lkml.org 
[lkml]   [2013]   [Dec]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 3.12 197/212] media: v4l2-async: Dont use dynamic static allocation
Date
3.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mauro Carvalho Chehab <m.chehab@samsung.com>

commit 24e9a47e14f0a97ee97abc3dd86b2ef254448a17 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/media/v4l2-core/v4l2-async.c | 30 +++++++++++++++++++++++++++---
1 file changed, 27 insertions(+), 3 deletions(-)

--- a/drivers/media/v4l2-core/v4l2-async.c
+++ b/drivers/media/v4l2-core/v4l2-async.c
@@ -189,30 +189,53 @@ void v4l2_async_notifier_unregister(stru
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(stru
}
put_device(d);
}
+ kfree(dev);

notifier->v4l2_dev = NULL;




\
 
 \ /
  Last update: 2013-12-03 00:41    [W:1.930 / U:0.684 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site