linux-kernel - [PATCH] io_uring/sqpoll: annotate data race for access in debug check

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Message-ID: <20250108151052.7944-1-minhquangbui99@gmail.com>
Date: Wed,  8 Jan 2025 22:10:51 +0700
From: Bui Quang Minh <minhquangbui99@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Bui Quang Minh <minhquangbui99@...il.com>,
	Jens Axboe <axboe@...nel.dk>,
	Pavel Begunkov <asml.silence@...il.com>,
	io-uring@...r.kernel.org,
	syzbot+5988142e8a69a67b1418@...kaller.appspotmail.com
Subject: [PATCH] io_uring/sqpoll: annotate data race for access in debug check

sqd->thread must only be access while holding sqd->lock. In
io_sq_thread_stop, the sqd->thread access to wake up the sq thread is
placed while holding sqd->lock, but the access in debug check is not. As
this access if for debug check only, we can safely ignore the data race
here. So we annotate this access with data_race to silence KCSAN.

Reported-by: syzbot+5988142e8a69a67b1418@...kaller.appspotmail.com
Signed-off-by: Bui Quang Minh <minhquangbui99@...il.com>
---
 io_uring/sqpoll.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/io_uring/sqpoll.c b/io_uring/sqpoll.c
index 9e5bd79fd2b5..2088c56dbaa0 100644
--- a/io_uring/sqpoll.c
+++ b/io_uring/sqpoll.c
@@ -57,7 +57,7 @@ void io_sq_thread_park(struct io_sq_data *sqd)
 
 void io_sq_thread_stop(struct io_sq_data *sqd)
 {
-	WARN_ON_ONCE(sqd->thread == current);
+	WARN_ON_ONCE(data_race(sqd->thread) == current);
 	WARN_ON_ONCE(test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state));
 
 	set_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
-- 
2.43.0