syzbot

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BUG: KCSAN: data-race in n_tty_kick_worker / n_tty_receive_buf_common

read to 0xffffc90017dad05c of 1 bytes by task 31536 on cpu 0:
 n_tty_kick_worker+0x2d/0x150 drivers/tty/n_tty.c:207
 n_tty_check_unthrottle+0x17a/0x1c0 drivers/tty/n_tty.c:276
 n_tty_read+0xe8f/0x1180 drivers/tty/n_tty.c:2278
 iterate_tty_read drivers/tty/tty_io.c:852 [inline]
 tty_read+0x16e/0x3e0 drivers/tty/tty_io.c:927
 call_read_iter include/linux/fs.h:1845 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x39a/0x560 fs/read_write.c:470
 ksys_read+0xeb/0x1a0 fs/read_write.c:613
 __do_sys_read fs/read_write.c:623 [inline]
 __se_sys_read fs/read_write.c:621 [inline]
 __x64_sys_read+0x42/0x50 fs/read_write.c:621
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

write to 0xffffc90017dad05c of 1 bytes by task 29427 on cpu 1:
 n_tty_receive_buf_common+0x255/0xb50 drivers/tty/n_tty.c:1701
 n_tty_receive_buf2+0x32/0x40 drivers/tty/n_tty.c:1746
 tty_ldisc_receive_buf+0x60/0xe0 drivers/tty/tty_buffer.c:457
 tty_port_default_receive_buf+0x58/0x80 drivers/tty/tty_port.c:39
 receive_buf drivers/tty/tty_buffer.c:515 [inline]
 flush_to_ldisc+0x1ca/0x400 drivers/tty/tty_buffer.c:565
 process_one_work+0x3e6/0x750 kernel/workqueue.c:2390
 process_scheduled_works kernel/workqueue.c:2453 [inline]
 worker_thread+0x79a/0xa10 kernel/workqueue.c:2539
 kthread+0x1a6/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

value changed: 0x01 -> 0x00

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 29427 Comm: kworker/u4:12 Not tainted 6.3.0-rc5-syzkaller-00032-g99ddf2254feb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
Workqueue: events_unbound flush_to_ldisc
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