syzbot

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BUG: KCSAN: data-race in n_tty_kick_worker / n_tty_receive_buf_common

read to 0xffffc9000172905c of 1 bytes by task 6559 on cpu 1:
 n_tty_kick_worker+0x2d/0x160 drivers/tty/n_tty.c:204
 n_tty_check_unthrottle+0x17b/0x1c0 drivers/tty/n_tty.c:273
 n_tty_read+0xec6/0x1170 drivers/tty/n_tty.c:2225
 iterate_tty_read drivers/tty/tty_io.c:858 [inline]
 tty_read+0x19d/0x420 drivers/tty/tty_io.c:933
 __kernel_read+0x2c5/0x4f0 fs/read_write.c:440
 kernel_read+0xaa/0x160 fs/read_write.c:458
 p9_fd_read net/9p/trans_fd.c:263 [inline]
 p9_read_work+0x1f5/0x880 net/9p/trans_fd.c:298
 process_one_work+0x3d3/0x720 kernel/workqueue.c:2289
 worker_thread+0x618/0xa70 kernel/workqueue.c:2436
 kthread+0x1a9/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

write to 0xffffc9000172905c of 1 bytes by task 36 on cpu 0:
 n_tty_receive_buf_common+0x378/0x4c40 drivers/tty/n_tty.c:1648
 n_tty_receive_buf2+0x2e/0x40 drivers/tty/n_tty.c:1693
 tty_ldisc_receive_buf+0x5b/0xf0 drivers/tty/tty_buffer.c:452
 tty_port_default_receive_buf+0x54/0x80 drivers/tty/tty_port.c:39
 receive_buf drivers/tty/tty_buffer.c:472 [inline]
 flush_to_ldisc+0x1ca/0x2f0 drivers/tty/tty_buffer.c:522
 process_one_work+0x3d3/0x720 kernel/workqueue.c:2289
 worker_thread+0x618/0xa70 kernel/workqueue.c:2436
 kthread+0x1a9/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

value changed: 0x01 -> 0x00

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 36 Comm: kworker/u4:2 Tainted: G        W         5.19.0-rc6-syzkaller-00418-g972a278fe60c-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022
Workqueue: events_unbound flush_to_ldisc
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