CVE-2024-56709

In the Linux kernel, the following vulnerability has been resolved:

io_uring: check if iowq is killed before queuing

task work can be executed after the task has gone through io_uring

termination, whether it's the final task_work run or the fallback path.

In this case, task work will find ->io_wq being already killed and

null'ed, which is a problem if it then tries to forward the request to

io_queue_iowq(). Make io_queue_iowq() fail requests in this case.

Note that it also checks PF_KTHREAD, because the user can first close

a DEFER_TASKRUN ring and shortly after kill the task, in which case

->iowq check would race.