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BUG: KCSAN: data-race in n_tty_receive_buf_common / n_tty_write

write to 0xffffc90000a89020 of 8 bytes by task 4169 on cpu 0:
 process_echoes drivers/tty/n_tty.c:798 [inline]
 n_tty_write+0x1b0/0xa80 drivers/tty/n_tty.c:2336
 do_tty_write drivers/tty/tty_io.c:1018 [inline]
 file_tty_write+0x3a0/0x600 drivers/tty/tty_io.c:1089
 tty_write+0x28/0x30 drivers/tty/tty_io.c:1110
 do_iter_write+0x418/0x700 fs/read_write.c:861
 vfs_iter_write+0x50/0x70 fs/read_write.c:902
 iter_file_splice_write+0x42b/0x7b0 fs/splice.c:686
 do_splice_from fs/splice.c:764 [inline]
 direct_splice_actor+0x84/0xa0 fs/splice.c:931
 splice_direct_to_actor+0x2ee/0x5f0 fs/splice.c:886
 do_splice_direct+0x104/0x180 fs/splice.c:974
 do_sendfile+0x3b8/0x950 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1323 [inline]
 __se_sys_sendfile64 fs/read_write.c:1309 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1309
 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 0xffffc90000a89020 of 8 bytes by task 34 on cpu 1:
 flush_echoes drivers/tty/n_tty.c:812 [inline]
 __receive_buf drivers/tty/n_tty.c:1615 [inline]
 n_tty_receive_buf_common+0x895/0xb50 drivers/tty/n_tty.c:1711
 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:2289
 worker_thread+0x5ef/0xa10 kernel/workqueue.c:2436
 kthread+0x1ac/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

value changed: 0x000000000000000b -> 0x000000000000001d

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 34 Comm: kworker/u4:2 Not tainted 6.2.0-rc7-syzkaller-00135-g38c1e0c65865-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023
Workqueue: events_unbound flush_to_ldisc
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