[PATCH v16 05/32] v4l: async: Correctly serialise async sub-device unregistration

Sakari Ailus
2017-10-26T07:53:15Z

The check whether an async sub-device is bound to a notifier was performed
without list_lock held, making it possible for another process to
unbind the async sub-device before the sub-device unregistration function
proceeds to take the lock.

Fix this by first acquiring the lock and then proceeding with the check.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
---
drivers/media/v4l2-core/v4l2-async.c | 18 +++++++-----------
1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
index 4924481451ca..cde2cf2ab4b0 100644
--- a/drivers/media/v4l2-core/v4l2-async.c
+++ b/drivers/media/v4l2-core/v4l2-async.c
@@ -298,20 +298,16 @@ EXPORT_SYMBOL(v4l2_async_register_subdev);

void v4l2_async_unregister_subdev(struct v4l2_subdev *sd)
{
- struct v4l2_async_notifier *notifier = sd->notifier;
-
- if (!sd->asd) {
- if (!list_empty(&sd->async_list))
- v4l2_async_cleanup(sd);
- return;
- }
-
mutex_lock(&list_lock);

- list_add(&sd->asd->list, &notifier->waiting);
+ if (sd->asd) {
+ struct v4l2_async_notifier *notifier = sd->notifier;

- if (notifier->unbind)
- notifier->unbind(notifier, sd, sd->asd);
+ list_add(&sd->asd->list, &notifier->waiting);
+
+ if (notifier->unbind)
+ notifier->unbind(notifier, sd, sd->asd);
+ }

v4l2_async_cleanup(sd);

--
2.11.0