Commit e7694611 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Tejun Heo
Browse files

workqueue: Put the pwq after detaching the rescuer from the pool 



The commit 68f83057("workqueue: Reap workers via kthread_stop() and
remove detach_completion") adds code to reap the normal workers but
mistakenly does not handle the rescuer and also removes the code waiting
for the rescuer in put_unbound_pool(), which caused a use-after-free bug
reported by Cheung Wall.

To avoid the use-after-free bug, the pool’s reference must be held until
the detachment is complete. Therefore, move the code that puts the pwq
after detaching the rescuer from the pool.

Reported-by: default avatarcheung wall <zzqq0103.hey@gmail.com>
Cc: cheung wall <zzqq0103.hey@gmail.com>
Link: https://lore.kernel.org/lkml/CAKHoSAvP3iQW+GwmKzWjEAOoPvzeWeoMO0Gz7Pp3_4kxt-RMoA@mail.gmail.com/


Fixes: 68f83057("workqueue: Reap workers via kthread_stop() and remove detach_completion")
Signed-off-by: default avatarLai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent ab18b8ff

kernel/workqueue.c

+6 −6
Original line number Diff line number Diff line
@@ -3516,12 +3516,6 @@ static int rescuer_thread(void *__rescuer) 
			}

		}



		/*

		 * Put the reference grabbed by send_mayday().  @pool won't

		 * go away while we're still attached to it.

		 */

		put_pwq(pwq);



		/*

		 * Leave this pool. Notify regular workers; otherwise, we end up

		 * with 0 concurrency and stalling the execution.
@@ -3532,6 +3526,12 @@ static int rescuer_thread(void *__rescuer) 


		worker_detach_from_pool(rescuer);



		/*

		 * Put the reference grabbed by send_mayday().  @pool might

		 * go away any time after it.

		 */

		put_pwq_unlocked(pwq);



		raw_spin_lock_irq(&wq_mayday_lock);

	}