V4L/DVB (9690): gspca: Lock the subdrivers via module_get/put.

The previous subdriver protection against rmmod was done via the
file operations table in the device descriptor. On device disconnection
while streaming, the device structure was freed at close time, and the
module_put still used the module name in the freed area.
Now, explicit module get/put are done on open and close.
Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/gspca/gspca.c

@@ -874,6 +874,13 @@ static int dev_open(struct inode *inode, struct file *file)
 		ret = -EBUSY;
 		goto out;
 	}
+
+	/* protect the subdriver against rmmod */
+	if (!try_module_get(gspca_dev->module)) {
+		ret = -ENODEV;
+		goto out;
+	}
+
 	gspca_dev->users++;
 
 	/* one more user */
@@ -920,6 +927,7 @@ static int dev_close(struct inode *inode, struct file *file)
 		gspca_dev->memory = GSPCA_MEMORY_NO;
 	}
 	file->private_data = NULL;
+	module_put(gspca_dev->module);
 	mutex_unlock(&gspca_dev->queue_lock);
 
 	PDEBUG(D_STREAM, "close done");
@@ -1870,9 +1878,8 @@ int gspca_dev_probe(struct usb_interface *intf,
 	/* init video stuff */
 	memcpy(&gspca_dev->vdev, &gspca_template, sizeof gspca_template);
 	gspca_dev->vdev.parent = &dev->dev;
-	memcpy(&gspca_dev->fops, &dev_fops, sizeof gspca_dev->fops);
-	gspca_dev->vdev.fops = &gspca_dev->fops;
-	gspca_dev->fops.owner = module;		/* module protection */
+	gspca_dev->vdev.fops = &dev_fops;
+	gspca_dev->module = module;
 	gspca_dev->present = 1;
 	ret = video_register_device(&gspca_dev->vdev,
 				  VFL_TYPE_GRABBER,

drivers/media/video/gspca/gspca.h

@@ -121,7 +121,7 @@ struct gspca_frame {
 
 struct gspca_dev {
 	struct video_device vdev;	/* !! must be the first item */
-	struct file_operations fops;
+	struct module *module;		/* subdriver handling the device */
 	struct usb_device *dev;
 	struct kref kref;
 	struct file *capt_file;		/* file doing video capture */