[PATCH AUTOSEL 5.4 259/350] media: v4l2-ctrl: Lock main_hdl on operations of requests_queued.

Sasha Levin
2019-12-10T21:20:30Z

From: Pi-Hsun Shih <pihsun@chromium.org>

[ Upstream commit df4a3e7f88e3b0d7ae46d70b9ff8e3c0ea730785 ]

There's a race condition between the list_del_init in the
v4l2_ctrl_request_complete, and the list_add_tail in the
v4l2_ctrl_request_queue, since they can be called in different thread
and the requests_queued list is not protected by a lock. This can lead
to that the v4l2_ctrl_handler is still in the requests_queued list while
the request_is_queued is already set to false, which would cause
use-after-free if the v4l2_ctrl_handler is later released.

Fix this by locking the ->lock of main_hdl (which is the owner of the
requests_queued list) when doing list operations on the
->requests_queued list.

Signed-off-by: Pi-Hsun Shih <pihsun@chromium.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/media/v4l2-core/v4l2-ctrls.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
index 1d8f388246313..cd84dbbf6a890 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -3144,6 +3144,7 @@ static void v4l2_ctrl_request_queue(struct media_request_object *obj)
struct v4l2_ctrl_handler *prev_hdl = NULL;
struct v4l2_ctrl_ref *ref_ctrl, *ref_ctrl_prev = NULL;

+ mutex_lock(main_hdl->lock);
if (list_empty(&main_hdl->requests_queued))
goto queue;

@@ -3175,18 +3176,22 @@ static void v4l2_ctrl_request_queue(struct media_request_object *obj)
queue:
list_add_tail(&hdl->requests_queued, &main_hdl->requests_queued);
hdl->request_is_queued = true;
+ mutex_unlock(main_hdl->lock);
}

static void v4l2_ctrl_request_unbind(struct media_request_object *obj)
{
struct v4l2_ctrl_handler *hdl =
container_of(obj, struct v4l2_ctrl_handler, req_obj);
+ struct v4l2_ctrl_handler *main_hdl = obj->priv;

list_del_init(&hdl->requests);
+ mutex_lock(main_hdl->lock);
if (hdl->request_is_queued) {
list_del_init(&hdl->requests_queued);
hdl->request_is_queued = false;
}
+ mutex_unlock(main_hdl->lock);
}

static void v4l2_ctrl_request_release(struct media_request_object *obj)
@@ -4128,9 +4133,11 @@ void v4l2_ctrl_request_complete(struct media_request *req,
v4l2_ctrl_unlock(ctrl);
}

+ mutex_lock(main_hdl->lock);
WARN_ON(!hdl->request_is_queued);
list_del_init(&hdl->requests_queued);
hdl->request_is_queued = false;
+ mutex_unlock(main_hdl->lock);
media_request_object_complete(obj);
media_request_object_put(obj);
}
--
2.20.1