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BUG: KCSAN: data-race in n_tty_flush_buffer / n_tty_lookahead_flow_ctrl

read-write to 0xffffc9000d49b270 of 8 bytes by task 5442 on cpu 0:
 n_tty_lookahead_flow_ctrl+0x46/0x120 drivers/tty/n_tty.c:1490
 tty_port_default_lookahead_buf+0x85/0xb0 drivers/tty/tty_port.c:61
 lookahead_bufs drivers/tty/tty_buffer.c:498 [inline]
 flush_to_ldisc+0x30a/0x400 drivers/tty/tty_buffer.c:568
 process_one_work+0x3e6/0x750 kernel/workqueue.c:2390
 worker_thread+0x5f2/0xa10 kernel/workqueue.c:2537
 kthread+0x1a6/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

write to 0xffffc9000d49b270 of 8 bytes by task 17618 on cpu 1:
 reset_buffer_flags drivers/tty/n_tty.c:340 [inline]
 n_tty_flush_buffer+0x9f/0x180 drivers/tty/n_tty.c:371
 tty_ldisc_hangup+0x6e/0x360 drivers/tty/tty_ldisc.c:694
 __tty_hangup+0x3ba/0x510 drivers/tty/tty_io.c:631
 tty_vhangup+0x17/0x20 drivers/tty/tty_io.c:701
 pty_close+0x262/0x280 drivers/tty/pty.c:79
 tty_release+0x204/0x930 drivers/tty/tty_io.c:1753
 __fput+0x245/0x570 fs/file_table.c:321
 ____fput+0x15/0x20 fs/file_table.c:349
 task_work_run+0x123/0x160 kernel/task_work.c:179
 exit_task_work include/linux/task_work.h:38 [inline]
 do_exit+0x5d7/0x1660 kernel/exit.c:869
 do_group_exit+0x141/0x150 kernel/exit.c:1019
 __do_sys_exit_group kernel/exit.c:1030 [inline]
 __se_sys_exit_group kernel/exit.c:1028 [inline]
 __x64_sys_exit_group+0x1f/0x20 kernel/exit.c:1028
 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

value changed: 0x00000000000004f4 -> 0x00000000000012f4

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 17618 Comm: syz-executor.0 Not tainted 6.3.0-rc5-syzkaller-00202-ga79d5c76f705 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
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