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Commit 24e9a47e authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab
Browse files

[media] v4l2-async: Don't use dynamic static allocation 



Dynamic static allocation is evil, as Kernel stack is too low, and
compilation complains about it on some archs:
	drivers/media/v4l2-core/v4l2-async.c:238:1: warning: 'v4l2_async_notifier_unregister' uses dynamic stack allocation [enabled by default]
Instead, let's enforce a limit for the buffer.
In this specific case, there's a hard limit imposed by V4L2_MAX_SUBDEVS,
with is currently 128. That means that the buffer size can be up to
128x8 = 1024 bytes (on a 64bits kernel), with is too big for stack.
Worse than that, someone could increase it and cause real troubles.
So, let's use dynamically allocated data, instead.

Signed-off-by: default avatarMauro Carvalho Chehab <m.chehab@samsung.com>
Reviewed-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: default avatarMauro Carvalho Chehab <m.chehab@samsung.com>
parent 278ba83a

drivers/media/v4l2-core/v4l2-async.c

+27 −3
Original line number Diff line number Diff line
@@ -189,30 +189,53 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier) 
	struct v4l2_subdev *sd, *tmp;

	unsigned int notif_n_subdev = notifier->num_subdevs;

	unsigned int n_subdev = min(notif_n_subdev, V4L2_MAX_SUBDEVS);

	struct device *dev[n_subdev];

	struct device **dev;

	int i = 0;



	if (!notifier->v4l2_dev)

		return;



	dev = kmalloc(n_subdev * sizeof(*dev), GFP_KERNEL);

	if (!dev) {

		dev_err(notifier->v4l2_dev->dev,

			"Failed to allocate device cache!\n");

	}



	mutex_lock(&list_lock);



	list_del(&notifier->list);



	list_for_each_entry_safe(sd, tmp, &notifier->done, async_list) {

		dev[i] = get_device(sd->dev);

		struct device *d;



		d = get_device(sd->dev);



		v4l2_async_cleanup(sd);



		/* If we handled USB devices, we'd have to lock the parent too */

		device_release_driver(dev[i++]);

		device_release_driver(d);



		if (notifier->unbind)

			notifier->unbind(notifier, sd, sd->asd);



		/*

		 * Store device at the device cache, in order to call

		 * put_device() on the final step

		 */

		if (dev)

			dev[i++] = d;

		else

			put_device(d);

	}



	mutex_unlock(&list_lock);



	/*

	 * Call device_attach() to reprobe devices

	 *

	 * NOTE: If dev allocation fails, i is 0, and the whole loop won't be

	 * executed.

	 */

	while (i--) {

		struct device *d = dev[i];
@@ -228,6 +251,7 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier) 
		}

		put_device(d);

	}

	kfree(dev);



	notifier->v4l2_dev = NULL;