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[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: Mauro Carvalho Chehab <m.chehab@samsung.com>
Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
This commit is contained in:
Mauro Carvalho Chehab 2013-11-02 06:20:16 -03:00
parent 278ba83a3a
commit 24e9a47e14
1 changed files with 27 additions and 3 deletions
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30
drivers/media/v4l2-core/v4l2-async.c
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@ -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;