linux-kernel - [PATCH 4.9 098/117] kthread_worker: prevent queuing delayed work from timer

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Message-Id: <20201109125030.351958579@linuxfoundation.org>
Date:   Mon,  9 Nov 2020 13:55:24 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Zqiang <qiang.zhang@...driver.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Petr Mladek <pmladek@...e.com>, Tejun Heo <tj@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.9 098/117] kthread_worker: prevent queuing delayed work from timer_fn when it is being canceled

From: Zqiang <qiang.zhang@...driver.com>

commit 6993d0fdbee0eb38bfac350aa016f65ad11ed3b1 upstream.

There is a small race window when a delayed work is being canceled and
the work still might be queued from the timer_fn:

	CPU0						CPU1
kthread_cancel_delayed_work_sync()
   __kthread_cancel_work_sync()
     __kthread_cancel_work()
        work->canceling++;
					      kthread_delayed_work_timer_fn()
						   kthread_insert_work();

BUG: kthread_insert_work() should not get called when work->canceling is
set.

Signed-off-by: Zqiang <qiang.zhang@...driver.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Reviewed-by: Petr Mladek <pmladek@...e.com>
Acked-by: Tejun Heo <tj@...nel.org>
Cc: <stable@...r.kernel.org>
Link: https://lkml.kernel.org/r/20201014083030.16895-1-qiang.zhang@windriver.com
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/kthread.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -828,7 +828,8 @@ void kthread_delayed_work_timer_fn(unsig
 	/* Move the work from worker->delayed_work_list. */
 	WARN_ON_ONCE(list_empty(&work->node));
 	list_del_init(&work->node);
-	kthread_insert_work(worker, work, &worker->work_list);
+	if (!work->canceling)
+		kthread_insert_work(worker, work, &worker->work_list);
 
 	spin_unlock(&worker->lock);
 }