6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
[ Upstream commit e76946110137703c16423baf6ee177b751a34b7e ]
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@xxxxxxxxx>
Cc: cheung wall <zzqq0103.hey@xxxxxxxxx>
Link: https://lore.kernel.org/lkml/CAKHoSAvP3iQW+GwmKzWjEAOoPvzeWeoMO0Gz7Pp3_4kxt-RMoA@xxxxxxxxxxxxxx/
Fixes: 68f83057b913("workqueue: Reap workers via kthread_stop() and remove detach_completion")
Signed-off-by: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
kernel/workqueue.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index cee65cb431081..a9d64e08dffc7 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3509,12 +3509,6 @@ 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.
@@ -3525,6 +3519,12 @@ 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);
}
--
2.39.5
