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

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The commit 68f83057b913("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: cheung 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: 68f83057b913("workqueue: Reap workers via kthread_stop() and remove detach_completion")
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Lai Jiangshan 2025-01-23 16:25:35 +08:00 • committed by Tejun Heo
parent ab18b8fff1
commit e769461101
1 changed files with 6 additions and 6 deletions
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12
kernel/workqueue.c
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@ -3516,12 +3516,6 @@ repeat:
}
}
/*
* 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 @@ repeat:
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);
}