linux-kernel - [PATCH v2] workqueue: Fix race condition in wq->stats incrementation

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Message-ID: <20250423161742.14429-1-jiayuan.chen@linux.dev>
Date: Thu, 24 Apr 2025 00:17:42 +0800
From: Jiayuan Chen <jiayuan.chen@...ux.dev>
To: linux-kernel@...r.kernel.org
Cc: mrpre@....com,
	mkoutny@...e.com,
	Jiayuan Chen <jiayuan.chen@...ux.dev>,
	syzbot+01affb1491750534256d@...kaller.appspotmail.com,
	Tejun Heo <tj@...nel.org>,
	Lai Jiangshan <jiangshanlai@...il.com>
Subject: [PATCH v2] workqueue: Fix race condition in wq->stats incrementation

Fixed a race condition in incrementing wq->stats[PWQ_STAT_COMPLETED] by
moving the operation under pool->lock.

Reported-by: syzbot+01affb1491750534256d@...kaller.appspotmail.com
Signed-off-by: Jiayuan Chen <jiayuan.chen@...ux.dev>
---
 kernel/workqueue.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index cf6203282737..1ea62b8c76b3 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3241,7 +3241,7 @@ __acquires(&pool->lock)
 	 * point will only record its address.
 	 */
 	trace_workqueue_execute_end(work, worker->current_func);
-	pwq->stats[PWQ_STAT_COMPLETED]++;
+
 	lock_map_release(&lockdep_map);
 	if (!bh_draining)
 		lock_map_release(pwq->wq->lockdep_map);
@@ -3272,6 +3272,8 @@ __acquires(&pool->lock)
 
 	raw_spin_lock_irq(&pool->lock);
 
+	pwq->stats[PWQ_STAT_COMPLETED]++;
+
 	/*
 	 * In addition to %WQ_CPU_INTENSIVE, @worker may also have been marked
 	 * CPU intensive by wq_worker_tick() if @work hogged CPU longer than
-- 
2.47.1