Re: [PATCH] [media] v4l2-async: Always unregister the subdev on failure

Javier Martinez Canillas
2016-05-11T16:22:55Z

Hello Alban,

On 05/11/2016 11:40 AM, Alban Bedel wrote:
> In v4l2_async_test_notify() if the registered_async callback or the
> complete notifier returns an error the subdev is not unregistered.
> This leave paths where v4l2_async_register_subdev() can fail but
> leave the subdev still registered.
>
> Add the required calls to v4l2_device_unregister_subdev() to plug
> these holes.
>
> Signed-off-by: Alban Bedel <alban.bedel@avionic-design.de>
> ---
> drivers/media/v4l2-core/v4l2-async.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> index ceb28d4..43393f8 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -121,13 +121,19 @@ static int v4l2_async_test_notify(struct v4l2_async_notifier *notifier,
>
> ret = v4l2_subdev_call(sd, core, registered_async);
> if (ret < 0 && ret != -ENOIOCTLCMD) {
> + v4l2_device_unregister_subdev(sd);
> if (notifier->unbind)
> notifier->unbind(notifier, sd, asd);
> return ret;
> }
>
> - if (list_empty(&notifier->waiting) && notifier->complete)
> - return notifier->complete(notifier);
> + if (list_empty(&notifier->waiting) && notifier->complete) {
> + ret = notifier->complete(notifier);
> + if (ret < 0) {
> + v4l2_device_unregister_subdev(sd);

Isn't a call to notifier->unbind() missing here as well?

Also, I think the error path is becoming too duplicated and complex, so
maybe we can have a single error path and use goto labels as is common
in Linux? For example something like the following (not tested) can be
squashed on top of your change:

diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
index 43393f8c1312..abe512d0b4cb 100644
--- a/drivers/media/v4l2-core/v4l2-async.c
+++ b/drivers/media/v4l2-core/v4l2-async.c
@@ -113,29 +113,28 @@ static int v4l2_async_test_notify(struct v4l2_async_notifier *notifier,
list_move(&sd->async_list, &notifier->done);

ret = v4l2_device_register_subdev(notifier->v4l2_dev, sd);
- if (ret < 0) {
- if (notifier->unbind)
- notifier->unbind(notifier, sd, asd);
- return ret;
- }
+ if (ret < 0)
+ goto err_subdev_register;

ret = v4l2_subdev_call(sd, core, registered_async);
- if (ret < 0 && ret != -ENOIOCTLCMD) {
- v4l2_device_unregister_subdev(sd);
- if (notifier->unbind)
- notifier->unbind(notifier, sd, asd);
- return ret;
- }
+ if (ret < 0 && ret != -ENOIOCTLCMD)
+ goto err_subdev_call;

if (list_empty(&notifier->waiting) && notifier->complete) {
ret = notifier->complete(notifier);
- if (ret < 0) {
- v4l2_device_unregister_subdev(sd);
- return ret;
- }
+ if (ret < 0)
+ goto err_subdev_call;
}

return 0;
+
+err_subdev_call:
+ v4l2_device_unregister_subdev(sd);
+err_subdev_register:
+ if (notifier->unbind)
+ notifier->unbind(notifier, sd, asd);
+
+ return ret;
}

static void v4l2_async_cleanup(struct v4l2_subdev *sd)

Best regards,
--
Javier Martinez Canillas
Open Source Group
Samsung Research America