Re: [PATCH] workqueue: Fix double kfree(rescuer) in destroy_workqueue()

[qzhang2]

Sorry I didn't describe clearly

I describe the meaning as follows:

 destroy_workqueue:
	if(wq->rescuer)
		struct worker *rescuer = wq->rescuer
		kfree(rescuer)  //first kfree
		

        if (!(wq->flags & WQ_UNBOUND))
		call_rcu(&wq->rcu, rcu_free_wq)
			
		rcu_free_wq
			kfree(wq->rescuer) //second kfree

there are double free.

On 5/24/20 11:33 PM, Markus Elfring wrote:
> > When destroy_workqueue if rescuer worker exist,wq->rescuer pointer be
> > kfree. if sanity checks passed. the func call_rcu(&wq->rcu, rcu_free_wq)
> > will be called if the wq->flags & WQ_UNBOUND is false,in rcu_free_wq
> > func wq->rescuer pointer was kfree again.
>
> 1. I suggest to improve also this change description.
>     Do you try to explain here that a call of the function âfree_workqueue_attrsâ
>     (or âfree_percpuâ) would perform sufficient clean-up of system resources
>     in this use case?
>
> 2. You proposed to delete the function call âkfree(wq->rescuer)â from
>     the implementation of the function ârcu_free_wqâ.
>     https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/kernel/workqueue.c?id=c11d28ab4a691736e30b49813fb801847bd44e83#n3482
>     https://elixir.bootlin.com/linux/v5.7-rc6/source/kernel/workqueue.c#L3482
>
>     This function name should be specified also in the patch subject,
>     shouldn't it?
>
> 3. Would you like to add the tag âFixesâ to the commit message?
>
> Regards,
> Markus