In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: hcisync: hcicmdsyncqueue_once() return -EEXIST if exists
hcicmdsyncqueueonce() needs to indicate whether a queue item was added, so caller can know if callbacks are called, so it can avoid leaking resources.
Change the function to return -EEXIST if queue item already exists.
Modify all callsites to handle that.