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media: v4l2-ctrl: Lock main_hdl on operations of requests_queued.

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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>
This commit is contained in:
Pi-Hsun Shih 2019-11-10 07:29:10 +01:00 committed by Mauro Carvalho Chehab
parent 2df200ab23
commit df4a3e7f88
1 changed files with 7 additions and 0 deletions
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7
drivers/media/v4l2-core/v4l2-ctrls.c
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@ -3302,6 +3302,7 @@ 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;
@ -3333,18 +3334,22 @@ 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)
@ -4298,9 +4303,11 @@ 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);
}