Re: [PATCH] workqueue: Prevent a new work item from queueing into a destruction wq

[Tejun Heo]

On Mon, Dec 12, 2022 at 02:18:36PM +0800, Richard Clark wrote:
> Currently the __WQ_DRAINING is used to prevent a new work item from queueing
> to a draining workqueue, but this flag will be cleared before the end of a
> RCU grace period. Because the workqueue instance is actually freed after
> the RCU grace period, this fact results in an opening window in which a new
> work item can be queued into a destorying workqueue and be scheduled
> consequently, for instance, the below code snippet demos this accident:

I mean, this is just use-after-free. The same scenario can happen with
non-RCU frees or if there happens to be an RCU grace period inbetween. I'm
not sure what's being protected here.

Thanks.

-- 
tejun