commit e4956dc7a84da074fd8dc10f7abd147f15b3ae58
author Jens Axboe <axboe@kernel.dk> Tue Aug 13 06:10:59 2024 -0600
committer Jens Axboe <axboe@kernel.dk> Tue Aug 13 06:10:59 2024 -0600
tree f4251e7f5e8f5d12efcdd93d0e0994b48bb17150
parent 48cc7ecd3a68e0fbfa281ef1ed6f6b6cb7638390

io_uring/sqpoll: annotate debug task == current with data_race()

There's a debug check in io_sq_thread_park() checking if it's the SQPOLL
thread itself calling park. KCSAN warns about this, as we should not be
reading sqd->thread outside of sqd->lock.

Just silence this with data_race(). The pointer isn't used for anything
but this debug check.

Reported-by: syzbot+2b946a3fd80caf971b21@syzkaller.appspotmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/sqpoll.c

diff --git a/io_uring/sqpoll.c b/io_uring/sqpoll.c
index b3722e5..3b50dc9 100644
--- a/io_uring/sqpoll.c
+++ b/io_uring/sqpoll.c
@@ -44,7 +44,7 @@ void io_sq_thread_unpark(struct io_sq_data *sqd)
 void io_sq_thread_park(struct io_sq_data *sqd)
 	__acquires(&sqd->lock)
 {
-	WARN_ON_ONCE(sqd->thread == current);
+	WARN_ON_ONCE(data_race(sqd->thread) == current);
 
 	atomic_inc(&sqd->park_pending);
 	set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);