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BUG: KCSAN: data-race in n_tty_flush_buffer / n_tty_lookahead_flow_ctrl

write to 0xffffc900018bf270 of 8 bytes by task 19167 on cpu 0:
 reset_buffer_flags drivers/tty/n_tty.c:328 [inline]
 n_tty_flush_buffer+0x9f/0x190 drivers/tty/n_tty.c:359
 tty_ldisc_hangup+0x72/0x370 drivers/tty/tty_ldisc.c:693
 __tty_hangup+0x3c6/0x540 drivers/tty/tty_io.c:630
 tty_vhangup+0x17/0x20 drivers/tty/tty_io.c:700
 pty_close+0x262/0x280 drivers/tty/pty.c:79
 tty_release+0x20c/0x940 drivers/tty/tty_io.c:1760
 __fput+0x2c1/0x660 fs/file_table.c:422
 ____fput+0x15/0x20 fs/file_table.c:450
 task_work_run+0x13a/0x1a0 kernel/task_work.c:180
 get_signal+0xeee/0x1080 kernel/signal.c:2683
 arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x59/0x130 kernel/entry/common.c:218
 do_syscall_64+0xe2/0x1d0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

read-write to 0xffffc900018bf270 of 8 bytes by task 49 on cpu 1:
 n_tty_lookahead_flow_ctrl+0x48/0x130 drivers/tty/n_tty.c:1507
 tty_port_default_lookahead_buf+0x8a/0xc0 drivers/tty/tty_port.c:59
 lookahead_bufs drivers/tty/tty_buffer.c:428 [inline]
 flush_to_ldisc+0x31c/0x410 drivers/tty/tty_buffer.c:498
 process_one_work kernel/workqueue.c:3254 [inline]
 process_scheduled_works+0x465/0x990 kernel/workqueue.c:3335
 worker_thread+0x526/0x730 kernel/workqueue.c:3416
 kthread+0x1d1/0x210 kernel/kthread.c:388
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243

value changed: 0xffffffffffffe872 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 49 Comm: kworker/u8:3 Not tainted 6.9.0-rc1-syzkaller-00009-g7033999ecd7b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
Workqueue: events_unbound flush_to_ldisc
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