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BUG: KCSAN: data-race in n_tty_receive_buf_common / n_tty_write

write to 0xffffc90000698020 of 8 bytes by task 16868 on cpu 0:
 process_echoes drivers/tty/n_tty.c:793 [inline]
 n_tty_write+0x1b9/0xb60 drivers/tty/n_tty.c:2370
 iterate_tty_write drivers/tty/tty_io.c:1017 [inline]
 file_tty_write+0x398/0x6b0 drivers/tty/tty_io.c:1088
 tty_write+0x28/0x30 drivers/tty/tty_io.c:1109
 do_iter_write+0x4b4/0x7b0 fs/read_write.c:860
 vfs_writev+0x1a8/0x320 fs/read_write.c:933
 do_writev+0xf8/0x220 fs/read_write.c:976
 __do_sys_writev fs/read_write.c:1049 [inline]
 __se_sys_writev fs/read_write.c:1046 [inline]
 __x64_sys_writev+0x45/0x50 fs/read_write.c:1046
 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

read to 0xffffc90000698020 of 8 bytes by task 26090 on cpu 1:
 flush_echoes drivers/tty/n_tty.c:807 [inline]
 __receive_buf drivers/tty/n_tty.c:1637 [inline]
 n_tty_receive_buf_common+0x87d/0xbc0 drivers/tty/n_tty.c:1734
 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1780
 tty_ldisc_receive_buf+0x60/0xe0 drivers/tty/tty_buffer.c:387
 tty_port_default_receive_buf+0x59/0x90 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:445 [inline]
 flush_to_ldisc+0x1ca/0x400 drivers/tty/tty_buffer.c:495
 process_one_work kernel/workqueue.c:2630 [inline]
 process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2703
 worker_thread+0x525/0x730 kernel/workqueue.c:2784
 kthread+0x1d7/0x210 kernel/kthread.c:388
 ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304

value changed: 0x000000000000007a -> 0x0000000000000080

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 26090 Comm: kworker/u4:18 Not tainted 6.6.0-rc6-syzkaller-00043-gdd72f9c7e512 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
Workqueue: events_unbound flush_to_ldisc
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