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BUG: KCSAN: data-race in n_tty_receive_char / n_tty_write

write to 0xffffc9000b895028 of 8 bytes by task 17924 on cpu 0:
 commit_echoes drivers/tty/n_tty.c:763 [inline]
 n_tty_receive_char+0x4be/0x670 drivers/tty/n_tty.c:1442
 n_tty_receive_buf_standard+0x4bd/0x2e20 drivers/tty/n_tty.c:1611
 __receive_buf drivers/tty/n_tty.c:1635 [inline]
 n_tty_receive_buf_common+0x7e5/0xbc0 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

read to 0xffffc9000b895028 of 8 bytes by task 28902 on cpu 1:
 process_echoes drivers/tty/n_tty.c:789 [inline]
 n_tty_write+0x161/0xb60 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
 call_write_iter include/linux/fs.h:1985 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x4ab/0x7d0 fs/read_write.c:584
 ksys_write+0xeb/0x1a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:646
 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: 0x00000000000000fa -> 0x00000000000000ff

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 28902 Comm: syz-executor.5 Not tainted 6.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
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