso_free(struct pwc_device *pdev)
+{
+	int i;
+
+	/* Freeing ISOC buffers one by one */
+	for (i = 0; i < MAX_ISO_BUFS; i++) {
+		struct urb *urb;
+
+		urb = pdev->sbuf[i].urb;
+		if (urb != 0) {
 			Trace(TRACE_MEMORY, "Freeing URB\n");
 			usb_free_urb(urb);
 			pdev->sbuf[i].urb = NULL;
 		}
 	}
+}
+
+void pwc_isoc_cleanup(struct pwc_device *pdev)
+{
+	Trace(TRACE_OPEN, ">> pwc_isoc_cleanup()\n");
+	if (pdev == NULL)
+		return;
+	if (pdev->iso_init == 0)
+		return;
+
+	pwc_iso_stop(pdev);
+	pwc_iso_free(pdev);
 
 	/* Stop camera, but only if we are sure the camera is still there (unplug
 	   is signalled by EPIPE) 
@@ -1115,6 +1135,7 @@ static int pwc_video_close(struct inode *inode, struct file *file)
 
 	Trace(TRACE_OPEN, ">> video_close called(vdev = 0x%p).\n", vdev);
 
+	lock_kernel();
 	pdev = (struct pwc_device *)vdev->priv;
 	if (pdev->vopen == 0)
 		Info("video_close() called on closed device?\n");
@@ -1146,7 +1167,6 @@ static int pwc_video_close(struct inode *inode, struct file *file)
 	pwc_isoc_cleanup(pdev);
 	pwc_free_buffers(pdev);
 
-	lock_kernel();
 	/* Turn off LEDS and power down camera, but only when not unplugged */
 	if (!pdev->unplugged) {
 		/* Turn LEDs off */
@@ -1192,7 +1212,7 @@ static ssize_t pwc_video_read(struct file *file, char __user * buf,
 	struct pwc_device *pdev;
 	int noblock = file->f_flags & O_NONBLOCK;
 	DECLARE_WAITQUEUE(wait, current);
-        int bytes_to_read;
+	int bytes_to_read, rv = 0;
 
 	Trace(TRACE_READ, "video_read(0x%p, %p, %zu) called.\n", vdev, buf, count);
 	if (vdev == NULL)
@@ -1200,8 +1220,12 @@ static ssize_t pwc_video_read(struct file *file, char __user * buf,
 	pdev = vdev->priv;
 	if (pdev == NULL)
 		return -EFAULT;
-	if (pdev->error_status)
-		return -pdev->error_status; /* Something happened, report what. */
+
+	down(&pdev->modlock);
+	if (pdev->error_status) {
+		rv = -pdev->error_status; /* Something happened, report what. */
+		goto err_out;
+	}
 
 	/* In case we're doing partial reads, we don't have to wait for a frame */
 	if (pdev->image_read_pos == 0) {
@@ -1212,17 +1236,20 @@ static ssize_t pwc_video_read(struct file *file, char __user * buf,
 			if (pdev->error_status) {
 				remove_wait_queue(&pdev->frameq, &wait);
 				set_current_state(TASK_RUNNING);
-				return -pdev->error_status ;
+				rv = -pdev->error_status ;
+				goto err_out;
 			}
 	                if (noblock) {
 	                	remove_wait_queue(&pdev->frameq, &wait);
 	                	set_current_state(TASK_RUNNING);
-	                	return -EWOULDBLOCK;
+				rv = -EWOULDBLOCK;
+				goto err_out;
 	                }
 	                if (signal_pending(current)) {
 	                	remove_wait_queue(&pdev->frameq, &wait);
 	                	set_current_state(TASK_RUNNING);
-	                	return -ERESTARTSYS;
+				rv = -ERESTARTSYS;
+				goto err_out;
 	                }
 	                schedule();
 	               	set_current_state(TASK_INTERRUPTIBLE);
@@ -1231,8 +1258,10 @@ static ssize_t pwc_video_read(struct file *file, char __user * buf,
 		set_current_state(TASK_RUNNING);
                                                                                                                                                                                 
 		/* Decompress and release frame */
-		if (pwc_handle_frame(pdev))
-			return -EFAULT;
+		if (pwc_handle_frame(pdev)) {
+			rv = -EFAULT;
+			goto err_out;
+		}
 	}
 
 	Trace(TRACE_READ, "Copying data to user space.\n");
@@ -1244,14 +1273,20 @@ static ssize_t pwc_video_read(struct file *file, char __user * buf,
 	/* copy bytes to user space; we allow for partial reads */
 	if (count + pdev->image_read_pos > bytes_to_read)
 		count = bytes_to_read - pdev->image_read_pos;
-	if (copy_to_user(buf, pdev->image_ptr[pdev->fill_image] + pdev->image_read_pos, count))
-		return -EFAULT;
+	if (copy_to_user(buf, pdev->image_ptr[pdev->fill_image] + pdev->image_read_pos, count)) {
+		rv = -EFAULT;
+		goto err_out;
+	}
 	pdev->image_read_pos += count;
 	if (pdev->image_read_pos >= bytes_to_read) { /* All data has been read */
 		pdev->image_read_pos = 0;
 		pwc_next_image(pdev);
 	}
+	up(&pdev->modlock);
 	return count;
+err_out:
+	up(&pdev->modlock);
+	return rv;
 }
 
 static unsigned int pwc_video_poll(struct file *file, poll_table *wait)
@@ -1615,7 +1650,20 @@ static int pwc_video_do_ioctl(struct inode *inode, struct file *file,
 static int pwc_video_ioctl(struct inode *inode, struct file *file,
 			   unsigned int cmd, unsigned long arg)
 {
-	return video_usercopy(inode, file, cmd, arg, pwc_video_do_ioctl);
+	struct video_device *vdev = file->private_data;
+	struct pwc_device *pdev;
+	int r = -ENODEV;
+
+	if (!vdev)
+		goto out;
+	pdev = vdev->priv;
+
+	down(&pdev->modlock);
+	if (!pdev->unplugged)
+		r = video_usercopy(inode, file, cmd, arg, pwc_video_do_ioctl);
+	up(&pdev->modlock);
+out:
+	return r;
 }
 
 
@@ -2007,7 +2055,10 @@ static void usb_pwc_disconnect(struct usb_interface *intf)
 	wake_up_interruptible(&pdev->frameq);
 	/* Wait until device is closed */
 	if(pdev->vopen) {
+		down(&pdev->modlock);
 		pdev->unplugged = 1;
+		up(&pdev->modlock);
+		pwc_iso_stop(pdev);
 	} else {
 		/* Device is closed, so we can safely unregister it */
 		Trace(TRACE_PROBE, "Unregistering video device in disconnect().\n");
@@ -2025,7 +2076,6 @@ static void usb_pwc_disconnect(struct usb_interface *intf)
 	unlock_kernel();
 }
 
-
 /* *grunt* We have to do atoi ourselves :-( */
 static int pwc_atoi(const char *s)
 {